Move md workspace symbol search to language service (#154874)

* Move md workspace symbol search to language service

Also implements more of IWorkspace for the server

* Revert extra change

17 files changed, 421 insertions, 323 deletions

diff --git a/extensions/markdown-language-features/server/.vscode/launch.json b/extensions/markdown-language-features/server/.vscode/launch.json
index 5753befac8b..1ea07e048c8 100644
--- a/extensions/markdown-language-features/server/.vscode/launch.json
+++ b/extensions/markdown-language-features/server/.vscode/launch.json
@@ -6,26 +6,7 @@
 			"name": "Attach",
 			"type": "node",
 			"request": "attach",
-			"port": 6044,
-			"protocol": "inspector",
-			"sourceMaps": true,
-			"outFiles": ["${workspaceFolder}/out/**/*.js"]
-		},
-		{
-			"name": "Unit Tests",
-			"type": "node",
-			"request": "launch",
-			"program": "${workspaceFolder}/../../../node_modules/mocha/bin/_mocha",
-			"stopOnEntry": false,
-			"args": [
-				"--timeout",
-				"999999",
-				"--colors"
-			],
-			"cwd": "${workspaceFolder}",
-			"runtimeExecutable": null,
-			"runtimeArgs": [],
-			"env": {},
+			"port": 7675,
 			"sourceMaps": true,
 			"outFiles": ["${workspaceFolder}/out/**/*.js"]
 		}
diff --git a/extensions/markdown-language-features/server/.vscode/tasks.json b/extensions/markdown-language-features/server/.vscode/tasks.json
index 6a159d6a5fa..ecc951a7baf 100644
--- a/extensions/markdown-language-features/server/.vscode/tasks.json
+++ b/extensions/markdown-language-features/server/.vscode/tasks.json
@@ -1,9 +1,27 @@
 {
-	"version": "0.1.0",
+	"version": "2.0.0",
 	"command": "npm",
-	"isShellCommand": true,
-	"showOutput": "silent",
-	"args": ["run", "watch"],
-	"isWatching": true,
-	"problemMatcher": "$tsc-watch"
+	"args": [
+		"run",
+		"watch"
+	],
+	"isBackground": true,
+	"problemMatcher": "$tsc-watch",
+	"tasks": [
+		{
+			"label": "npm",
+			"type": "shell",
+			"command": "npm",
+			"args": [
+				"run",
+				"watch"
+			],
+			"isBackground": true,
+			"problemMatcher": "$tsc-watch",
+			"group": {
+				"_id": "build",
+				"isDefault": false
+			}
+		}
+	]
 }
\ No newline at end of file
diff --git a/extensions/markdown-language-features/server/package.json b/extensions/markdown-language-features/server/package.json
index 2ca66e39347..f3cfb2292a1 100644
--- a/extensions/markdown-language-features/server/package.json
+++ b/extensions/markdown-language-features/server/package.json
@@ -14,7 +14,7 @@
     "vscode-uri": "^3.0.3",
     "vscode-languageserver-textdocument": "^1.0.5",
     "vscode-languageserver-types": "^3.17.1",
-    "vscode-markdown-languageservice": "mjbvz/vscode-markdown-languageservice"
+    "vscode-markdown-languageservice": "microsoft/vscode-markdown-languageservice"
   },
   "devDependencies": {
     "@types/node": "16.x"
diff --git a/extensions/markdown-language-features/server/src/protocol.ts b/extensions/markdown-language-features/server/src/protocol.ts
new file mode 100644
index 00000000000..9f49c277ae2
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/protocol.ts
@@ -0,0 +1,15 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { RequestType } from 'vscode-languageserver';
+import * as md from 'vscode-markdown-languageservice';
+
+declare const TextDecoder: any;
+
+export const parseRequestType: RequestType<{ uri: string }, md.Token[], any> = new RequestType('markdown/parse');
+
+export const readFileRequestType: RequestType<{ uri: string }, number[], any> = new RequestType('markdown/readFile');
+
+export const findFilesRequestTypes: RequestType<{}, string[], any> = new RequestType('markdown/findFiles');
diff --git a/extensions/markdown-language-features/server/src/server.ts b/extensions/markdown-language-features/server/src/server.ts
index 8bc1d4b9271..ad2491d9688 100644
--- a/extensions/markdown-language-features/server/src/server.ts
+++ b/extensions/markdown-language-features/server/src/server.ts
@@ -3,37 +3,15 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import { Connection, Emitter, Event, InitializeParams, InitializeResult, RequestType, TextDocuments } from 'vscode-languageserver';
+import { Connection, InitializeParams, InitializeResult, TextDocuments } from 'vscode-languageserver';
 import { TextDocument } from 'vscode-languageserver-textdocument';
 import * as lsp from 'vscode-languageserver-types';
 import * as md from 'vscode-markdown-languageservice';
-import { URI } from 'vscode-uri';
 import { LogFunctionLogger } from './logging';
+import { parseRequestType } from './protocol';
+import { VsCodeClientWorkspace } from './workspace';
 
