add getEnvFile Function to api

src/client/apiTypes.ts

@@ -70,6 +70,7 @@ export interface IExtensionApi {
              */
             execCommand: string[] | undefined;
         };
+        getEnvFile(workspaceFolder?:Uri) : string;
     };
 
     datascience: {

src/test/api.functional.test.ts

@@ -72,6 +72,19 @@ suite('Extension API', () => {
         assert.deepEqual(execDetails, { execCommand: undefined });
     });
 
+    test('getEnvFile API returns expected object if interpreter is set', async () => {
+        const resource = Uri.parse('a');
+        when(configurationService.getSettings(resource)).thenReturn({ envFile: 'envFile' } as any);
+
+        const envFile = buildApi(
+            Promise.resolve(),
+            instance(serviceManager),
+            instance(serviceContainer),
+        ).settings.getEnvFile(resource);
+
+        assert.equal(envFile, 'envFile');
+    });
+
     test('Provide a callback which is called when interpreter setting changes', async () => {
         const expectedEvent = Typemoq.Mock.ofType<Event<Uri | undefined>>().object;
         when(interpreterService.onDidChangeInterpreterConfiguration).thenReturn(expectedEvent);