added the workspace symbol provider for markdown #46406 (#47610)

* added the workspace symbol provider for markdown 46406

* fixed the review comments 46406

extensions/markdown-language-features/src/features/workspaceSymbolProvider.ts

@@ -0,0 +1,61 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { workspace, WorkspaceSymbolProvider, SymbolInformation, TextDocument, Disposable } from 'vscode';
+import { isMarkdownFile } from '../util/file';
+import MDDocumentSymbolProvider from './documentSymbolProvider';
+import { Dictionary, flatMap } from 'lodash';
+
+export default class MarkdownWorkspaceSymbolProvider implements WorkspaceSymbolProvider {
+	private symbolProvider: MDDocumentSymbolProvider;
+	private symbolCache: Dictionary<SymbolInformation[]> = {};
+	private symbolCachePopulated: boolean;
+	private deRegisterOnSaveEvent: Disposable;
+
+	public constructor(symbolProvider: MDDocumentSymbolProvider) {
+		this.symbolProvider = symbolProvider;
+		this.symbolCachePopulated = false;
+		this.deRegisterOnSaveEvent = this.registerOnSaveEvent();
+	}
+
+	public async provideWorkspaceSymbols(query: string): Promise<SymbolInformation[]> {
+		if (!this.symbolCachePopulated) {
+			await this.populateSymbolCache();
+			this.symbolCachePopulated = true;
+		}
+
+		return flatMap(this.symbolCache)
+			.filter(symbolInformation => symbolInformation.name.toLowerCase().indexOf(query.toLowerCase()) !== -1);
+	}
+
+	public async populateSymbolCache(): Promise<void> {
+		const markDownDocumentUris = await workspace.findFiles('**/*.md');
+		for (const uri of markDownDocumentUris) {
+			const document = await workspace.openTextDocument(uri);
+			if (isMarkdownFile(document)) {
+				const symbols = await this.getSymbol(document);
+				this.symbolCache[document.fileName] = symbols;
+			}
+		}
+	}
+
+	public dispose(): void {
+		this.deRegisterOnSaveEvent.dispose();
+	}
+
+	private async getSymbol(document: TextDocument): Promise<SymbolInformation[]> {
+		return this.symbolProvider.provideDocumentSymbols(document);
+	}
+
+	private registerOnSaveEvent(): Disposable {
+		return workspace.onDidSaveTextDocument(async document => {
+			if (isMarkdownFile(document)) {
+				const symbols = await this.getSymbol(document);
+				this.symbolCache[document.fileName] = symbols;
+			}
+		});
+	}
+
+}