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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Build silently produces broken firmware when submodules aren't initialised (dangling symlinks)","articleBody":"## Summary\n\n`internal_filesystem/lib/nostr` is a symlink to `../../micropython-nostr/nostr/`. If the `micropython-nostr` submodule hasn't been populated (i.e. the user cloned MPOS without `--recurse-submodules` and didn't run `git submodule update --init --recursive` after), the symlink dangles, and the manifest's `freeze('../internal_filesystem/lib', '')` step **silently skips it** — no error, no warning. The build succeeds and produces a firmware that's missing the `nostr` module.\n\nAny app that depends on `nostr` (e.g. Lightning Piggy's `nwc_wallet.py`) then fails at runtime with `ImportError: no module named 'nostr'` when launched. From the user's perspective the app just doesn't open — no obvious clue from the build log.\n\nThis bit me while testing an unrelated firmware change; LP wouldn't launch after a fresh build and it took a serial-REPL session to surface the actual cause.\n\n## Reproduction\n\n```bash\ngit clone https://github.com/MicroPythonOS/MicroPythonOS.git\ncd MicroPythonOS\ngit submodule update --init lvgl_micropython  # but not micropython-nostr\n./scripts/build_mpos.sh esp32s3\n# Build succeeds. Flash the firmware. Try to launch Lightning Piggy. ImportError.\n```\n\nConfirm by inspecting `frozen_content.c`:\n\n```bash\ngrep -c nostr lvgl_micropython/lib/micropython/ports/esp32/build-*/frozen_content.c\n# 0 — the freezer silently dropped the dangling symlink\n```\n\nThe same trap potentially applies to any other symlink under `internal_filesystem/lib/` that points into an un-init'd submodule. Today only `nostr` is structured this way (`find internal_filesystem/lib -maxdepth 2 -type l` is just the one entry), but the failure mode is generic.\n\n## Suggested fix\n\nTwo complementary safety-nets, take either or both:\n\n1. **`build_mpos.sh` pre-flight check** — before invoking `make.py`, walk `internal_filesystem/lib/` for symlinks and verify each one resolves. Abort with a clear error like:\n   ```\n   ERROR: internal_filesystem/lib/nostr -\u003e ../../micropython-nostr/nostr/\n          target does not exist. Run:\n              git submodule update --init --recursive\n          and try again.\n   ```\n2. **Eager submodule init at the top of `build_mpos.sh`** — `git submodule update --init` for the MPOS-side siblings that are known build inputs (`micropython-nostr`, `secp256k1-embedded-ecdh`, `c_mpos`, `micropython-camera-API`). Cheap on subsequent builds (no-op if already populated), bulletproof on fresh clones.\n\nHappy to send a PR for either approach if there's a preference.","author":{"url":"https://github.com/bitcoin3us","@type":"Person","name":"bitcoin3us"},"datePublished":"2026-05-30T20:38:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/149/MicroPythonOS/issues/149"}