test: property-based fuzz testing for js->zig->js roundtrip - #41
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nazarhussain wants to merge 22 commits into
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test: property-based fuzz testing for js->zig->js roundtrip#41nazarhussain wants to merge 22 commits into
nazarhussain wants to merge 22 commits into
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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
NAPI sets word_count to the required size even when the buffer is smaller than needed; the previous code returned words[0..word_count], which is UB when word_count > words.len. Clamping via @min makes the function safe and gives callers the semantics of truncate-to-low-N-bits.
Previous toI128 panicked on three input classes: zero (result[0] on empty slice), minInt(i128) (@intcast overflow during negation), and out-of-range magnitudes. Reworks the function to use a pre-zeroed local buffer and wrapping arithmetic, returning BigInt.asIntN(128, b) semantics for out-of-domain inputs. Documents the in-domain (exact) and out-of-domain (truncation) contract in the doc comment, and adds an explicit comment on the magnitude == 0 guard for out-of-range negatives whose low 128 bits are all zero (e.g. -2^128n), where asIntN(128, b) === 0n.
Thin DSL wrapper over napi_create_bigint_words. Required for round-tripping i128 and larger values through the DSL without going through the i64/u64 path. Accepts a sign bit and a little-endian u64-word slice; the resulting BigInt equals (sign == 1 ? -1 : 1) * sum(words[i] << (64 * i)).
Round-trips JS BigInt → i128 → JS BigInt via toI128 and fromWords. Property test covers the i128 boundary plus out-of-range truncation via BigInt.asIntN(128, ·). Oracle test adds deterministic boundary cases for zero, I128_MIN/MAX (exact), just-out-of-range ±1, and oversized values whose low 128 bits are all zero (expected result: 0n).
Zig 0.16's `zig fmt` reorders `@alignCast(@ptrCast(x))` to `@ptrCast(@aligncast(x))`. The pre-existing form was triggering format churn in working trees across every `zig build` invocation; applying the canonical order once stops the noise.
The seeds-workflow doc claimed NaN/Infinity could be persisted via a
{"__special": ...} encoding, but no corresponding reviver exists in
fuzz.test.ts — following the README literally would silently corrupt
test input. NaN/Infinity are already in edgeNumbers and exercised every
run, so persisting them adds nothing. Trim the README to match reality.
wemeetagain
reviewed
Jul 24, 2026
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seems a little strange to fuzz in CI
wemeetagain
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Jul 24, 2026
wemeetagain
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I think the API changes and additional comments are good
# Conflicts: # build.zig.zon # src/js/bigint.zig
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Adds a property-based fuzz harness for zapi
Number,BigIntandUint8Arrayconverters and (vitest + fast-check, driven through a dedicatedtest_fuzz_numeric.nodeaddon). The harness immediately surfaced multiple latent bugs and an API sharp edge, all addressed in this branch.API changes
toI64/toU64/toI128: these now returnerror.InvalidArgon out-of-range BigInts instead of silently truncating. Callers who explicitly want low-bits semantics use the newtoI64LowBits/toU64LowBits/toI128LowBitsvariants. NAPI's lossless flag is exposed as thelosslessout-pointer on the*LowBitscalls.BigInt.fromWords(sign_bit, words)— DSL surface for constructing BigInts whose magnitude exceeds u64 (e.g., i128). Closes the gap the existingBigInt.fromdoc comment noted but couldn't fill.Number.toI32/U32/F64/I64updated to accurately describe N-API conversion semantics (NaN/Inf → 0, range clamping, etc.).