Correctly construct LiteralTypes for properties that are "const" (#559)

* Added tests to check defintion of const properties

* fixed typo

* Added first draft of "const" assertion detection in TypeGenerator

* Correctly define LiteralType for const properties

---------

Co-authored-by: Hendrik Lücke-Tieke <[email protected]>

packages/swagger-ts/mocks/discriminator.yaml

@@ -0,0 +1,65 @@
+info:
+  title: Swagger Petstore
+openapi: 3.1.0
+components:
+  schemas:
+    Cat:
+      title: Cat
+      type: object
+      properties:
+        id:
+          format: uuid
+          title: Id
+          type: string
+        type:
+          const: Cat
+          title: Type
+        meow:
+          type: boolean
+          title: Meowing prevalence
+      required:
+      - id
+      - type
+    Dog:
+      title: Dog
+      type: object
+      properties:
+        id:
+          format: uuid
+          title: Id
+          type: string
+        bark:
+          type: number
+          title: Barking frequency
+        type:
+          const: Dog
+          title: Type
+      required:
+      - id
+      - type
+    Petstore:
+      title: Petstore
+      type: object
+      description: A project is an analysis project. It has a name, an id, and has
+        a dataset
+      properties:
+        id:
+          title: Id
+          type: integer
+        pets:
+          default: []
+          items:
+            discriminator:
+              mapping:
+                Cat: "#/components/schemas/Cat"
+                Dog: "#/components/schemas/Dog"
+              propertyName: type
+            oneOf:
+            - "$ref": "#/components/schemas/Cat"
+            - "$ref": "#/components/schemas/Dog"
+          title: Pets
+          type: array
+      required:
+      - id
+
+paths:

packages/swagger-ts/src/generators/TypeGenerator.test.ts

@@ -182,3 +182,63 @@ describe('TypeGenerator with refs', () => {
 
   test.todo('generate type for Pets and Pet')
 })
+
+describe('TypeGenerator with discriminators', () => {
+  const path = pathParser.resolve(__dirname, "../../mocks/discriminator.yaml")
+
+  test('PetStore defined as array with type union', async () => {
+    const oas = await oasPathParser(path)
+    const generator = new TypeGenerator({
+      withJSDocs: false,
+      resolveName: ({ name }) => name,
+      enumType: 'asConst',
+      dateType: 'string',
+      optionalType: 'questionToken',
+    })
+
+    const schemas = oas.getDefinition().components?.schemas
+    const node = generator.build({ schema: schemas?.Petstore as OpenAPIV3.SchemaObject, baseName: 'Petstore' })
+
+    const output = print(node, undefined)
+
+    expect(output).toBeDefined()
+    expect(output).toMatchSnapshot()
+  })
+
+  test('Cat.type defined as const', async () => {
+    const oas = await oasPathParser(path)
+    const generator = new TypeGenerator({
+      withJSDocs: false,
+      resolveName: ({ name }) => name,
+      enumType: 'asConst',
+      dateType: 'string',
+      optionalType: 'questionToken',
+    })
+
+    const schemas = oas.getDefinition().components?.schemas
+    const cat = generator.build({ schema: schemas?.Cat as OpenAPIV3.SchemaObject, baseName: 'Cat' })
+
+    const cat_output = print(cat, undefined)
+    expect(cat_output).toBeDefined()
+    expect(cat_output).toMatchSnapshot()
+  })
+
+  test('Dog.type defined as const', async () => {
+    const oas = await oasPathParser(path)
+    const generator = new TypeGenerator({
+      withJSDocs: false,
+      resolveName: ({ name }) => name,
+      enumType: 'asConst',
+      dateType: 'string',
+      optionalType: 'questionToken',
+    })
+
+    const schemas = oas.getDefinition().components?.schemas
+    const dog = generator.build({ schema: schemas?.Dog as OpenAPIV3.SchemaObject, baseName: 'Dog' })
+
+    const dog_output = print(dog, undefined)
+    expect(dog_output).toBeDefined()
+    expect(dog_output).toMatchSnapshot()
+    })
+
+})

packages/swagger-ts/src/generators/TypeGenerator.ts

@@ -378,6 +378,11 @@ export class TypeGenerator extends SchemaGenerator<Options, OpenAPIV3.SchemaObje
       return factory.createTypeReferenceNode('Blob', [])
     }
 
+    // detect assertion "const" and define the type property as a Literal
+    if("const" in schema && schema["const"] !== undefined && typeof schema["const"] === "string") {
+      return factory.createLiteralTypeNode(factory.createStringLiteral(schema["const"]));
+    }
+
     return keywordTypeNodes.any
   }
 }

packages/swagger-ts/src/generators/__snapshots__/TypeGenerator.test.ts.snap

@@ -0,0 +1,27 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`TypeGenerator with discriminators > Cat.type defined as const 1`] = `
+"export type Cat = {
+    id: string;
+    type: \\"Cat\\";
+    meow?: boolean;
+};
+"
+`;
+
+exports[`TypeGenerator with discriminators > Dog.type defined as const 1`] = `
+"export type Dog = {
+    id: string;
+    bark?: number;
+    type: \\"Dog\\";
+};
+"
+`;
+
+exports[`TypeGenerator with discriminators > PetStore defined as array with type union 1`] = `
+"export type Petstore = {
+    id: number;
+    pets?: (Cat | Dog)[];
+};
+"
+`;