fix(types): Require TypeScript 4.0; remove broken TS 3.x declarations

[ntucker]

Requested by Nathaniel · project thread

Follow-up from #4122 / #4140.

Motivation

Before: package.json typesVersions advertised ">=3.4", but the ts3.4/ declarations didn't type-check on any TypeScript 3.x (with skipLibCheck: false):

• TS 3.4: endpoint/normalizr overlays use import type (TS 3.8+), and recursive type aliases need 3.7
• TS 3.9: variadic tuple spreads (...args: readonly [...Parameters<E>]) in endpoint/normalizr SnapshotInterface, core Controller, and every react hook, plus React.JSX and default React imports
• @data-client/rest never had a 3.x entry, so react + rest never worked on 3.x

After: TypeScript 4.0 is the minimum, matching rest and the oldest TS in the esmodule-types CI matrix.

- "typescript": "^3.9.0"
+ "typescript": "^4.0.0"

Solution

• Remove the ">=3.4" typesVersions entry, ts3.4 from files, and the ts3.4 build from core, endpoint, normalizr, react, graphql, img and test; delete endpoint/src-3.4-types.
• @data-client/use-enhanced-reducer keeps its ts3.4 output: it type-checks on TS 3.4 and 3.9, and it isn't version-linked.
• LEGACY_MIN_TS is now a no-op (no outputs below 4.0), so it's removed from ci:build:legacy-types and build-legacy-types.sh.
• Installation docs: "TypeScript 3.7+" → "TypeScript 4.0+". Minor changeset (breaking for 0.x).

Verified: ts4.* outputs for endpoint/normalizr/rest are byte-identical to master; yarn build:types passes; typetest-libcheck passes on TS 4.0.8.

🤖 Generated with Claude Code

https://claude.ai/code/session_0112vdfv1WoJN5LqwMkiksab

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Generated by Claude Code

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Note

Medium Risk
Breaking for consumers on TypeScript 3.x; runtime behavior is unchanged but published typings and minimum compiler version shift across multiple packages.

Overview
BREAKING: Published @data-client/* packages now require TypeScript 4.0+. The broken ts3.4 declaration trees and typesVersions ">=3.4" entries are removed from core, endpoint, normalizr, react, graphql, img, and test; endpoint’s src-3.4-types overlay is deleted.

Legacy type publishing is trimmed to TS ≥ 4.0 only: build:legacy-types no longer emits 3.4, LEGACY_MIN_TS is dropped from CI and build-legacy-types.sh, and endpoint drops the old schemas-3.7 babel ignore. @data-client/use-enhanced-reducer still ships ts3.4 (unchanged).

Docs and release notes state 4.0+; a minor changeset marks the break for the affected packages.

^{Reviewed by Cursor Bugbot for commit ede4059. Bugbot is set up for automated code reviews on this repo. Configure here.}

[changeset-bot]

🦋 Changeset detected

Latest commit: ede4059

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

This PR includes changesets to release 16 packages

Name	Type
@data-client/core	Minor
@data-client/endpoint	Minor
@data-client/normalizr	Minor
@data-client/react	Minor
@data-client/graphql	Minor
@data-client/img	Minor
@data-client/test	Minor
@data-client/vue	Minor
example-benchmark	Patch
example-benchmark-react	Patch
@data-client/rest	Minor
normalizr-github-example	Patch
normalizr-redux-example	Patch
normalizr-relationships	Patch
test-bundlesize	Patch
coinbase-lite	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs-site	Ignored	Preview	Oct 4, 2026 3:26pm UTC

[github-actions]

Size Change: 0 B

Total Size: 103 kB

ℹ️ View Unchanged

Filename	Size
examples/test-bundlesize/dist/App.js	1.46 kB
examples/test-bundlesize/dist/polyfill.js	307 B
examples/test-bundlesize/dist/rdcClient.js	10.9 kB
examples/test-bundlesize/dist/rdcEndpoint.js	8.07 kB
examples/test-bundlesize/dist/rdcNextjs.js	12.3 kB
examples/test-bundlesize/dist/rdcPipeableStream.js	9.63 kB
examples/test-bundlesize/dist/react.js	59.7 kB
examples/test-bundlesize/dist/webpack-runtime.js	784 B

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.92%. Comparing base (b4b502d) to head (ede4059).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4151   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files         158      158           
  Lines        3079     3079           
  Branches      616      616           
=======================================
  Hits         3015     3015           
  Misses         18       18           
  Partials       46       46           

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