acacode · bjohnso5 · Jun 10, 2025
diff --git a/.changeset/honest-feet-worry.md b/.changeset/honest-feet-worry.md
@@ -0,0 +1,5 @@
+---
+"swagger-typescript-api": minor
+---
+
+Implement const object-style enum generation
diff --git a/index.ts b/index.ts
@@ -181,6 +181,12 @@ const generateCommand = defineCommand({
       description: 'generate all "enum" types as union types (T1 | T2 | TN)',
       default: codeGenBaseConfig.generateUnionEnums,
     },
+    "generate-const-object-enums": {
+      type: "boolean",
+      description:
+        'generate all "enum" types as pairs of const objects and types derived from those objects\' keys. Mutually exclusive with, and pre-empted by, generateUnionEnums',
+      default: codeGenBaseConfig.generateConstObjectEnums, // TODO: collapse enum booleans into a single field taking an enum?
+    },
     "http-client": {
       type: "string",
       description: `http client type (possible values: ${Object.values(
@@ -311,6 +317,7 @@ const generateCommand = defineCommand({
       generateResponses: args.responses,
       generateRouteTypes: args["route-types"],
       generateUnionEnums: args["generate-union-enums"],
+      generateConstObjectEnums: args["generate-const-object-enums"],
       httpClientType:
         args["http-client"] || args.axios
           ? HTTP_CLIENT.AXIOS

diff --git a/src/configuration.ts b/src/configuration.ts
@@ -33,6 +33,7 @@ const TsKeyword = {
   Record: "Record",
   Intersection: "&",
   Union: "|",
+  Const: "const",
 };
 
 const TsCodeGenKeyword = {
@@ -54,6 +55,8 @@ export class CodeGenConfig {
   /** CLI flag */
   generateUnionEnums = false;
   /** CLI flag */
+  generateConstObjectEnums = false;
+  /** CLI flag */
   addReadonly = false;
   enumNamesAsValues = false;
   /** parsed swagger schema from getSwaggerObject() */

diff --git a/src/schema-parser/schema-formatters.ts b/src/schema-parser/schema-formatters.ts
@@ -29,6 +29,21 @@ export class SchemaFormatters {
         };
       }
 
+      if (this.config.generateConstObjectEnums) {
+        const entries = parsedSchema.content
+          .map(({ key, value }) => {
+            return `${key}: ${value}`;
+          })
+          .join(",\n  ");
+        return {
+          ...parsedSchema,
+          $content: parsedSchema.content,
+          typeIdentifier: this.config.Ts.Keyword.Const,
+          content: `{\n  ${entries}\n} as const;\nexport type ${parsedSchema.name} = (typeof ${parsedSchema.name})[keyof typeof ${parsedSchema.name}];`,
+        };
+      }
+
+      // Fallback: classic TypeScript enum
       return {
         ...parsedSchema,
         $content: parsedSchema.content,

diff --git a/templates/base/data-contracts.ejs b/templates/base/data-contracts.ejs
@@ -25,6 +25,9 @@ const dataContractTemplates = {
   type: (contract) => {
     return `type ${contract.name}${buildGenerics(contract)} = ${contract.content}`;
   },
+  'const': (contract) => {
+    return `const ${contract.name}${buildGenerics(contract)} = ${contract.content}`;
+  },
 }
 %>
 

