1 files changed, 312 insertions, 0 deletions
diff --git a/src/vs/base/common/observableImpl/logging.ts b/src/vs/base/common/observableImpl/logging.ts
new file mode 100644
index 00000000000..0c221d0c700
--- /dev/null
+++ b/src/vs/base/common/observableImpl/logging.ts
@@ -0,0 +1,312 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { AutorunObserver } from 'vs/base/common/observableImpl/autorun';
+import { IObservable, ObservableValue, TransactionImpl } from 'vs/base/common/observableImpl/base';
+import { Derived } from 'vs/base/common/observableImpl/derived';
+import { FromEventObservable } from 'vs/base/common/observableImpl/utils';
+
+let globalObservableLogger: IObservableLogger | undefined;
+
+export function setLogger(logger: IObservableLogger): void {
+	globalObservableLogger = logger;
+}
+
+export function getLogger(): IObservableLogger | undefined {
+	return globalObservableLogger;
+}
+
+interface IChangeInformation {
+	oldValue: unknown;
+	newValue: unknown;
+	change: unknown;
+	didChange: boolean;
+}
+
+export interface IObservableLogger {
+	handleObservableChanged(observable: ObservableValue<unknown, unknown>, info: IChangeInformation): void;
+	handleFromEventObservableTriggered(observable: FromEventObservable<any, any>, info: IChangeInformation): void;
+
+	handleAutorunCreated(autorun: AutorunObserver): void;
+	handleAutorunTriggered(autorun: AutorunObserver): void;
+
+	handleDerivedCreated(observable: Derived<unknown>): void;
+	handleDerivedRecomputed(observable: Derived<unknown>, info: IChangeInformation): void;
+
+	handleBeginTransaction(transaction: TransactionImpl): void;
+	handleEndTransaction(): void;
+}
+
+export class ConsoleObservableLogger implements IObservableLogger {
+	private indentation = 0;
+
+	private textToConsoleArgs(text: ConsoleText): unknown[] {
+		return consoleTextToArgs([
+			normalText(repeat('|  ', this.indentation)),
+			text,
+		]);
+	}
+
+	private formatInfo(info: IChangeInformation): ConsoleText[] {
+		return info.didChange
+			? [
+				normalText(` `),
+				styled(formatValue(info.oldValue, 70), {
+					color: 'red',
+					strikeThrough: true,
+				}),
+				normalText(` `),
+				styled(formatValue(info.newValue, 60), {
+					color: 'green',
+				}),
+			]
+			: [normalText(` (unchanged)`)];
+	}
+
+	handleObservableChanged(observable: IObservable<unknown, unknown>, info: IChangeInformation): void {
+		console.log(...this.textToConsoleArgs([
+			formatKind('observable value changed'),
+			styled(observable.debugName, { color: 'BlueViolet' }),
+			...this.formatInfo(info),
+		]));
+	}
+
+	private readonly changedObservablesSets = new WeakMap<object, Set<IObservable<any, any>>>();
+
+	formatChanges(changes: Set<IObservable<any, any>>): ConsoleText | undefined {
+		if (changes.size === 0) {
+			return undefined;
+		}
+		return styled(
+			' (changed deps: ' +
+			[...changes].map((o) => o.debugName).join(', ') +
+			')',
+			{ color: 'gray' }
+		);
+	}
+
+	handleDerivedCreated(derived: Derived<unknown>): void {
+		const existingHandleChange = derived.handleChange;
+		this.changedObservablesSets.set(derived, new Set());
+		derived.handleChange = (observable, change) => {
+			this.changedObservablesSets.get(derived)!.add(observable);
+			return existingHandleChange.apply(derived, [observable, change]);
+		};
+	}
+
+	handleDerivedRecomputed(derived: Derived<unknown>, info: IChangeInformation): void {
+		const changedObservables = this.changedObservablesSets.get(derived)!;
+		console.log(...this.textToConsoleArgs([
+			formatKind('derived recomputed'),
+			styled(derived.debugName, { color: 'BlueViolet' }),
+			...this.formatInfo(info),
+			this.formatChanges(changedObservables)
+		]));
+		changedObservables.clear();
+	}
+
+	handleFromEventObservableTriggered(observable: FromEventObservable<any, any>, info: IChangeInformation): void {
+		console.log(...this.textToConsoleArgs([
+			formatKind('observable from event triggered'),
+			styled(observable.debugName, { color: 'BlueViolet' }),
+			...this.formatInfo(info),
+		]));
+	}
+
+	handleAutorunCreated(autorun: AutorunObserver): void {
+		const existingHandleChange = autorun.handleChange;
+		this.changedObservablesSets.set(autorun, new Set());
+		autorun.handleChange = (observable, change) => {
+			this.changedObservablesSets.get(autorun)!.add(observable);
+			return existingHandleChange.apply(autorun, [observable, change]);
