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Throw a clear error when anything other than an object with an collection is passed to "from" - #875

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claude/investigate-issue-873-017Thtu7vSQ8GXDpBvDs8yKY
Nov 21, 2025
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Throw a clear error when anything other than an object with an collection is passed to "from"#875
KyleAMathews merged 3 commits into
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claude/investigate-issue-873-017Thtu7vSQ8GXDpBvDs8yKY

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Fixes#873

The issue was that users were getting a confusing error message when passing a string (or other invalid type) to the .from() method instead of an object with a collection.

For example:

// Incorrect usageq.from("conversations")// String instead of object// Correct usageq.from({conversations: conversationsCollection})

When a string was passed, Object.keys("conversations") would return an array of character indices ['0', '1', ...], which has length > 1, triggering the "Only one source is allowed in the from clause" error. This was misleading because the real issue was passing a string instead of an object.

Changes:

  • Added validation to check if the source is a plain object before checking its key count
  • Improved error message to explicitly state the expected format with an example: .from({ alias: collection })
  • Added comprehensive tests for various invalid input types (string, null, array, undefined)

The new error message is:
"Invalid source for from clause: Expected an object with a single key-value pair like { alias: collection }. For example: .from({ todos: todosCollection }). Got: string "conversations""

🎯 Changes

✅ Checklist

  • I have followed the steps in the Contributing guide.
  • I have tested this code locally with pnpm test:pr.

🚀 Release Impact

  • This change affects published code, and I have generated a changeset.
  • This change is docs/CI/dev-only (no release).

Fixes#873
The issue was that users were getting a confusing error message when
passing a string (or other invalid type) to the .from() method instead
of an object with a collection.
For example:
```javascript
// Incorrect usage
q.from("conversations") // String instead of object
// Correct usage
q.from({ conversations: conversationsCollection })
```
When a string was passed, Object.keys("conversations") would return
an array of character indices ['0', '1', ...], which has length > 1,
triggering the "Only one source is allowed in the from clause" error.
This was misleading because the real issue was passing a string instead
of an object.
Changes:
- Added validation to check if the source is a plain object before
checking its key count
- Improved error message to explicitly state the expected format with
an example: .from({ alias: collection })
- Added comprehensive tests for various invalid input types (string,
null, array, undefined)
The new error message is:
"Invalid source for from clause: Expected an object with a single
key-value pair like { alias: collection }. For example:
.from({ todos: todosCollection }). Got: string \"conversations\""
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🦋 Changeset detected

Latest commit: 28444e1

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

This PR includes changesets to release 11 packages
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@tanstack/dbPatch
@tanstack/angular-dbPatch
@tanstack/db-collection-e2ePatch
@tanstack/electric-db-collectionPatch
@tanstack/powersync-db-collectionPatch
@tanstack/react-dbPatch
@tanstack/rxdb-db-collectionPatch
@tanstack/solid-dbPatch
@tanstack/svelte-dbPatch
@tanstack/trailbase-db-collectionPatch
@tanstack/vue-dbPatch

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commit: 28444e1

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Size Change: +214 B (+0.25%)

Total Size: 86.1 kB

FilenameSizeChange
./packages/db/dist/esm/errors.js4.19 kB+77 B (+1.87%)
./packages/db/dist/esm/index.js2.64 kB+13 B (+0.49%)
./packages/db/dist/esm/query/builder/index.js3.96 kB+124 B (+3.23%)
ℹ️ View Unchanged
FilenameSize
./packages/db/dist/esm/collection/change-events.js1.38 kB
./packages/db/dist/esm/collection/changes.js977 B
./packages/db/dist/esm/collection/events.js388 B
./packages/db/dist/esm/collection/index.js3.24 kB
./packages/db/dist/esm/collection/indexes.js1.1 kB
./packages/db/dist/esm/collection/lifecycle.js1.67 kB
./packages/db/dist/esm/collection/mutations.js2.26 kB
./packages/db/dist/esm/collection/state.js3.43 kB
./packages/db/dist/esm/collection/subscription.js2.42 kB
./packages/db/dist/esm/collection/sync.js2.29 kB
./packages/db/dist/esm/deferred.js207 B
./packages/db/dist/esm/event-emitter.js748 B
./packages/db/dist/esm/indexes/auto-index.js742 B
./packages/db/dist/esm/indexes/base-index.js766 B
./packages/db/dist/esm/indexes/btree-index.js1.87 kB
./packages/db/dist/esm/indexes/lazy-index.js1.1 kB
./packages/db/dist/esm/indexes/reverse-index.js513 B
./packages/db/dist/esm/local-only.js837 B
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./packages/db/dist/esm/optimistic-action.js359 B
./packages/db/dist/esm/paced-mutations.js496 B
./packages/db/dist/esm/proxy.js3.22 kB
./packages/db/dist/esm/query/builder/functions.js733 B
./packages/db/dist/esm/query/builder/ref-proxy.js917 B
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./packages/db/dist/esm/utils/type-guards.js157 B

compressed-size-action::db-package-size

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Size Change: 0 B

Total Size: 3.34 kB

ℹ️ View Unchanged
FilenameSize
./packages/react-db/dist/esm/index.js225 B
./packages/react-db/dist/esm/useLiveInfiniteQuery.js1.17 kB
./packages/react-db/dist/esm/useLiveQuery.js1.11 kB
./packages/react-db/dist/esm/useLiveSuspenseQuery.js431 B
./packages/react-db/dist/esm/usePacedMutations.js401 B

compressed-size-action::react-db-package-size

Simplified the validation logic in _createRefForSource to use positive
checks instead of negative checks:
- Check if it's a valid object (handles null/undefined via try-catch)
- Check if it's an array (arrays pass Object.keys but aren't valid)
- Check if it has exactly one key
- Check if keys look like numeric indices (indicates string was passed)
This approach is cleaner and handles all edge cases including when
callers bypass TypeScript's type checks with 'as any'.
Also added a changeset documenting the improvement.

@samwillissamwillis left a comment

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Once small change, but other than that great addition. Approving for once the errors have been combined and moved

Comment on lines +70 to +74
throw new QueryBuilderError(
`Invalid source for ${context}: Expected an object with a single key-value pair like { alias: collection }. ` +
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
`For example: .from({ todos: todosCollection }). Got: ${source === null ? `null` : `undefined`}`
)

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Can we move this error into the error.ts and then use it in all four places rather than duplicate the strings?

Addresses code review feedback by creating InvalidSourceTypeError
class in errors.ts and using it consistently across all validation
cases instead of duplicating error message strings.
Changes:
- Added InvalidSourceTypeError class to errors.ts that takes context
and type parameters
- Updated _createRefForSource to use InvalidSourceTypeError in all
four validation cases (null/undefined, array, empty object, string)
- Updated tests to expect InvalidSourceTypeError instead of
QueryBuilderError
- This eliminates string duplication and makes error messages
consistent across .from() and .join() methods
@KyleAMathews
KyleAMathews merged commit 464805d into mainNov 21, 2025
7 checks passed
@KyleAMathews
KyleAMathews deleted the claude/investigate-issue-873-017Thtu7vSQ8GXDpBvDs8yKY branch November 21, 2025 15:02
@github-actionsgithub-actionsBot mentioned this pull request Nov 21, 2025
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"Only one source is allowed in the from clause" but not realy my code

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@KyleAMathews@samwillis@claude