-
-const parseRequestType: RequestType<{ uri: string }, md.Token[], any> = new RequestType('markdown/parse');
-
-class TextDocumentToITextDocumentAdapter implements md.ITextDocument {
-	public readonly uri: md.IUri;
-
-	public get version(): number { return this._doc.version; }
-
-	public get lineCount(): number { return this._doc.lineCount; }
-
-	constructor(
-		private readonly _doc: TextDocument,
-	) {
-		this.uri = URI.parse(this._doc.uri);
-	}
-
-	getText(range?: md.IRange | undefined): string {
-		return this._doc.getText(range);
-	}
-
-	positionAt(offset: number): md.IPosition {
-		return this._doc.positionAt(offset);
-	}
-}
+declare const TextDecoder: any;
 
 export function startServer(connection: Connection) {
 	const documents = new TextDocuments(TextDocument);
@@ -45,11 +23,11 @@ export function startServer(connection: Connection) {
 				documentSymbolProvider: true,
 				foldingRangeProvider: true,
 				selectionRangeProvider: true,
+				workspaceSymbolProvider: true,
 			}
 		};
 	});
 
-
 	const parser = new class implements md.IMdParser {
 		slugifier = md.githubSlugifier;
 
@@ -58,42 +36,15 @@ export function startServer(connection: Connection) {
 		}
 	};
 
-	const workspace = new class implements md.IMdWorkspace {
-
-		private readonly _onDidChangeMarkdownDocument = new Emitter<md.ITextDocument>();
-		onDidChangeMarkdownDocument: Event<md.ITextDocument> = this._onDidChangeMarkdownDocument.event;
-
-		private readonly _onDidCreateMarkdownDocument = new Emitter<md.ITextDocument>();
-		onDidCreateMarkdownDocument: Event<md.ITextDocument> = this._onDidCreateMarkdownDocument.event;
-
-		private readonly _onDidDeleteMarkdownDocument = new Emitter<md.IUri>();
-		onDidDeleteMarkdownDocument: Event<md.IUri> = this._onDidDeleteMarkdownDocument.event;
-
-		async getAllMarkdownDocuments(): Promise<Iterable<md.ITextDocument>> {
-			return documents.all().map(doc => new TextDocumentToITextDocumentAdapter(doc));
-		}
-		hasMarkdownDocument(resource: md.IUri): boolean {
-			return !!documents.get(resource.toString());
-		}
-		async getOrLoadMarkdownDocument(_resource: md.IUri): Promise<md.ITextDocument | undefined> {
-			return undefined;
-		}
-		async pathExists(_resource: md.IUri): Promise<boolean> {
-			return false;
-		}
-		async readDirectory(_resource: md.IUri): Promise<[string, { isDir: boolean }][]> {
-			return [];
-		}
-	};
-
+	const workspace = new VsCodeClientWorkspace(connection, documents);
 	const logger = new LogFunctionLogger(connection.console.log.bind(connection.console));
-	const provider = md.createLanguageService(workspace, parser, logger);
+	const provider = md.createLanguageService({ workspace, parser, logger });
 
 	connection.onDocumentSymbol(async (params, token): Promise<lsp.DocumentSymbol[]> => {
 		try {
 			const document = documents.get(params.textDocument.uri);
 			if (document) {
-				return await provider.provideDocumentSymbols(new TextDocumentToITextDocumentAdapter(document), token);
+				return await provider.provideDocumentSymbols(document, token);
 			}
 		} catch (e) {
 			console.error(e.stack);
@@ -105,7 +56,7 @@ export function startServer(connection: Connection) {
 		try {
 			const document = documents.get(params.textDocument.uri);
 			if (document) {
-				return await provider.provideFoldingRanges(new TextDocumentToITextDocumentAdapter(document), token);
+				return await provider.provideFoldingRanges(document, token);
 			}
 		} catch (e) {
 			console.error(e.stack);
@@ -117,7 +68,7 @@ export function startServer(connection: Connection) {
 		try {
 			const document = documents.get(params.textDocument.uri);
 			if (document) {
-				return await provider.provideSelectionRanges(new TextDocumentToITextDocumentAdapter(document), params.positions, token);
+				return await provider.provideSelectionRanges(document, params.positions, token);
 			}
 		} catch (e) {
 			console.error(e.stack);
@@ -125,5 +76,15 @@ export function startServer(connection: Connection) {
 		return [];
 	});
 
