Keep Stream.range advancing with a zero-sized chunk

[fubhy]

Summary

Stream.range with chunkSize zero emits the lower bound forever instead of the finite inclusive range.

Important

This PR starts with focused failing reproduction tests. Add the implementation fix to this same branch; CI is expected to fail until that fix is included.

Zero-sized range chunks never advance

Module: Stream
Audit ID: core-s-z-testing-stream-range-zero-chunk
Severity / confidence: high / high

What happens

Stream.range with chunkSize zero emits the lower bound forever instead of the finite inclusive range.

Why it happens

With chunkSize === 0, the remaining > chunkSize branch emits [start] and advances start by zero, so every pull repeats the lower bound.

Expected behavior

range(min, max, chunkSize) emits the finite inclusive integer range when min <= max; chunkSize controls batching, not values, and no positive-only precondition is documented.

Relevant implementation

These links and excerpts are pinned to audit base c9b56ab507f224426ee8388dc450da447ec4715f.

• packages/effect/src/Stream.ts:1567-1585

View problematic code at packages/effect/src/Stream.ts:1567-1585

export const range = (
  min: number,
  max: number,
  chunkSize = Channel.DefaultChunkSize
): Stream<number> =>
  min > max ? empty : fromPull(Effect.sync(() => {
    let start = min
    let done = false
    return Effect.suspend(() => {
      if (done) return Cause.done()
      const remaining = max - start + 1
      if (remaining > chunkSize) {
        const chunk = Arr.range(start, start + chunkSize - 1)
        start += chunkSize
        return Effect.succeed(chunk)
      }
      const chunk = Arr.range(start, start + remaining - 1)
      done = true
      return Effect.succeed(chunk)

View exact lines on GitHub

Reproduction

pnpm test --run packages/effect/test/Stream.test.ts -t "range - zero chunk size does not change the emitted range"

Observed failure: [1, 1, 1, 1] instead of [1, 2, 3]

Implementation handoff

The initial reproduction tests on this branch are the regression specification for the implementation fix that should follow in this PR.

1. Start with the pinned implementation excerpts and the Why it happens analysis above.
2. Change the implementation so it satisfies the stated Expected behavior; do not weaken or remove the reproduction assertions.
3. Run the focused reproduction command(s) and confirm the observed failures become passing tests:

pnpm test --run packages/effect/test/Stream.test.ts -t "range - zero chunk size does not change the emitted range"

4. Run the affected package's existing tests, then the repository lint and type checks before requesting review.

Audit provenance

• Audit base: c9b56ab507f224426ee8388dc450da447ec4715f
• Reproduction base: c9b56ab507f224426ee8388dc450da447ec4715f
• Findings: core-s-z-testing-stream-range-zero-chunk
• Initial patch: focused reproduction tests; implementation fix pending

Closes EFF-349

[changeset-bot]

🦋 Changeset detected

Latest commit: 68fe429

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 30 packages

Name	Type
effect	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-deno	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/vitest	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-pglite	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/docgen	Patch
@effect/doctest	Patch
@effect/openapi-generator	Patch

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[pullfrog]

✅ No new issues found.

Reviewed changes

• Reproduction test for Stream.range with zero chunk size: Added a test at packages/effect/test/Stream.test.ts:407 that calls Stream.range(1, 3, 0) and expects [1, 2, 3]. The test correctly uses take(4) to bound collection so the buggy infinite-emit path doesn't hang.

Tracing Stream.range (Stream.ts:1567) confirms the bug: when chunkSize = 0, Arr.range(start, start + 0 - 1) ⇒ Arr.range(start, start - 1) returns [start], and start += 0 never advances the cursor, so every pull emits the same value. The assertion [1, 2, 3] correctly represents the expected contract and will fail against the buggy output [1, 1, 1, 1].

The test follows all conventions — it.effect, Effect.gen, assert from @effect/vitest, proper placement adjacent to the existing range test.

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[github-actions]

Bundle Size Analysis

Generated from PR build output; treat the content below as untrusted.

File Name	Current Size	Previous Size	Difference
basic.ts	7.06 KB	7.06 KB	0.00 KB (0.00%)
batching.ts	9.86 KB	9.86 KB	0.00 KB (0.00%)
brand.ts	6.34 KB	6.34 KB	0.00 KB (0.00%)
cache.ts	10.62 KB	10.62 KB	0.00 KB (0.00%)
config.ts	20.60 KB	20.60 KB	0.00 KB (0.00%)
differ.ts	20.20 KB	20.20 KB	0.00 KB (0.00%)
http-client.ts	21.49 KB	21.49 KB	0.00 KB (0.00%)
logger.ts	10.76 KB	10.76 KB	0.00 KB (0.00%)
metric.ts	8.99 KB	8.99 KB	0.00 KB (0.00%)
optic.ts	7.18 KB	7.18 KB	0.00 KB (0.00%)
pubsub.ts	14.90 KB	14.90 KB	0.00 KB (0.00%)
queue.ts	11.58 KB	11.58 KB	0.00 KB (0.00%)
schedule.ts	10.74 KB	10.74 KB	0.00 KB (0.00%)
schema-class.ts	19.14 KB	19.14 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	28.96 KB	28.96 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	25.29 KB	25.29 KB	0.00 KB (0.00%)
schema-string-transformation.ts	13.30 KB	13.30 KB	0.00 KB (0.00%)
schema-string.ts	10.94 KB	10.94 KB	0.00 KB (0.00%)
schema-template-literal.ts	15.17 KB	15.17 KB	0.00 KB (0.00%)
schema-toArbitraryLazy.ts	21.94 KB	21.94 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	24.34 KB	24.34 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	19.18 KB	19.18 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	19.01 KB	19.01 KB	0.00 KB (0.00%)
schema-toFormatter.ts	18.87 KB	18.87 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	22.60 KB	22.60 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	19.52 KB	19.52 KB	0.00 KB (0.00%)
schema.ts	18.41 KB	18.41 KB	0.00 KB (0.00%)
stm.ts	12.54 KB	12.54 KB	0.00 KB (0.00%)
stream.ts	9.80 KB	9.79 KB	+0.01 KB (+0.08%)