add tsserverWeb to patch in dynamic import

Gulpfile.js

@@ -214,20 +214,29 @@ task("watch-services").flags = {
     "   --built": "Compile using the built version of the compiler."
 };
 
-const buildServer = () => buildProject("src/tsserver", cmdLineOptions);
+const buildServerWeb = () => buildProject("src/tsserverWeb", cmdLineOptions);
+task("tsserverWeb", buildServerWeb);
+
+const buildServerMain = () => buildProject("src/tsserver", cmdLineOptions);
+const buildServer = series(buildServerWeb, buildServerMain);
+buildServer.displayName = "buildServer";
 task("tsserver", series(preBuild, buildServer));
 task("tsserver").description = "Builds the language server";
 task("tsserver").flags = {
     "   --built": "Compile using the built version of the compiler."
 };
 
-const cleanServer = () => cleanProject("src/tsserver");
+const cleanServerWeb = () => cleanProject("src/tsserverWeb");
+const cleanServerMain = () => cleanProject("src/tsserver");
+const cleanServer = series(cleanServerWeb, cleanServerMain);
+cleanServer.displayName = "cleanServer";
 cleanTasks.push(cleanServer);
 task("clean-tsserver", cleanServer);
 task("clean-tsserver").description = "Cleans outputs for the language server";
 
+const watchServerWeb = () => watchProject("src/tsserverWeb", cmdLineOptions);
 const watchServer = () => watchProject("src/tsserver", cmdLineOptions);
-task("watch-tsserver", series(preBuild, parallel(watchLib, watchDiagnostics, watchServer)));
+task("watch-tsserver", series(preBuild, parallel(watchLib, watchDiagnostics, watchServerWeb, watchServer)));
 task("watch-tsserver").description = "Watch for changes and rebuild the language server only";
 task("watch-tsserver").flags = {
     "   --built": "Compile using the built version of the compiler."
@@ -549,6 +558,7 @@ const produceLKG = async () => {
         "built/local/typescriptServices.js",
         "built/local/typescriptServices.d.ts",
         "built/local/tsserver.js",
+        "built/local/tsserverWeb.js",
         "built/local/typescript.js",
         "built/local/typescript.d.ts",
         "built/local/tsserverlibrary.js",

scripts/produceLKG.ts

@@ -62,6 +62,7 @@ async function copyScriptOutputs() {
     await copyWithCopyright("cancellationToken.js");
     await copyWithCopyright("tsc.release.js", "tsc.js");
     await copyWithCopyright("tsserver.js");
+    await copyWithCopyright("tsserverWeb.js");
     await copyFromBuiltLocal("tsserverlibrary.js"); // copyright added by build
     await copyFromBuiltLocal("typescript.js"); // copyright added by build
     await copyFromBuiltLocal("typescriptServices.js"); // copyright added by build

src/tsconfig.json

@@ -9,6 +9,7 @@
         { "path": "./watchGuard" },
         { "path": "./debug" },
         { "path": "./cancellationToken" },
+        { "path": "./tsserverWeb" },
         { "path": "./testRunner" }
     ]
 }

src/tsserverWeb/tsconfig.json

@@ -0,0 +1,16 @@
+{
+    "extends": "../tsconfig-library-base",
+    "compilerOptions": {
+        "outDir": "../../built/local",
+        "rootDir": ".",
+        "target": "esnext",
+        "module": "esnext",
+        "lib": ["esnext"],
+        "declaration": false,
+        "sourceMap": true,
+        "tsBuildInfoFile": "../../built/local/tsserverWeb.tsbuildinfo"
+    },
+    "files": [
+        "tsserverWeb.ts",
+    ]
+}

src/tsserverWeb/tsserverWeb.ts

@@ -0,0 +1,3 @@
+namespace ts.server {
+    export const dynamicImport = (id: string) => import(id);
+}

src/webServer/webServer.ts

@@ -1,5 +1,6 @@
 /*@internal*/
 /// <reference lib="dom" />
+/// <reference lib="webworker.importscripts" />
 
 namespace ts.server {
     export interface HostWithWriteMessage {
@@ -111,11 +112,35 @@ namespace ts.server {
         }
     }
 
+    export declare const dynamicImport: ((id: string) => Promise<any>) | undefined;
+
+    // Attempt to load `dynamicImport`
+    if (typeof importScripts === "function") {
+        try {
+            // NOTE: importScripts is synchronous
+            importScripts("tsserverWeb.js");
+        }
+        catch {
+            // ignored
+        }
+    }
+
     export function createWebSystem(host: WebHost, args: string[], getExecutingFilePath: () => string): ServerHost {
         const returnEmptyString = () => "";
         const getExecutingDirectoryPath = memoize(() => memoize(() => ensureTrailingDirectorySeparator(getDirectoryPath(getExecutingFilePath()))));
         // Later we could map ^memfs:/ to do something special if we want to enable more functionality like module resolution or something like that
         const getWebPath = (path: string) => startsWith(path, directorySeparator) ? path.replace(directorySeparator, getExecutingDirectoryPath()) : undefined;
+
+        const dynamicImport = async (id: string): Promise<any> => {
+            // Use syntactic dynamic import first, if available
+            if (ts.server.dynamicImport) {
+                return ts.server.dynamicImport(id);
+            }
+
+            // Fall back to `eval` if dynamic import wasn't avaialble.
+            return eval(`import(${JSON.stringify(id)})`); // eslint-disable-line no-eval
+        };
+
         return {
             args,
             newLine: "\r\n", // This can be configured by clients
@@ -157,11 +182,8 @@ namespace ts.server {
                 }
 
                 const scriptPath = combinePaths(packageRoot, browser);
-
-                // TODO: TS rewrites `import(...)` to `require`. Use eval to bypass this
-                // eslint-disable-next-line no-eval
                 try {
-                    const module = (await eval(`import(${JSON.stringify(scriptPath)})`)).default;
+                    const { default: module } = await dynamicImport(scriptPath);
                     return { module, error: undefined };
                 }
                 catch (e) {