+		};
+	}
+
+	handleAutorunTriggered(autorun: AutorunObserver): void {
+		const changedObservables = this.changedObservablesSets.get(autorun)!;
+		console.log(...this.textToConsoleArgs([
+			formatKind('autorun'),
+			styled(autorun.debugName, { color: 'BlueViolet' }),
+			this.formatChanges(changedObservables)
+		]));
+		changedObservables.clear();
+	}
+
+	handleBeginTransaction(transaction: TransactionImpl): void {
+		let transactionName = transaction.getDebugName();
+		if (transactionName === undefined) {
+			transactionName = '';
+		}
+		console.log(...this.textToConsoleArgs([
+			formatKind('transaction'),
+			styled(transactionName, { color: 'BlueViolet' }),
+		]));
+		this.indentation++;
+	}
+
+	handleEndTransaction(): void {
+		this.indentation--;
+	}
+}
+
+type ConsoleText =
+	| (ConsoleText | undefined)[]
+	| { text: string; style: string; data?: Record<string, unknown> }
+	| { data: Record<string, unknown> };
+
+function consoleTextToArgs(text: ConsoleText): unknown[] {
+	const styles = new Array<any>();
+	const initial = {};
+	const data = initial;
+	let firstArg = '';
+
+	function process(t: ConsoleText): void {
+		if ('length' in t) {
+			for (const item of t) {
+				if (item) {
+					process(item);
+				}
+			}
+		} else if ('text' in t) {
+			firstArg += `%c${t.text}`;
+			styles.push(t.style);
+			if (t.data) {
+				Object.assign(data, t.data);
+			}
+		} else if ('data' in t) {
+			Object.assign(data, t.data);
+		}
+	}
+
+	process(text);
+
+	const result = [firstArg, ...styles];
+	if (Object.keys(data).length > 0) {
+		result.push(data);
+	}
+
+	return result;
+}
+
+function normalText(text: string): ConsoleText {
+	return styled(text, { color: 'black' });
+}
+
+function formatKind(kind: string): ConsoleText {
+	return styled(padStr(`${kind}: `, 10), { color: 'black', bold: true });
+}
+
+function styled(
+	text: string,
+	options: { color: string; strikeThrough?: boolean; bold?: boolean } = {
+		color: 'black',
+	}
+): ConsoleText {
+	function objToCss(styleObj: Record<string, string>): string {
+		return Object.entries(styleObj).reduce(
+			(styleString, [propName, propValue]) => {
+				return `${styleString}${propName}:${propValue};`;
+			},
+			''
+		);
+	}
+
+	const style: Record<string, string> = {
+		color: options.color,
+	};
+	if (options.strikeThrough) {
+		style['text-decoration'] = 'line-through';
+	}
+	if (options.bold) {
+		style['font-weight'] = 'bold';
+	}
+
+	return {
+		text,
+		style: objToCss(style),
+	};
+}
+
+function formatValue(value: unknown, availableLen: number): string {
+	switch (typeof value) {
+		case 'number':
+			return '' + value;
+		case 'string':
+			if (value.length + 2 <= availableLen) {
+				return `"${value}"`;
+			}
+			return `"${value.substr(0, availableLen - 7)}"+...`;
+
+		case 'boolean':
+			return value ? 'true' : 'false';
+		case 'undefined':
+			return 'undefined';
+		case 'object':
+			if (value === null) {
+				return 'null';
+			}
+			if (Array.isArray(value)) {
+				return formatArray(value, availableLen);
+			}
+			return formatObject(value, availableLen);
+		case 'symbol':
+			return value.toString();
+		case 'function':
+			return `[[Function${value.name ? ' ' + value.name : ''}]]`;
+		default:
+			return '' + value;
+	}
+}
+
+function formatArray(value: unknown[], availableLen: number): string {
+	let result = '[ ';
+	let first = true;
+	for (const val of value) {
+		if (!first) {
+			result += ', ';
+		}
+		if (result.length - 5 > availableLen) {
+			result += '...';
+			break;
+		}
+		first = false;
+		result += `${formatValue(val, availableLen - result.length)}`;
+	}
+	result += ' ]';
+	return result;
+}
+
+function formatObject(value: object, availableLen: number): string {
+	let result = '{ ';
+	let first = true;
+	for (const [key, val] of Object.entries(value)) {
+		if (!first) {
+			result += ', ';
+		}
+		if (result.length - 5 > availableLen) {
+			result += '...';
+			break;
+		}
+		first = false;
+		result += `${key}: ${formatValue(val, availableLen - result.length)}`;
+	}
+	result += ' }';
+	return result;
+}
+
+function repeat(str: string, count: number): string {
+	let result = '';
+	for (let i = 1; i <= count; i++) {
+		result += str;
+	}
+	return result;
+}
+
+function padStr(str: string, length: number): string {
+	while (str.length < length) {
+		str += ' ';
+	}
+	return str;
+}