fix: no crash when headers are already sent

src/index.js

@@ -305,7 +305,7 @@ function wdm(compiler, options = {}) {
 /**
  * @template S
  * @template O
- * @typedef {HapiPluginBase<S, O> & { pkg: { name: string } }} HapiPlugin
+ * @typedef {HapiPluginBase<S, O> & { pkg: { name: string }, multiple: boolean }} HapiPlugin
  */
 
 /**
@@ -322,6 +322,8 @@ function hapiWrapper() {
     pkg: {
       name: "webpack-dev-middleware",
     },
+    // Allow to have multiple middleware
+    multiple: true,
     register(server, options) {
       const { compiler, ...rest } = options;
 
@@ -332,7 +334,11 @@ function hapiWrapper() {
       const devMiddleware = wdm(compiler, rest);
 
       // @ts-ignore
-      server.decorate("server", "webpackDevMiddleware", devMiddleware);
+      if (!server.decorations.server.includes("webpackDevMiddleware")) {
+        // @ts-ignore
+        server.decorate("server", "webpackDevMiddleware", devMiddleware);
+      }
+
       // @ts-ignore
       server.ext("onRequest", (request, h) =>
         new Promise((resolve, reject) => {
@@ -568,6 +574,8 @@ function honoWrapper(compiler, options) {
 
     res.getReadyReadableStreamState = () => "readable";
 
+    res.getHeadersSent = () => c.env.outgoing.headersSent;
+
     let body;
 
     try {

src/middleware.js

@@ -15,6 +15,7 @@ const {
   setResponseHeader,
   removeResponseHeader,
   getResponseHeaders,
+  getHeadersSent,
   send,
   finish,
   pipe,
@@ -494,56 +495,44 @@ function wrapper(context) {
         return;
       }
 
+      if (getHeadersSent(res)) {
+        await goNext();
+        return;
+      }
+
       const { size } = /** @type {import("fs").Stats} */ (extra.stats);
 
       let len = size;
       let offset = 0;
 
       // Send logic
-      let { headers } = context.options;
+      if (context.options.headers) {
+        let { headers } = context.options;
 
-      if (typeof headers === "function") {
-        headers = /** @type {NormalizedHeaders} */ (headers(req, res, context));
-      }
-
-      /**
-       * @type {{key: string, value: string | number}[]}
-       */
-      const allHeaders = [];
-
-      if (typeof headers !== "undefined") {
-        if (!Array.isArray(headers)) {
-          // eslint-disable-next-line guard-for-in
-          for (const name in headers) {
-            allHeaders.push({ key: name, value: headers[name] });
-          }
-
-          headers = allHeaders;
+        if (typeof headers === "function") {
+          headers = /** @type {NormalizedHeaders} */ (
+            headers(req, res, context)
+          );
         }
 
-        for (const { key, value } of headers) {
-          setResponseHeader(res, key, value);
-        }
-      }
+        /**
+         * @type {{key: string, value: string | number}[]}
+         */
+        const allHeaders = [];
 
-      if (
-        !getResponseHeader(res, "Content-Type") ||
-        getStatusCode(res) === 404
-      ) {
-        removeResponseHeader(res, "Content-Type");
-        // content-type name(like application/javascript; charset=utf-8) or false
-        const contentType = mime.contentType(path.extname(filename));
+        if (typeof headers !== "undefined") {
+          if (!Array.isArray(headers)) {
+            // eslint-disable-next-line guard-for-in
+            for (const name in headers) {
+              allHeaders.push({ key: name, value: headers[name] });
+            }
 
-        // Only set content-type header if media type is known
-        // https://tools.ietf.org/html/rfc7231#section-3.1.1.5
-        if (contentType) {
-          setResponseHeader(res, "Content-Type", contentType);
-        } else if (context.options.mimeTypeDefault) {
-          setResponseHeader(
-            res,
-            "Content-Type",
-            context.options.mimeTypeDefault,
-          );
+            headers = allHeaders;
+          }
+
+          for (const { key, value } of headers) {
+            setResponseHeader(res, key, value);
+          }
         }
       }
 
