new(bool): Add onlyFalse() and onlyTrue() methods.

docs/predicates.md

@@ -64,7 +64,10 @@ optimal(
 ## Boolean
 
 The `bool(default?: boolean)` predicate verifies a value is a boolean. Defaults to `false` but can
-be customized with the 1st argument.
+be customized with the 1st argument. Boolean builder supports the following additional methods:
+
+- `onlyFalse()` - Validate the value is only ever `false` (or undefined).
+- `onlyTrue()` - Validate the value is only ever `true` (or undefined).
 
 ```ts
 optimal(

src/BooleanBuilder.ts

@@ -0,0 +1,37 @@
+import Builder from './Builder';
+
+export default class BooleanBuilder<T extends boolean = boolean> extends Builder<T> {
+  constructor(defaultValue?: T) {
+    super('boolean', defaultValue || (false as T));
+  }
+
+  onlyFalse(): BooleanBuilder<false> {
+    this.defaultValue = false as T;
+    this.addCheck(this.checkOnlyFalse);
+
+    return (this as unknown) as BooleanBuilder<false>;
+  }
+
+  checkOnlyFalse(path: string, value: T) {
+    if (__DEV__) {
+      this.invariant(value === false, 'May only be `false`.', path);
+    }
+  }
+
+  onlyTrue(): BooleanBuilder<true> {
+    this.defaultValue = true as T;
+    this.addCheck(this.checkOnlyTrue);
+
+    return (this as unknown) as BooleanBuilder<true>;
+  }
+
+  checkOnlyTrue(path: string, value: T) {
+    if (__DEV__) {
+      this.invariant(value === true, 'May only be `true`.', path);
+    }
+  }
+}
+
+export function bool(defaultValue: boolean = false) /* infer */ {
+  return new BooleanBuilder<boolean>(defaultValue);
+}

src/Builder.ts

@@ -406,10 +406,6 @@ export default class Builder<T> {
   }
 }
 
-export function bool(defaultValue: boolean = false) /* infer */ {
-  return new Builder<boolean>('boolean', defaultValue);
-}
-
 export function custom<T>(callback: CustomCallback<T>, defaultValue: T) /* infer */ {
   return new Builder<T>('custom', defaultValue).custom(callback);
 }

src/index.ts

@@ -4,8 +4,9 @@
  */
 
 import optimal from './optimal';
-import Builder, { bool, custom, func } from './Builder';
+import Builder, { custom, func } from './Builder';
 import ArrayBuilder, { array } from './ArrayBuilder';
+import BooleanBuilder, { bool } from './BooleanBuilder';
 import InstanceBuilder, { builder, instance, date, regex } from './InstanceBuilder';
 import NumberBuilder, { number } from './NumberBuilder';
 import ObjectBuilder, { object, blueprint } from './ObjectBuilder';
@@ -50,6 +51,7 @@ export {
 export {
   Builder,
   ArrayBuilder,
+  BooleanBuilder,
   InstanceBuilder,
   NumberBuilder,
   ObjectBuilder,

tests/BooleanBuilder.test.ts

@@ -0,0 +1,107 @@
+import BooleanBuilder, { bool } from '../src/BooleanBuilder';
+
+describe('BooleanBuilder', () => {
+  let builder: BooleanBuilder<boolean>;
+
+  beforeEach(() => {
+    builder = bool();
+  });
+
+  describe('bool()', () => {
+    it('returns a builder', () => {
+      expect(bool(true)).toBeInstanceOf(BooleanBuilder);
+    });
+
+    it('sets type and default value', () => {
+      builder = bool(true);
+
+      expect(builder.type).toBe('boolean');
+      expect(builder.defaultValue).toBe(true);
+    });
+
+    it('errors if a non-boolean value is used', () => {
+      expect(() => {
+        bool().runChecks(
+          'key',
+          // @ts-ignore Test invalid type
+          123,
+          {},
+        );
+      }).toThrowErrorMatchingSnapshot();
+    });
+
+    it('returns the type alias', () => {
+      expect(bool().typeAlias()).toBe('boolean');
+    });
+  });
+
+  describe('onlyFalse()', () => {
+    it('adds a checker', () => {
+      builder.onlyFalse();
+
+      expect(builder.checks[1]).toEqual({
+        callback: builder.checkOnlyFalse,
+        args: [],
+      });
+    });
+
+    it('errors if value is `true`', () => {
+      builder.onlyFalse();
+
+      expect(() => {
+        builder.runChecks('key', true, { key: true });
+      }).toThrowErrorMatchingSnapshot();
+    });
+
+    it('passes if value is `false`', () => {
+      builder.onlyFalse();
+
+      expect(() => {
+        expect(builder.runChecks('key', false, { key: false })).toBe(false);
+      }).not.toThrow();
+    });
+
+    it('passes if value is undefined', () => {
+      builder.onlyFalse();
+
+      expect(() => {
+        expect(builder.runChecks('key', undefined, { key: undefined })).toBe(false);
+      }).not.toThrow();
+    });
+  });
+
+  describe('onlyTrue()', () => {
+    it('adds a checker', () => {
+      builder.onlyTrue();
+
+      expect(builder.checks[1]).toEqual({
+        callback: builder.checkOnlyTrue,
