feat(fmt): add --lsp language server mode

packages/rstack/THIRD_PARTY_NOTICES.md

@@ -462,3 +462,40 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
+
+## vscode-languageserver
+
+The language server started by `rs fmt --lsp` includes bundled code from
+[vscode-languageserver](https://github.com/microsoft/vscode-languageserver-node).
+
+License: MIT
+
+The bundled code also contains MIT-licensed code from:
+
+- vscode-jsonrpc 9.0.1, copyright Microsoft Corporation
+- vscode-languageserver-protocol 3.18.2, copyright Microsoft Corporation
+- vscode-languageserver-types 3.18.0, copyright Microsoft Corporation
+
+Copyright (c) Microsoft Corporation
+
+All rights reserved.
+
+MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED _AS IS_, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/rstack/package.json

@@ -100,7 +100,9 @@
     "sort-package-json": "catalog:",
     "svelte": "catalog:",
     "tiny-readdir": "catalog:",
-    "typescript": "catalog:"
+    "typescript": "catalog:",
+    "vscode-languageserver": "catalog:",
+    "vscode-languageserver-textdocument": "catalog:"
   },
   "peerDependencies": {
     "@rspress/core": "^2.0.17"

packages/rstack/rslib.config.ts

@@ -2,7 +2,7 @@ import { defineConfig } from '@rslib/core';
 import prettierPkgJson from 'prettier/package.json' with { type: 'json' };
 import pkgJson from './package.json' with { type: 'json' };
 
-const fullyMinifiedChunks = /(?:fmt(?:Plugins)?|sortPackageJsonPlugin|staged)\.js$/;
+const fullyMinifiedChunks = /(?:fmt(?:Lsp|Plugins)?|sortPackageJsonPlugin|staged)\.js$/;
 
 export default defineConfig({
   dts: true,

packages/rstack/src/cli/commands.ts

@@ -1,4 +1,4 @@
-import { join } from 'node:path';
+import { join, resolve } from 'node:path';
 import { getConfigState } from '../config.ts';
 import { insertConfigArg, parseArgs, parseCliArgs } from './args.ts';
 import { hasHelpFlag, renderHelp } from './help.ts';
@@ -606,7 +606,12 @@ export async function setupCommands(): Promise<void> {
   const { args, configPath } = parseCliArgs(process.argv.slice(2));
   const command = args[0];
 
-  getConfigState().configPath = configPath;
+  // Resolved for every command so that a relative `--config` path always means
+  // the same file: it is anchored to the directory the CLI was invoked in, even
+  // when the config is later loaded from another directory. The motivating case
+  // is `rs fmt --lsp`, which loads the config from the LSP workspace root the
+  // client reports, and that root need not be the process working directory.
+  getConfigState().configPath = configPath === undefined ? undefined : resolve(configPath);
 
   if (!command || command === '-h' || command === '--help') {
     console.log(renderRootHelp());

packages/rstack/src/config.ts

@@ -30,10 +30,16 @@ export type LoadedRstackConfig = {
 export type LoadRstackConfigOptions = {
   /**
    * The path to the Rstack config file, can be a relative or absolute path.
+   * A relative path is resolved from `cwd`.
    * If `configFilePath` is not provided, the config path set by the CLI is used.
-   * If neither path is provided, the function will search for the config file in the current working directory.
+   * If neither path is provided, the function will search for the config file in `cwd`.
    */
   configFilePath?: string;
+  /**
+   * The directory the config file is searched in and relative config paths are resolved from.
+   * Defaults to the current working directory.
+   */
+  cwd?: string;
 };
 
 type ConfigSession = {
@@ -42,6 +48,11 @@ type ConfigSession = {
 };
 
 type ConfigState = {
+  /**
+   * Config file path from the global `--config` flag. Always absolute: the CLI
+   * resolves it at parse time so it stays independent of later cwd choices
+   * (`loadRstackConfig` may be called with an LSP workspace root as `cwd`).
+   */
   configPath?: string;
 };
 