+	connection.onWorkspaceSymbol(async (params, token): Promise<lsp.WorkspaceSymbol[]> => {
+		try {
+			return await provider.provideWorkspaceSymbols(params.query, token);
+		} catch (e) {
+			console.error(e.stack);
+		}
+		return [];
+	});
+
 	connection.listen();
 }
+
diff --git a/extensions/markdown-language-features/server/src/util/arrays.ts b/extensions/markdown-language-features/server/src/util/arrays.ts
new file mode 100644
index 00000000000..3ed55d8f077
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/util/arrays.ts
@@ -0,0 +1,11 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/**
+ * @returns New array with all falsy values removed. The original array IS NOT modified.
+ */
+export function coalesce<T>(array: ReadonlyArray<T | undefined | null>): T[] {
+	return <T[]>array.filter(e => !!e);
+}
diff --git a/extensions/markdown-language-features/server/src/util/file.ts b/extensions/markdown-language-features/server/src/util/file.ts
new file mode 100644
index 00000000000..45b072a82dc
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/util/file.ts
@@ -0,0 +1,27 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import * as URI from 'vscode-uri';
+
+const markdownFileExtensions = Object.freeze<string[]>([
+	'.md',
+	'.mkd',
+	'.mdwn',
+	'.mdown',
+	'.markdown',
+	'.markdn',
+	'.mdtxt',
+	'.mdtext',
+	'.workbook',
+]);
+
+export function looksLikeMarkdownPath(resolvedHrefPath: URI.URI) {
+	return markdownFileExtensions.includes(URI.Utils.extname(URI.URI.from(resolvedHrefPath)).toLowerCase());
+}
+
+export function isMarkdownDocument(document: TextDocument): boolean {
+	return document.languageId === 'markdown';
+}
diff --git a/extensions/markdown-language-features/server/src/util/limiter.ts b/extensions/markdown-language-features/server/src/util/limiter.ts
new file mode 100644
index 00000000000..bd4153cd08b
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/util/limiter.ts
@@ -0,0 +1,67 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+interface ILimitedTaskFactory<T> {
+	factory: ITask<Promise<T>>;
+	c: (value: T | Promise<T>) => void;
+	e: (error?: unknown) => void;
+}
+
+interface ITask<T> {
+	(): T;
+}
+
+/**
+ * A helper to queue N promises and run them all with a max degree of parallelism. The helper
+ * ensures that at any time no more than M promises are running at the same time.
+ *
+ * Taken from 'src/vs/base/common/async.ts'
+ */
+export class Limiter<T> {
+
+	private _size = 0;
+	private runningPromises: number;
+	private readonly maxDegreeOfParalellism: number;
+	private readonly outstandingPromises: ILimitedTaskFactory<T>[];
+
+	constructor(maxDegreeOfParalellism: number) {
+		this.maxDegreeOfParalellism = maxDegreeOfParalellism;
+		this.outstandingPromises = [];
+		this.runningPromises = 0;
+	}
+
+	get size(): number {
+		return this._size;
+	}
+
+	queue(factory: ITask<Promise<T>>): Promise<T> {
+		this._size++;
+
+		return new Promise<T>((c, e) => {
+			this.outstandingPromises.push({ factory, c, e });
+			this.consume();
+		});
+	}
+
+	private consume(): void {
+		while (this.outstandingPromises.length && this.runningPromises < this.maxDegreeOfParalellism) {
+			const iLimitedTask = this.outstandingPromises.shift()!;
+			this.runningPromises++;
+
+			const promise = iLimitedTask.factory();
+			promise.then(iLimitedTask.c, iLimitedTask.e);
+			promise.then(() => this.consumed(), () => this.consumed());
+		}
+	}
+
+	private consumed(): void {
+		this._size--;
+		this.runningPromises--;
+
+		if (this.outstandingPromises.length > 0) {
+			this.consume();
+		}
+	}
+}
diff --git a/extensions/markdown-language-features/server/src/util/resourceMap.ts b/extensions/markdown-language-features/server/src/util/resourceMap.ts
new file mode 100644
index 00000000000..7cec9d661d3
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/util/resourceMap.ts
@@ -0,0 +1,69 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { URI } from 'vscode-uri';
+
+
+type ResourceToKey = (uri: URI) => string;
+
+const defaultResourceToKey = (resource: URI): string => resource.toString();
+
+export class ResourceMap<T> {
+
+	private readonly map = new Map<string, { readonly uri: URI; readonly value: T }>();
+
+	private readonly toKey: ResourceToKey;
+
+	constructor(toKey: ResourceToKey = defaultResourceToKey) {
+		this.toKey = toKey;
+	}
+
+	public set(uri: URI, value: T): this {
+		this.map.set(this.toKey(uri), { uri, value });
+		return this;
+	}
+
+	public get(resource: URI): T | undefined {
+		return this.map.get(this.toKey(resource))?.value;
+	}
+
+	public has(resource: URI): boolean {
+		return this.map.has(this.toKey(resource));
+	}
+
+	public get size(): number {
+		return this.map.size;
+	}
+
+	public clear(): void {
+		this.map.clear();
+	}
+
+	public delete(resource: URI): boolean {
+		return this.map.delete(this.toKey(resource));
+	}
+
+	public *values(): IterableIterator<T> {
+		for (const entry of this.map.values()) {
+			yield entry.value;
+		}
+	}
+
+	public *keys(): IterableIterator<URI> {
+		for (const entry of this.map.values()) {
+			yield entry.uri;
+		}
+	}
+
+	public *entries(): IterableIterator<[URI, T]> {
+		for (const entry of this.map.values()) {
+			yield [entry.uri, entry.value];
+		}
+	}
+
+	public [Symbol.iterator](): IterableIterator<[URI, T]> {
+		return this.entries();
+	}
+}
diff --git a/extensions/markdown-language-features/server/src/workspace.ts b/extensions/markdown-language-features/server/src/workspace.ts
new file mode 100644
index 00000000000..964ff369d50
--- /dev/null
