Expose Metrics counters as accessors

[TastyPi]

Closes #1658

Metrics increments a counter for every Assign, Create, Clone, Discard and Update call. The counters are data properties, so the increment throws TypeError once Metrics is frozen — and since every Type.* constructor routes through at least one of those five, schema construction fails outright rather than merely losing its metrics. The issue has a self-contained reproduction.

This keeps the counters as module-scope variables and exposes them through accessors. A freeze cannot disable an accessor, so the increments keep working.

TMetrics is unchanged, and Object.keys(Metrics) and { ...Metrics } produce identical output before and after, so the counters stay readable, enumerable and spreadable.

Tests

Two tests in test/typebox/runtime/system/memory.ts: that the counters increment, and that they still increment after Object.freeze(Memory.Metrics).

They assert the behaviour rather than the mechanism, so they do not pin the implementation to accessors specifically.

Verification

• deno task lint — clean, 685 files
• deno task test — 35,188 passing, 0 failing
• deno task build — clean
• packed that build and ran the issue's reproduction against it: prints Metrics frozen? true and then does not throw, where typebox@1.3.8 throws at create.mjs:25

Note

Happy to drop this in favour of a Settings flag (Settings.Set({ metrics: false })) if you would rather metrics were opt-out than freeze-tolerant — the tradeoff is that a flag has to be set before the first schema is constructed, which a library depending on TypeBox cannot guarantee.

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🤖 Drafted with Claude Code