to_build_set conflates "nothing to build" with "parse failure" → warm cache reported as cold #5

New Issue

2026-07-08T16:13:29+03:00

issuer-agent commented

2026-07-08 16:13:29 +03:00

In nix_estimator/graph.py:95, return built or None makes an empty parse result (fully warm cache: dry-run prints only "will be fetched") indistinguishable from an unparseable dry-run. Callers treat None as "assume cold cache" and cost the ENTIRE closure — so the best case (nothing to build) is reported as the worst case. The est.to_build == 0 branch in cli.py:27 is dead code.

Implementation:

Change the return contract to a tri-state — return set() when parsing succeeded but nothing will be built (detect that the dry-run exited 0 and/or a "will be fetched"/"will be built" header was seen), and None only when no recognizable dry-run output was found.
Update build_dag/cli.py accordingly.
Add a unit test with captured dry-run outputs (warm, partial, garbage).

In `nix_estimator/graph.py:95`, `return built or None` makes an empty parse result (fully warm cache: dry-run prints only "will be fetched") indistinguishable from an unparseable dry-run. Callers treat `None` as "assume cold cache" and cost the ENTIRE closure — so the best case (nothing to build) is reported as the worst case. The `est.to_build == 0` branch in `cli.py:27` is dead code. **Implementation**: - Change the return contract to a tri-state — return `set()` when parsing succeeded but nothing will be built (detect that the dry-run exited 0 and/or a "will be fetched"/"will be built" header was seen), and `None` only when no recognizable dry-run output was found. - Update `build_dag`/`cli.py` accordingly. - Add a unit test with captured dry-run outputs (warm, partial, garbage).

oleks referenced this issue from a commit

2026-07-08 16:30:51 +03:00

graph: tri-state to_build_set — empty means nothing to build (#5)

oleks referenced this issue from a commit

2026-07-08 16:30:52 +03:00

graph: prefer nix build --dry-run --json, fall back to text scraper (#8)

oleks commented

2026-07-08 17:48:19 +03:00

Fixed and merged to main (commit 837b885).

Fixed and merged to main (commit 837b885).

oleks closed this issue

2026-07-08 17:50:07 +03:00