Optimize extendShape

[Andarist]

It has been proposed here and, in fact, it cuts AnswerOverflow/apps/dashboard's instantiations from 13672403 to 3538464 (74% reduction) and check time from 6.5s to 4s (38% reduction).

Summary by CodeRabbit

• Refactor
  • Improved the efficiency of type-level merging for object shapes, resulting in faster and more direct merging when object keys do not overlap. This change affects only type definitions and does not impact runtime behavior.

[coderabbitai]

Walkthrough

The changes update two TypeScript utility types, MergeShapes and extendShape, within the objectUtil namespace. Both types now include a conditional check to determine if the key sets of the objects being merged overlap. If there are no overlapping keys, the types are combined using a simple intersection; if there are overlapping keys, the merge uses the original exclusion-based logic. These modifications affect only the type-level behavior and do not alter any runtime code.

Changes

File(s)	Change Summary
deno/lib/helpers/util.ts, src/helpers/util.ts	Updated MergeShapes and extendShape types in the objectUtil namespace to include a conditional fast path for merging.

Poem

In the warren of types where the helpers reside,
Two shapes now merge with a swifter stride.
If keys don’t collide, they simply unite,
But if there’s a clash, they merge as they might.
Type rabbits rejoice—less hopping around!
For merging is faster when overlaps aren’t found.
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between e6017b0 and 6a4fdfc.

📒 Files selected for processing (2)

• deno/lib/helpers/util.ts (2 hunks)
• src/helpers/util.ts (2 hunks)

🔇 Additional comments (4)

src/helpers/util.ts (2)

100-106: Excellent performance optimization for MergeShapes type!

This optimization introduces a fast path for merging object types when there are no overlapping keys. By using a direct intersection (U & V) in cases where keys don't overlap, the TypeScript compiler can avoid the more complex exclusion-based merging, significantly reducing type instantiations. This aligns with the PR objectives, which report a 74% reduction in instantiations and 38% improvement in type checking time.

---

138-146: Well-implemented optimization for extendShape type utility

Similar to the MergeShapes optimization, this adds a fast path for cases where object keys don't overlap. The implementation is correct and maintains the same semantics - if keys overlap, it falls back to the original exclusion-based logic. When keys don't overlap, using a simple intersection (A & B) is more efficient and produces equivalent results.

The comment explaining the optimization is clear and helpful for future maintainers.

deno/lib/helpers/util.ts (2)

100-106: Excellent performance optimization for MergeShapes type!

This optimization introduces a fast path for merging object types when there are no overlapping keys. By using a direct intersection (U & V) in cases where keys don't overlap, the TypeScript compiler can avoid the more complex exclusion-based merging, significantly reducing type instantiations.

The changes are identical to those in src/helpers/util.ts, maintaining consistency across the codebase.

---

138-146: Well-implemented optimization for extendShape type utility

This optimization mirrors the one applied to MergeShapes, creating a fast path for object type merging when keys don't overlap. The implementation is correct and preserves the original behavior while improving performance.

The consistent approach between this file and src/helpers/util.ts ensures unified behavior across different parts of the codebase.

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[samchungy]

It has been proposed here and, in fact, it cuts AnswerOverflow/apps/dashboard's instantiations from 13672403 to 3538464 (74% reduction) and check time from 6.5s to 4s (38% reduction).

Summary by CodeRabbit

• Documentation

  • Added "fullproduct.dev" to the "Powered by Zod" section in the README.

• Refactor

  • Improved type-level merging logic for utility types, optimizing for cases where object keys do not overlap. No impact on runtime behavior.

btw @Andarist, I think this may have already been optimised in Zod 4:
https://v4.zod.dev/v4
#4074

[Andarist]

Given how popular v3 is, I think it still would be good to backport this but, of course, it's up to @colinhacks

[colinhacks]

Just when I thought I'd tried every conceivable implementation of ExtendShape Anders drops this fast-path approach. Glorious.

[colinhacks]

Benchmarks. This builds the somewhat adversarial script in this gist — a chain of .omit() and .extend() calls. I chained as many calls as possible before TS threw an Excessively Deep error, so basically this benchmark is designed to be as impressive as possible 🤷‍♂️ And it is :)

Metric	Zod 3.24.2 (Pre-change)	Zod 3.24.3 (Post-change)	Factor
Total Time	3.15s	0.50s	6.3× faster
Check Time	2.15s	0.15s	14.3× faster
Emit Time	0.69s	0.03s	23.0× faster
Transform Time	0.68s	0.02s	34.0× faster
Instantiations	15,415,384	165,263	98.9% reduction

Zod 3.24.2 (pre-change)

$ pnpm run build:bench

> @zod/tsc-perftest@1.0.0 build:bench /Users/colinmcd94/Documents/projects/zod/packages/tsc
> tsc -p tsconfig.bench.json

Files:                          162
Lines of Library:             39498
Lines of Definitions:         54853
Lines of TypeScript:            107
Lines of JavaScript:              0
Lines of JSON:                    0
Lines of Other:                   0
Identifiers:                  87917
Symbols:                      82218
Types:                         9900
Instantiations:            15415384
Memory used:                119682K
Assignability cache size:      2548
Identity cache size:              6
Subtype cache size:               0
Strict subtype cache size:        0
I/O Read time:                0.01s
Parse time:                   0.16s
ResolveModule time:           0.02s
ResolveTypeReference time:    0.00s
ResolveLibrary time:          0.01s
Program time:                 0.23s
Bind time:                    0.08s
Check time:                   2.15s
transformTime time:           0.68s
commentTime time:             0.00s
I/O Write time:               0.00s
printTime time:               0.69s
Emit time:                    0.69s
Total time:                   3.15s

Zod 3.24.3 (post-change)

$ pnpm run build:bench
> @zod/tsc-perftest@1.0.0 build:bench /Users/colinmcd94/Documents/projects/zod/packages/tsc
> tsc -p tsconfig.bench.json

Files:                         163
Lines of Library:            39498
Lines of Definitions:        54891
Lines of TypeScript:           107
Lines of JavaScript:             0
Lines of JSON:                   0
Lines of Other:                  0
Identifiers:                 87903
Symbols:                     83156
Types:                       10054
Instantiations:             165263
Memory used:               122090K
Assignability cache size:     2673
Identity cache size:             6
Subtype cache size:              0
Strict subtype cache size:       0
I/O Read time:               0.02s
Parse time:                  0.16s
ResolveModule time:          0.02s
ResolveTypeReference time:   0.00s
ResolveLibrary time:         0.01s
Program time:                0.24s
Bind time:                   0.08s
Check time:                  0.15s
transformTime time:          0.02s
commentTime time:            0.00s
I/O Write time:              0.00s
printTime time:              0.03s
Emit time:                   0.03s
Total time:                  0.50s

[jakebailey]

How did emit time end up shrinking?

[Andarist]

@jakebailey serializeTypeForDeclaration can lead to instantiateType calls - and I've verified that this particular emit involves many of those. So given the instantiations were reduced by a large margin - the emit time could also easily go down here.

[Andarist]

This builds the somewhat adversarial script in this gist — a chain of .omit() and .extend() calls

I thought this would still perform poorly but it doesnt 🤔