TL;DR — A batch of micro-optimizations across the shared parser (hoisted regexps, in-place mutation, fast paths, iterator-free loops, delete → = undefined) reportedly shaves ~9% off Stripe spec generation. The wins look solid, but a few of the spread-to-push rewrites cross from "harmless in-place mutation of fresh IR objects" into "mutation of arrays aliased from the input spec".

Key changes

• Hoist top-level IR pattern regexps — move the Record<IrTopLevelKind, RegExp> table out of matchIrPointerToGroup so the regex literals aren't re-created on each call.
• Switch object-emptiness checks to a running flag — parseObject now tracks isSchemaPropertiesEmpty / isPatternPropertiesEmpty during iteration instead of calling Object.keys(...).length afterward, and skips the inner allocation when schema.properties / schema.patternProperties are absent.
• getSchemaType / getSchemaTypes accept the schema directly — drop the unused destructuring wrapper at every call site across 2.0.x / 3.0.x / 3.1.x parsers.
• parseEnum uses an index loop and hoists x-enum* lookups — avoids the iterator-protocol overhead of entries() and the per-iteration property reads.
• In-place merges over spread — Object.assign(target, source) replaces target = {...target, ...source} in deduplicateSchema, addItemsToSchema, and the parseArray composition-lift branches.
• delete → = undefined — for state.inAllOf reset and the result.items / result.logicalOperator cleanup in deduplicateSchema, to keep V8 hidden-class shapes stable.
• buildIndexKeySpace accumulates into a shared entries array — recursion passes the array down instead of spreading sub-results back up.
• Fast path in jsonPointerToPath — skip the .map(replaceAll) decode pass entirely when the pointer contains no ~.
• Fast path in isTopLevelComponent for string input — segment-count via indexOf instead of parsing the pointer into an array and discarding it.
• Lazy Set allocation in collectPointerDependencies — switch subtreeDependencies / transitiveDependencies to Set<string> | null, allocate only when there's something to add, and use Map.has instead of Map.get truthy-checks so null results cache correctly.
• Move patternProperties parsing before additionalProperties branch — lets the isPatternPropertiesEmpty flag participate in the isEmptyObjectInAllOf check.

_{Summary ｜ 12 files ｜ 11 commits ｜ base: main ← more-performance-improvement}

In-place push onto aliased required arrays

Before: spread allocated a fresh array, leaving the input spec untouched.
After: required.push(...) mutates whatever array irCompositionSchema.required (or inlineSchema.required) currently points at — which may be the source spec's array.

In parseType, irSchema.required = schema.required aliases the source schema's required array directly into the IR (no copy). When a $ref'd composition schema is later processed in parseAllOf and the parent schema.required is non-empty, the new irCompositionSchema.required.push(...schema.required) writes into the referenced spec node's required array. The same hazard applies to the discriminator inlineSchema.required.push(discriminator.propertyName) rewrites. The original spread ([...a, ...b]) avoided this by always producing a fresh array; the safe fix here is the same — either keep the spread on this hot path, or guard with a "clone if aliased" check.

packages/shared/src/openApi/3.1.x/parser/schema.ts · packages/shared/src/openApi/3.0.x/parser/schema.ts · packages/shared/src/openApi/2.0.x/parser/schema.ts

isTopLevelComponent string fast path and pointer encoding

Before: decoded the pointer through jsonPointerToPath and checked segment count.
After: counts / characters directly in the raw string.

The fast path treats encoded slashes (~1) inside a component name as real segment separators, so e.g. a hypothetical #/components/schemas/foo~1bar (name containing a /) now returns false where the array path returned true. The OpenAPI spec restricts component-key names to ^[a-zA-Z0-9.\-_]+$, so this is unreachable for conformant specs — flagging only because the previous behavior was documented as "decode then count" and this is a quiet semantic narrowing. Not worth fixing unless there's an appetite for an explicit guard.

packages/shared/src/utils/ref.ts

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using Claude Opus ｜ 𝕏}