fix: address code review — existence check, comment fix, better diagnostics

- Add `existsSync` check before copying `node_python_bridge.py` with
  a clear error message if the file is missing from the dependency
- Fix misleading comment that said "no fallback needed" while fallback
  code existed — now accurately describes the `__require` fallback
- Log the nearest `__dirname` match on pattern mismatch to aid debugging

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: anandgupta42

packages/dbt-tools/script/copy-python.ts

@@ -1,4 +1,4 @@
-import { cpSync, readFileSync, writeFileSync } from "fs"
+import { cpSync, existsSync, readFileSync, writeFileSync } from "fs"
 import { dirname, join } from "path"
 
 const dist = join(import.meta.dir, "..", "dist")
@@ -12,6 +12,11 @@ console.log(`Copied altimate_python_packages → dist/`)
 // 2. Copy node_python_bridge.py into dist so it lives next to index.js
 // node_python_bridge.py is shipped in dbt-integration's dist
 const bridgePy = join(dirname(resolved), "node_python_bridge.py")
+if (!existsSync(bridgePy)) {
+  console.error(`ERROR: node_python_bridge.py not found at ${bridgePy}`)
+  console.error(`  Is @altimateai/dbt-integration up to date?`)
+  process.exit(1)
+}
 cpSync(bridgePy, join(dist, "node_python_bridge.py"))
 console.log(`Copied node_python_bridge.py → dist/`)
 
@@ -23,12 +28,15 @@ let code = readFileSync(indexPath, "utf8")
 const pattern = /var __dirname\s*=\s*"[^"]*python-bridge[^"]*"/
 if (pattern.test(code)) {
   // import.meta.dirname is supported by Bun and Node >= 20.11.0.
-  // Node 18 is EOL (April 2025), so no fallback needed.
+  // Fallback via __require handles older runtimes where import.meta.dirname is unavailable.
   const replacement = `var __dirname = typeof import.meta.dirname === "string" ? import.meta.dirname : __require("path").dirname(__require("url").fileURLToPath(import.meta.url))`
   code = code.replace(pattern, replacement)
   writeFileSync(indexPath, code)
   console.log(`Patched __dirname in dist/index.js`)
 } else {
+  const found = code.match(/var __dirname[^;]*/)?.[0] ?? "(not found)"
   console.error(`ERROR: could not find python-bridge __dirname to patch — the bundle format may have changed`)
+  console.error(`  Pattern: ${pattern}`)
+  console.error(`  Nearest match: ${found}`)
   process.exit(1)
 }