diff --git a/tests/spec/constObjectEnums/__snapshots__/basic.test.ts.snap b/tests/spec/constObjectEnums/__snapshots__/basic.test.ts.snap
@@ -0,0 +1,314 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`basic > --generate-const-object-enums 1`] = `
+"/* eslint-disable */
+/* tslint:disable */
+// @ts-nocheck
+/*
+ * ---------------------------------------------------------------
+ * ## THIS FILE WAS GENERATED VIA SWAGGER-TYPESCRIPT-API        ##
+ * ##                                                           ##
+ * ## AUTHOR: acacode                                           ##
+ * ## SOURCE: https://github.com/acacode/swagger-typescript-api ##
+ * ---------------------------------------------------------------
+ */
+
+/**
+ * FooBar
+ * @format int32
+ */
+export const IntEnumWithNames = {
+  Unknown: 0,
+  String: 1,
+  Int32: 2,
+  Int64: 3,
+  Double: 4,
+  DateTime: 5,
+  Test2: 6,
+  Test23: 7,
+  Tess44: 8,
+  BooFar: 9,
+} as const;
+export type IntEnumWithNames =
+  (typeof IntEnumWithNames)[keyof typeof IntEnumWithNames];
+
+export const BooleanEnum = {
+  True: true,
+  False: false,
+} as const;
+export type BooleanEnum = (typeof BooleanEnum)[keyof typeof BooleanEnum];
+
+export const NumberEnum = {
+  Value1: 1,
+  Value2: 2,
+  Value3: 3,
+  Value4: 4,
+} as const;
+export type NumberEnum = (typeof NumberEnum)[keyof typeof NumberEnum];
+
+export const StringEnum = {
+  String1: "String1",
+  String2: "String2",
+  String3: "String3",
+  String4: "String4",
+} as const;
+export type StringEnum = (typeof StringEnum)[keyof typeof StringEnum];
+
+export type QueryParamsType = Record<string | number, any>;
+export type ResponseFormat = keyof Omit<Body, "body" | "bodyUsed">;
+
+export interface FullRequestParams extends Omit<RequestInit, "body"> {
+  /** set parameter to \`true\` for call \`securityWorker\` for this request */
+  secure?: boolean;
+  /** request path */
+  path: string;
+  /** content type of request body */
+  type?: ContentType;
+  /** query params */
+  query?: QueryParamsType;
+  /** format of response (i.e. response.json() -> format: "json") */
+  format?: ResponseFormat;
+  /** request body */
+  body?: unknown;
+  /** base url */
+  baseUrl?: string;
+  /** request cancellation token */
+  cancelToken?: CancelToken;
+}
+
+export type RequestParams = Omit<
+  FullRequestParams,
+  "body" | "method" | "query" | "path"
+>;
+
+export interface ApiConfig<SecurityDataType = unknown> {
+  baseUrl?: string;
+  baseApiParams?: Omit<RequestParams, "baseUrl" | "cancelToken" | "signal">;
+  securityWorker?: (
+    securityData: SecurityDataType | null,
+  ) => Promise<RequestParams | void> | RequestParams | void;
+  customFetch?: typeof fetch;
+}
+
+export interface HttpResponse<D extends unknown, E extends unknown = unknown>
+  extends Response {
+  data: D;
+  error: E;
+}
+
+type CancelToken = Symbol | string | number;
+
+export enum ContentType {
+  Json = "application/json",
+  JsonApi = "application/vnd.api+json",
+  FormData = "multipart/form-data",
+  UrlEncoded = "application/x-www-form-urlencoded",
+  Text = "text/plain",
+}
+
+export class HttpClient<SecurityDataType = unknown> {
+  public baseUrl: string = "http://localhost:8080/api/v1";
+  private securityData: SecurityDataType | null = null;
+  private securityWorker?: ApiConfig<SecurityDataType>["securityWorker"];
+  private abortControllers = new Map<CancelToken, AbortController>();
+  private customFetch = (...fetchParams: Parameters<typeof fetch>) =>
+    fetch(...fetchParams);
+
+  private baseApiParams: RequestParams = {
+    credentials: "same-origin",
+    headers: {},
+    redirect: "follow",
+    referrerPolicy: "no-referrer",
+  };
+
+  constructor(apiConfig: ApiConfig<SecurityDataType> = {}) {
+    Object.assign(this, apiConfig);
+  }
+
+  public setSecurityData = (data: SecurityDataType | null) => {
+    this.securityData = data;
+  };
+
+  protected encodeQueryParam(key: string, value: any) {
+    const encodedKey = encodeURIComponent(key);
+    return \`\${encodedKey}=\${encodeURIComponent(typeof value === "number" ? value : \`\${value}\`)}\`;
+  }
+
+  protected addQueryParam(query: QueryParamsType, key: string) {
+    return this.encodeQueryParam(key, query[key]);
+  }
+
+  protected addArrayQueryParam(query: QueryParamsType, key: string) {
+    const value = query[key];
+    return value.map((v: any) => this.encodeQueryParam(key, v)).join("&");
+  }
+
+  protected toQueryString(rawQuery?: QueryParamsType): string {
+    const query = rawQuery || {};
+    const keys = Object.keys(query).filter(
+      (key) => "undefined" !== typeof query[key],
+    );
+    return keys
+      .map((key) =>
+        Array.isArray(query[key])
+          ? this.addArrayQueryParam(query, key)