+++ b/extensions/markdown-language-features/server/src/workspace.ts
@@ -0,0 +1,155 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Connection, Emitter, FileChangeType, TextDocuments } from 'vscode-languageserver';
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import * as md from 'vscode-markdown-languageservice';
+import { URI } from 'vscode-uri';
+import * as protocol from './protocol';
+import { coalesce } from './util/arrays';
+import { isMarkdownDocument, looksLikeMarkdownPath } from './util/file';
+import { Limiter } from './util/limiter';
+import { ResourceMap } from './util/resourceMap';
+
+declare const TextDecoder: any;
+
+export class VsCodeClientWorkspace implements md.IWorkspace {
+
+	private readonly _onDidCreateMarkdownDocument = new Emitter<md.ITextDocument>();
+	public readonly onDidCreateMarkdownDocument = this._onDidCreateMarkdownDocument.event;
+
+	private readonly _onDidChangeMarkdownDocument = new Emitter<md.ITextDocument>();
+	public readonly onDidChangeMarkdownDocument = this._onDidChangeMarkdownDocument.event;
+
+	private readonly _onDidDeleteMarkdownDocument = new Emitter<URI>();
+	public readonly onDidDeleteMarkdownDocument = this._onDidDeleteMarkdownDocument.event;
+
+	private readonly _documentCache = new ResourceMap<md.ITextDocument>();
+
+	private readonly _utf8Decoder = new TextDecoder('utf-8');
+
+	constructor(
+		private readonly connection: Connection,
+		private readonly documents: TextDocuments<TextDocument>,
+	) {
+		documents.onDidOpen(e => {
+			this._documentCache.delete(URI.parse(e.document.uri));
+			if (this.isRelevantMarkdownDocument(e.document)) {
+				this._onDidCreateMarkdownDocument.fire(e.document);
+			}
+		});
+
+		documents.onDidChangeContent(e => {
+			if (this.isRelevantMarkdownDocument(e.document)) {
+				this._onDidChangeMarkdownDocument.fire(e.document);
+			}
+		});
+
+		documents.onDidClose(e => {
+			this._documentCache.delete(URI.parse(e.document.uri));
+		});
+
+		connection.onDidChangeWatchedFiles(async ({ changes }) => {
+			for (const change of changes) {
+				const resource = URI.parse(change.uri);
+				switch (change.type) {
+					case FileChangeType.Changed: {
+						this._documentCache.delete(resource);
+						const document = await this.getOrLoadMarkdownDocument(resource);
+						if (document) {
+							this._onDidChangeMarkdownDocument.fire(document);
+						}
+						break;
+					}
+					case FileChangeType.Created: {
+						const document = await this.getOrLoadMarkdownDocument(resource);
+						if (document) {
+							this._onDidCreateMarkdownDocument.fire(document);
+						}
+						break;
+					}
+					case FileChangeType.Deleted: {
+						this._documentCache.delete(resource);
+						this._onDidDeleteMarkdownDocument.fire(resource);
+						break;
+					}
+				}
+			}
+		});
+	}
+
+	async getAllMarkdownDocuments(): Promise<Iterable<md.ITextDocument>> {
+		const maxConcurrent = 20;
+
+		const foundFiles = new ResourceMap<void>();
+		const limiter = new Limiter<md.ITextDocument | undefined>(maxConcurrent);
+
+		// Add files on disk
+		const resources = await this.connection.sendRequest(protocol.findFilesRequestTypes, {});
+		const onDiskResults = await Promise.all(resources.map(strResource => {
+			return limiter.queue(async () => {
+				const resource = URI.parse(strResource);
+				const doc = await this.getOrLoadMarkdownDocument(resource);
+				if (doc) {
+					foundFiles.set(resource);
+				}
+				return doc;
+			});
+		}));
+
+		// Add opened files (such as untitled files)
+		const openTextDocumentResults = await Promise.all(this.documents.all()
+			.filter(doc => !foundFiles.has(URI.parse(doc.uri)) && this.isRelevantMarkdownDocument(doc)));
+
+		return coalesce([...onDiskResults, ...openTextDocumentResults]);
+	}
+
+	hasMarkdownDocument(resource: URI): boolean {
+		return !!this.documents.get(resource.toString());
+	}
+
+	async getOrLoadMarkdownDocument(resource: URI): Promise<md.ITextDocument | undefined> {
+		const existing = this._documentCache.get(resource);
+		if (existing) {
+			return existing;
+		}
+
+		const matchingDocument = this.documents.get(resource.toString());
+		if (matchingDocument) {
+			this._documentCache.set(resource, matchingDocument);
+			return matchingDocument;
+		}
+
+		if (!looksLikeMarkdownPath(resource)) {
+			return undefined;
+		}
+
+		try {
+			const response = await this.connection.sendRequest(protocol.readFileRequestType, { uri: resource.toString() });
+			// TODO: LSP doesn't seem to handle Array buffers well
+			const bytes = new Uint8Array(response);
+
+			// We assume that markdown is in UTF-8
+			const text = this._utf8Decoder.decode(bytes);
+			const doc = new md.InMemoryDocument(resource, text, 0);
+			this._documentCache.set(resource, doc);
+			return doc;
+		} catch (e) {
+			return undefined;
+		}
+	}
+
+	async pathExists(_resource: URI): Promise<boolean> {
+		return false;
+	}
+
+	async readDirectory(_resource: URI): Promise<[string, { isDir: boolean }][]> {
+		return [];
+	}
+
+	private isRelevantMarkdownDocument(doc: TextDocument) {
+		return isMarkdownDocument(doc) && URI.parse(doc.uri).scheme !== 'vscode-bulkeditpreview';
+	}
+}
diff --git a/extensions/markdown-language-features/server/yarn.lock b/extensions/markdown-language-features/server/yarn.lock
index d0bce38f189..e46f1b1b8db 100644
--- a/extensions/markdown-language-features/server/yarn.lock
+++ b/extensions/markdown-language-features/server/yarn.lock
@@ -42,9 +42,9 @@ vscode-languageserver@^8.0.2-next.4:
   dependencies:
     vscode-languageserver-protocol "3.17.2-next.6"
 
