acacode · Upgrade220 · May 21, 2026 · May 21, 2026
diff --git a/.changeset/fix-union-content-type.md b/.changeset/fix-union-content-type.md
@@ -0,0 +1,5 @@
+---
+"swagger-typescript-api": patch
+---
+
+Fix `ContentType` in http-client not respecting `enumStyle: "union"`. It now generates a plain type alias instead of an enum, and all call sites emit string literals instead of `ContentType.Json` etc.
diff --git a/templates/base/content-type-accessors.ejs b/templates/base/content-type-accessors.ejs
@@ -0,0 +1,18 @@
+<%
+const { config } = it;
+const isUnion = config.enumStyle === "union";
+
+// camelCase keys (Json, FormData, …) are used by http-client templates as CT.Json, CT.FormData, …
+// They mirror the ContentType property names so the access pattern is identical regardless of enumStyle.
+const v = {
+  Json:       isUnion ? '"application/json"'                  : "ContentType.Json",
+  JsonApi:    isUnion ? '"application/vnd.api+json"'          : "ContentType.JsonApi",
+  FormData:   isUnion ? '"multipart/form-data"'               : "ContentType.FormData",
+  UrlEncoded: isUnion ? '"application/x-www-form-urlencoded"' : "ContentType.UrlEncoded",
+  Text:       isUnion ? '"text/plain"'                        : "ContentType.Text",
+};
+
+// UPPER_SNAKE aliases (JSON, FORM_DATA, …) are used by procedure-call templates as
+// requestContentKind["JSON"], matching the CONTENT_KIND constants produced by schema-routes.ts.
+return { ...v, JSON: v.Json, JSON_API: v.JsonApi, FORM_DATA: v.FormData, URL_ENCODED: v.UrlEncoded, TEXT: v.Text };
+%>
diff --git a/templates/base/http-clients/axios-http-client.ejs b/templates/base/http-clients/axios-http-client.ejs
@@ -1,5 +1,6 @@
 <%
 const { apiConfig, generateResponses, config } = it;
+const CT = includeFile("@base/content-type-accessors", { config });
 %>
 
 import type { AxiosInstance, AxiosRequestConfig, HeadersDefaults, ResponseType, AxiosResponse } from "axios";
@@ -39,6 +40,8 @@ export const ContentType = {
   Text: "text/plain",
 } as const;
 export type ContentType = (typeof ContentType)[keyof typeof ContentType];
+<% } else if (config.enumStyle === "union") { %>
+export type ContentType = "application/json" | "application/vnd.api+json" | "multipart/form-data" | "application/x-www-form-urlencoded" | "text/plain";
 <% } else { %>
 export enum ContentType {
   Json = "application/json",
@@ -127,11 +130,11 @@ export class HttpClient<SecurityDataType = unknown> {
         const requestParams = this.mergeRequestParams(params, secureParams);
         const responseFormat = (format || this.format) || undefined;
 
-        if (type === ContentType.FormData && body && body !== null && typeof body === "object") {
+        if (type === <%~ CT.FormData %> && body && body !== null && typeof body === "object") {
           body = this.createFormData(body as Record<string, unknown>);
         }
 
-        if (type === ContentType.Text && body && body !== null && typeof body !== "string") {
+        if (type === <%~ CT.Text %> && body && body !== null && typeof body !== "string") {
           body = JSON.stringify(body);
         }
 

diff --git a/templates/base/http-clients/fetch-http-client.ejs b/templates/base/http-clients/fetch-http-client.ejs
@@ -1,5 +1,6 @@
 <%
 const { apiConfig, generateResponses, config } = it;
+const CT = includeFile("@base/content-type-accessors", { config });
 %>
 
 export type QueryParamsType = Record<string | number, any>;
@@ -50,6 +51,8 @@ export const ContentType = {
     Text: "text/plain",
 } as const;
 export type ContentType = (typeof ContentType)[keyof typeof ContentType];
+<% } else if (config.enumStyle === "union") { %>
+export type ContentType = "application/json" | "application/vnd.api+json" | "multipart/form-data" | "application/x-www-form-urlencoded" | "text/plain";
 <% } else { %>
 export enum ContentType {
     Json = "application/json",
@@ -114,10 +117,10 @@ export class HttpClient<SecurityDataType = unknown> {
     }
 