+        args: [],
+      });
+    });
+
+    it('errors if value is `false`', () => {
+      builder.onlyTrue();
+
+      expect(() => {
+        builder.runChecks('key', false, { key: false });
+      }).toThrowErrorMatchingSnapshot();
+    });
+
+    it('passes if value is `true`', () => {
+      builder.onlyTrue();
+
+      expect(() => {
+        expect(builder.runChecks('key', true, { key: true })).toBe(true);
+      }).not.toThrow();
+    });
+
+    it('passes if value is undefined', () => {
+      builder.onlyTrue();
+
+      expect(() => {
+        expect(builder.runChecks('key', undefined, { key: undefined })).toBe(true);
+      }).not.toThrow();
+    });
+  });
+});

tests/Builder.test.ts

@@ -1,4 +1,4 @@
-import Builder, { bool, custom, func } from '../src/Builder';
+import Builder, { custom, func } from '../src/Builder';
 
 describe('Builder', () => {
   let builder: Builder<unknown>;
@@ -215,16 +215,12 @@ describe('Builder', () => {
   describe('custom()', () => {
     it('errors if no callback', () => {
       // @ts-ignore
-      expect(() => builder.custom()).toThrow(
-        'Custom blueprints require a validation function.',
-      );
+      expect(() => builder.custom()).toThrow('Custom blueprints require a validation function.');
     });
 
     it('errors if callback is not a function', () => {
       // @ts-ignore
-      expect(() => builder.custom(123)).toThrow(
-        'Custom blueprints require a validation function.',
-      );
+      expect(() => builder.custom(123)).toThrow('Custom blueprints require a validation function.');
     });
   });
 
@@ -450,7 +446,9 @@ describe('Builder', () => {
         builder.deprecate('Use something else.');
         builder.runChecks('key', undefined, {});
 
-        expect(console.info).not.toHaveBeenCalledWith('Field "key" is deprecated. Use something else.');
+        expect(console.info).not.toHaveBeenCalledWith(
+          'Field "key" is deprecated. Use something else.',
+        );
       });
     });
   });
@@ -588,34 +586,6 @@ describe('Builder', () => {
   });
 });
 
-describe('bool()', () => {
-  it('returns a builder', () => {
-    expect(bool(true)).toBeInstanceOf(Builder);
-  });
-
-  it('sets type and default value', () => {
-    const builder = bool(true);
-
-    expect(builder.type).toBe('boolean');
-    expect(builder.defaultValue).toBe(true);
-  });
-
-  it('errors if a non-boolean value is used', () => {
-    expect(() => {
-      bool().runChecks(
-        'key',
-        // @ts-ignore Test invalid type
-        123,
-        {},
-      );
-    }).toThrowErrorMatchingSnapshot();
-  });
-
-  it('returns the type alias', () => {
-    expect(bool().typeAlias()).toBe('boolean');
-  });
-});
-
 describe('custom()', () => {
   it('returns a builder', () => {
     expect(custom(() => {}, '')).toBeInstanceOf(Builder);

tests/ShapeBuilder.test.ts

@@ -1,7 +1,7 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
 import ShapeBuilder, { shape } from '../src/ShapeBuilder';
-import { bool } from '../src/Builder';
+import { bool } from '../src/BooleanBuilder';
 import { number } from '../src/NumberBuilder';
 import { string } from '../src/StringBuilder';
 

tests/UnionBuilder.test.ts

@@ -1,6 +1,7 @@
 import UnionBuilder, { union } from '../src/UnionBuilder';
-import { bool, custom } from '../src/Builder';
+import { custom } from '../src/Builder';
 import { array } from '../src/ArrayBuilder';
+import { bool } from '../src/BooleanBuilder';
 import { object } from '../src/ObjectBuilder';
 import { instance } from '../src/InstanceBuilder';
 import { number } from '../src/NumberBuilder';

tests/__snapshots__/BooleanBuilder.test.ts.snap

@@ -0,0 +1,7 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`BooleanBuilder bool() errors if a non-boolean value is used 1`] = `"Invalid field \\"key\\". Must be a boolean."`;
+
+exports[`BooleanBuilder onlyFalse() errors if value is \`true\` 1`] = `"Invalid field \\"key\\". May only be \`false\`."`;
+
+exports[`BooleanBuilder onlyTrue() errors if value is \`false\` 1`] = `"Invalid field \\"key\\". May only be \`true\`."`;

tests/__snapshots__/Builder.test.ts.snap

@@ -68,6 +68,4 @@ exports[`Builder runChecks() uses custom message 1`] = `"Invalid field \\"key\\"
 
 exports[`Builder xor() errors if no keys are defined 1`] = `"XOR requires a list of field names."`;
 
-exports[`bool() errors if a non-boolean value is used 1`] = `"Invalid field \\"key\\". Must be a boolean."`;
-
 exports[`func() errors if a non-function value is used 1`] = `"Invalid field \\"key\\". Must be a function."`;