feat(dart): use proto presence info to generate null-safe code by devoncarew · Pull Request #2726 · googleapis/librarian

devoncarew · 2025-10-30T19:20:03Z

Use proto presence info to generate null-safe code:

annotateField updated to use information from proto optional annotations
toJson() implementations write values if they're nullable and have a non-null value, or if they're not nullable and have a non-default value for that type
fromJson parses a value for parse a value for nullable fields if one is given; it will parse any value for non-null field or fall back to using the default value for that type
properly dereference null values when referring to request fields for use in url paths
enums definitions now get a default value (EnumClass.$default)
removed the older annotate.requiredFields and tests (based on usage in service calls)
closes use the proto 'optional' keyword and proto3 field presence rules for field nullability google-cloud-dart#24

Tests are updated for buildQueryLines() to include optional fields. Tests were added for the createFromJsonLine() and createToJsonLine() methods; previously we got our testing here from being on the same repo as the dart code, and running the dart unit tests on the generator's putput.

In-lined from the PR:

proto 3 fields default to implicit presence

the 'optional' keyword changes a field to explicit presence

types like lists (repeated) and maps are always implicit presence

Explicit presence means that you can know whether the user set a value or
not. Implicit presence means you can always retrieve a value; if one had
not been set, you'll see the default value for that type.

We translate explicit presence (a optional annotation) to using a nullable
type for that field. We translate implicit presence (always returning some
value) to a non-null type.

Some short-hand:
- optional == explicit == nullable
- implicit == non-nullable
- lists and maps == implicit == non-nullable
- singular message == explicit == nullable

Sample output can be seen at googleapis/google-cloud-dart#58.

gemini-code-assist · 2025-10-30T19:20:31Z

Summary of Changes

Hello @devoncarew, 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 introduces comprehensive null-safety support into the generated Dart code by leveraging protobuf field presence information. The changes ensure that the generated Dart classes correctly reflect the nullability semantics of their corresponding proto definitions, leading to more robust and type-safe code. This involves significant updates to how fields are annotated, how JSON serialization and deserialization are handled, and how URL paths are constructed, ultimately improving the reliability and maintainability of the generated Dart API clients.

Highlights

Null-Safety Integration: The code generation now leverages protobuf presence information to produce null-safe Dart code, distinguishing between explicit (nullable) and implicit (non-nullable) presence.
Field Annotation Logic: The annotateField function has been significantly updated to determine field nullability and calculate appropriate default values based on proto field properties (e.g., repeated, map, optional, oneof).
JSON Serialization/Deserialization: toJson() implementations now conditionally write values: if a field is nullable and has a non-null value, or if it's non-nullable and has a non-default value. fromJson() parsing correctly handles nullable fields and falls back to default values for non-nullable ones.
URL Path Handling: Dereferencing of request fields in URL paths has been improved to correctly handle potentially null values, using Dart's null-aware operators (!.).
Enum Enhancements: Generated enum definitions now include a static $default field (set to the first enum value) and an isNotDefault getter for checking against this default.
Removed Legacy Logic: The older annotate.requiredFields mechanism and its associated calculateRequiredFields function have been removed, streamlining the annotation process.
Expanded Test Coverage: New unit tests have been added for createFromJsonLine() and createToJsonLine() methods, and existing buildQueryLines() tests were updated to reflect the new null-safety and default value handling.

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gemini-code-assist

Code Review

This pull request makes significant strides in generating null-safe Dart code by leveraging protobuf field presence information. The approach to handling nullability in toJson and fromJson is largely well-executed, and the addition of new tests is a great improvement. However, I've identified a couple of critical issues that could lead to incorrect or non-compilable generated code. Specifically, there's a flaw in how the nullability of singular message fields is determined, and there are incorrect null-assertions on repeated fields when generating query parameters. I've also included a suggestion to enhance code maintainability.

internal/sidekick/internal/dart/annotate.go

codecov · 2025-10-30T19:24:30Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.92%. Comparing base (01675b7) to head (1064995).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2726      +/-   ##
==========================================
+ Coverage   86.72%   86.92%   +0.19%     
==========================================
  Files         118      118              
  Lines        9824     9896      +72     
==========================================
+ Hits         8520     8602      +82     
+ Misses        920      915       -5     
+ Partials      384      379       -5

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internal/sidekick/internal/dart/annotate.go

brianquinlan

There are a few unconvered lines. Could you see if it is possible to add tests for them?

devoncarew · 2025-10-31T18:41:47Z

There are a few unconvered lines. Could you see if it is possible to add tests for them?

For sure (I haven't gotten into the habit of looking at the coverage output).

devoncarew

I added a few more cases for existing tests - this PR now increases overall test coverage by 0.19% 🚀

brianquinlan · 2025-10-31T19:28:19Z

I added a few more cases for existing tests - this PR now increases overall test coverage by 0.19% 🚀

Awesome, merge at will.

