fix(extraction): warn when parse errors leave no symbols (#1522) (#1799)

Co-authored-by: Colby McHenry <colbymchenry@users.noreply.github.com>

__tests__/cpp-raw-string-delimiter-haserror.test.ts

@@ -0,0 +1,77 @@
+import { beforeAll, describe, expect, it } from 'vitest';
+import { extractFromSource } from '../src/extraction';
+import { getParser, initGrammars, loadGrammarsForLanguages } from '../src/extraction/grammars';
+
+function rawStringSource(delimiter: string): string {
+  return `const char* kTemplate = R"${delimiter}(
+struct Ignored { int v; };
+)${delimiter}";
+
+int after_the_raw_string(int x) {
+  return x + 1;
+}
+`;
+}
+
+describe('C++ raw-string delimiter parse collapse (#1522)', () => {
+  beforeAll(async () => {
+    await initGrammars();
+    await loadGrammarsForLanguages(['cpp', 'c']);
+  });
+
+  it('warns when a legal 16-character delimiter swallows every symbol', () => {
+    const result = extractFromSource('min.cpp', rawStringSource('FILE_TEMPLATE_V1'));
+
+    // The vendored tree-sitter-cpp scanner currently rejects the standard's
+    // maximum delimiter length, consuming the following function as ERROR.
+    expect(result.nodes.filter((n) => n.kind === 'function')).toEqual([]);
+    expect(result.nodes.map((n) => n.kind)).toEqual(['file']);
+    expect(result.errors).toEqual([
+      {
+        message:
+          'min.cpp: parse produced no symbols (tree has errors) — ' +
+          'the file is indexed but contributes nothing to the graph',
+        severity: 'warning',
+        code: 'parse_error',
+      },
+    ]);
+  });
+
+  it('extracts the function after a 15-character delimiter without warning', () => {
+    const result = extractFromSource('min.cpp', rawStringSource('FILE_TEMPLATE_V'));
+
+    expect(result.nodes.filter((n) => n.kind === 'function').map((n) => n.name))
+      .toEqual(['after_the_raw_string']);
+    expect(result.errors).toEqual([]);
+  });
+
+  it.each(['min.cpp', 'min.c', 'min.h'])('does not warn on a healthy include-only %s', (filePath) => {
+    const result = extractFromSource(filePath, '#include <stdio.h>\n#include <stdlib.h>\n');
+
+    expect(result.nodes.filter((n) => n.kind !== 'file' && n.kind !== 'import')).toEqual([]);
+    expect(result.errors).toEqual([]);
+  });
+
+  it('does not warn on a healthy empty file with zero symbols', () => {
+    const result = extractFromSource('empty.cpp', '');
+
+    expect(result.nodes.map((n) => n.kind)).toEqual(['file']);
+    expect(result.errors).toEqual([]);
+  });
+
+  it('does not warn on parse errors when a function survives', () => {
+    const source = 'int before_the_raw_string() { return 0; }\n' + rawStringSource('FILE_TEMPLATE_V1');
+    const tree = getParser('cpp')!.parse(source)!;
+    try {
+      expect(tree.rootNode.hasError).toBe(true);
+    } finally {
+      tree.delete();
+    }
+
+    const result = extractFromSource('min.cpp', source);
+
+    expect(result.nodes.filter((n) => n.kind === 'function').map((n) => n.name))
+      .toEqual(['before_the_raw_string']);
+    expect(result.errors).toEqual([]);
+  });
+});