feat(firestore): literals pipeline stage by Linchin · Pull Request #16028 · googleapis/google-cloud-python

Linchin · 2026-03-05T00:27:41Z

Succeeding googleapis/python-firestore#1170 for the monorepo migration.

gemini-code-assist · 2026-03-05T00:28:01Z

Summary of Changes

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This pull request enhances the Firestore client library by introducing a new literals pipeline stage. This stage provides a mechanism to inject a fixed set of predefined document objects directly into a pipeline, offering greater flexibility for testing individual pipeline stages and serving as initial inputs for complex operations like join conditions. The change includes the necessary class implementation, method integration into the base pipeline, and corresponding test coverage.

Highlights

New literals pipeline stage: Introduced a new literals method to the _BasePipeline class, allowing users to define documents from a fixed set of predefined objects. This stage is particularly useful for testing other pipeline stages in isolation or as inputs for join conditions.
Implementation of Literals class: Added the Literals class in pipeline_stages.py to represent the new pipeline stage, including its constructor and methods for protobuf serialization.
Comprehensive testing: Included new system-level and unit tests to ensure the correct functionality, behavior, and integration of the literals pipeline stage.

Changelog

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py
- Added the literals method to _BasePipeline, enabling the definition of documents from a fixed set.
- Included detailed docstrings with examples and behavior descriptions for the new literals method.
packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_stages.py
- Introduced the Literals class, inheriting from Stage, to represent the new pipeline stage.
- Implemented the __init__ and _pb_args methods for the Literals class to handle document arguments and their protobuf serialization.
packages/google-cloud-firestore/tests/system/pipeline_e2e/general.yaml
- Appended a new system test case for the literals pipeline stage, demonstrating its usage with a sample document and asserting the expected results and protobuf structure.
packages/google-cloud-firestore/tests/unit/v1/test_pipeline.py
- Updated the test_pipeline_methods parameterized test to include the new literals stage, ensuring it can be correctly appended to a pipeline.
packages/google-cloud-firestore/tests/unit/v1/test_pipeline_stages.py
- Added a new test class TestLiterals with unit tests for the Literals stage's constructor, representation (repr), and protobuf serialization (_to_pb).

Activity

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Code Review

This pull request introduces a new literals pipeline stage, which allows specifying a fixed set of documents as the starting point of a pipeline. The implementation includes the literals method on the pipeline builder, the Literals stage class, and corresponding unit and end-to-end tests. My review focuses on improving the clarity and correctness of the type hints and docstrings for the new functionality. I've suggested changes to make the API easier to understand and use correctly.

gemini-code-assist · 2026-03-05T00:29:59Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

            stages.FindNearest(field, vector, distance_measure, options)
        )

+    def literals(self, *documents: str | Selectable) -> "_BasePipeline":


The type hint for *documents is incomplete. It should include dict as documents are often passed as dictionaries, which is not covered by str | Selectable.

Suggested change

def literals(self, *documents: str | Selectable) -> "_BasePipeline":

def literals(self, *documents: dict | str | Selectable) -> "_BasePipeline":

You can probably ignore this, unless that's how other languages handle it

Actually, looking at go, it seems like it accepts dicts, but not strings?

I don't know much about this stage, but from what I've seen, it's supposed to deal with maps. So maybe this should be def literals(self, *documents: Map | dict[str, CONSTANT_TYPE] | Selectable)?

Upon further thoughts, I think it should be def literals(self, *documents: dict | Expression):. In this case both Constant and Map are child classes of Expression.

gemini-code-assist · 2026-03-05T00:29:59Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

+            documents: A `str` or `Selectable` expression. If a `str`, it's
+                       treated as a field path to an array of documents.
+                       If a `Selectable`, it's usually a `Constant`
+                       containing an array of documents (as dictionaries).


The Args section of the docstring is misleading. It describes a single argument, but the method accepts *documents. It also incorrectly states that a str is treated as a field path; the implementation treats it as a string literal. To use a field path, field() should be used explicitly.

Suggested change

documents: A `str` or `Selectable` expression. If a `str`, it's

treated as a field path to an array of documents.

If a `Selectable`, it's usually a `Constant`

containing an array of documents (as dictionaries).

documents: One or more documents to be returned by this stage.

Each can be a `dict`, a `str` literal, or a

`Selectable` expression (e.g. `field("path")` or

`Constant.of(...)`).