-vscode-markdown-languageservice@mjbvz/vscode-markdown-languageservice:
-  version "0.0.0-alpha.1"
-  resolved "https://codeload.github.com/mjbvz/vscode-markdown-languageservice/tar.gz/e1a0e00bf6a99cc543da64964cc0995537647d15"
+vscode-markdown-languageservice@microsoft/vscode-markdown-languageservice:
+  version "0.0.0-alpha.2"
+  resolved "https://codeload.github.com/microsoft/vscode-markdown-languageservice/tar.gz/db497ada376aae9a335519dbfb406c6a1f873446"
   dependencies:
     vscode-languageserver-types "^3.17.1"
     vscode-uri "^3.0.3"
diff --git a/extensions/markdown-language-features/src/client.ts b/extensions/markdown-language-features/src/client.ts
index 0bf5588ec38..aabd09f4633 100644
--- a/extensions/markdown-language-features/src/client.ts
+++ b/extensions/markdown-language-features/src/client.ts
@@ -8,23 +8,30 @@ import * as vscode from 'vscode';
 import { BaseLanguageClient, LanguageClientOptions, RequestType } from 'vscode-languageclient';
 import * as nls from 'vscode-nls';
 import { IMdParser } from './markdownEngine';
+import { markdownFileExtensions } from './util/file';
 import { IMdWorkspace } from './workspace';
 
