Incremental compilation

Parallel dependency-discovery pre-pass (preNifle)

Type feature · Status Shipped · Measured discovery wall 0.43s → 0.24s (1.77×) · ← ledger

Symptom

Cold module dependency discovery was serial: traverseDeps’ DFS ran nifler one module at a time via a blocking exec before recursing into it.

The change

A breadth-first pre-pass, preNifle, runs nifler over the whole import closure in parallel (osproc.execProcesses) before the DFS starts. It only writes the on-disk .p.nif / .p.deps.nif cache files the DFS would have written anyway and mutates nothing on the node graph. After pre-warming, every execNifler inside the DFS hits the staleness short-circuit and becomes a no-op, so the DFS does only cheap in-memory work.

Correctness is preserved by construction: if the harvest ever misses a module, the DFS’s own execNifler runs it as a self-healing serial fallback. Over-nifling (ignoring when pruning, plugin/include deps) is harmless — it only warms an unused cache entry.

Files touched: nimony/deps.nim (niflerCommandFor extracted from execNifler; preNifle wired into initDepContext).

Verification

Discovery-phase wall time 0.43s → 0.24s median (1.77×) on the measured tree. Full build output byte-identical to the serial path.