jsperf evidence policy

GateCopy Anchor Link

A JP rule may be documented / treated as error only if both exist under packages/jsperf/evidence/:

1. <RULE>.md — claim, harness, Node/V8 versions, limits
2. <RULE>.jsonl — ≥1 before/after measurement pair with fields rule, case, node, v8, median_ms, ops, ratio, ts (optional role: before = smell, after = fix)

Otherwise the rule is hint (review prompt): fine for dogfood and fixtures, not a “must fix for speed” signal.

Evidence alone is necessary, not sufficient for error. Escalate only when wall-clock agrees and the failure mode matches the rule’s keep contract (shape / holey / hot delete). Alloc/GC or env-dependent I/O smells may keep hint / off even with JSONL.

Current mapCopy Anchor Link

As of 2026-10-23. "Default" is the app preset; --preset all raises every rule to error.

| jp-string-plus-in-loop | removed | tombstone | push + join was not ~2× on the matched shapes; matcher deleted | | jp-map-filter-chain | hint | jp-map-filter-chain.md · jsonl | 35000 rows about 4.6× / 9.8×; a 3-row filter+map is 1.28×; stay hint | | jp-regex-ctor-hot | hint | measured (jp-regex-ctor-hot.md + jp-regex-ctor-hot.jsonl); stay hint | new RegExp (stable pattern); not corpus-triaged | | jp-json-hot | hint | measured (jp-json-hot.md + jp-json-hot.jsonl); stay hint | JSON.parse / stringify (stable text); not corpus-triaged | | jp-dom-query-hot | hint | measured (jp-dom-query-hot.md + jp-dom-query-hot.jsonl); stay hint | DOM query (stable selector); about 16× on Node 26, a tiny linkedom document | | jp-intl-datetimeformat-hot | hint | measured (jp-intl-datetimeformat-hot.md + jp-intl-datetimeformat-hot.jsonl); stay hint | new Intl.DateTimeFormat; Node 26 about 36×; not corpus-triaged | | jp-readfile-sync-hot | hint | measured (jp-readfile-sync-hot.md + jp-readfile-sync-hot.jsonl); stay hint | readFileSync (stable path); not corpus-triaged | | jp-clock-hot | hint | measured (jp-clock-hot.md + jp-clock-hot.jsonl); stay hint | Date.now / performance.now; not corpus-triaged |

Hint text states the measured premise (unchanged path, text, pattern, selector, or formatter; a tight loop with no await for the clock). A rule with no JSONL does not name a replacement. A call that only looks like the bench is not given the bench's rewrite. This policy is the keep / escalate contract for guides and --preset.

RegeneratingCopy Anchor Link

cd packages/jsperf
bash scripts/regen-evidence.sh
# or:
# node examples/bench/evidence_jp003_jp004.js
# node examples/bench/evidence_jp001_jp002.js
# node examples/bench/evidence_jp005_jp006.js

Re-run after Node major upgrades; update the matching .md tables.

CLI presetsCopy Anchor Link

• Default --preset app: jp-delete-array-hole=error; jp-map-filter-chain, jp-regex-ctor-hot, jp-json-hot, jp-dom-query-hot, jp-intl-datetimeformat-hot, jp-readfile-sync-hot, and jp-clock-hot = hint; jp-alloc-hot, jp-console-hot, jp-delete-shape = off (G3 2026-10-22 for the off rules). jp-string-plus-in-loop is removed.
• engine: same as app, except jp-console-hot = hint.
• all: every rule is error.
• Overrides: --severity RULE=error|hint|off (repeatable; wins over the preset).