 const localize = nls.loadMessageBundle();
 
 const parseRequestType: RequestType<{ uri: string }, Token[], any> = new RequestType('markdown/parse');
 
+const readFileRequestType: RequestType<{ uri: string }, number[], any> = new RequestType('markdown/readFile');
+
+const findFilesRequestTypes: RequestType<{}, string[], any> = new RequestType('markdown/findFiles');
+
 export type LanguageClientConstructor = (name: string, description: string, clientOptions: LanguageClientOptions) => BaseLanguageClient;
 
 
 export async function startClient(factory: LanguageClientConstructor, workspace: IMdWorkspace, parser: IMdParser): Promise<BaseLanguageClient> {
 
 	const documentSelector = ['markdown'];
+	const mdFileGlob = `**/*.{${markdownFileExtensions.join(',')}}`;
 
 	const clientOptions: LanguageClientOptions = {
 		documentSelector,
 		synchronize: {
-			configurationSection: ['markdown']
+			configurationSection: ['markdown'],
+			fileEvents: vscode.workspace.createFileSystemWatcher(mdFileGlob),
 		},
 		initializationOptions: {}
 	};
@@ -43,6 +50,15 @@ export async function startClient(factory: LanguageClientConstructor, workspace:
 		}
 	});
 
+	client.onRequest(readFileRequestType, async (e): Promise<number[]> => {
+		const uri = vscode.Uri.parse(e.uri);
+		return Array.from(await vscode.workspace.fs.readFile(uri));
+	});
+
+	client.onRequest(findFilesRequestTypes, async (): Promise<string[]> => {
+		return (await vscode.workspace.findFiles(mdFileGlob, '**/node_modules/**')).map(x => x.toString());
+	});
+
 	await client.start();
 
 	return client;
diff --git a/extensions/markdown-language-features/src/extension.shared.ts b/extensions/markdown-language-features/src/extension.shared.ts
index 2a850191004..c5ebe5650c0 100644
--- a/extensions/markdown-language-features/src/extension.shared.ts
+++ b/extensions/markdown-language-features/src/extension.shared.ts
@@ -10,13 +10,11 @@ import { registerPasteSupport } from './languageFeatures/copyPaste';
 import { registerDefinitionSupport } from './languageFeatures/definitions';
 import { registerDiagnosticSupport } from './languageFeatures/diagnostics';
 import { MdLinkProvider, registerDocumentLinkSupport } from './languageFeatures/documentLinks';
-import { MdDocumentSymbolProvider } from './languageFeatures/documentSymbols';
 import { registerDropIntoEditorSupport } from './languageFeatures/dropIntoEditor';
 import { registerFindFileReferenceSupport } from './languageFeatures/fileReferences';
 import { registerPathCompletionSupport } from './languageFeatures/pathCompletions';
 import { MdReferencesProvider, registerReferencesSupport } from './languageFeatures/references';
 import { registerRenameSupport } from './languageFeatures/rename';
-import { registerWorkspaceSymbolSupport } from './languageFeatures/workspaceSymbols';
 import { ILogger } from './logging';
 import { IMdParser, MarkdownItEngine, MdParsingProvider } from './markdownEngine';
 import { MarkdownContributionProvider } from './markdownExtensions';
@@ -67,7 +65,6 @@ function registerMarkdownLanguageFeatures(
 
 	const linkProvider = new MdLinkProvider(parser, workspace, logger);
 	const referencesProvider = new MdReferencesProvider(parser, workspace, tocProvider, logger);
-	const symbolProvider = new MdDocumentSymbolProvider(tocProvider, logger);
 
 	return vscode.Disposable.from(
 		linkProvider,
@@ -83,7 +80,6 @@ function registerMarkdownLanguageFeatures(
 		registerPathCompletionSupport(selector, workspace, parser, linkProvider),
 		registerReferencesSupport(selector, referencesProvider),
 		registerRenameSupport(selector, workspace, referencesProvider, parser.slugifier),
-		registerWorkspaceSymbolSupport(workspace, symbolProvider),
 	);
 }
 