+          : this.addQueryParam(query, key),
+      )
+      .join("&");
+  }
+
+  protected addQueryParams(rawQuery?: QueryParamsType): string {
+    const queryString = this.toQueryString(rawQuery);
+    return queryString ? \`?\${queryString}\` : "";
+  }
+
+  private contentFormatters: Record<ContentType, (input: any) => any> = {
+    [ContentType.Json]: (input: any) =>
+      input !== null && (typeof input === "object" || typeof input === "string")
+        ? JSON.stringify(input)
+        : input,
+    [ContentType.JsonApi]: (input: any) =>
+      input !== null && (typeof input === "object" || typeof input === "string")
+        ? JSON.stringify(input)
+        : input,
+    [ContentType.Text]: (input: any) =>
+      input !== null && typeof input !== "string"
+        ? JSON.stringify(input)
+        : input,
+    [ContentType.FormData]: (input: any) =>
+      Object.keys(input || {}).reduce((formData, key) => {
+        const property = input[key];
+        formData.append(
+          key,
+          property instanceof Blob
+            ? property
+            : typeof property === "object" && property !== null
+              ? JSON.stringify(property)
+              : \`\${property}\`,
+        );
+        return formData;
+      }, new FormData()),
+    [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
+  };
+
+  protected mergeRequestParams(
+    params1: RequestParams,
+    params2?: RequestParams,
+  ): RequestParams {
+    return {
+      ...this.baseApiParams,
+      ...params1,
+      ...(params2 || {}),
+      headers: {
+        ...(this.baseApiParams.headers || {}),
+        ...(params1.headers || {}),
+        ...((params2 && params2.headers) || {}),
+      },
+    };
+  }
+
+  protected createAbortSignal = (
+    cancelToken: CancelToken,
+  ): AbortSignal | undefined => {
+    if (this.abortControllers.has(cancelToken)) {
+      const abortController = this.abortControllers.get(cancelToken);
+      if (abortController) {
+        return abortController.signal;
+      }
+      return void 0;
+    }
+
+    const abortController = new AbortController();
+    this.abortControllers.set(cancelToken, abortController);
+    return abortController.signal;
+  };
+
+  public abortRequest = (cancelToken: CancelToken) => {
+    const abortController = this.abortControllers.get(cancelToken);
+
+    if (abortController) {
+      abortController.abort();
+      this.abortControllers.delete(cancelToken);
+    }
+  };
+
+  public request = async <T = any, E = any>({
+    body,
+    secure,
+    path,
+    type,
+    query,
+    format,
+    baseUrl,
+    cancelToken,
+    ...params
+  }: FullRequestParams): Promise<HttpResponse<T, E>> => {
+    const secureParams =
+      ((typeof secure === "boolean" ? secure : this.baseApiParams.secure) &&
+        this.securityWorker &&
+        (await this.securityWorker(this.securityData))) ||
+      {};
+    const requestParams = this.mergeRequestParams(params, secureParams);
+    const queryString = query && this.toQueryString(query);
+    const payloadFormatter = this.contentFormatters[type || ContentType.Json];
+    const responseFormat = format || requestParams.format;
+
+    return this.customFetch(
+      \`\${baseUrl || this.baseUrl || ""}\${path}\${queryString ? \`?\${queryString}\` : ""}\`,
+      {
+        ...requestParams,
+        headers: {
+          ...(requestParams.headers || {}),
+          ...(type && type !== ContentType.FormData
+            ? { "Content-Type": type }
+            : {}),
+        },
+        signal:
+          (cancelToken
+            ? this.createAbortSignal(cancelToken)
+            : requestParams.signal) || null,
+        body:
+          typeof body === "undefined" || body === null
+            ? null
+            : payloadFormatter(body),
+      },
+    ).then(async (response) => {
+      const r = response.clone() as HttpResponse<T, E>;
+      r.data = null as unknown as T;
+      r.error = null as unknown as E;
+
+      const data = !responseFormat
+        ? r
+        : await response[responseFormat]()
+            .then((data) => {
+              if (r.ok) {
+                r.data = data;
+              } else {
+                r.error = data;
+              }
+              return r;
+            })
+            .catch((e) => {
+              r.error = e;
+              return r;
+            });
+
+      if (cancelToken) {
+        this.abortControllers.delete(cancelToken);
+      }
+
+      if (!response.ok) throw data;
+      return data;
+    });
+  };
+}
+
+/**
+ * @title No title
+ * @baseUrl http://localhost:8080/api/v1
+ */
+export class Api<
+  SecurityDataType extends unknown,
+> extends HttpClient<SecurityDataType> {}
+"
+`;