@@ -161,6 +172,7 @@ export const define: Define = {
 
 export const loadRstackConfig = async ({
   configFilePath,
+  cwd,
 }: LoadRstackConfigOptions = {}): Promise<LoadedRstackConfig> => {
   const state = getConfigState();
   const configPath = configFilePath ?? state.configPath;
@@ -175,6 +187,7 @@ export const loadRstackConfig = async ({
         loader: 'native',
         exportName: false,
         fresh: true,
+        cwd,
         ...(configPath !== undefined
           ? { path: configPath }
           : {

packages/rstack/src/fmt/cli.ts

@@ -25,6 +25,8 @@ interface ParsedFmtCLIArgs {
   help: boolean;
   /** Path the stdin content is formatted as; it need not exist on disk. */
   stdinFilepath?: string;
+  /** Serve formatting over the Language Server Protocol instead of exiting. */
+  lsp: boolean;
 }
 
 const renderFmtHelp = (): string =>
@@ -46,6 +48,7 @@ const renderFmtHelp = (): string =>
           ['--with-node-modules', 'Process files inside node_modules'],
           ['--parallel-workers <count>', 'Number of parallel workers'],
           ['--stdin-filepath <path>', 'Format stdin as if it were saved at <path>'],
+          ['--lsp', 'Run a language server on stdio'],
           ['-c, --config <path>', 'Specify Rstack config file path'],
           ['-h, --help', 'Display this help message'],
         ],
@@ -66,6 +69,19 @@ const parseMaxWorkers = (value: string | undefined): number | undefined => {
   return maxWorkers;
 };
 
+/** Rejects the mode flags and file arguments that a server-like option replaces. */
+const assertExclusiveMode = (option: string, hasMode: boolean, positionals: string[]): void => {
+  if (hasMode) {
+    throw new Error(
+      `The ${option} option cannot be used with --write, --check, or --list-different.`,
+    );
+  }
+
+  if (positionals.length > 0) {
+    throw new Error(`The ${option} option cannot be used with file arguments.`);
+  }
+};
+
 const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
   const { values, positionals } = parseArgs({
     args,
@@ -81,6 +97,7 @@ const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
       'with-node-modules': { type: 'boolean' },
       'parallel-workers': { type: 'string' },
       'stdin-filepath': { type: 'string' },
+      lsp: { type: 'boolean' },
       help: { type: 'boolean', short: 'h' },
     },
     allowPositionals: true,
@@ -110,19 +127,20 @@ const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
   const maxWorkers = parseMaxWorkers(parallelWorkers);
   const help = values.help ?? false;
   const stdinFilepath = values.stdinFilepath;
+  const lsp = values.lsp ?? false;
 
-  if (stdinFilepath !== undefined) {
-    if (modes.length > 0) {
-      throw new Error(
-        'The --stdin-filepath option cannot be used with --write, --check, or --list-different.',
-      );
-    }
+  if (lsp) {
+    assertExclusiveMode('--lsp', modes.length > 0, positionals);
 
-    if (positionals.length > 0) {
-      throw new Error('The --stdin-filepath option cannot be used with file arguments.');
+    if (stdinFilepath !== undefined) {
+      throw new Error('The --lsp option cannot be used with --stdin-filepath.');
     }
   }
 
+  if (stdinFilepath !== undefined) {
+    assertExclusiveMode('--stdin-filepath', modes.length > 0, positionals);
+  }
+
   return {
     cache,
     cacheLocation,
@@ -135,6 +153,7 @@ const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
     maxWorkers,
     help,
     stdinFilepath,
+    lsp,
   };
 };
 
@@ -244,7 +263,7 @@ const logFmtResult = (
 };
 
 const loadFmtConfig = async (cwd: string): Promise<ResolvedFmtConfig> => {
-  const { configs, filePath } = await loadRstackConfig();
+  const { configs, filePath } = await loadRstackConfig({ cwd });
 
   return resolveFmtConfig({
     definition: configs.fmt,
@@ -266,6 +285,7 @@ const runFmtCLI = async (args: string[]): Promise<void> => {
       help,
       ignorePaths,
       ignoreUnknown,
+      lsp,
       maxWorkers,
       mode,
       noErrorOnUnmatchedPattern,
@@ -278,6 +298,23 @@ const runFmtCLI = async (args: string[]): Promise<void> => {
       return;
     }
 
