Improve performance with inline typecheck for string parsing #4058

mattyhempstead · 2025-03-28T23:18:47Z

This small change improves the benchmarked speed of string parsing by up to ~70% and realworld by ~20%.

Benchmark

These were run on my Macbook Pro M3.

Before the change:

realworld: valid x 8,305 ops/sec ±1.33% (97 runs sampled)

z.string: empty string x 13,717,506 ops/sec ±0.52% (95 runs sampled)
z.string: short string x 13,772,114 ops/sec ±0.97% (96 runs sampled)
z.string: long string x 13,713,146 ops/sec ±1.06% (97 runs sampled)
z.string: optional string x 10,406,774 ops/sec ±0.44% (95 runs sampled)
z.string: nullable string x 8,216,808 ops/sec ±0.73% (95 runs sampled)
z.string: nullable (null) string x 12,463,414 ops/sec ±0.50% (97 runs sampled)
z.string: invalid: null x 181,548 ops/sec ±1.22% (93 runs sampled)
z.string: manual parser: long x 224,317,422 ops/sec ±6.58% (79 runs sampled)

After the change:

realworld: valid x 9,900 ops/sec ±1.89% (96 runs sampled)

z.string: empty string x 23,594,188 ops/sec ±1.29% (94 runs sampled)
z.string: short string x 24,173,253 ops/sec ±0.82% (98 runs sampled)
z.string: long string x 24,042,133 ops/sec ±1.05% (95 runs sampled)
z.string: optional string x 13,433,944 ops/sec ±1.04% (95 runs sampled)
z.string: nullable string x 9,788,757 ops/sec ±1.66% (95 runs sampled)
z.string: nullable (null) string x 12,800,957 ops/sec ±2.00% (91 runs sampled)
z.string: invalid: null x 178,741 ops/sec ±1.65% (93 runs sampled)
z.string: manual parser: long x 229,858,255 ops/sec ±4.72% (80 runs sampled)

Explanation

In the parse function for ZodString, we are calling getParsedType (utils.ts) through a layer of indirection (this._getType -> getParsedType) in order to determine whether the data type is not a string. Since we don't actually need the full range of responses from getParsedType, we can simplify the logic by performing this negative typecheck inline.

The same is true for most other parse methods (we perform a != type check which can be moved inline), although making this change for strings is the simplest and probably the largest impact.

Summary by CodeRabbit

Refactor
- Streamlined string input validation by replacing an indirect evaluation step with a direct type check. This update reduces unnecessary processing, resulting in improved performance while maintaining consistent error handling for invalid inputs.

coderabbitai · 2025-03-28T23:18:55Z

Walkthrough

The changes update the validation logic in the ZodString class across both deno/lib/types.ts and src/types.ts. The previous method call to _getType(input) has been removed in favor of a direct inline type check using typeof input.data !== "string". In cases where the input is not a string, a context is generated and an issue is recorded, maintaining the existing issue reporting mechanism. There are no alterations to exported or public entities.

Changes

File(s)	Change Summary
deno/lib/types.ts, src/types.ts	Replaced the `_getType(input)` call with a direct inline check using `typeof input.data !== "string"`, removing the intermediate variable and simplifying control flow while retaining issue reporting for type mismatches.

Sequence Diagram(s)

sequenceDiagram
    participant Caller as Caller
    participant ZodString as ZodString
    participant Context as ParsingContext

    Caller->>ZodString: _parse(input)
    alt input.data is string
        ZodString->>ZodString: Validate string properties
        ZodString-->>Caller: Return parsed string
    else input.data is not string
        ZodString->>Context: _getOrReturnCtx(input)
        Context-->>ZodString: Return error context with type details
        ZodString->>Context: Record type mismatch issue
        ZodString-->>Caller: Return error context
    end

Poem

I'm a rabbit with a joyful leap,
Hopping through changes wide and deep.
The code now dances with a simpler check,
No extra hops to trip on tech.
Easter cheers and code so sleek! 🥕✨

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📥 Commits

Reviewing files that changed from the base of the PR and between 19c6d2e and cc553fe.

📒 Files selected for processing (2)

deno/lib/types.ts (1 hunks)
src/types.ts (1 hunks)

🧰 Additional context used

🧬 Code Definitions (2)

src/types.ts (1)

deno/lib/types.ts (1)

input (52-52)

deno/lib/types.ts (1)

src/types.ts (1)

input (52-52)

🔇 Additional comments (2)

src/types.ts (1)

779-780: Excellent optimization using inline type checking.

The direct type check typeof input.data !== "string" eliminates the function call overhead of _getType(input), resulting in the significant performance improvements mentioned in the PR objectives (70% in benchmarks, 20% in real-world scenarios).

deno/lib/types.ts (1)
779-780: Excellent performance optimization!

This change replaces a function call to _getType(input) with a direct inline type check. By eliminating the function call overhead, you achieve the ~70% performance improvement mentioned in the PR. Since string parsing is one of the most common operations in Zod, this is a high-value optimization with minimal risk.

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Inline typecheck in string parsing method

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