@brianquinlan

Update the packages here using the null-safety generator change: - a follow up to googleapis/librarian#2726 - update sidekick version reference - re-generate the code - update the hand-written code (part files, examples, and tests) Previously as a draft at #58; done as separate commits to make review a little easier. @brianquinlan, this does not include sidekick / dart package version changes. I assume we'll want to bump everything (to 0.2.0?). Not sure if we're bumping on changes or on publish (or don't have a specific process yet).

PR created by the Librarian CLI to initialize a release. Merging this PR will auto trigger a release. Librarian Version: not available Language Image: us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/librarian-release-container:latest <details><summary>librarian: 1.0.0</summary> ## [1.0.0](v0.5.0...v1.0.0) (2025-11-06) ### Features * Remove `..._gax` dependency (#2713) ([01675b7](01675b72)) * add context to Librarian PRs (#2698) ([0523329](0523329a)) * add a package comment linter (#2712) ([1bd3e32](1bd3e32e)) * generate pom.xml files (#2682) ([50b95f2](50b95f20)) * add test-container test logic (#2656) ([514cf7e](514cf7e5)) * improve rust-publish logging (#2671) ([585ed50](585ed50b)) * write a timing log at the end of update-image (#2771) ([5fc9e3b](5fc9e3b6)) * migrate Java container from sdk-platform-java (#2670) ([69ac47f](69ac47fd)) * switch to original head after running update-image (#2696) ([7a3e404](7a3e404a)) * format bulk commit from other sources in release notes (#2665) ([7c52da2](7c52da2b)) * enable multi-version API generation (#2699) ([86c5250](86c52507)) * release stage to update pom.xml files (#2772) ([be56755](be567550)) * use proto presence info to generate null-safe code (#2726) ([e36fb81](e36fb81a)) * Base messages in google_cloud_protobuf (#2660) ([e607ea6](e607ea63)) ### Bug Fixes * retry Github 503 requests up to 3 times (#2650) ([09468fa](09468faf)) * Changed docs to ConfigurationException (#2697) ([0950c1e](0950c1e3)) * fix the reference to the old "librariangen" folder (#2677) ([09dc53f](09dc53fe)) * run godoclint via golangci-lint (#2751) ([264a6a0](264a6a0e)) * pass context as the first argument (#2769) ([298a3bd](298a3bd8)) * Move HTTP client creation to `_gax` (#2672) ([4968d63](4968d63d)) * deduplicate bulk commits (#2758) ([4dfae9a](4dfae9ae)) * Support additional api paths for an existing library (#2666) ([50046f5](50046f55)) * remove stray TODO (#2748) ([5072f0e](5072f0e0)) * omit status field when empty (#2654) ([572ae4f](572ae4f3)) * use T.Context in tests (#2768) ([7e7cd2d](7e7cd2dd)) * wrap error to provide more context for commitAndPush (#2767) ([a2a41a4](a2a41a4a)) * use t.Fatal in tests for proper failure handling (#2759) ([cdabb28](cdabb287)) * enforce removal before copying library files (#2765) ([d5ac6c8](d5ac6c87)) * change log level to debug (#2798) ([f042d0b](f042d0bd)) * change path to `doc.go` in docgen test (#2700) ([fd6bae4](fd6bae40)) ### Documentation * use consistent library id in flags and examples (#2770) ([87a1005](87a10056)) </details>

feat(dart): use proto presence info to generate null-safe code

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devoncarew requested review from a team and brianquinlan October 30, 2025 19:20

gemini-code-assist bot reviewed Oct 30, 2025

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brianquinlan reviewed Oct 30, 2025

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devoncarew added 3 commits October 30, 2025 18:46

check and use the field.Behavior / api.FIELD_BEHAVIOR_REQUIRED info

57f8df9

improve message presence logic

b33a291

merge to main

3bc34e6

brianquinlan previously approved these changes Oct 31, 2025

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add tests for uncovered lines

1064995

devoncarew dismissed brianquinlan’s stale review via 1064995 October 31, 2025 19:01

devoncarew commented Oct 31, 2025

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brianquinlan approved these changes Oct 31, 2025

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devoncarew merged commit e36fb81 into googleapis:main Oct 31, 2025
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devoncarew mentioned this pull request Oct 31, 2025

feat: update using null-safety generator change googleapis/google-cloud-dart#69

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cloud-sdk-librarian-robot mentioned this pull request Nov 6, 2025

chore: librarian release pull request: 20251106T080249Z #2805

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ldetmer mentioned this pull request Nov 6, 2025

chore: librarian release pull request: 20251106T145301Z #2808

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feat(dart): use proto presence info to generate null-safe code#2726

feat(dart): use proto presence info to generate null-safe code#2726
devoncarew merged 5 commits intogoogleapis:mainfrom
devoncarew:dart_null_safety

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