diff --git a/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache b/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
index 697438906315..1db1321381b4 100644
--- a/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache
@@ -66,13 +66,14 @@ export class {{classname}} {
 {{/useHttpClient}}
 
     constructor(protected {{#useHttpClient}}httpClient: HttpClient{{/useHttpClient}}{{^useHttpClient}}http: Http{{/useHttpClient}}, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
 {{#useHttpClient}}
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
diff --git a/samples/client/petstore/typescript-angular-v2/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v2/default/api/pet.service.ts
index 62bfcb0f6892..9c9ee52b1e56 100644
--- a/samples/client/petstore/typescript-angular-v2/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/default/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/default/api/store.service.ts b/samples/client/petstore/typescript-angular-v2/default/api/store.service.ts
index 31b3c7046918..2c7456394027 100644
--- a/samples/client/petstore/typescript-angular-v2/default/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/default/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/default/api/user.service.ts b/samples/client/petstore/typescript-angular-v2/default/api/user.service.ts
index 42bac67fac3b..9ce463aa8299 100644
--- a/samples/client/petstore/typescript-angular-v2/default/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/default/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v2/npm/api/pet.service.ts
index 62bfcb0f6892..9c9ee52b1e56 100644
--- a/samples/client/petstore/typescript-angular-v2/npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/npm/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v2/npm/api/store.service.ts
index 31b3c7046918..2c7456394027 100644
--- a/samples/client/petstore/typescript-angular-v2/npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/npm/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v2/npm/api/user.service.ts
index 42bac67fac3b..9ce463aa8299 100644
--- a/samples/client/petstore/typescript-angular-v2/npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/npm/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/pet.service.ts b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/pet.service.ts
index 7aebfe5fef43..c75e5e46dddd 100644
--- a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/pet.service.ts
@@ -36,13 +36,14 @@ export class PetService implements PetServiceInterface {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/store.service.ts b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/store.service.ts
index 7fdd6d038832..147e0c8dfd57 100644
--- a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/store.service.ts
@@ -35,13 +35,14 @@ export class StoreService implements StoreServiceInterface {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/user.service.ts b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/user.service.ts
index d852fae20a1c..d9acd360ef3a 100644
--- a/samples/client/petstore/typescript-angular-v2/with-interfaces/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v2/with-interfaces/api/user.service.ts
@@ -35,13 +35,14 @@ export class UserService implements UserServiceInterface {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
index 52f9e5ee8d91..1d5843d4042c 100644
--- a/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v4.3/npm/api/pet.service.ts
@@ -33,13 +33,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v4.3/npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v4.3/npm/api/store.service.ts
index d853a0f4c88d..eb7539d0d529 100644
--- a/samples/client/petstore/typescript-angular-v4.3/npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v4.3/npm/api/store.service.ts
@@ -32,13 +32,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v4.3/npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v4.3/npm/api/user.service.ts
index b8f2a9f32d9a..0f0a22e8234d 100644
--- a/samples/client/petstore/typescript-angular-v4.3/npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v4.3/npm/api/user.service.ts
@@ -32,13 +32,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v4/npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v4/npm/api/pet.service.ts
index 62bfcb0f6892..9c9ee52b1e56 100644
--- a/samples/client/petstore/typescript-angular-v4/npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v4/npm/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v4/npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v4/npm/api/store.service.ts
index 31b3c7046918..2c7456394027 100644
--- a/samples/client/petstore/typescript-angular-v4/npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v4/npm/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v4/npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v4/npm/api/user.service.ts
index 42bac67fac3b..9ce463aa8299 100644
--- a/samples/client/petstore/typescript-angular-v4/npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v4/npm/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: QueryEncoder;
 