     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) => {
+        [<%~ CT.Json %>]: (input:any) => input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
+        [<%~ CT.JsonApi %>]: (input:any) => input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
+        [<%~ CT.Text %>]: (input:any) => input !== null && typeof input !== "string" ? JSON.stringify(input) : input,
+        [<%~ CT.FormData %>]: (input: any) => {
             if (input instanceof FormData) {
                 return input;
             }
@@ -135,7 +138,7 @@ export class HttpClient<SecurityDataType = unknown> {
                 return formData;
             }, new FormData());
         },
-        [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
+        [<%~ CT.UrlEncoded %>]: (input: any) => this.toQueryString(input),
     }
 
     protected mergeRequestParams(params1: RequestParams, params2?: RequestParams): RequestParams {
@@ -192,7 +195,7 @@ export class HttpClient<SecurityDataType = unknown> {
         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 payloadFormatter = this.contentFormatters[type || <%~ CT.Json %>];
         const responseFormat = format || requestParams.format;
 
         return this.customFetch(
@@ -201,7 +204,7 @@ export class HttpClient<SecurityDataType = unknown> {
             ...requestParams,
             headers: {
             ...(requestParams.headers || {}),
-            ...(type && type !== ContentType.FormData ? { "Content-Type": type } : {}),
+            ...(type && type !== <%~ CT.FormData %> ? { "Content-Type": type } : {}),
             },
             signal: (cancelToken ? this.createAbortSignal(cancelToken) : requestParams.signal) || null,
             body: typeof body === "undefined" || body === null ? null : payloadFormatter(body),

diff --git a/templates/default/procedure-call.ejs b/templates/default/procedure-call.ejs
@@ -53,13 +53,7 @@ const wrapperArgs = _
     .join(', ')
 
 // RequestParams["type"]
-const requestContentKind = {
-    "JSON": "ContentType.Json",
-    "JSON_API": "ContentType.JsonApi",
-    "URL_ENCODED": "ContentType.UrlEncoded",
-    "FORM_DATA": "ContentType.FormData",
-    "TEXT": "ContentType.Text",
-}
+const requestContentKind = includeFile("@base/content-type-accessors", { config });
 // RequestParams["format"]
 const responseContentKind = {
     "JSON": '"json"',

diff --git a/templates/modular/api.ejs b/templates/modular/api.ejs
@@ -8,7 +8,11 @@ const dataContracts = _.map(modelTypes, "name");
 
 <% if (config.httpClientType === config.constants.HTTP_CLIENT.AXIOS) { %> import type { AxiosRequestConfig, AxiosResponse } from "axios"; <% } %>
 
+<% if (config.enumStyle === "union") { %>
+import { HttpClient, RequestParams, type ContentType, HttpResponse } from "./<%~ config.fileNames.httpClient %>";
+<% } else { %>
 import { HttpClient, RequestParams, ContentType, HttpResponse } from "./<%~ config.fileNames.httpClient %>";
+<% } %>
 <% if (dataContracts.length) { %>
 import { <%~ dataContracts.join(", ") %> } from "./<%~ config.fileNames.dataContracts %>"
 <% } %>

diff --git a/templates/modular/procedure-call.ejs b/templates/modular/procedure-call.ejs
@@ -53,13 +53,7 @@ const wrapperArgs = _
     .join(', ')
 
 // RequestParams["type"]
-const requestContentKind = {
-    "JSON": "ContentType.Json",
-    "JSON_API": "ContentType.JsonApi",
-    "URL_ENCODED": "ContentType.UrlEncoded",
-    "FORM_DATA": "ContentType.FormData",
-    "TEXT": "ContentType.Text",
-}
+const requestContentKind = includeFile("@base/content-type-accessors", { config });
 // RequestParams["format"]
 const responseContentKind = {
     "JSON": '"json"',