feat: support Trusted Types for client overlay

bin/cli-flags.js

@@ -121,6 +121,21 @@ module.exports = {
     simpleType: "boolean",
     multiple: false,
   },
+  "client-overlay-trusted-types-policy-name": {
+    configs: [
+      {
+        description:
+          "The name of a Trusted Types policy for the overlay. Defaults to 'webpack-dev-server#overlay'.",
+        multiple: false,
+        path: "client.overlay.trustedTypesPolicyName",
+        type: "string",
+      },
+    ],
+    description:
+      "The name of a Trusted Types policy for the overlay. Defaults to 'webpack-dev-server#overlay'.",
+    multiple: false,
+    simpleType: "string",
+  },
   "client-overlay-warnings": {
     configs: [
       {

client-src/index.js

@@ -15,7 +15,7 @@ import createSocketURL from "./utils/createSocketURL.js";
  * @property {boolean} hot
  * @property {boolean} liveReload
  * @property {boolean} progress
- * @property {boolean | { warnings?: boolean, errors?: boolean }} overlay
+ * @property {boolean | { warnings?: boolean, errors?: boolean, trustedTypesPolicyName?: string }} overlay
  * @property {string} [logging]
  * @property {number} [reconnect]
  */
@@ -230,7 +230,10 @@ const onSocketMessage = {
         : options.overlay && options.overlay.warnings;
 
     if (needShowOverlayForWarnings) {
-      show("warning", warnings);
+      const trustedTypesPolicyName =
+        typeof options.overlay === "object" &&
+        options.overlay.trustedTypesPolicyName;
+      show("warning", warnings, trustedTypesPolicyName || null);
     }
 
     if (params && params.preventReloading) {
@@ -263,7 +266,10 @@ const onSocketMessage = {
         : options.overlay && options.overlay.errors;
 
     if (needShowOverlayForErrors) {
-      show("error", errors);
+      const trustedTypesPolicyName =
+        typeof options.overlay === "object" &&
+        options.overlay.trustedTypesPolicyName;
+      show("error", errors, trustedTypesPolicyName || null);
     }
   },
   /**

client-src/overlay.js

@@ -23,10 +23,25 @@ let iframeContainerElement;
 let containerElement;
 /** @type {Array<(element: HTMLDivElement) => void>} */
 let onLoadQueue = [];
+/** @type {TrustedTypePolicy | undefined} */
+let overlayTrustedTypesPolicy;
 
 ansiHTML.setColors(colors);
 
-function createContainer() {
+/**
+ * @param {string | null} trustedTypesPolicyName
+ */
+function createContainer(trustedTypesPolicyName) {
+  // Enable Trusted Types if they are available in the current browser.
+  if (window.trustedTypes) {
+    overlayTrustedTypesPolicy = window.trustedTypes.createPolicy(
+      trustedTypesPolicyName || "webpack-dev-server#overlay",
+      {
+        createHTML: (value) => value,
+      }
+    );
+  }
+
   iframeContainerElement = document.createElement("iframe");
   iframeContainerElement.id = "webpack-dev-server-client-overlay";
   iframeContainerElement.src = "about:blank";
@@ -109,8 +124,9 @@ function createContainer() {
 
 /**
  * @param {(element: HTMLDivElement) => void} callback
+ * @param {string | null} trustedTypesPolicyName
  */
-function ensureOverlayExists(callback) {
+function ensureOverlayExists(callback, trustedTypesPolicyName) {
   if (containerElement) {
     // Everything is ready, call the callback right away.
     callback(containerElement);
@@ -124,7 +140,7 @@ function ensureOverlayExists(callback) {
     return;
   }
 
-  createContainer();
+  createContainer(trustedTypesPolicyName);
 }
 
 // Successful compilation.
@@ -178,8 +194,9 @@ function formatProblem(type, item) {
 /**
  * @param {string} type
  * @param {Array<string  | { file?: string, moduleName?: string, loc?: string, message?: string }>} messages
+ * @param {string | null} trustedTypesPolicyName
  */
-function show(type, messages) {
+function show(type, messages, trustedTypesPolicyName) {
   ensureOverlayExists(() => {
     messages.forEach((message) => {
       const entryElement = document.createElement("div");
@@ -193,7 +210,9 @@ function show(type, messages) {
       const text = ansiHTML(encode(body));
       const messageTextNode = document.createElement("div");
 
-      messageTextNode.innerHTML = text;
+      messageTextNode.innerHTML = overlayTrustedTypesPolicy
+        ? overlayTrustedTypesPolicy.createHTML(text)
+        : text;
 
       entryElement.appendChild(typeElement);
       entryElement.appendChild(document.createElement("br"));
@@ -205,7 +224,7 @@ function show(type, messages) {
       /** @type {HTMLDivElement} */
       (containerElement).appendChild(entryElement);
     });
-  });
+  }, trustedTypesPolicyName);
 }
 
 export { formatProblem, show, hide };

