Do not tree shake interfaces or classes that extend or inherit from symbols...

Do not tree shake interfaces or classes that extend or inherit from symbols defined in the default library

build/gulpfile.editor.js

@@ -127,6 +127,7 @@ const createESMSourcesAndResourcesTask = task.define('extract-editor-esm', () =>
 
 const compileEditorESMTask = task.define('compile-editor-esm', () => {
 	const KEEP_PREV_ANALYSIS = false;
+	const FAIL_ON_PURPOSE = false;
 	console.log(`Launching the TS compiler at ${path.join(__dirname, '../out-editor-esm')}...`);
 	let result;
 	if (process.platform === 'win32') {
@@ -142,7 +143,7 @@ const compileEditorESMTask = task.define('compile-editor-esm', () => {
 	console.log(result.stdout.toString());
 	console.log(result.stderr.toString());
 
-	if (result.status !== 0) {
+	if (FAIL_ON_PURPOSE || result.status !== 0) {
 		console.log(`The TS Compilation failed, preparing analysis folder...`);
 		const destPath = path.join(__dirname, '../../vscode-monaco-editor-esm-analysis');
 		const keepPrevAnalysis = (KEEP_PREV_ANALYSIS && fs.existsSync(destPath));

build/lib/treeshaking.js

@@ -420,7 +420,7 @@ function markNodes(languageService, options) {
                         // (they can be the declaration of a module import)
                         continue;
                     }
-                    if (options.shakeLevel === 2 /* ClassMembers */ && (ts.isClassDeclaration(declaration) || ts.isInterfaceDeclaration(declaration))) {
+                    if (options.shakeLevel === 2 /* ClassMembers */ && (ts.isClassDeclaration(declaration) || ts.isInterfaceDeclaration(declaration)) && !isLocalCodeExtendingOrInheritingFromDefaultLibSymbol(program, checker, declaration)) {
                         enqueue_black(declaration.name);
                         for (let j = 0; j < declaration.members.length; j++) {
                             const member = declaration.members[j];
@@ -614,6 +614,34 @@ function generateResult(languageService, shakeLevel) {
 }
 //#endregion
 //#region Utils
+function isLocalCodeExtendingOrInheritingFromDefaultLibSymbol(program, checker, declaration) {
+    if (!program.isSourceFileDefaultLibrary(declaration.getSourceFile()) && declaration.heritageClauses) {
+        for (const heritageClause of declaration.heritageClauses) {
+            for (const type of heritageClause.types) {
+                const symbol = findSymbolFromHeritageType(checker, type);
+                if (symbol) {
+                    const decl = symbol.valueDeclaration || (symbol.declarations && symbol.declarations[0]);
+                    if (decl && program.isSourceFileDefaultLibrary(decl.getSourceFile())) {
+                        return true;
+                    }
+                }
+            }
+        }
+    }
+    return false;
+}
+function findSymbolFromHeritageType(checker, type) {
+    if (ts.isExpressionWithTypeArguments(type)) {
+        return findSymbolFromHeritageType(checker, type.expression);
+    }
+    if (ts.isIdentifier(type)) {
+        return getRealNodeSymbol(checker, type)[0];
+    }
+    if (ts.isPropertyAccessExpression(type)) {
+        return findSymbolFromHeritageType(checker, type.name);
+    }
+    return null;
+}
 /**
  * Returns the node's symbol and the `import` node (if the symbol resolved from a different module)
  */

build/lib/treeshaking.ts

@@ -536,7 +536,7 @@ function markNodes(languageService: ts.LanguageService, options: ITreeShakingOpt
 						continue;
 					}
 
-					if (options.shakeLevel === ShakeLevel.ClassMembers && (ts.isClassDeclaration(declaration) || ts.isInterfaceDeclaration(declaration))) {
+					if (options.shakeLevel === ShakeLevel.ClassMembers && (ts.isClassDeclaration(declaration) || ts.isInterfaceDeclaration(declaration)) && !isLocalCodeExtendingOrInheritingFromDefaultLibSymbol(program, checker, declaration)) {
 						enqueue_black(declaration.name!);
 
 						for (let j = 0; j < declaration.members.length; j++) {
@@ -752,6 +752,36 @@ function generateResult(languageService: ts.LanguageService, shakeLevel: ShakeLe
 
 //#region Utils
 
+function isLocalCodeExtendingOrInheritingFromDefaultLibSymbol(program: ts.Program, checker: ts.TypeChecker, declaration: ts.ClassDeclaration | ts.InterfaceDeclaration): boolean {
+	if (!program.isSourceFileDefaultLibrary(declaration.getSourceFile()) && declaration.heritageClauses) {
+		for (const heritageClause of declaration.heritageClauses) {
+			for (const type of heritageClause.types) {
+				const symbol = findSymbolFromHeritageType(checker, type);
+				if (symbol) {
+					const decl = symbol.valueDeclaration || (symbol.declarations && symbol.declarations[0]);
+					if (decl && program.isSourceFileDefaultLibrary(decl.getSourceFile())) {
+						return true;
+					}
+				}
+			}
+		}
+	}
+	return false;
+}
+
+function findSymbolFromHeritageType(checker: ts.TypeChecker, type: ts.ExpressionWithTypeArguments | ts.Expression | ts.PrivateIdentifier): ts.Symbol | null {
+	if (ts.isExpressionWithTypeArguments(type)) {
+		return findSymbolFromHeritageType(checker, type.expression);
+	}
+	if (ts.isIdentifier(type)) {
+		return getRealNodeSymbol(checker, type)[0];
+	}
+	if (ts.isPropertyAccessExpression(type)) {
+		return findSymbolFromHeritageType(checker, type.name);
+	}
+	return null;
+}
+
 /**
  * Returns the node's symbol and the `import` node (if the symbol resolved from a different module)
  */