fix(tool-server): fall back to raw locations when inspect-element symbolication fails

[latekvo]

Problem

debugger-inspect-element, called with the default resolveSourceMaps: true, returned source: null and code: null for every item whenever Metro symbolication did not yield a usable original location. This made the tool effectively useless in its default mode — the caller got a list of component names with no file:line and no code fragment to edit.

Root cause

Two independent issues compounded:

1. No raw fallback in the tool. In debugger-inspect-element.ts, the resolveSourceMaps branch only assigned source/code when symbolicate() returned a result. When it returned null (symbolication failed, or was filtered out — see below), the item was left with source: null / code: null, discarding the raw bundled frame the tool already had in item.frame.

2. Over-broad node_modules rejection in the resolver. In source-resolver.ts, symbolicateFrame did if (frame.file.includes("node_modules")) return null;. That was meant to drop frames that symbolication couldn't map (where Metro echoes the bundle URL back). But it also threw away genuinely-mapped sources whose real path legitimately lives in node_modules — e.g. expo-router / react-navigation route components — turning a perfectly good resolved location into null, which then hit issue (1) and nulled the whole item.

Fix

Two minimal, localized changes:

• debugger-inspect-element.ts — add an else to the resolveSourceMaps branch that falls back to the raw bundled frame { file: item.frame.file, line: item.frame.line, column: item.frame.col }, mirroring the exact shape produced by the resolveSourceMaps: false branch. When symbolication can't map a frame, the caller now still gets the bundled location instead of null.

• source-resolver.ts (line ~93) — replace the includes("node_modules") guard with if (/^https?:\/\//.test(frame.file)) return null;. A successful symbolication yields a real file path (kept, including legitimate node_modules route components); a failed one yields the original http(s) bundle URL echoed back (rejected). This keeps the diff to a single line + comment at line ~93 to stay easy to reconcile.

Testing

cd packages/tool-server && vitest run test/metro/source-resolver.test.ts test/debugger/inspect-element-filter.test.ts

Added fail-before / pass-after coverage at two layers:

• Resolver level (test/metro/source-resolver.test.ts): mocks fetch for /symbolicate and asserts that

  • a frame mapping to a node_modules/.../*.js path is kept (returned that mapped, project-relative location),
  • an echoed-back http(s) bundle URL is rejected (null),
  • a real app-source path is mapped relative to the project root,
  • a thrown request returns null.

• Tool level (test/debugger/inspect-element-filter.test.ts): drives debuggerInspectElementTool.execute() with a fake JsRuntimeDebuggerApi (no live CDP) and asserts that when symbolicate() returns null, the item retains the raw { file, line, column } (and reads no source fragment); when it returns a mapped location, that location and its code fragment are used.

Verified the fail-before / pass-after cycle by checking out origin/main for the two source files only (keeping the new tests): the 3 new assertions fail on origin/main (source is null for the raw-fallback case; the node_modules-mapped source is null; the echoed bundle URL is wrongly accepted), then pass once the fixes are restored. All 34 tests pass with the fix; the 31 pre-existing tests are unaffected.

tsc --noEmit -p tsconfig.test.json reports no errors in any changed file (the only errors are pre-existing module-resolution artifacts from the symlinked node_modules: pngjs, @argent/native-devtools-android, @argent/update-core).

Known limitation / follow-up

User-defined and route component frames that lack _debugStack under React 19 (where _debugSource was removed) are still null even in raw mode, because there is no bundled frame to fall back to in the first place. That is a separate, riskier change (it requires a different source for the frame entirely) and is intentionally out of scope here.

Note for reconcilers

There are other open branches touching source-resolver.ts (fix/source-resolver-traversal, fix/source-map-ssrf). This change is deliberately confined to the single guard at line ~93 (plus an explanatory comment) to keep it trivially mergeable alongside them.