don't update markers when there is no real change, #57875

src/vs/base/common/arrays.ts

@@ -27,6 +27,14 @@ export function tail2<T>(arr: T[]): [T[], T] {
 }
 
 export function equals<T>(one: ReadonlyArray<T>, other: ReadonlyArray<T>, itemEquals: (a: T, b: T) => boolean = (a, b) => a === b): boolean {
+	if (one === other) {
+		return true;
+	}
+
+	if (!one || !other) {
+		return false;
+	}
+
 	if (one.length !== other.length) {
 		return false;
 	}

src/vs/workbench/api/node/extHostDiagnostics.ts

@@ -9,9 +9,9 @@ import { IMarkerData, MarkerSeverity } from 'vs/platform/markers/common/markers'
 import { URI } from 'vs/base/common/uri';
 import * as vscode from 'vscode';
 import { MainContext, MainThreadDiagnosticsShape, ExtHostDiagnosticsShape, IMainContext } from './extHost.protocol';
-import { DiagnosticSeverity } from './extHostTypes';
+import { DiagnosticSeverity, Diagnostic } from './extHostTypes';
 import * as converter from './extHostTypeConverters';
-import { mergeSort } from 'vs/base/common/arrays';
+import { mergeSort, equals } from 'vs/base/common/arrays';
 import { Event, Emitter, debounceEvent, mapEvent } from 'vs/base/common/event';
 import { keys } from 'vs/base/common/map';
 
@@ -62,9 +62,13 @@ export class DiagnosticCollection implements vscode.DiagnosticCollection {
 
 		this._checkDisposed();
 		let toSync: vscode.Uri[];
+		let hasChanged = true;
 
 		if (first instanceof URI) {
 
+			// check if this has actually changed
+			hasChanged = hasChanged && !equals(diagnostics, this.get(first), Diagnostic.isEqual);
+
 			if (!diagnostics) {
 				// remove this entry
 				this.delete(first);
@@ -103,6 +107,17 @@ export class DiagnosticCollection implements vscode.DiagnosticCollection {
 			}
 		}
 
+		// send event for extensions
+		this._onDidChangeDiagnostics.fire(toSync);
+
+		// if nothing has changed then there is nothing else to do
+		// we have updated the diagnostics but we don't send a message
+		// to the renderer. tho we have still send an event for other
+		// extensions because the diagnostic might carry more information
+		// than known to us
+		if (!hasChanged) {
+			return;
+		}
 		// compute change and send to main side
 		const entries: [URI, IMarkerData[]][] = [];
 		for (let uri of toSync) {
@@ -142,7 +157,6 @@ export class DiagnosticCollection implements vscode.DiagnosticCollection {
 			entries.push([uri, marker]);
 		}
 
-		this._onDidChangeDiagnostics.fire(toSync);
 		this._proxy.$changeMany(this._owner, entries);
 	}
 

src/vs/workbench/api/node/extHostTypes.ts

@@ -14,7 +14,7 @@ import { IRelativePattern } from 'vs/base/common/glob';
 import { relative } from 'path';
 import { startsWith } from 'vs/base/common/strings';
 import { values } from 'vs/base/common/map';
-import { coalesce } from 'vs/base/common/arrays';
+import { coalesce, equals } from 'vs/base/common/arrays';
 
 export class Disposable {
 
@@ -771,6 +771,18 @@ export class DiagnosticRelatedInformation {
 		this.location = location;
 		this.message = message;
 	}
+
+	static isEqual(a: DiagnosticRelatedInformation, b: DiagnosticRelatedInformation): boolean {
+		if (a === b) {
+			return true;
+		}
+		if (!a || !b) {
+			return false;
+		}
+		return a.message === b.message
+			&& a.location.range.isEqual(b.location.range)
+			&& a.location.uri.toString() === b.location.uri.toString();
+	}
 }
 
 export class Diagnostic {
@@ -798,6 +810,23 @@ export class Diagnostic {
 			code: this.code,
 		};
 	}
+
+	static isEqual(a: Diagnostic, b: Diagnostic): boolean {
+		if (a === b) {
+			return true;
+		}
+		if (!a || !b) {
+			return false;
+		}
+		return a.message === b.message
+			&& a.severity === b.severity
+			&& a.code === b.code
+			&& a.severity === b.severity
+			&& a.source === b.source
+			&& a.range.isEqual(b.range)
+			&& equals(a.tags, b.tags)
+			&& equals(a.relatedInformation, b.relatedInformation, DiagnosticRelatedInformation.isEqual);
+	}
 }
 
 export class Hover {

src/vs/workbench/test/electron-browser/api/extHostDiagnostics.test.ts

@@ -190,6 +190,31 @@ suite('ExtHostDiagnostics', () => {
 		lastEntries = undefined;
 	});
 
+	test('don\'t send message when not making a change', function () {
+
+		let changeCount = 0;
+		let eventCount = 0;
+
+		const emitter = new Emitter<any>();
+		emitter.event(_ => eventCount += 1);
+		const collection = new DiagnosticCollection('test', 'test', 100, new class extends DiagnosticsShape {
+			$changeMany() {
+				changeCount += 1;
+			}
+		}, emitter);
+
+		let uri = URI.parse('sc:hightower');
+		let diag = new Diagnostic(new Range(0, 0, 0, 1), 'ffff');
+
+		collection.set(uri, [diag]);
+		assert.equal(changeCount, 1);
+		assert.equal(eventCount, 1);
+
+		collection.set(uri, [diag]);
+		assert.equal(changeCount, 1);
+		assert.equal(eventCount, 2);
+	});
+
 	test('diagnostics collection, tuples and undefined (small array), #15585', function () {
 
 		const collection = new DiagnosticCollection('test', 'test', 100, new DiagnosticsShape(), new Emitter());