feat(rest): add ProgressEndpoint with download progress via ReadableStream

[ntucker]

Motivation

Closes the feature gap versus axios's onDownloadProgress / onUploadProgress callbacks. Users of @data-client/rest previously had no built-in way to track download progress for file downloads or large API responses.

Solution

Adds a new ProgressEndpoint class that extends RestEndpoint with download progress tracking using the ReadableStream API. This keeps the core RestEndpoint untouched -- users opt in by using ProgressEndpoint directly or via resource({ Endpoint: ProgressEndpoint }).

Key design decisions:

• Subclass approach: ProgressEndpoint overrides fetchResponse() to intercept the response body stream between super.fetchResponse() and parseResponse(), reading chunks via ReadableStream and calling the progress callback per chunk.
• Response reconstruction: After reading all chunks, a new Response is constructed from the collected Blob so parseResponse() works unchanged. response.url is preserved via Object.defineProperty.
• Edge cases handled:
  • Content-Encoding (gzip/br) → sets lengthComputable: false since Content-Length reflects compressed size
  • Mid-stream TypeError from reader.read() → tagged with .status = 500 to match fetchResponse's error handling
  • Abort signals propagate automatically; reader.releaseLock() in finally for cleanup
  • whatwg-fetch polyfill (no response.body) → gracefully skips progress tracking
  • 204 No Content / null body → handled by truthiness check

Usage:

import { ProgressEndpoint, resource } from '@data-client/rest';

const FileResource = resource({
  path: '/files/:id',
  schema: FileEntity,
  Endpoint: ProgressEndpoint,
});

const downloadWithProgress = FileResource.get.extend({
  onDownloadProgress({ loaded, total, lengthComputable }) {
    setProgress(lengthComputable ? loaded / total : undefined);
  },
});

New exports from @data-client/rest:

• ProgressEndpoint — the class
• DownloadProgress — the progress event type

Bug fix: TypeError from onDownloadProgress callback no longer tagged as network error

The catch block in fetchResponse previously tagged any TypeError with status = 500. Since the onProgress callback is invoked inside readWithProgress's try block, a TypeError from user code (e.g., accessing a property of undefined in the callback) would be incorrectly classified as a network error, causing errorPolicy to return 'soft' and triggering retry logic.

Fix: Moved the TypeError tagging into readWithProgress, scoped only around the reader.read() call. Callback errors now propagate unmodified. Added a test to verify this behavior.

Open questions

• Upload progress (onUploadProgress) via ReadableStream body + duplex: 'half' is left for a follow-up. The onDownloadProgress naming anticipates this.
• onDownloadProgress is not currently in RestEndpointOptions/RestInstanceBase to avoid leaking into the generic O type parameter. It can be passed via the ProgressEndpoint constructor or .extend() (where the base Endpoint constructor's Object.assign picks it up at runtime).

  

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🦋 Changeset detected

Latest commit: 5beebc3

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

This PR includes changesets to release 4 packages

Name	Type
@data-client/rest	Minor
example-benchmark-react	Patch
test-bundlesize	Patch
coinbase-lite	Patch

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.10%. Comparing base (17d938b) to head (5beebc3).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3863      +/-   ##
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+ Coverage   98.08%   98.10%   +0.01%     
==========================================
  Files         152      153       +1     
  Lines        2876     2902      +26     
  Branches      564      564              
==========================================
+ Hits         2821     2847      +26     
  Misses         11       11              
  Partials       44       44              

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[github-actions]

Size Change: 0 B

Total Size: 80.9 kB

ℹ️ View Unchanged

Filename	Size
examples/test-bundlesize/dist/App.js	3.25 kB
examples/test-bundlesize/dist/polyfill.js	307 B
examples/test-bundlesize/dist/rdcClient.js	10.4 kB
examples/test-bundlesize/dist/rdcEndpoint.js	6.39 kB
examples/test-bundlesize/dist/react.js	59.7 kB
examples/test-bundlesize/dist/webpack-runtime.js	938 B

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