feat: add tsserver.fallbackPath to initialization options (#831)

docs/configuration.md

@@ -34,6 +34,8 @@ Specifies additional options related to the internal `tsserver` process, like tr
 
 **path** [string] The path to the `tsserver.js` file or the typescript lib directory. For example: `/Users/me/typescript/lib/tsserver.js`. Note: The path should point at the `[...]/typescript/lib/tssserver.js` file or the `[...]/typescript/lib/` directory and not the shell script (`[...]/node_modules/.bin/tsserver`) but for backward-compatibility reasons, the server will try to do the right thing even when passed a path to the shell script. **Default**: `undefined`
 
+**fallbackPath** [string] The path to the `tsserver.js` file or the typescript lib directory to use when `tsserver.path` is unspecified/invalid and the `tsserver` isn't available via the current workspace. For example: `/Users/me/typescript/lib/tsserver.js`. Note: The path should point at the `[...]/typescript/lib/tssserver.js` file or the `[...]/typescript/lib/` directory and not the shell script (`[...]/node_modules/.bin/tsserver`) but for backward-compatibility reasons, the server will try to do the right thing even when passed a path to the shell script. **Default**: `undefined`
+
 **trace** [string] The verbosity of logging of the tsserver communication. Delivered through the LSP messages and not related to file logging. Allowed values are: `'off'`, `'messages'`, `'verbose'`. **Default**: `'off'`
 
 **useSyntaxServer** [string] Whether a dedicated server is launched to more quickly handle syntax related operations, such as computing diagnostics or code folding. **Default**: `'auto'`. Allowed values:
@@ -216,4 +218,4 @@ implicitProjectConfiguration.strictNullChecks: boolean;
  * @default 'ES2020'
  */
 implicitProjectConfiguration.target: string;
-```
+```

src/lsp-server.ts

@@ -107,7 +107,7 @@ export class LspServer {
             pluginProbeLocations.push(plugin.location);
         }
 
-        const typescriptVersion = this.findTypescriptVersion(tsserver?.path);
+        const typescriptVersion = this.findTypescriptVersion(tsserver?.path, tsserver?.fallbackPath);
         if (typescriptVersion) {
             this.options.lspClient.logMessage({ type: lsp.MessageType.Info, message: `Using Typescript version (${typescriptVersion.source}) ${typescriptVersion.versionString} from path "${typescriptVersion.tsServerPath}"` });
         } else {
@@ -315,7 +315,7 @@ export class LspServer {
         });
     }
 
-    private findTypescriptVersion(userTsserverPath: string | undefined): TypeScriptVersion | null {
+    private findTypescriptVersion(userTsserverPath: string | undefined, fallbackTsserverPath: string | undefined): TypeScriptVersion | null {
         const typescriptVersionProvider = new TypeScriptVersionProvider(userTsserverPath, this.logger);
         // User-provided tsserver path.
         const userSettingVersion = typescriptVersionProvider.getUserSettingVersion();
@@ -332,6 +332,16 @@ export class LspServer {
                 return workspaceVersion;
             }
         }
+
+        const fallbackVersionProvider = new TypeScriptVersionProvider(fallbackTsserverPath, this.logger);
+        const fallbackSettingVersion = fallbackVersionProvider.getUserSettingVersion();
+        if (fallbackSettingVersion) {
+            if (fallbackSettingVersion.isValid) {
+                return fallbackSettingVersion;
+            }
+            this.logger.logIgnoringVerbosity(LogLevel.Warning, `Typescript specified through fallback setting ignored due to invalid path "${fallbackSettingVersion.path}"`);
+        }
+
         // Bundled version
         const bundledVersion = typescriptVersionProvider.bundledVersion();
         if (bundledVersion?.isValid) {

src/ts-protocol.ts

@@ -374,6 +374,12 @@ interface TsserverOptions {
      * The path to the `tsserver.js` file or the typescript lib directory. For example: `/Users/me/typescript/lib/tsserver.js`.
      */
     path?: string;
+    /**
+     * The fallback path to the `tsserver.js` file or the typescript lib directory. For example: `/Users/me/typescript/lib/tsserver.js`.
+     *
+     * This path gets used when `.path` isn't set or valid, and detecting the file from the current active workspace fails.
+     */
+    fallbackPath?: string;
     /**
      * The verbosity of logging the tsserver communication through the LSP messages.
      * This doesn't affect the file logging.