Honor writeFile flags in Deno

[tim-smart]

Summary

• honor every FileSystem.writeFile open flag in the Deno adapter
• preserve native AbortSignal cancellation for w, wx, a, and ax writes
• use Deno.open for read and + modes that Deno.writeFile cannot faithfully represent
• handle empty writes without raising WriteZero
• add shared filesystem coverage for read-only, read/write, append, exclusive-create, and empty-write behavior
• add a patch changeset for @effect/platform-deno

Root cause

Deno.writeFile exposes only append/create/createNew booleans, so it cannot represent every Node-style open flag. In particular, r was writable and r+ truncated the file. Routing every mode through Deno.open fixed those semantics but regressed empty writes and cancellation. The hybrid implementation keeps the native, cancellable path where its semantics are sufficient and uses the complete Deno.open mapping for the remaining flags.

Validation

• deno task test --run packages/platform-deno/test/DenoFileSystem.test.ts (19 passed, 1 skipped)
• pnpm test --run packages/platform-node-shared/test/NodeFileSystem.test.ts (23 passed)
• pnpm lint-fix
• pnpm check

Closes EFF-522

[changeset-bot]

🦋 Changeset detected

Latest commit: 049202c

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

This PR includes changesets to release 30 packages

Name	Type
@effect/platform-deno	Patch
effect	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/docgen	Patch
@effect/doctest	Patch
@effect/openapi-generator	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node	Patch
@effect/platform-node-shared	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/vitest	Patch

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[pullfrog]

Caution

This PR introduces a regression for empty-file writes and drops the AbortSignal propagation that the previous Deno.writeFile implementation supported. Both issues stem from routing writeFile through Deno.open + FileImpl.writeAll; see the inline comment for details.

Reviewed changes

• Replaced Deno Deno.writeFile with Deno.open + FileImpl.writeAll in packages/platform-deno/src/DenoFileSystem.ts to honor all OpenFlag semantics.
• Added shared regression tests for r+, r, a, and wx write modes in packages/effect/test/FileSystem.test-utils.ts.
• Added a patch changeset for @effect/platform-deno.

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[pullfrog]

Follow-up detail for the CHANGES_REQUESTED review above: the inline comment did not attach, so here are the technical specifics for the two regressions.

Both issues center on packages/platform-deno/src/DenoFileSystem.ts:445, where writeFile now calls new FileImpl(file, ...).writeAll(data).

1. Empty writes now fail. FileImpl.writeAllChunk treats 0 bytes written as a WriteZero system error, so writeFile(path, new Uint8Array()) and writeFileString(path, "") now fail instead of creating/truncating the file to empty. A minimal fix is to guard FileImpl.writeAll against empty buffers:

   writeAll(buffer: Uint8Array) {
     return buffer.length === 0 ? Effect.void : this.writeAllChunk(buffer)
   }

2. Cancellation support is dropped. The previous implementation passed the AbortSignal from tryPromise into Deno.writeFile. Deno.open and Deno.FsFile.write do not accept a signal, so a long-running write can no longer be aborted. One option is a hybrid implementation that uses Deno.writeFile with signal for flags it can represent correctly (w, wx, a, ax) and falls back to Deno.open only for flags that require read or non-truncating write (r, r+, w+, wx+, a+, ax+).

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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
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batching.ts	9.92 KB	9.92 KB	0.00 KB (0.00%)
brand.ts	6.40 KB	6.40 KB	0.00 KB (0.00%)
cache.ts	10.78 KB	10.78 KB	0.00 KB (0.00%)
config.ts	20.79 KB	20.79 KB	0.00 KB (0.00%)
differ.ts	20.37 KB	20.37 KB	0.00 KB (0.00%)
http-client.ts	21.59 KB	21.59 KB	0.00 KB (0.00%)
logger.ts	10.90 KB	10.90 KB	0.00 KB (0.00%)
metric.ts	9.05 KB	9.05 KB	0.00 KB (0.00%)
optic.ts	7.25 KB	7.25 KB	0.00 KB (0.00%)
pubsub.ts	15.05 KB	15.05 KB	0.00 KB (0.00%)
queue.ts	11.72 KB	11.72 KB	0.00 KB (0.00%)
schedule.ts	10.89 KB	10.89 KB	0.00 KB (0.00%)
schema-class.ts	19.33 KB	19.33 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	29.15 KB	29.15 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	25.47 KB	25.47 KB	0.00 KB (0.00%)
schema-string-transformation.ts	13.48 KB	13.48 KB	0.00 KB (0.00%)
schema-string.ts	11.01 KB	11.01 KB	0.00 KB (0.00%)
schema-template-literal.ts	15.27 KB	15.27 KB	0.00 KB (0.00%)
schema-toArbitraryLazy.ts	22.11 KB	22.11 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	24.50 KB	24.50 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	19.34 KB	19.34 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	19.17 KB	19.17 KB	0.00 KB (0.00%)
schema-toFormatter.ts	19.03 KB	19.03 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	22.75 KB	22.75 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	19.66 KB	19.66 KB	0.00 KB (0.00%)
schema.ts	18.57 KB	18.57 KB	0.00 KB (0.00%)
stm.ts	12.69 KB	12.69 KB	0.00 KB (0.00%)
stream.ts	9.86 KB	9.86 KB	0.00 KB (0.00%)

[pullfrog]

Run failed. View the logs →

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