@@ -667,6 +656,27 @@ function wrapper(context) {
         }
       }
 
+      if (
+        !getResponseHeader(res, "Content-Type") ||
+        getStatusCode(res) === 404
+      ) {
+        removeResponseHeader(res, "Content-Type");
+        // content-type name(like application/javascript; charset=utf-8) or false
+        const contentType = mime.contentType(path.extname(filename));
+
+        // Only set content-type header if media type is known
+        // https://tools.ietf.org/html/rfc7231#section-3.1.1.5
+        if (contentType) {
+          setResponseHeader(res, "Content-Type", contentType);
+        } else if (context.options.mimeTypeDefault) {
+          setResponseHeader(
+            res,
+            "Content-Type",
+            context.options.mimeTypeDefault,
+          );
+        }
+      }
+
       // Conditional GET support
       if (isConditionalGET()) {
         if (isPreconditionFailure()) {

src/utils/compatibleAPI.js

@@ -19,6 +19,7 @@
  * @property {(data: string | Buffer) => void} [send]
  * @property {(data?: string | Buffer) => void} [finish]
  * @property {() => string[]} [getResponseHeaders]
+ * @property {() => boolean} [getHeadersSent]
  * @property {(data: any) => void} [stream]
  * @property {() => any} [getOutgoing]
  * @property {(name: string, value: any) => void} [setState]
@@ -147,6 +148,20 @@ function getResponseHeaders(res) {
   return res.getHeaderNames();
 }
 
+/**
+ * @template {ServerResponse & ExpectedServerResponse} Response
+ * @param {Response} res
+ * @returns {boolean}
+ */
+function getHeadersSent(res) {
+  // Pseudo API
+  if (typeof res.getHeadersSent === "function") {
+    return res.getHeadersSent();
+  }
+
+  return res.headersSent;
+}
+
 /**
  * @template {ServerResponse & ExpectedServerResponse} Response
  * @param {Response} res
@@ -305,6 +320,7 @@ module.exports = {
   setResponseHeader,
   removeResponseHeader,
   getResponseHeaders,
+  getHeadersSent,
   pipe,
   send,
   finish,

src/utils/getFilenameFromUrl.js

@@ -129,6 +129,7 @@ function getFilenameFromUrl(context, url, extra = {}) {
             pathname.slice(publicPathObject.pathname.length),
           );
 
+          // eslint-disable-next-line no-param-reassign
           extra.immutable = assetInfo ? assetInfo.immutable : false;
         }
 

