First draft of the language service plugin

.vscode/settings.json

@@ -7,5 +7,6 @@
         "out": true // set this to false to include "out" folder in search results
     },
     // Turn off tsc task auto detection since we have the necessary tasks as npm scripts
-    "typescript.tsc.autoDetect": "off"
+    "typescript.tsc.autoDetect": "off",
+    "typescript.tsserver.log": "normal"
 }

packages/language-service-plugin/README.MD

@@ -0,0 +1,11 @@
+# Language Service Plugin
+
+[Reference](https://github.com/microsoft/TypeScript/wiki/Writing-a-Language-Service-Plugin)
+
+To test this plugin out, compile the code and open the `example` folder in a VSCode instance:
+
+```
+code ./example
+```
+
+Also, please, make sure the workspace version of TypeScript is used. Use the `TypeScript: Select TypeScript version` command for this.

packages/language-service-plugin/example/.vscode/settings.json

@@ -0,0 +1,4 @@
+{
+  "typescript.tsserver.log": "normal",
+  "typescript.tsdk": "node_modules/typescript/lib"
+}

packages/language-service-plugin/example/index.ts

@@ -0,0 +1,9 @@
+let a;
+
+export function A(b: number): number {
+  if (true) {
+    return 1;
+  } {
+    3;
+  }
+}

packages/language-service-plugin/example/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@total-typescript/language-service-plugin-example",
+  "version": "0.1.0",
+  "dependencies": {
+    "ts-error-translator-tssplugin": "file:..",
+    "typescript": "^4.8.3"
+  }
+}

packages/language-service-plugin/example/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "plugins": [{
+      "name": "ts-error-translator-tssplugin"
+    }]
+  }
+}

packages/language-service-plugin/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "ts-error-translator-tssplugin",
+  "version": "0.1.0",
+  "license": "MIT",
+  "main": "./out/index.js",
+  "private": true,
+  "files": ["./out/**"],
+  "scripts": {
+    "dev": "tsc --watch",
+    "build": "tsc"
+  },
+  "devDependencies": {
+    "tsconfig": "workspace:*",
+    "typescript": "^4.5.3"
+  }
+}

packages/language-service-plugin/src/index.ts

@@ -0,0 +1,32 @@
+function init(modules: { typescript: typeof import("typescript/lib/tsserverlibrary") }) {
+  const ts = modules.typescript;
+
+  function enrichDiagnostic(diagnostic: ts.Diagnostic): ts.Diagnostic {
+    // diagnostic.code: number
+    // diagnostic.category === ts.DiagnosticCategory (Error, Message, Suggestion, Warning)
+    diagnostic.messageText = `${diagnostic.messageText}\n\nHello from plugin!\n`
+    return diagnostic;
+  }
+
+  function create(info: ts.server.PluginCreateInfo) {
+    // Set up decorator object
+    const proxy: ts.LanguageService = Object.create(null);
+
+    for (let k of Object.keys(info.languageService) as Array<keyof ts.LanguageService>) {
+      const x = info.languageService[k]!;
+      // @ts-expect-error - JS runtime trickery which is tricky to type tersely
+      proxy[k] = (...args: Array<{}>) => x.apply(info.languageService, args);
+    }
+
+    proxy.getSemanticDiagnostics = (filename) => {
+      return info.languageService.getSemanticDiagnostics(filename).map(enrichDiagnostic);
+    }
+
+    return proxy;
+  }
+
+  return { create };
+
+}
+
+export = init;

packages/language-service-plugin/tsconfig.json

@@ -0,0 +1,19 @@
+{
+  "extends": "tsconfig/base.json",
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "ES2019",
+    "outDir": "./out",
+    "rootDir": "src",
+    "strict": true,
+    "declaration": true,
+    "sourceMap": true,
+    "skipLibCheck": true
+  },
+  "include": [
+    "src"
+  ],
+  "exclude": [
+    "node_modules"
+  ]
+}

pnpm-workspace.yaml

@@ -1,3 +1,4 @@
 packages:
   - 'packages/*'
+  - 'packages/language-service-plugin/*'
   - 'apps/*'