diff --git a/extensions/markdown-language-features/src/languageFeatures/documentSymbols.ts b/extensions/markdown-language-features/src/languageFeatures/documentSymbols.ts
deleted file mode 100644
index 2152e7bd46c..00000000000
--- a/extensions/markdown-language-features/src/languageFeatures/documentSymbols.ts
+++ /dev/null
@@ -1,77 +0,0 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) Microsoft Corporation. All rights reserved.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
-
-import * as vscode from 'vscode';
-import { ILogger } from '../logging';
-import { MdTableOfContentsProvider, TocEntry } from '../tableOfContents';
-import { ITextDocument } from '../types/textDocument';
-
-interface MarkdownSymbol {
-	readonly level: number;
-	readonly parent: MarkdownSymbol | undefined;
-	readonly children: vscode.DocumentSymbol[];
-}
-
-export class MdDocumentSymbolProvider implements vscode.DocumentSymbolProvider {
-
-	constructor(
-		private readonly tocProvider: MdTableOfContentsProvider,
-		private readonly logger: ILogger,
-	) { }
-
-	public async provideDocumentSymbolInformation(document: ITextDocument): Promise<vscode.SymbolInformation[]> {
-		this.logger.verbose('DocumentSymbolProvider', `provideDocumentSymbolInformation - ${document.uri}`);
-		const toc = await this.tocProvider.getForDocument(document);
-		return toc.entries.map(entry => this.toSymbolInformation(entry));
-	}
-
-	public async provideDocumentSymbols(document: ITextDocument): Promise<vscode.DocumentSymbol[]> {
-		const toc = await this.tocProvider.getForDocument(document);
-		const root: MarkdownSymbol = {
-			level: -Infinity,
-			children: [],
-			parent: undefined
-		};
-		this.buildTree(root, toc.entries);
-		return root.children;
-	}
-
-	private buildTree(parent: MarkdownSymbol, entries: readonly TocEntry[]) {
-		if (!entries.length) {
-			return;
-		}
-
-		const entry = entries[0];
-		const symbol = this.toDocumentSymbol(entry);
-		symbol.children = [];
-
-		while (entry.level <= parent.level) {
-			parent = parent.parent!;
-		}
-		parent.children.push(symbol);
-		this.buildTree({ level: entry.level, children: symbol.children, parent }, entries.slice(1));
-	}
-
-	private toSymbolInformation(entry: TocEntry): vscode.SymbolInformation {
-		return new vscode.SymbolInformation(
-			this.getSymbolName(entry),
-			vscode.SymbolKind.String,
-			'',
-			entry.sectionLocation);
-	}
-
-	private toDocumentSymbol(entry: TocEntry) {
-		return new vscode.DocumentSymbol(
-			this.getSymbolName(entry),
-			'',
-			vscode.SymbolKind.String,
-			entry.sectionLocation.range,
-			entry.sectionLocation.range);
-	}
-
-	private getSymbolName(entry: TocEntry): string {
-		return '#'.repeat(entry.level) + ' ' + entry.text;
-	}
-}
diff --git a/extensions/markdown-language-features/src/languageFeatures/workspaceSymbols.ts b/extensions/markdown-language-features/src/languageFeatures/workspaceSymbols.ts
deleted file mode 100644
index 1bbef509791..00000000000
--- a/extensions/markdown-language-features/src/languageFeatures/workspaceSymbols.ts
+++ /dev/null
@@ -1,36 +0,0 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) Microsoft Corporation. All rights reserved.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
-
-import * as vscode from 'vscode';
-import { Disposable } from '../util/dispose';
-import { MdWorkspaceInfoCache } from '../util/workspaceCache';
-import { IMdWorkspace } from '../workspace';
-import { MdDocumentSymbolProvider } from './documentSymbols';
-
-export class MdWorkspaceSymbolProvider extends Disposable implements vscode.WorkspaceSymbolProvider {
-
-	private readonly _cache: MdWorkspaceInfoCache<vscode.SymbolInformation[]>;
-
-	public constructor(
-		symbolProvider: MdDocumentSymbolProvider,
-		workspace: IMdWorkspace,
-	) {
-		super();
-
-		this._cache = this._register(new MdWorkspaceInfoCache(workspace, doc => symbolProvider.provideDocumentSymbolInformation(doc)));
-	}
-
-	public async provideWorkspaceSymbols(query: string): Promise<vscode.SymbolInformation[]> {
-		const allSymbols = (await this._cache.values()).flat();
-		return allSymbols.filter(symbolInformation => symbolInformation.name.toLowerCase().indexOf(query.toLowerCase()) !== -1);
-	}
-}
-
-export function registerWorkspaceSymbolSupport(
-	workspace: IMdWorkspace,
-	symbolProvider: MdDocumentSymbolProvider,
-): vscode.Disposable {
-	return vscode.languages.registerWorkspaceSymbolProvider(new MdWorkspaceSymbolProvider(symbolProvider, workspace));
-}
diff --git a/extensions/markdown-language-features/src/test/workspaceSymbolProvider.test.ts b/extensions/markdown-language-features/src/test/workspaceSymbolProvider.test.ts
deleted file mode 100644
index 3762a5a4ba1..00000000000
--- a/extensions/markdown-language-features/src/test/workspaceSymbolProvider.test.ts
+++ /dev/null
@@ -1,105 +0,0 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) Microsoft Corporation. All rights reserved.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
-
-import * as assert from 'assert';
-import 'mocha';
-import * as vscode from 'vscode';
-import { MdDocumentSymbolProvider } from '../languageFeatures/documentSymbols';
-import { MdWorkspaceSymbolProvider } from '../languageFeatures/workspaceSymbols';
-import { MdTableOfContentsProvider } from '../tableOfContents';
