Support realpaths with config

$shared/settings.ts

@@ -168,6 +168,7 @@ export type ConfigurationSettings = {
 	packageManager: PackageManagers;
 	useESLintClass: boolean;
 	useFlatConfig?: boolean | undefined;
+	useRealpaths: boolean;
 	experimental?: {
 		useFlatConfig: boolean;
 	};

client/src/client.ts

@@ -678,6 +678,7 @@ export namespace ESLintClient {
 					packageManager: config.get<PackageManagers>('packageManager', 'npm'),
 					useESLintClass: config.get<boolean>('useESLintClass', false),
 					useFlatConfig: useFlatConfig === null ? undefined : useFlatConfig,
+					useRealpaths: config.get<boolean>('useRealpaths', false),
 					experimental: {
 						useFlatConfig: config.get<boolean>('experimental.useFlatConfig', false),
 					},
@@ -962,7 +963,7 @@ export namespace ESLintClient {
 			}
 
 			if (detail !== undefined && languageStatus.detail !== detail) {
-				 languageStatus.detail = detail;
+				languageStatus.detail = detail;
 			}
 			if (languageStatus.severity !== severity) {
 				languageStatus.severity = severity;

package.json

@@ -196,6 +196,12 @@
 					"deprecationMessage": "Use ESLint version 8.57 or later and `eslint.useFlatConfig` instead.",
 					"description": "Enables support of experimental Flat Config (aka eslint.config.js). Requires ESLint version >= 8.21 < 8.57.0)."
 				},
+				"eslint.useRealpaths": {
+					"scope": "resource",
+					"type": "boolean",
+					"default": false,
+					"description": "Whether ESLint should use real paths when resolving files. This is useful when working with symlinks or when the casing of file paths is inconsistent."
+				},
 				"eslint.workingDirectories": {
 					"scope": "resource",
 					"type": "array",

server/src/eslint.ts

@@ -478,11 +478,11 @@ export type SaveRuleConfigItem = { offRules: Set<string>; onRules: Set<string>;
  */
 export namespace SaveRuleConfigs {
 
-	export let inferFilePath: (documentOrUri: string | TextDocument | URI | undefined) => string | undefined;
+	export let inferFilePath: (documentOrUri: string | TextDocument | URI | undefined, useRealpaths: boolean) => string | undefined;
 
 	const saveRuleConfigCache = new LRUCache<string, SaveRuleConfigItem | null>(128);
 	export async function get(uri: string, settings: TextDocumentSettings  & { library: ESLintModule }): Promise<SaveRuleConfigItem | undefined> {
-		const filePath = inferFilePath(uri);
+		const filePath = inferFilePath(uri, settings.useRealpaths);
 		let result = saveRuleConfigCache.get(uri);
 		if (filePath === undefined || result === null) {
 			return undefined;
@@ -755,7 +755,7 @@ export namespace ESLint {
 
 	let connection: ProposedFeatures.Connection;
 	let documents: TextDocuments<TextDocument>;
-	let inferFilePath: (documentOrUri: string | TextDocument | URI | undefined) => string | undefined;
+	let inferFilePath: (documentOrUri: string | TextDocument | URI | undefined, useRealpaths: boolean) => string | undefined;
 	let loadNodeModule: <T>(moduleName: string) => T | undefined;
 
 	const languageId2ParserRegExp: Map<string, RegExp[]> = function createLanguageId2ParserRegExp() {
@@ -823,7 +823,7 @@ export namespace ESLint {
 	const document2Settings: Map<string, Promise<TextDocumentSettings>> = new Map<string, Promise<TextDocumentSettings>>();
 	const formatterRegistrations: Map<string, Promise<Disposable>> = new Map();
 
-	export function initialize($connection: ProposedFeatures.Connection, $documents: TextDocuments<TextDocument>, $inferFilePath: (documentOrUri: string | TextDocument | URI | undefined) => string | undefined, $loadNodeModule: <T>(moduleName: string) => T | undefined) {
+	export function initialize($connection: ProposedFeatures.Connection, $documents: TextDocuments<TextDocument>, $inferFilePath: (documentOrUri: string | TextDocument | URI | undefined, useRealpaths: boolean) => string | undefined, $loadNodeModule: <T>(moduleName: string) => T | undefined) {
 		connection = $connection;
 		documents = $documents;
 		inferFilePath = $inferFilePath;
@@ -870,8 +870,8 @@ export namespace ESLint {
 				return settings;
 			}
 			settings.resolvedGlobalPackageManagerPath = GlobalPaths.get(settings.packageManager);
-			const filePath = inferFilePath(document);
-			const workspaceFolderPath = settings.workspaceFolder !== undefined ? inferFilePath(settings.workspaceFolder.uri) : undefined;
+			const filePath = inferFilePath(document, settings.useRealpaths);
+			const workspaceFolderPath = settings.workspaceFolder !== undefined ? inferFilePath(settings.workspaceFolder.uri, settings.useRealpaths) : undefined;
 			let assumeFlatConfig:boolean = false;
 			const hasUserDefinedWorkingDirectories: boolean = configuration.workingDirectory !== undefined;
 			const workingDirectoryConfig = configuration.workingDirectory ?? { mode: ModeEnum.location };
@@ -1097,7 +1097,7 @@ export namespace ESLint {
 						if (!isFile) {
 							formatterRegistrations.set(uri, connection.client.register(DocumentFormattingRequest.type, options));
 						} else {
-							const filePath = inferFilePath(uri)!;
+							const filePath = inferFilePath(uri, settings.useRealpaths)!;
 							await ESLint.withClass(async (eslintClass) => {
 								if (!await eslintClass.isPathIgnored(filePath)) {
 									formatterRegistrations.set(uri, connection.client.register(DocumentFormattingRequest.type, options));
@@ -1183,14 +1183,14 @@ export namespace ESLint {
 		if (uri.scheme !== 'file') {
 			if (settings.workspaceFolder !== undefined) {
 				const ext = LanguageDefaults.getExtension(document.languageId);
-				const workspacePath = inferFilePath(settings.workspaceFolder.uri);
+				const workspacePath = inferFilePath(settings.workspaceFolder.uri, settings.useRealpaths);
 				if (workspacePath !== undefined && ext !== undefined) {
 					return path.join(workspacePath, `test.${ext}`);
 				}
 			}
 			return undefined;
 		} else {
-			return inferFilePath(uri);
+			return inferFilePath(uri, settings.useRealpaths);
 		}
 	}
 
