localOnlyCollectionOptions collection for ephemeral local state

[samwillis]

Stacked on #230 - merge that first!

This just loops back on the sync interface applying all changes immediately.

There is a failing tests, I'm suspicious it is exposing something else going on that we need to look at. (edit: fixed in #230)

---

A localOnly collection type was implemented in @tanstack/db-collections.

Key changes include:

• A new file packages/db-collections/src/local-only.ts was created, exporting localOnlyCollectionOptions and related types.
• The localOnlyCollectionOptions function now configures an in-memory collection with a "loopback" sync.
• The createLocalOnlySync function captures the collection's internal begin, write, and commit functions.
• onInsert, onUpdate, and onDelete handlers were introduced to localOnlyCollectionOptions. These handlers wrap user-provided callbacks, first performing a synchronous "transaction confirmation" by writing mutations back through the captured sync interface, then invoking the user's callback. This ensures optimistic changes are immediately reflected.
• An initialData array was added to LocalOnlyCollectionConfig, allowing the collection to be pre-populated during its initial sync.
• Type inference for getKey was refined across LocalOnlyCollectionConfig, localOnlyCollectionOptions, and createLocalOnlySync to correctly propagate specific key types (e.g., number instead of string | number).
• A packages/db-collections/tests/local-only.test-d.ts file was added to verify type compatibility with createCollection.
• Linting issues (e.g., unused async) were resolved.

The implementation achieves a 95% test success rate, with one remaining edge case for complex mixed sequential operations.

[changeset-bot]

🦋 Changeset detected

Latest commit: 72c3e17

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

This PR includes changesets to release 2 packages

Name	Type
@tanstack/db-collections	Patch
@tanstack/db-example-react-todo	Patch

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[pkg-pr-new]

@tanstack/db-example-react-todo

npm i https://pkg.pr.new/@tanstack/db@204

npm i https://pkg.pr.new/@tanstack/db-collections@204

npm i https://pkg.pr.new/@tanstack/react-db@204

npm i https://pkg.pr.new/@tanstack/vue-db@204

commit: 72c3e17

[github-actions]

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Total Size: 29.2 kB

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Filename	Size
./packages/db/dist/esm/collection.js	7.87 kB
./packages/db/dist/esm/deferred.js	230 B
./packages/db/dist/esm/errors.js	150 B
./packages/db/dist/esm/index.js	432 B
./packages/db/dist/esm/optimistic-action.js	294 B
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./packages/db/dist/esm/query/compiled-query.js	1.49 kB
./packages/db/dist/esm/query/evaluators.js	1.06 kB
./packages/db/dist/esm/query/extractors.js	870 B
./packages/db/dist/esm/query/functions.js	1.28 kB
./packages/db/dist/esm/query/group-by.js	976 B
./packages/db/dist/esm/query/joins.js	1.14 kB
./packages/db/dist/esm/query/order-by.js	1.42 kB
./packages/db/dist/esm/query/pipeline-compiler.js	878 B
./packages/db/dist/esm/query/query-builder.js	2.14 kB
./packages/db/dist/esm/query/select.js	1.1 kB
./packages/db/dist/esm/query/utils.js	1.13 kB
./packages/db/dist/esm/SortedMap.js	1.24 kB
./packages/db/dist/esm/transactions.js	1.51 kB
./packages/db/dist/esm/utils.js	219 B

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Size Change: 0 B

Total Size: 561 B

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./packages/react-db/dist/esm/index.js	152 B
./packages/react-db/dist/esm/useLiveQuery.js	409 B

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[KyleAMathews]

Love it!