feat(firestore): Add array expressions by milaGGL · Pull Request #9492 · firebase/firebase-js-sdk

milaGGL · 2026-02-11T21:16:02Z

Add new array expressions arrayFirst, arrayFirstN,arrayLast,arrayLastN,arrayMinimum,arrayMinimumN,arrayMaximum,arrayMaximumN,arrayFilter,arraySlice,arrayIndexOf, arrayLastIndexOf,arrayIndexOfAll.

NOTE: Do not merge as arrayFilter needs to be updated.

changeset-bot · 2026-02-11T21:16:08Z

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gemini-code-assist · 2026-02-11T21:16:27Z

Summary of Changes

Hello @milaGGL, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request expands the array processing capabilities within the Firestore SDK by adding eight new expressions. These functions provide developers with enhanced tools to extract specific elements (first, last, or a specified number of elements) and calculate statistical values (minimum, maximum, or a specified number of min/max elements) directly from arrays within their data pipelines, streamlining array-based data transformations.

Highlights

New Array Expressions: Eight new array manipulation functions have been introduced: arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN.
API and Documentation Updates: The API definitions and documentation for both firestore-lite and full Firestore pipelines have been updated to include these new expressions.
Comprehensive Testing: Integration and lite-mode tests have been added to ensure the correct functionality of all new array expressions.

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Changelog

common/api-review/firestore-lite-pipelines.api.md
- Added API definitions for arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN.
common/api-review/firestore-pipelines.api.md
- Added API definitions for arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN.
docs-devsite/firestore_lite_pipelines.expression.md
- Documented the new arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN expressions with signatures and examples.
docs-devsite/firestore_pipelines.expression.md
- Documented the new arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN expressions with signatures and examples.
packages/firestore/lite/pipelines/pipelines.ts
- Exported the newly implemented array functions.
packages/firestore/src/api_pipelines.ts
- Exported the newly implemented array functions from the lite-api expressions.
packages/firestore/src/lite-api/expressions.ts
- Implemented the arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN methods on the Expression class and as standalone functions.
packages/firestore/test/integration/api/pipeline.test.ts
- Added integration tests to verify the functionality of arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN.
packages/firestore/test/lite/pipeline.test.ts
- Added lite-mode tests to verify the functionality of arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN.

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gemini-code-assist

Code Review

This pull request introduces eight new array expression functions to Firestore pipelines, enhancing the query capabilities for array fields. The new functions are arrayFirst, arrayFirstN, arrayLast, arrayLastN, arrayMaximum, arrayMaximumN, arrayMinimum, and arrayMinimumN. The changes are well-implemented and include corresponding API definitions, documentation, and comprehensive tests. I have identified a few areas for improvement, primarily concerning API documentation consistency and formatting in the generated documentation files.

packages/firestore/src/lite-api/expressions.ts

docs-devsite/firestore_lite_pipelines.expression.md

docs-devsite/firestore_pipelines.expression.md

gemini-code-assist

Code Review

This PR introduces a comprehensive set of new array expressions for Firestore pipelines, including functions for filtering, slicing, and finding elements within arrays. The implementation is well-tested with extensive integration tests. My feedback is primarily focused on improving the accuracy and consistency of the documentation for these new features to ensure clarity for developers. I've pointed out a few places where examples are missing or descriptions of return values could be more precise based on the test cases.

docs-devsite/firestore_lite_pipelines.expression.md

docs-devsite/firestore_pipelines.expression.md

packages/firestore/src/lite-api/expressions.ts

milaGGL · 2026-02-13T16:57:43Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces a comprehensive set of new array expressions to Firestore pipelines, which is a great feature enhancement. The implementation and tests are thorough. My feedback is mainly focused on improving code organization, documentation clarity, and minor code simplification for better maintainability. I've pointed out some redundant function calls, suggested reordering of exports and methods for consistency, and highlighted some areas in the documentation that could be confusing for users due to duplicated entries and incorrect links.

docs-devsite/firestore_lite_pipelines.expression.md

docs-devsite/firestore_pipelines.expression.md

packages/firestore/lite/pipelines/pipelines.ts

packages/firestore/src/api_pipelines.ts

packages/firestore/src/lite-api/expressions.ts

dlarocque · 2026-02-13T16:41:43Z

packages/firestore/lite/pipelines/pipelines.ts

+  arrayIndexOf,
+  arrayLastIndexOf,
+  arrayIndexOfAll,
+  arrayFilter


nit: i think these should be grouped with the other array exports.

cherylEnkidu · 2026-02-13T22:03:57Z

common/api-review/firestore-lite-pipelines.api.md


 // @beta
-export function arrayFilter(fieldName: string, variable: string, predicate: Expression): FunctionExpression;
+export function arrayFilter(fieldName: string, variable: string, predicate: BooleanExpression): FunctionExpression;


What about naming the variable alias in arrayFilter? It may not matter much in the JS SDK, but it would be helpful when porting to Swift, since it would become a labeled parameter there. https://www.hackingwithswift.com/sixty/5/4/parameter-labels

add 8 new expressions

08bd0e8

gemini-code-assist bot reviewed Feb 11, 2026

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milaGGL added 4 commits February 11, 2026 16:39

update the .md files

19577b1

format

711c256

update docs-devsite

71be25d

add the remaining 4 expressions

4889715

milaGGL changed the title ~~add 8 new expressions~~ feat(firestore): Add array expressions Feb 12, 2026

milaGGL marked this pull request as ready for review February 13, 2026 15:21

milaGGL requested review from a team as code owners February 13, 2026 15:21

gemini-code-assist bot reviewed Feb 13, 2026

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update documentation

b7d9767

gemini-code-assist bot reviewed Feb 13, 2026

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dlarocque reviewed Feb 13, 2026

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update documents

d0c864c

milaGGL added the do-not-merge label Feb 13, 2026

cherylEnkidu reviewed Feb 13, 2026

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milaGGL commented Feb 11, 2026 •

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