refactor(fetch): make Body extend Blob

[medz]

Type

Refactor

Summary

• Make Body extend the conditional platform Blob implementation and implement Stream<Uint8List> directly.
• Simplify Body construction by delegating Blob-compatible inputs to Blob, while keeping Body, FormData, and stream-specific handling in Body.
• Preserve Fetch body helpers and bodyUsed semantics, and update public surface coverage for the new inheritance shape.

Notes

• This is a follow-up to feat(fetch): expose Body size #49.
• Body now depends on the conditional blob.dart surface rather than importing blob.native.dart directly.

Validation

• dart format --output=none --set-exit-if-changed .
• dart analyze
• dart test -p vm -p node -p chrome

Closes #50

Summary by CodeRabbit

Release Notes

• Breaking Changes

  • Body.stream is now a method with an optional chunkSize parameter; use body.stream() instead of body.stream.
  • Body.size may throw UnsupportedError for stream-backed bodies with unknown length.
  • Body now extends Blob and implements Stream<Uint8List>.

• Documentation

  • Updated changelog documenting breaking changes to the Body API and interface hierarchy.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a0d7c5ce-0fb5-4252-aaa7-54f2763b523a

📥 Commits

Reviewing files that changed from the base of the PR and between 0546d13 and 8349abd.

📒 Files selected for processing (4)

• CHANGELOG.md
• lib/src/fetch/body.dart
• test/body_test.dart
• test/public_api_surface_test.dart

---

📝 Walkthrough

Walkthrough

Body is refactored from a block.Block-backed Stream<Uint8List> to a class that extends the platform Blob implementation and directly implements Stream<Uint8List>. Internal storage is replaced with blobParts/_streamHost/_streamSize, the stream getter becomes a chunked method, and all read/clone/slice paths are updated. Tests and the public API surface test are extended to cover the new shape, and a BREAKING entry is added to the changelog.

Changes

Body extends Blob + Stream refactor

Layer / File(s)	Summary
Body class shape, storage model, and read methods lib/src/fetch/body.dart	Changes Body to extends Blob with Stream<Uint8List> implements Stream<Uint8List>, rewrites storage to blobParts + _streamHost/_streamSize, overrides size (throws for unknown-length stream-backed bodies), converts stream getter to a chunked method with chunkSize validation, and updates bytes()/arrayBuffer() to route through _readStream or super.arrayBuffer().
blob(), clone(), slice(), and listen() lib/src/fetch/body.dart	blob() uses super.slice(...) for blobParts-backed bodies and materializes stream-backed ones via bytes(); clone() uses streamTee for stream-backed or super.slice(...) for blobParts-backed; slice(...) throws UnsupportedError for stream-backed; listen(...) calls stream() instead of the removed getter.
Static normalization helpers lib/src/fetch/body.dart	Adds _fromBlobInit, _fromFormData, _fromStream, _readStream, and _blobInitType static helpers, replacing prior inline construction and stream materialization.
Tests, public API surface, and changelog test/body_test.dart, test/public_api_surface_test.dart, CHANGELOG.md	Adds _ThrowingReadBlob test double; covers Body as Blob/Stream<Uint8List>, snapshot semantics, no source read-method invocations, stream-backed size/slice rejection, chunkSize validation, chunk copy-on-consume, and updated stream access; extends public API surface test with type checks; documents breaking change.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant Body
    participant Blob
    participant StreamHost

    Note over Caller,StreamHost: Blob-backed read path
    Caller->>Body: arrayBuffer()
    Body->>Blob: super.arrayBuffer()
    Blob-->>Body: ByteBuffer
    Body-->>Caller: ByteBuffer

    Note over Caller,StreamHost: Stream-backed read path
    Caller->>Body: arrayBuffer()
    Body->>StreamHost: _readStream(_streamHost)
    StreamHost-->>Body: accumulated Uint8List chunks
    Body-->>Caller: ByteBuffer

    Note over Caller,StreamHost: clone() on stream-backed body
    Caller->>Body: clone()
    Body->>Body: streamTee(_streamHost)
    Body-->>Body: update _streamHost with tee[0]
    Body-->>Caller: new Body with tee[1] as _streamHost

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related issues

• refactor(fetch): make Body extend platform Blob and implement Stream #50 — This PR directly implements the refactor described in that issue: Body now extends the platform Blob implementation, implements Stream<Uint8List>, preserves bodyUsed semantics, and adds tests covering the inherited Blob surface.
• feat(fetch): make Body subclassable by downstream wrappers #52 — The PR achieves the Body extends Blob shape that issue #52 identifies as the prerequisite for making Body subclassable by downstream packages.
• bug(fetch): audit Blob snapshot semantics #53 — The retrieved issue audits semantic concerns about stream-backed Body instances having empty inherited Blob backings; this PR introduces exactly that shape (stream-backed bodies with no Blob content), so #53 is a direct follow-up concern.

Possibly related PRs

• medz/ht#12: This PR's clone() rewrite for stream-backed bodies uses the streamTee helper introduced in PR #12, making the connection direct.
• medz/ht#45: This PR delegates Body.slice(...) and blob() to super.slice(...) via Blob internals, which depend on the MIME-type normalization and slice contentType handling introduced in PR #45.
• medz/ht#54: This PR's Body delegates read behavior to Blob internals, and PR #54 changes Blob part normalization and snapshot/defensive-copy semantics that Body now relies on.

Poem

🐇 Hoppity-hop through the byte stream I go,
extends Blob now, what a delightful show!
No more old getter, just stream() with a size,
streamTee for cloning — oh, how very wise.
Each chunk is a copy, safe in my paw,
The Body is Blob — the best change I saw! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly summarizes the main change: refactoring Body to extend the Blob class, which is the primary focus of this PR.
Linked Issues check	✅ Passed	The PR fulfills all acceptance criteria from issue #50: Body extends platform Blob, implements Stream, exposes Blob-compatible surface, preserves bodyUsed semantics, and includes comprehensive test coverage.
Out of Scope Changes check	✅ Passed	All changes are scoped to the Body refactoring: CHANGELOG documents the breaking change, body.dart implements the new structure, and tests validate both inherited Blob behavior and stream functionality.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/body-blob-stream

---

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

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Reviewed commit: 8349abd386

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[chatgpt-codex-connector]

Preserve native Blob content types

When users pass a native web.Blob or web.File directly as BodyInit on the web target, Blob now accepts and reads that host-backed part, but this fallback leaves the type as '', so Body(web.Blob(...type: 'text/plain')).contentType is null. Request/Response only auto-populate the content-type header from body.contentType, so these accepted native Blob/File bodies lose their MIME type even though package Blob bodies still preserve it; please extract the host Blob/File type when delegating these inputs.

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