+    if (lsp) {
+      const { runFmtLsp } = await import(
+        /* rspackChunkName: 'fmtLsp' */
+        './lsp/server.ts'
+      );
+      await runFmtLsp({
+        // The client's workspace root is not necessarily the directory the
+        // editor spawned the server in; the server resolves relative
+        // `--ignore-path` values from this cwd so they stay based on the same
+        // directory as a relative `--config`.
+        cwd,
+        ignorePaths,
+        loadConfig: loadFmtConfig,
+      });
+      return;
+    }
+
     if (stdinFilepath !== undefined) {
       const { runFmtStdin } = await import(
         /* rspackChunkName: 'fmtStdin' */

packages/rstack/src/fmt/discovery.ts

@@ -2,6 +2,7 @@ import path from 'node:path';
 import { createFmtOptionsResolver, type FmtOptionsResolver } from './config.ts';
 import { discoverFmtPaths } from './discoverPaths.ts';
 import { createIgnoreMatcher } from './ignore.ts';
+import type { FmtPluginResolver } from './plugins.ts';
 import type { DiscoverFmtFilesOptions, FmtFileRequest } from './types.ts';
 
 const createFileRequest = (
@@ -12,6 +13,26 @@ const createFileRequest = (
   options: resolveOptions(filePath),
 });
 
+/** Imports the plugin chunk on first use and shares the resolver across calls. */
+const createLazyPluginResolver = (rootPath: string): (() => Promise<FmtPluginResolver>) => {
+  let resolver: Promise<FmtPluginResolver> | undefined;
+
+  return () =>
+    (resolver ??= import(
+      /* rspackChunkName: 'fmtPlugins' */
+      './plugins.ts'
+    ).then(({ createFmtPluginResolver }) => createFmtPluginResolver(rootPath)));
+};
+
+/** Resolves the plugin specifiers of a request whose options configure plugins. */
+const resolveFileRequestPlugins = async (
+  file: FmtFileRequest,
+  getPluginResolver: () => Promise<FmtPluginResolver>,
+): Promise<FmtFileRequest> =>
+  file.options.plugins?.length
+    ? { ...file, options: (await getPluginResolver())(file.options) }
+    : file;
+
 const createDirMatcher = (dirPath: string): ((filePath: string) => boolean) => {
   const prefix = dirPath.endsWith(path.sep) ? dirPath : `${dirPath}${path.sep}`;
   return (filePath) => filePath === dirPath || filePath.startsWith(prefix);
@@ -43,21 +64,13 @@ const discoverFmtFiles = async ({
   }
 
   const resolveOptions = createFmtOptionsResolver(config);
-  const files = filePaths.map((filePath) => createFileRequest(filePath, resolveOptions));
-  if (!files.some((file) => file.options.plugins?.length)) {
-    return files;
-  }
+  const getPluginResolver = createLazyPluginResolver(config.rootPath);
 
-  const { createFmtPluginResolver } = await import(
-    /* rspackChunkName: 'fmtPlugins' */
-    './plugins.ts'
+  return Promise.all(
+    filePaths.map((filePath) =>
+      resolveFileRequestPlugins(createFileRequest(filePath, resolveOptions), getPluginResolver),
+    ),
   );
-  const resolvePlugins = createFmtPluginResolver(config.rootPath);
-
-  return files.map((file) => ({
-    ...file,
-    options: resolvePlugins(file.options),
-  }));
 };
 
-export { createFileRequest, discoverFmtFiles };
+export { createFileRequest, createLazyPluginResolver, discoverFmtFiles, resolveFileRequestPlugins };

packages/rstack/src/fmt/ignore.ts

@@ -80,3 +80,4 @@ const createIgnoreMatcher = async ({
 };
 
 export { createIgnoreMatcher };
+export type { IgnorePredicate };