-import { ITextDocument } from '../types/textDocument';
-import { DisposableStore } from '../util/dispose';
-import { InMemoryDocument } from '../util/inMemoryDocument';
-import { IMdWorkspace } from '../workspace';
-import { createNewMarkdownEngine } from './engine';
-import { InMemoryMdWorkspace } from './inMemoryWorkspace';
-import { nulLogger } from './nulLogging';
-import { withStore, workspacePath } from './util';
-
-function getWorkspaceSymbols(store: DisposableStore, workspace: IMdWorkspace, query = ''): Promise<vscode.SymbolInformation[]> {
-	const engine = createNewMarkdownEngine();
-	const tocProvider = store.add(new MdTableOfContentsProvider(engine, workspace, nulLogger));
-	const symbolProvider = new MdDocumentSymbolProvider(tocProvider, nulLogger);
-	const workspaceSymbolProvider = store.add(new MdWorkspaceSymbolProvider(symbolProvider, workspace));
-	return workspaceSymbolProvider.provideWorkspaceSymbols(query);
-}
-
-suite('markdown.WorkspaceSymbolProvider', () => {
-	test('Should not return anything for empty workspace', withStore(async (store) => {
-		const workspace = store.add(new InMemoryMdWorkspace([]));
-		assert.deepStrictEqual(await getWorkspaceSymbols(store, workspace, ''), []);
-	}));
-
-	test('Should return symbols from workspace with one markdown file', withStore(async (store) => {
-		const workspace = store.add(new InMemoryMdWorkspace([
-			new InMemoryDocument(workspacePath('test.md'), `# header1\nabc\n## header2`)
-		]));
-
-		const symbols = await getWorkspaceSymbols(store, workspace, '');
-		assert.strictEqual(symbols.length, 2);
-		assert.strictEqual(symbols[0].name, '# header1');
-		assert.strictEqual(symbols[1].name, '## header2');
-	}));
-
-	test('Should return all content  basic workspace', withStore(async (store) => {
-		const fileNameCount = 10;
-		const files: ITextDocument[] = [];
-		for (let i = 0; i < fileNameCount; ++i) {
-			const testFileName = workspacePath(`test${i}.md`);
-			files.push(new InMemoryDocument(testFileName, `# common\nabc\n## header${i}`));
-		}
-
-		const workspace = store.add(new InMemoryMdWorkspace(files));
-
-		const symbols = await getWorkspaceSymbols(store, workspace, '');
-		assert.strictEqual(symbols.length, fileNameCount * 2);
-	}));
-
-	test('Should update results when markdown file changes symbols', withStore(async (store) => {
-		const testFileName = workspacePath('test.md');
-		const workspace = store.add(new InMemoryMdWorkspace([
-			new InMemoryDocument(testFileName, `# header1`, 1 /* version */)
-		]));
-
-		assert.strictEqual((await getWorkspaceSymbols(store, workspace, '')).length, 1);
-
-		// Update file
-		workspace.updateDocument(new InMemoryDocument(testFileName, `# new header\nabc\n## header2`, 2 /* version */));
-		const newSymbols = await getWorkspaceSymbols(store, workspace, '');
-		assert.strictEqual(newSymbols.length, 2);
-		assert.strictEqual(newSymbols[0].name, '# new header');
-		assert.strictEqual(newSymbols[1].name, '## header2');
-	}));
-
-	test('Should remove results when file is deleted', withStore(async (store) => {
-		const testFileName = workspacePath('test.md');
-
-		const workspace = store.add(new InMemoryMdWorkspace([
-			new InMemoryDocument(testFileName, `# header1`)
-		]));
-
-		assert.strictEqual((await getWorkspaceSymbols(store, workspace, '')).length, 1);
-
-		// delete file
-		workspace.deleteDocument(testFileName);
-		const newSymbols = await getWorkspaceSymbols(store, workspace, '');
-		assert.strictEqual(newSymbols.length, 0);
-	}));
-
-	test('Should update results when markdown file is created', withStore(async (store) => {
-		const testFileName = workspacePath('test.md');
-
-		const workspace = store.add(new InMemoryMdWorkspace([
-			new InMemoryDocument(testFileName, `# header1`)
-		]));
-
-		assert.strictEqual((await getWorkspaceSymbols(store, workspace, '')).length, 1);
-
-		// Create file
-		workspace.createDocument(new InMemoryDocument(workspacePath('test2.md'), `# new header\nabc\n## header2`));
-		const newSymbols = await getWorkspaceSymbols(store, workspace, '');
-		assert.strictEqual(newSymbols.length, 3);
-	}));
-});
diff --git a/extensions/markdown-language-features/src/util/file.ts b/extensions/markdown-language-features/src/util/file.ts
index 6d5f22e95e0..e97ab743929 100644
--- a/extensions/markdown-language-features/src/util/file.ts
+++ b/extensions/markdown-language-features/src/util/file.ts
@@ -6,16 +6,16 @@
 import * as vscode from 'vscode';
 import * as URI from 'vscode-uri';
 
-const markdownFileExtensions = Object.freeze<string[]>([
-	'.md',
-	'.mkd',
-	'.mdwn',
-	'.mdown',
-	'.markdown',
-	'.markdn',
-	'.mdtxt',
-	'.mdtext',
-	'.workbook',
+export const markdownFileExtensions = Object.freeze<string[]>([
+	'md',
+	'mkd',
+	'mdwn',
+	'mdown',
+	'markdown',
+	'markdn',
+	'mdtxt',
+	'mdtext',
+	'workbook',
 ]);
 
 export function isMarkdownFile(document: vscode.TextDocument) {
@@ -23,5 +23,5 @@ export function isMarkdownFile(document: vscode.TextDocument) {
 }
 
 export function looksLikeMarkdownPath(resolvedHrefPath: vscode.Uri) {
-	return markdownFileExtensions.includes(URI.Utils.extname(resolvedHrefPath).toLowerCase());
+	return markdownFileExtensions.includes(URI.Utils.extname(resolvedHrefPath).toLowerCase().replace('.', ''));
 }