test/middleware.test.js

@@ -3287,6 +3287,97 @@ describe.each([
           );
         });
       });
+
+      describe("should work when headers are already sent", () => {
+        let compiler;
+
+        const outputPath = path.resolve(
+          __dirname,
+          "./outputs/basic-test-errors-headers-sent",
+        );
+
+        beforeAll(async () => {
+          compiler = getCompiler({
+            ...webpackConfig,
+            output: {
+              filename: "bundle.js",
+              path: outputPath,
+            },
+          });
+
+          [server, req, instance] = await frameworkFactory(
+            name,
+            framework,
+            compiler,
+            {},
+            {
+              setupMiddlewares: (middlewares) => {
+                if (name === "hapi") {
+                  // There's no such thing as "the next route handler" in hapi. One request is matched to one or no route handlers.
+                } else if (name === "koa") {
+                  middlewares.push(async (ctx, next) => {
+                    // eslint-disable-next-line no-param-reassign
+                    ctx.url = "/index.html";
+
+                    await next();
+                  });
+                  middlewares.push(middleware.koaWrapper(compiler, {}));
+                } else if (name === "hono") {
+                  middlewares.unshift(async (c, next) => {
+                    await next();
+
+                    return new Response("Hello Node.js!");
+                  });
+                  middlewares.push(middleware.honoWrapper(compiler, {}));
+                } else {
+                  middlewares.push({
+                    route: "/",
+                    fn: (req, res, next) => {
+                      // eslint-disable-next-line no-param-reassign
+                      req.url = "/index.html";
+                      next();
+                    },
+                  });
+                  middlewares.push(middleware(compiler, {}));
+                }
+
+                return middlewares;
+              },
+            },
+          );
+
+          instance.context.outputFileSystem.mkdirSync(outputPath, {
+            recursive: true,
+          });
+          instance.context.outputFileSystem.writeFileSync(
+            path.resolve(outputPath, "index.html"),
+            "HTML",
+          );
+        });
+
+        afterAll(async () => {
+          await close(server, instance);
+        });
+
+        it('should return the "200" code for the "GET" request to the bundle file', async () => {
+          const response = await req.get("/");
+
+          expect(response.statusCode).toEqual(200);
+          expect(response.headers["content-type"]).toEqual(
+            "text/html; charset=utf-8",
+          );
+        });
+
+        it('should return the "200" code for the "HEAD" request to the bundle file', async () => {
+          const response = await req.head("/");
+
+          expect(response.statusCode).toEqual(200);
+          expect(response.headers["content-type"]).toEqual(
+            "text/html; charset=utf-8",
+          );
+          expect(response.text).toBeUndefined();
+        });
+      });
     });
 
     describe("mimeTypes option", () => {
@@ -4467,6 +4558,7 @@ describe.each([
                 middlewares.push(async (ctx, next) => {
                   locals = ctx.state;
 
+                  // eslint-disable-next-line no-param-reassign
                   ctx.status = 200;
 
                   await next();

types/index.d.ts

@@ -213,7 +213,7 @@ declare namespace wdm {
 /**
  * @template S
  * @template O
- * @typedef {HapiPluginBase<S, O> & { pkg: { name: string } }} HapiPlugin
+ * @typedef {HapiPluginBase<S, O> & { pkg: { name: string }, multiple: boolean }} HapiPlugin
  */
 /**
  * @typedef {Options & { compiler: Compiler | MultiCompiler }} HapiOptions
@@ -409,6 +409,7 @@ type HapiPlugin<S, O> = HapiPluginBase<S, O> & {
   pkg: {
     name: string;
   };
+  multiple: boolean;
 };
 type HapiOptions = Options & {
   compiler: Compiler | MultiCompiler;

types/utils/compatibleAPI.d.ts

@@ -22,6 +22,7 @@ export type ExpectedServerResponse = {
   send?: ((data: string | Buffer) => void) | undefined;
   finish?: ((data?: string | Buffer) => void) | undefined;
   getResponseHeaders?: (() => string[]) | undefined;
+  getHeadersSent?: (() => boolean) | undefined;
   stream?: ((data: any) => void) | undefined;
   getOutgoing?: (() => any) | undefined;
   setState?: ((name: string, value: any) => void) | undefined;
@@ -64,6 +65,7 @@ export function getStatusCode<
  * @property {(data: string | Buffer) => void} [send]
  * @property {(data?: string | Buffer) => void} [finish]
  * @property {() => string[]} [getResponseHeaders]
+ * @property {() => boolean} [getHeadersSent]
  * @property {(data: any) => void} [stream]
  * @property {() => any} [getOutgoing]
  * @property {(name: string, value: any) => void} [setState]
@@ -133,6 +135,14 @@ export function removeResponseHeader<
 export function getResponseHeaders<
   Response extends ServerResponse & ExpectedServerResponse,
 >(res: Response): string[];
+/**
+ * @template {ServerResponse & ExpectedServerResponse} Response
+ * @param {Response} res
+ * @returns {boolean}
+ */
+export function getHeadersSent<
+  Response extends ServerResponse & ExpectedServerResponse,
+>(res: Response): boolean;
 /**
  * @template {ServerResponse & ExpectedServerResponse} Response
  * @param {Response} res