Chart builder: drop unparseable expressions mid-edit, polite glyphed inline feedback

src/core/chart-builder.test.ts

@@ -974,6 +974,29 @@ describe('buildTransforms (predicate coercion + shape)', () => {
     };
     expect(buildTransforms(config)).toEqual([]);
   });
+
+  it('drops a syntactically-invalid expression filter (mid-edit preview resilience)', () => {
+    const t = buildTransforms(
+      withFilters(
+        filter({ mode: 'expression', expr: 'datum.value *' }), // half-typed → unparseable
+        filter({ id: 'f2', mode: 'expression', expr: 'datum.value > 0' }), // valid stays
+      ),
+    );
+    expect(t).toEqual([{ filter: 'datum.value > 0' }]);
+  });
+
+  it('drops a calculated field whose expression does not parse', () => {
+    const config: BuilderConfig = {
+      datasetName: 'D',
+      mark: 'bar',
+      encodings: {},
+      calculates: [
+        calc({ as: 'bad', expr: 'datum.a +' }),
+        calc({ id: 'c2', as: 'ok', expr: 'datum.a' }),
+      ],
+    };
+    expect(buildTransforms(config)).toEqual([{ calculate: 'datum.a', as: 'ok' }]);
+  });
 });
 
 describe('buildChartSpec — transform integration', () => {