+1. Usually I'd put the * in here too: *documents:

Updated the docstring to be more accurate.

packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_stages.py

daniel-sanche · 2026-03-05T22:21:10Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

+            documents: A `str` or `Selectable` expression. If a `str`, it's
+                       treated as a field path to an array of documents.
+                       If a `Selectable`, it's usually a `Constant`
+                       containing an array of documents (as dictionaries).


+1. Usually I'd put the * in here too: *documents:

daniel-sanche · 2026-03-05T22:25:45Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

            stages.FindNearest(field, vector, distance_measure, options)
        )

+    def literals(self, *documents: str | Selectable) -> "_BasePipeline":


You can probably ignore this, unless that's how other languages handle it

daniel-sanche · 2026-03-05T22:30:50Z

packages/google-cloud-firestore/tests/system/pipeline_e2e/general.yaml

+    pipeline:
+      - Literals:
+        - title: "The Hitchhiker's Guide to the Galaxy"
+          author: "Douglas Adams"


Maybe it's been a while since I looked at this, but this doesn't seem like the right syntax to me. Isn't this essentially sending Literals({"title": ""The Hitchhiker's Guide to the Galaxy", "author", "Douglas Adams"})? That doesn't seem to match the str | Selectable

Does the test pass?

It does pass. I think Literals should be able to accept dicts, as well as other Expression types. I have updated the system test to include dict and Constant (a child class of Expression).

daniel-sanche · 2026-03-05T22:34:23Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

+            ...     {"name": "alice", "age": 40}
+            ... ]
+            >>> pipeline = client.pipeline()
+            ...     .literals(Constant.of(documents))


Looking at the code, it seems like:

Constant isn't a Selectable

Constant doesn't seem like it supports dict types. (We do have a Map, which serves that purpose, but it doesn't seem Selectable either)

Thanks for catching this! I spent some time to check the internal docs, and I think Expression class and dict should be supported per the following language:

While literal values are the most common, it is also possible to pass in expressions, which will be evaluated and returned, making it possible to test out different query / expression behavior without first needing to create some test data.

daniel-sanche · 2026-03-05T22:36:58Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

            stages.FindNearest(field, vector, distance_measure, options)
        )

+    def literals(self, *documents: str | Selectable) -> "_BasePipeline":


Actually, looking at go, it seems like it accepts dicts, but not strings?

I don't know much about this stage, but from what I've seen, it's supposed to deal with maps. So maybe this should be def literals(self, *documents: Map | dict[str, CONSTANT_TYPE] | Selectable)?

daniel-sanche · 2026-03-05T22:38:17Z

packages/google-cloud-firestore/tests/unit/v1/test_pipeline_stages.py

+        val2 = Constant.of({"b": 2})
+        instance = self._make_one(val1, val2)
+        assert instance.documents == (val1, val2)
+        assert instance.name == "literals"


We should have tests that cover all supported input types. I don't see anything using str (and looking at go, I'm not sure if we should be supporting str?)

Indeed, I don't think we should support str. Here the test includes dict and Constant, which serves as an example of Expression's child class. It seems too cumbersome to test for each and every child class of Expression? What do you think.

daniel-sanche · 2026-03-05T22:38:39Z

packages/google-cloud-firestore/tests/system/pipeline_e2e/general.yaml

+                  stringValue: "Douglas Adams"
+                title:
+                  stringValue: "The Hitchhiker's Guide to the Galaxy"
+          name: literals


We should also have tests here that cover the different input types we support

Good catch! I added additional type to test.

feat: literals pipeline stage

2a8213c

Linchin requested review from a team as code owners March 5, 2026 00:27

Linchin changed the title ~~feat: literals pipeline stage~~ feat(firestore): literals pipeline stage Mar 5, 2026

gemini-code-assist bot reviewed Mar 5, 2026

View reviewed changes

Linchin assigned daniel-sanche Mar 5, 2026

daniel-sanche requested changes Mar 5, 2026

View reviewed changes

Linchin added 6 commits March 6, 2026 21:37

add dict as supported type and update docstring

28acee9

correct docstring and type annotation

a2e11ed

type annotation

a97cb13

add more unit tests

cc1b737

correct docstring

3861223

add cases to system test

7bad13c

Linchin requested a review from daniel-sanche March 9, 2026 21:38

	def literals(self, *documents: str \| Selectable) -> "_BasePipeline":
	def literals(self, *documents: dict \| str \| Selectable) -> "_BasePipeline":

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