feat(typescript-angular): update enum definitions to use 'as const' for improved type safety (#20958)

fixes #20809

Author: daniel-sc

modules/openapi-generator/src/main/resources/typescript-angular/modelEnum.mustache

@@ -13,18 +13,18 @@ export enum {{classname}} {
 }
 {{/stringEnums}}
 {{^stringEnums}}
-export type {{classname}} = {{#allowableValues}}{{#enumVars}}{{{value}}}{{^-last}} | {{/-last}}{{/enumVars}}{{/allowableValues}};
-
 export const {{classname}} = {
 {{#allowableValues}}
 {{#enumVars}}
 {{#enumDescription}}
 
     /**
      * {{.}}
-     */{{/enumDescription}}
-    {{name}}: {{{value}}} as {{classname}}{{^-last}},{{/-last}}
+     */
+{{/enumDescription}}
+    {{name}}: {{{value}}}{{^-last}},{{/-last}}
 {{/enumVars}}
 {{/allowableValues}}
-};
+} as const;
+export type {{classname}} = typeof {{classname}}[keyof typeof {{classname}}];
 {{/stringEnums}}

modules/openapi-generator/src/main/resources/typescript-angular/modelGenericEnums.mustache

@@ -15,14 +15,14 @@ export enum {{classname}}{{enumName}} {
 };
 {{/stringEnums}}
 {{^stringEnums}}
-    export type {{enumName}} = {{#allowableValues}}{{#enumVars}}{{{value}}}{{^-last}} | {{/-last}}{{/enumVars}}{{/allowableValues}};
     export const {{enumName}} = {
     {{#allowableValues}}
     {{#enumVars}}
-        {{name}}: {{{value}}} as {{enumName}}{{^-last}},{{/-last}}
+        {{name}}: {{{value}}}{{^-last}},{{/-last}}
     {{/enumVars}}
     {{/allowableValues}}
-    };
+    } as const;
+    export type {{enumName}} = typeof {{enumName}}[keyof typeof {{enumName}}];
 {{/stringEnums}}
     {{/isEnum}}
 {{/vars}}

modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/typescriptangular/TypeScriptAngularClientCodegenTest.java

@@ -439,4 +439,29 @@ public void testBasePath() throws IOException {
         final String fileContents = Files.readString(Paths.get(output + "/api.base.service.ts"));
         assertThat(fileContents).containsOnlyOnce("basePath = '/relative/url'");
     }
+
+    @Test
+    public void testEnumAsConst() throws IOException {
+        // GIVEN
+        final String specPath = "src/test/resources/3_0/enum.yaml";
+
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        // WHEN
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+            .setGeneratorName("typescript-angular")
+            .setInputSpec(specPath)
+            .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+
+        Generator generator = new DefaultGenerator();
+        generator.opts(clientOptInput).generate();
+
+        // THEN
+        final String fileContents = Files.readString(Paths.get(output + "/model/type.ts"));
+        assertThat(fileContents).containsOnlyOnce("} as const;");
+        assertThat(fileContents).doesNotContain(" as Type");
+    }
 }

samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/model/order.ts

@@ -24,12 +24,12 @@ export interface Order {
     complete?: boolean;
 }
 export namespace Order {
-    export type StatusEnum = 'placed' | 'approved' | 'delivered';
     export const StatusEnum = {
-        Placed: 'placed' as StatusEnum,
-        Approved: 'approved' as StatusEnum,
-        Delivered: 'delivered' as StatusEnum
-    };
+        Placed: 'placed',
+        Approved: 'approved',
+        Delivered: 'delivered'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/model/pet.ts

@@ -26,12 +26,12 @@ export interface Pet {
     status?: Pet.StatusEnum;
 }
 export namespace Pet {
-    export type StatusEnum = 'available' | 'pending' | 'sold';
     export const StatusEnum = {
-        Available: 'available' as StatusEnum,
-        Pending: 'pending' as StatusEnum,
-        Sold: 'sold' as StatusEnum
-    };
+        Available: 'available',
+        Pending: 'pending',
+        Sold: 'sold'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/model/order.ts

@@ -24,12 +24,12 @@ export interface Order {
     complete?: boolean;
 }
 export namespace Order {
-    export type StatusEnum = 'placed' | 'approved' | 'delivered';
     export const StatusEnum = {
-        Placed: 'placed' as StatusEnum,
-        Approved: 'approved' as StatusEnum,
-        Delivered: 'delivered' as StatusEnum
-    };
+        Placed: 'placed',
+        Approved: 'approved',
+        Delivered: 'delivered'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/model/pet.ts

@@ -26,12 +26,12 @@ export interface Pet {
     status?: Pet.StatusEnum;
 }
 export namespace Pet {
-    export type StatusEnum = 'available' | 'pending' | 'sold';
     export const StatusEnum = {
-        Available: 'available' as StatusEnum,
-        Pending: 'pending' as StatusEnum,
-        Sold: 'sold' as StatusEnum
-    };
+        Available: 'available',
+        Pending: 'pending',
+        Sold: 'sold'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/model/order.ts

@@ -24,12 +24,12 @@ export interface Order {
     complete?: boolean;
 }
 export namespace Order {
-    export type StatusEnum = 'placed' | 'approved' | 'delivered';
     export const StatusEnum = {
-        Placed: 'placed' as StatusEnum,
-        Approved: 'approved' as StatusEnum,
-        Delivered: 'delivered' as StatusEnum
-    };
+        Placed: 'placed',
+        Approved: 'approved',
+        Delivered: 'delivered'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/model/pet.ts

@@ -26,12 +26,12 @@ export interface Pet {
     status?: Pet.StatusEnum;
 }
 export namespace Pet {
-    export type StatusEnum = 'available' | 'pending' | 'sold';
     export const StatusEnum = {
-        Available: 'available' as StatusEnum,
-        Pending: 'pending' as StatusEnum,
-        Sold: 'sold' as StatusEnum
-    };
+        Available: 'available',
+        Pending: 'pending',
+        Sold: 'sold'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }
 
 

samples/client/petstore/typescript-angular-v13-provided-in-any/builds/default/model/order.ts

@@ -24,12 +24,12 @@ export interface Order {
     complete?: boolean;
 }
 export namespace Order {
-    export type StatusEnum = 'placed' | 'approved' | 'delivered';
     export const StatusEnum = {
-        Placed: 'placed' as StatusEnum,
-        Approved: 'approved' as StatusEnum,
-        Delivered: 'delivered' as StatusEnum
-    };
+        Placed: 'placed',
+        Approved: 'approved',
+        Delivered: 'delivered'
+    } as const;
+    export type StatusEnum = typeof StatusEnum[keyof typeof StatusEnum];
 }