Merge commit 'be3e8236086165e5e45a5a10783823874b3f3ebd' as 'lib/vscode'

lib/vscode/extensions/markdown-language-features/src/features/foldingProvider.ts

@@ -0,0 +1,106 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Token } from 'markdown-it';
+import * as vscode from 'vscode';
+import { MarkdownEngine } from '../markdownEngine';
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+import { flatten } from '../util/arrays';
+
+const rangeLimit = 5000;
+
+export default class MarkdownFoldingProvider implements vscode.FoldingRangeProvider {
+
+	constructor(
+		private readonly engine: MarkdownEngine
+	) { }
+
+	public async provideFoldingRanges(
+		document: vscode.TextDocument,
+		_: vscode.FoldingContext,
+		_token: vscode.CancellationToken
+	): Promise<vscode.FoldingRange[]> {
+		const foldables = await Promise.all([
+			this.getRegions(document),
+			this.getHeaderFoldingRanges(document),
+			this.getBlockFoldingRanges(document)
+		]);
+		return flatten(foldables).slice(0, rangeLimit);
+	}
+
+	private async getRegions(document: vscode.TextDocument): Promise<vscode.FoldingRange[]> {
+		const tokens = await this.engine.parse(document);
+		const regionMarkers = tokens.filter(isRegionMarker)
+			.map(token => ({ line: token.map[0], isStart: isStartRegion(token.content) }));
+
+		const nestingStack: { line: number, isStart: boolean }[] = [];
+		return regionMarkers
+			.map(marker => {
+				if (marker.isStart) {
+					nestingStack.push(marker);
+				} else if (nestingStack.length && nestingStack[nestingStack.length - 1].isStart) {
+					return new vscode.FoldingRange(nestingStack.pop()!.line, marker.line, vscode.FoldingRangeKind.Region);
+				} else {
+					// noop: invalid nesting (i.e. [end, start] or [start, end, end])
+				}
+				return null;
+			})
+			.filter((region: vscode.FoldingRange | null): region is vscode.FoldingRange => !!region);
+	}
+
+	private async getHeaderFoldingRanges(document: vscode.TextDocument) {
+		const tocProvider = new TableOfContentsProvider(this.engine, document);
+		const toc = await tocProvider.getToc();
+		return toc.map(entry => {
+			let endLine = entry.location.range.end.line;
+			if (document.lineAt(endLine).isEmptyOrWhitespace && endLine >= entry.line + 1) {
+				endLine = endLine - 1;
+			}
+			return new vscode.FoldingRange(entry.line, endLine);
+		});
+	}
+
+	private async getBlockFoldingRanges(document: vscode.TextDocument): Promise<vscode.FoldingRange[]> {
+		const tokens = await this.engine.parse(document);
+		const multiLineListItems = tokens.filter(isFoldableToken);
+		return multiLineListItems.map(listItem => {
+			const start = listItem.map[0];
+			let end = listItem.map[1] - 1;
+			if (document.lineAt(end).isEmptyOrWhitespace && end >= start + 1) {
+				end = end - 1;
+			}
+			return new vscode.FoldingRange(start, end, this.getFoldingRangeKind(listItem));
+		});
+	}
+
+	private getFoldingRangeKind(listItem: Token): vscode.FoldingRangeKind | undefined {
+		return listItem.type === 'html_block' && listItem.content.startsWith('<!--')
+			? vscode.FoldingRangeKind.Comment
+			: undefined;
+	}
+}
+
+const isStartRegion = (t: string) => /^\s*<!--\s*#?region\b.*-->/.test(t);
+const isEndRegion = (t: string) => /^\s*<!--\s*#?endregion\b.*-->/.test(t);
+
+const isRegionMarker = (token: Token) =>
+	token.type === 'html_block' && (isStartRegion(token.content) || isEndRegion(token.content));
+
+const isFoldableToken = (token: Token): boolean => {
+	switch (token.type) {
+		case 'fence':
+		case 'list_item_open':
+			return token.map[1] > token.map[0];
+
+		case 'html_block':
+			if (isRegionMarker(token)) {
+				return false;
+			}
+			return token.map[1] > token.map[0] + 1;
+
+		default:
+			return false;
+	}
+};