perf(pm): read each config file once per command via an mtime-validated cache

[jdalton]

The pm_engine re-read and re-parsed the same config files several times per command — root package.json (3x via aube's parser, 3x via serde), .yarnrc.yml (once per key), and the .npmrc ancestor chain (re-walked per key). This caches each per-invocation so every file is read once.

A per-process cache in nub-core (config_cache::MtimeCache), path-keyed and validated on a (mtime, size) stamp. The serde package.json, the aube-parsed manifest, and the yarnrc/npmrc/bunfig readers route through it.

Output-preserving with no stale read: every lookup re-stats the file and serves the cached value only when the stamp is unchanged, so a mid-command rewrite re-reads; a missing/unparseable file is never cached, matching the prior .ok() paths exactly.

Verified: reads of each existing config file drop 3x to 1x on an install fixture; cached vs uncached install/list/why/outdated give byte-identical stdout, stderr, and exit codes. New config_cache unit tests cover hit, mtime invalidation, size invalidation, and not-cached-on-missing. clippy --all-targets --all-features -D warnings, fmt --check, and test -p nub-cli -p nub-core pass.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
nub	Ready	Preview, Comment	Jun 25, 2026 4:04pm

[pullfrog]

✅ No new issues found.

Reviewed changes — a per-process, mtime+size-validated config-read cache that collapses the PM engine's repeated per-command reads/parses of the same config files to a single read each.

• Add MtimeCache<V> primitive — new crates/nub-core/src/config_cache.rs: a path-keyed OnceLock<RwLock<HashMap<…, Entry<V>>>> storing Arc<V>, validated on a (mtime, size) Stamp re-read on every lookup; a None read (missing/unparseable) is never cached, and the value is re-stamped after the read.
• Route the aube manifest parses through a cache — AUBE_MANIFEST_CACHE + cached_aube_manifest() in pm_engine/mod.rs, used by apply_config_scope, first_catalog_specifier, manifest_has_injected, and manifest_has_pnpm_overrides.
• Route the unsupported-config readers through a cache — CONFIG_TEXT_CACHE + read_config_text() in unsupported_config.rs for the .npmrc/.yarnrc.yml/.yarnrc/bunfig readers (is_ok_and → is_some_and on the classic-yarnrc path).
• Cache the root manifest in pin resolution — ROOT_MANIFEST_CACHE in pm/resolve.rs; root_manifest now returns Option<Arc<serde_json::Value>>, resolves the manifest path before keying the cache, and reuses the already-parsed project.manifest on the no-distinct-workspace-root miss path.

The no-stale-read property is structural — every lookup re-stats and serves the cached value only when the (mtime, size) stamp is unchanged, and the only manifest mutator (write_declared_pm) runs after all config reads. The cache key/content correspondence in root_manifest is sound: detect_project parses root/package.json into project.manifest, and the reuse happens only on the arm where the cache key is exactly that path. The shared statics are test-safe because the unit tests use unique per-test temp dirs, and the config reads run single-threaded before the install fan-out. Unit tests cover hit, mtime invalidation, size invalidation, and not-cached-on-missing.

  ^{｜ View workflow run ｜ Using Claude Opus ｜ 𝕏}

[colinhacks]

Shipped in v0.2.1: https://github.com/nubjs/nub/releases/tag/v0.2.1