my-pi/pi-permission-system/docs/plans/archive/0060-bump-tsconfig-target.md

issue, issue_title

issue	issue_title
60	Investigate bumping tsconfig target/lib to ES2023+

Investigate bumping tsconfig target/lib to ES2023+

Problem Statement

The project pins target: ES2022 in tsconfig.json (with no explicit lib), mirroring pi-mono's tsconfig.base.json. Node ≥ 20 is required, and Node 20 fully supports ES2023 APIs (findLast, Array.fromAsync, Object.groupBy, etc.) at runtime. Since noEmit: true, bumping lib/target only affects type-checking — there is zero runtime risk. The current constraint forces manual workarounds (reverse loops instead of findLast) and a corresponding AGENTS.md rule that forbids post-ES2022 APIs.

Goals

• Determine whether pi-mono's ES2022 pin is intentional policy or inertia.
• If safe, bump lib (and optionally target) to ES2023 so newer built-in type definitions are available.
• Update AGENTS.md to reflect the new minimum (remove the ES2022 restriction, document ES2023 as the floor).
• Simplify any existing manual workarounds that findLast or other ES2023 APIs would replace.

Non-Goals

• Bumping to ES2024 or later — out of scope; ES2023 is the conservative step.
• Proposing the bump upstream in pi-mono — that can be done independently.
• Refactoring code that does not benefit from ES2023 APIs.

Background

• tsconfig.json sets target: ES2022, no explicit lib (inherits from target).
• AGENTS.md lines 47–48 explicitly forbid post-ES2022 APIs.
• Issue #55 (closed) required replacing findLast with a manual loop (commit 1911f37).
• src/rule.ts evaluate() and src/wildcard-matcher.ts findCompiledWildcardMatch use reverse iteration that findLast would simplify.
• pi-mono's tsconfig.base.json pins ES2022 with engines.node: ">=20.0.0".

Permission surface

None — this is a build/tooling change with no permission semantics impact.

Design Overview

Since noEmit: true, both target and lib only gate which type definitions TypeScript makes available. Bumping either (or both) to ES2023 has identical effect: Array.prototype.findLast, Array.prototype.findLastIndex, and related types become available.

Decision

Bump both target and lib to ES2023. Rationale: with noEmit: true there is no emitted-code difference between the two fields, and keeping them aligned is simplest. This diverges from pi-mono's base config, which is acceptable — this repo already has its own tsconfig.json.

Module-Level Changes

File	Change
tsconfig.json	Set target: "ES2023" (lib inherits automatically).
AGENTS.md	Update lines 47–48: replace ES2022 floor with ES2023; list newly allowed APIs.
src/wildcard-matcher.ts	Replace manual reverse loop in findCompiledWildcardMatch with findLast if applicable.
src/rule.ts	Replace manual reverse loop in evaluate() with findLast if applicable.

TDD Order

1. feat: bump tsconfig target to ES2023 — Change target in tsconfig.json. Run pnpm run build to verify no type errors. Commit: feat: bump tsconfig target to ES2023 (#60).
2. docs: update AGENTS.md ES2022 constraint to ES2023 — Rewrite the two-line restriction. Commit: docs: update AGENTS.md ES version floor to ES2023 (#60).
3. refactor: use findLast in wildcard-matcher and rule — Replace manual reverse loops with findLast. Existing tests must continue to pass (no new tests needed — behavior is unchanged). Commit: refactor: use findLast in evaluate and wildcard matcher (#60).

Risks and Mitigations

Risk	Mitigation
Could this silently weaken a permission?	No — purely a type-checking change; no permission logic is altered.
Diverging from pi-mono tsconfig	Acceptable — this repo already maintains its own tsconfig. Document the divergence in a code comment.
findLast not available at runtime	Node ≥ 20 is required by engines.node; findLast shipped in Node 18.0. No risk.

Open Questions

• Whether to propose the same bump upstream in pi-mono (deferred — independent concern).