fix(union): ensure union type with null or unknown will mock the first type (#322)

BREAKING CHANGE: union types that resolve in null or unknown will now not be converted to undefined.

before
```ts
type = string | null // undefined
```

after
```ts
type = string | null // '' (empty string)
```

Author: uittorio

src/transformer/descriptor/union/union.ts

@@ -17,8 +17,5 @@ export function GetUnionDescriptor(node: ts.UnionTypeNode, scope: Scope): ts.Exp
 }
 
 function isNotDefinedType(typeNode: ts.Node): boolean {
-  return typeNode.kind === ts.SyntaxKind.VoidKeyword
-        || typeNode.kind === ts.SyntaxKind.NullKeyword
-        || typeNode.kind === ts.SyntaxKind.UnknownKeyword
-        || typeNode.kind === ts.SyntaxKind.UndefinedKeyword;
+  return typeNode.kind === ts.SyntaxKind.VoidKeyword || typeNode.kind === ts.SyntaxKind.UndefinedKeyword;
 }

test/transformer/descriptor/union/union.test.ts

@@ -1,4 +1,5 @@
 import { createMock } from 'ts-auto-mock';
+import { ImportInterface } from '../utils/interfaces/importInterface';
 
 describe('for union', () => {
   interface Interface {
@@ -10,22 +11,14 @@ describe('for union', () => {
     expect(properties.a).toBe('');
   });
 
-  describe('union optional', () => {
+  describe('type interface import', () => {
     class MyClass {
-      public test: string | void;
-      public test2: string | null;
-      public test3: string | unknown;
-      public test4: string | undefined;
-      public test5: undefined | string | number;
+      public test: string | ImportInterface;
     }
 
-    it('should not set the value', () => {
+    it('should set the value', () => {
       const properties: MyClass = createMock<MyClass>();
-      expect(properties.test).toBeUndefined();
-      expect(properties.test2).toBeUndefined();
-      expect(properties.test3).toBeUndefined();
-      expect(properties.test4).toBeUndefined();
-      expect(properties.test5).toBeUndefined();
+      expect(properties.test).toBe('');
     });
   });
 
@@ -69,4 +62,26 @@ describe('for union', () => {
       expect(properties.test).toEqual([]);
     });
   });
+
+  describe('union type null', () => {
+    interface Interface {
+      a: string | null;
+    }
+
+    it('should set the first type', () => {
+      const properties: Interface = createMock<Interface>();
+      expect(properties.a).toBe('');
+    });
+  });
+
+  describe('union type unknown', () => {
+    interface Interface {
+      a: string | unknown;
+    }
+
+    it('should set the first type', () => {
+      const properties: Interface = createMock<Interface>();
+      expect(properties.a).toBe('');
+    });
+  });
 });

test/transformer/descriptor/union/unionOptional.test.ts

@@ -1,10 +1,10 @@
 import { createMock } from 'ts-auto-mock';
-import { ImportInterface } from '../utils/interfaces/importInterface';
 import { ImportType } from '../utils/types/type';
 
 describe('union optional', () => {
   describe('type reference', () => {
-    type Type = null;
+    type Type = void;
+
     class MyClass {
       public test: string | Type;
     }
@@ -26,20 +26,20 @@ describe('union optional', () => {
     });
   });
 
-  describe('type interface import', () => {
+  describe('type object declared', () => {
     class MyClass {
-      public test: string | ImportInterface;
+      public test: string | { a: string } | undefined;
     }
 
     it('should not set the value', () => {
       const properties: MyClass = createMock<MyClass>();
-      expect(properties.test).toBe('');
+      expect(properties.test).toBeUndefined();
     });
   });
 
-  describe('type object declared', () => {
+  describe('type declared value', () => {
     class MyClass {
-      public test: string | { a: string } | null;
+      public test: '2' | undefined;
     }
 
     it('should not set the value', () => {
@@ -48,9 +48,11 @@ describe('union optional', () => {
     });
   });
 
-  describe('type declared value', () => {
+  describe('type reference optional', () => {
+    type TypeOptional = string | void;
+
     class MyClass {
-      public test: '2' | null;
+      public test: TypeOptional | number;
     }
 
     it('should not set the value', () => {
@@ -59,42 +61,29 @@ describe('union optional', () => {
     });
   });
 
-  describe('type reference optional', () => {
-        type TypeOptional = string | null;
-
-        class MyClass {
-          public test: TypeOptional | number;
-        }
-
-        it('should not set the value', () => {
-          const properties: MyClass = createMock<MyClass>();
-          expect(properties.test).toBeUndefined();
-        });
-  });
-
-  describe('type reference optional second', () => {
-        type TypeOptional = string | null;
+  describe('type reference optional as second type', () => {
+    type TypeOptional = string | void;
 
-        class MyClass {
-          public test: number | TypeOptional;
-        }
+    class MyClass {
+      public test: number | TypeOptional;
+    }
 
-        it('should not set the value', () => {
-          const properties: MyClass = createMock<MyClass>();
-          expect(properties.test).toBeUndefined();
-        });
+    it('should not set the value', () => {
+      const properties: MyClass = createMock<MyClass>();
+      expect(properties.test).toBeUndefined();
+    });
   });
 
   describe('type reference optional and extends', () => {
-        type TypeOptional = { a: string} & { b: number} | null;
+    type TypeOptional = { a: string } & { b: number } | void;
 
-        class MyClass {
-          public test: number | TypeOptional;
-        }
+    class MyClass {
+      public test: number | TypeOptional;
+    }
 
-        it('should not set the value', () => {
-          const properties: MyClass = createMock<MyClass>();
-          expect(properties.test).toBeUndefined();
-        });
+    it('should not set the value', () => {
+      const properties: MyClass = createMock<MyClass>();
+      expect(properties.test).toBeUndefined();
+    });
   });
 });