fix: error when processing private properties with a map

Fixes #1824

CHANGELOG.md

@@ -4,7 +4,7 @@ This changelog records changes to stable releases since 1.50.2. "TBA" changes he
 
 ## Nightly (only)
 
-Nothing, yet
+- fix: error when processing private properties with a map ([#1824](https://github.com/microsoft/vscode-js-debug/issues/1824))
 
 ## v1.83 (September 2023)
 

src/adapter/variableStore.ts

@@ -854,9 +854,9 @@ class SetOrMapVariable extends ObjectVariable {
 
   constructor(context: VariableContext, remoteObject: Cdp.Runtime.RemoteObject) {
     super(context, remoteObject, NoCustomStringRepr);
-    const cast = remoteObject.preview as MapPreview | SetPreview;
-    this.isMap = cast.subtype === 'map';
-    this.size = Number(cast.properties.find(p => p.name === 'size')?.value) ?? undefined;
+    this.isMap = remoteObject.subtype === 'map';
+    const cast = remoteObject.preview as MapPreview | SetPreview | undefined;
+    this.size = Number(cast?.properties.find(p => p.name === 'size')?.value) ?? undefined;
   }
 
   public override async toDap(previewContext: PreviewContextType): Promise<Dap.Variable> {

src/test/variables/variables-map-variable-without-preview-1824.txt

@@ -0,0 +1,3 @@
+> result: A {#bar: Map(1)}
+    > #bar: Map(1)
+    > [[Prototype]]: Object

src/test/variables/variablesTest.ts

@@ -421,6 +421,14 @@ describe('variables', () => {
     });
   });
 
+  itIntegrates('map variable without preview (#1824)', async ({ r }) => {
+    const p = await r.launchAndLoad('blank');
+    await p.logger.evaluateAndLog(`
+      class A { #bar = new Map([[1, 2]]) }
+      new A();`);
+    p.assertLog();
+  });
+
   itIntegrates('readMemory/writeMemory', async ({ r }) => {
     const p = await r.launchAndLoad('blank');
     p.cdp.Runtime.evaluate({