Fix ESM resolver fallback for pnpm symlinked dependencies

[infiton]

Fix ESM resolver fallback for pnpm symlinked dependencies

Problem

When using wds with ESM mode (esm: true) in pnpm workspaces, module resolution fails for symlinked peer dependencies. For example, trying to import graphql from within graphql-ws results in:

Error: Cannot find module 'graphql': graphql cannot be resolved in file:///Users/.../node_modules/.pnpm/graphql-ws@5.16.2_graphql@16.8.1/node_modules/graphql-ws/lib/server.mjs

Workaround: Setting esm: false resolves the issue because the CJS hook uses Node's native require() resolution which handles pnpm symlinks correctly.

Root Cause

The bug was in child-process-esm-loader.ts (lines 80-83). When oxc-resolver failed to resolve a module, it immediately threw an error instead of falling back to Node's built-in resolver:

if (resolved.error) {
  debugLog?.("esm custom resolver error", { specifier, parentURL, resolved, error: resolved.error });
  throw new Error(`${resolved.error}: ${specifier} cannot be resolved in ${context.parentURL}`);
}

This prevented the existing fallback logic (lines 103-129) from ever running.

Solution

Restructured the resolution logic to gracefully handle oxc-resolver failures:

1. ✅ Try oxc-resolver first (for TypeScript extension aliasing)
2. ✅ If oxc-resolver fails, log and continue to Node's native resolver (which handles pnpm symlinks)
3. ✅ If Node's resolver fails, try CommonJS require as last resort