@@ -1418,14 +1418,14 @@ export namespace ESLint {
 			missingModuleReported.clear();
 		}
 
-		function tryHandleMissingModule(error: any, document: TextDocument, library: ESLintModule): Status | undefined {
+		function tryHandleMissingModule(error: any, document: TextDocument, library: ESLintModule, settings: TextDocumentSettings): Status | undefined {
 			if (!error.message) {
 				return undefined;
 			}
 
 			function handleMissingModule(plugin: string, module: string, error: ESLintError): Status {
 				if (!missingModuleReported.has(plugin)) {
-					const fsPath = inferFilePath(document);
+					const fsPath = inferFilePath(document, settings.useRealpaths);
 					missingModuleReported.set(plugin, library);
 					if (error.messageTemplate === 'plugin-missing') {
 						connection.console.error([

server/src/eslintServer.ts

@@ -116,20 +116,20 @@ process.on('uncaughtException', (error: any) => {
  * cell document it uses the file path from the notebook with a corresponding
  * extension (e.g. TypeScript -> ts)
  */
-function inferFilePath(documentOrUri: string | TextDocument | URI | undefined): string | undefined {
+function inferFilePath(documentOrUri: string | TextDocument | URI | undefined, useRealpaths: boolean): string | undefined {
 	if (!documentOrUri) {
 		return undefined;
 	}
 	const uri = getUri(documentOrUri);
 	if (uri.scheme === 'file') {
-		return getFileSystemPath(uri);
+		return getFileSystemPath(uri, useRealpaths);
 	}
 
 	const notebookDocument = notebooks.findNotebookDocumentForCell(uri.toString());
 	if (notebookDocument !== undefined ) {
 		const notebookUri = URI.parse(notebookDocument.uri);
 		if (notebookUri.scheme === 'file') {
-			const filePath = getFileSystemPath(uri);
+			const filePath = getFileSystemPath(uri, useRealpaths);
 			if (filePath !== undefined) {
 				const textDocument = documents.get(uri.toString());
 				if (textDocument !== undefined) {
@@ -299,7 +299,7 @@ connection.onDidChangeWatchedFiles(async (params) => {
 	SaveRuleConfigs.clear();
 
 	await Promise.all(params.changes.map(async (change) => {
-		const fsPath = inferFilePath(change.uri);
+		const fsPath = inferFilePath(change.uri, false);
 		if (fsPath === undefined || fsPath.length === 0 || isUNC(fsPath)) {
 			return;
 		}
@@ -756,7 +756,7 @@ async function computeAllFixes(identifier: VersionedTextDocumentIdentifier, mode
 	if (settings.validate !== Validate.on || !TextDocumentSettings.hasLibrary(settings) || (mode === AllFixesMode.format && !settings.format)) {
 		return [];
 	}
-	const filePath = inferFilePath(textDocument);
+	const filePath = inferFilePath(textDocument, settings.useRealpaths);
 	const problems = CodeActions.get(uri);
 	const originalContent = textDocument.getText();
 	let start = Date.now();

server/src/paths.ts

@@ -76,30 +76,37 @@ export function isUNC(path: string): boolean {
 	return true;
 }
 
-export function getFileSystemPath(uri: URI): string {
+export function getFileSystemPath(uri: URI, useRealpaths: boolean): string {
 	let result = uri.fsPath;
 	if (process.platform === 'win32' && result.length >= 2 && result[1] === ':') {
 		// Node by default uses an upper case drive letter and ESLint uses
 		// === to compare paths which results in the equal check failing
 		// if the drive letter is lower case in th URI. Ensure upper case.
 		result = result[0].toUpperCase() + result.substr(1);
 	}
-	if (process.platform === 'win32' || process.platform === 'darwin') {
-		try {
-			const realpath = fs.realpathSync.native(result);
-			// Only use the real path if only the casing has changed.
-			if (realpath.toLowerCase() === result.toLowerCase()) {
-				result = realpath;
-			}
-		} catch {
-			// Silently ignore errors from `fs.realpathSync` to handle scenarios where
-			// the file being linted is not yet written to disk. This occurs in editors
-			// such as Neovim for non-written buffers.
+	if (useRealpaths) {
+		result = tryRealpath(result);
+	} else if (process.platform === 'win32' || process.platform === 'darwin') {
+		const realpath = tryRealpath(result);
+		// Only use the real path if only the casing has changed.
+		if (realpath.toLowerCase() === result.toLowerCase()) {
+			result = realpath;
 		}
 	}
 	return result;
 }
 
+function tryRealpath(path: string): string {
+	try {
+		return fs.realpathSync.native(path);
+	} catch (error) {
+		// Silently ignore errors from `fs.realpathSync` to handle scenarios where
+		// the file being linted is not yet written to disk. This occurs in editors
+		// such as Neovim for non-written buffers.
+		return path;
+	}
+}
+
 export function normalizePath(path: string): string;
 export function normalizePath(path: undefined): undefined;
 export function normalizePath(path: string | undefined): string | undefined {