examples/client/trusted-types-overlay/README.md

@@ -0,0 +1,36 @@
+# client.overlay.trustedTypesPolicyName option
+
+**webpack.config.js**
+
+```js
+module.exports = {
+  // ...
+  output: {
+    trustedTypes: { policyName: "webpack" },
+  },
+  devServer: {
+    client: {
+      overlay: {
+        trustedTypesPolicyName: "webpack#dev-overlay",
+      },
+    },
+  },
+};
+```
+
+Usage via CLI:
+
+```shell
+npx webpack serve --open
+```
+
+## What Should Happen
+
+1. The script should open `http://localhost:8080/` in your default browser.
+2. You should see an overlay in browser for compilation errors.
+3. Modify `devServer.client.overlay.trustedTypesPolicyName` in webpack.config.js to `disallowed-policy` and save.
+4. Restart the command and you should not see an overlay at all. In the console you should see the following error:
+
+```
+Refused to create a TrustedTypePolicy named 'disallowed-policy' because it violates the following Content Security Policy directive: "trusted-types webpack webpack#dev-overlay".
+```

examples/client/trusted-types-overlay/app.js

@@ -0,0 +1,6 @@
+"use strict";
+
+const target = document.querySelector("#target");
+
+target.classList.add("pass");
+target.textContent = "Success!";

examples/client/trusted-types-overlay/layout.html

@@ -0,0 +1,38 @@
+<!-- Originally copied from "../../.assets/layout.html" -->
+<!DOCTYPE html>
+<html>
+  <head>
+    <!-- Enable Trusted Types -->
+    <meta
+      http-equiv="Content-Security-Policy"
+      content="require-trusted-types-for 'script'; trusted-types webpack webpack#dev-overlay;"
+    />
+
+    <title>WDS ▻ <%= htmlWebpackPlugin.options.title %></title>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <link rel="shortcut icon" href=".assets/favicon.ico" />
+    <link
+      rel="stylesheet"
+      href="https://fonts.googleapis.com/css?family=Source+Code+Pro:400,600|Source+Sans+Pro:400,400i,500,600"
+    />
+    <link rel="stylesheet" href=".assets/style.css" />
+  </head>
+  <body>
+    <main>
+      <header>
+        <h1>
+          <img
+            src=".assets/icon-square.svg"
+            style="width: 35px; height: 35px"
+          />
+          webpack-dev-server
+        </h1>
+      </header>
+      <section>
+        <h2><%= htmlWebpackPlugin.options.title %></h2>
+        <div id="target"></div>
+      </section>
+    </main>
+  </body>
+</html>

examples/client/trusted-types-overlay/webpack.config.js

@@ -0,0 +1,32 @@
+"use strict";
+
+const path = require("path");
+const HtmlWebpackPlugin = require("html-webpack-plugin");
+// our setup function adds behind-the-scenes bits to the config that all of our
+// examples need
+const { setup } = require("../../util");
+
+const config = setup({
+  context: __dirname,
+  // create error for overlay
+  entry: "./invalid.js",
+  output: {
+    trustedTypes: { policyName: "webpack" },
+  },
+  devServer: {
+    client: {
+      overlay: {
+        trustedTypesPolicyName: "webpack#dev-overlay",
+      },
+    },
+  },
+});
+
+// overwrite the index.html with our own to enable Trusted Types
+config.plugins[0] = new HtmlWebpackPlugin({
+  filename: "index.html",
+  template: path.join(__dirname, "./layout.html"),
+  title: "trusted types overlay",
+});
+
+module.exports = config;

lib/options.json

@@ -110,6 +110,10 @@
               "cli": {
                 "negatedDescription": "Disables the full-screen overlay in the browser when there are compiler warnings."
               }
+            },
+            "trustedTypesPolicyName": {
+              "description": "The name of a Trusted Types policy for the overlay. Defaults to 'webpack-dev-server#overlay'.",
+              "type": "string"
             }
           }
         }

package.json

@@ -78,6 +78,7 @@
     "@types/default-gateway": "^3.0.1",
     "@types/rimraf": "^3.0.2",
     "@types/sockjs-client": "^1.5.1",
+    "@types/trusted-types": "^2.0.2",
     "acorn": "^8.2.4",
     "babel-jest": "^27.5.1",
     "babel-loader": "^8.2.4",

test/__snapshots__/validate-options.test.js.snap.webpack5

@@ -90,19 +90,19 @@ exports[`options validate should throw an error on the "client" option with '{"o
    -> Read more at https://webpack.js.org/configuration/dev-server/#devserverclient
    Details:
     * options.client.overlay should be one of these:
-      boolean | object { errors?, warnings? }
+      boolean | object { errors?, warnings?, trustedTypesPolicyName? }
       Details:
        * options.client.overlay should be a boolean.
          -> Enables a full-screen overlay in the browser when there are compiler errors or warnings.
          -> Read more at https://webpack.js.org/configuration/dev-server/#overlay
        * options.client.overlay should be an object:
-         object { errors?, warnings? }"
+         object { errors?, warnings?, trustedTypesPolicyName? }"
 `;
 
 exports[`options validate should throw an error on the "client" option with '{"overlay":{"arbitrary":""}}' value 1`] = `
 "ValidationError: Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
  - options.client.overlay has an unknown property 'arbitrary'. These properties are valid:
-   object { errors?, warnings? }"
+   object { errors?, warnings?, trustedTypesPolicyName? }"
 `;
 
 exports[`options validate should throw an error on the "client" option with '{"overlay":{"errors":""}}' value 1`] = `