     constructor(protected http: Http, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomQueryEncoderHelper();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
index 989d91b5c028..380838570e9d 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/pet.service.ts
@@ -33,13 +33,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/store.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/store.service.ts
index 97392be5f22a..f1fc543ad0c2 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/store.service.ts
@@ -32,13 +32,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/user.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/user.service.ts
index 5357ddadaa8f..89ca23713a24 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/default/api/user.service.ts
@@ -32,13 +32,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
index 989d91b5c028..380838570e9d 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -33,13 +33,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/store.service.ts
index 97392be5f22a..f1fc543ad0c2 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/store.service.ts
@@ -32,13 +32,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/user.service.ts
index 5357ddadaa8f..89ca23713a24 100644
--- a/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-not-provided-in-root/builds/with-npm/api/user.service.ts
@@ -32,13 +32,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
index a0df069e6a4a..25f4cdfc7f4a 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/store.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/store.service.ts
index 6264d975e002..8fba3b49de87 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/user.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/user.service.ts
index a85d85649952..a9fc0b74c1a6 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/default/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
index a0df069e6a4a..25f4cdfc7f4a 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/store.service.ts
index 6264d975e002..8fba3b49de87 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/user.service.ts
index a85d85649952..a9fc0b74c1a6 100644
--- a/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v6-provided-in-root/builds/with-npm/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
index 989d91b5c028..380838570e9d 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/pet.service.ts
@@ -33,13 +33,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/store.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/store.service.ts
index 97392be5f22a..f1fc543ad0c2 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/store.service.ts
@@ -32,13 +32,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/user.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/user.service.ts
index 5357ddadaa8f..89ca23713a24 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/default/api/user.service.ts
@@ -32,13 +32,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
index 989d91b5c028..380838570e9d 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -33,13 +33,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/store.service.ts
index 97392be5f22a..f1fc543ad0c2 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/store.service.ts
@@ -32,13 +32,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/user.service.ts
index 5357ddadaa8f..89ca23713a24 100644
--- a/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-not-provided-in-root/builds/with-npm/api/user.service.ts
@@ -32,13 +32,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
index a0df069e6a4a..25f4cdfc7f4a 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/store.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/store.service.ts
index 6264d975e002..8fba3b49de87 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/user.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/user.service.ts
index a85d85649952..a9fc0b74c1a6 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/default/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
index a0df069e6a4a..25f4cdfc7f4a 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/store.service.ts
index 6264d975e002..8fba3b49de87 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/user.service.ts
index a85d85649952..a9fc0b74c1a6 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/builds/with-npm/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v7-provided-in-root/tests/default/src/test/configuration.spec.ts b/samples/client/petstore/typescript-angular-v7-provided-in-root/tests/default/src/test/configuration.spec.ts
index 0b8ec658ac1d..120c9d284cb0 100644
--- a/samples/client/petstore/typescript-angular-v7-provided-in-root/tests/default/src/test/configuration.spec.ts
+++ b/samples/client/petstore/typescript-angular-v7-provided-in-root/tests/default/src/test/configuration.spec.ts
@@ -91,3 +91,68 @@ describe(`API (with ConfigurationFactory)`, () => {
   });
 
 });
+
+describe(`API (with ConfigurationFactory and empty basePath)`, () => {
+  let httpClient: HttpClient;
+  let httpTestingController: HttpTestingController;
+
+  const pet: Pet = {
+    name: `pet`,
+    photoUrls: []
+  };
+
+  let apiConfigurationParams: ConfigurationParameters = {
+    // add configuration params here
+    basePath: ''
+  };
+
+  let apiConfig: Configuration = new Configuration(apiConfigurationParams);
+
+  const getApiConfig = () => {
+    return apiConfig;
+  };
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      imports: [
+        HttpClientTestingModule ,
+        ApiModule.forRoot(getApiConfig)
+      ],
+      providers: [
+        PetService,
+      ]
+    });
+
+    // Inject the http service and test controller for each test
+    httpClient = TestBed.get(HttpClient);
+    httpTestingController = TestBed.get(HttpTestingController);
+  });
+
+  afterEach(() => {
+    // After every test, assert that there are no more pending requests.
+    httpTestingController.verify();
+  });
+
+  describe(`PetService`, () => {
+    it(`should be provided`, () => {
+      const petService = TestBed.get(PetService);
+      expect(petService).toBeTruthy();
+    });
+
+    it(`should call initially configured empty basePath /pet`, async(() => {
+      const petService = TestBed.get(PetService);
+
+      petService.addPet(pet).subscribe(
+        result => expect(result).toEqual(pet),
+        error => fail(`expected a result, not the error: ${error.message}`),
+      );
+
+      const req = httpTestingController.expectOne('/pet');
+
+      expect(req.request.method).toEqual('POST');
+
+      req.flush(pet);
+    }));
+  });
+
+});
diff --git a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/pet.service.ts b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/pet.service.ts
index a0df069e6a4a..25f4cdfc7f4a 100644
--- a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/pet.service.ts
+++ b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/pet.service.ts
@@ -35,13 +35,14 @@ export class PetService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/store.service.ts b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/store.service.ts
index 6264d975e002..8fba3b49de87 100644
--- a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/store.service.ts
+++ b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/store.service.ts
@@ -34,13 +34,14 @@ export class StoreService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }
diff --git a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/user.service.ts b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/user.service.ts
index a85d85649952..a9fc0b74c1a6 100644
--- a/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/user.service.ts
+++ b/samples/client/petstore/typescript-angular-v8-provided-in-root/builds/with-npm/api/user.service.ts
@@ -34,13 +34,14 @@ export class UserService {
     public encoder: HttpParameterCodec;
 
     constructor(protected httpClient: HttpClient, @Optional()@Inject(BASE_PATH) basePath: string, @Optional() configuration: Configuration) {
-
         if (configuration) {
             this.configuration = configuration;
-            this.configuration.basePath = configuration.basePath || basePath || this.basePath;
-
-        } else {
-            this.configuration.basePath = basePath || this.basePath;
+        }
+        if (typeof this.configuration.basePath !== 'string') {
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
         }
         this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
     }