feat(storage): Support GCS Get Service Account by ccbcqbz · Pull Request #5738 · googleapis/google-cloud-rust

ccbcqbz · 2026-05-26T00:50:55Z

feat(storage): Support GCS Get Service Account REST endpoint

Closes a GCS feature gap by implementing the control plane feature. This retrieves the email address of the Google Cloud Storage service agent for a given project, creating it under the hood if it does not yet exist.

Main changes:

Data Modeling: Created JSON deserializer in using for robust unknown fields preservation (forward compatibility).
Request Builder: Added a public fluent request builder and runner in utilizing standard GAX execution pipelines.
Client Integration: Wired the API cleanly into the mockable trait (), handwritten REST client (), and (plain and traced paths).
Unit & E2E Tests: Added mock HTTP REST server unit tests, deserialization unit tests, and wired up a live end-to-end integration test in hitting the live GCS control plane.

gemini-code-assist

Code Review

This pull request implements the get_service_account API for the GCS client, allowing users to fetch the service account email address for a given project. The review feedback highlights three main issues: a compilation error when passing a LazyLock<String> to HeaderValue::from_static, a potential double-prefix bug in tracing if the projects/ prefix is not stripped early, and a lack of percent-encoding for project IDs containing domain names.

codecov · 2026-05-26T00:59:30Z

Codecov Report

❌ Patch coverage is 77.10280% with 49 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.80%. Comparing base (2f2c1e7) to head (cfe6e6d).

Files with missing lines	Patch %	Lines
src/storage/src/storage/get_service_account.rs	83.33%	25 Missing ⚠️
src/storage/src/storage/transport.rs	54.05%	17 Missing ⚠️
src/storage/src/storage/stub.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5738      +/-   ##
==========================================
- Coverage   97.88%   97.80%   -0.08%     
==========================================
  Files         226      227       +1     
  Lines       55797    56011     +214     
==========================================
+ Hits        54619    54784     +165     
- Misses       1178     1227      +49

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joshuatants · 2026-05-26T02:29:19Z

In Rust, it is possible to have impl blocks for a given struct split across different files, as long as all the files are in the same crate.

https://doc.rust-lang.org/reference/items/implementations.html#r-items.impl.inherent.coherence
https://doc.rust-lang.org/book/ch05-03-method-syntax.html#multiple-impl-blocks

Therefore, even if there is an impl block for StorageControl in generated/client.rs, you can still add hand-written code to StorageControl by starting another impl block, say in control/client.rs itself.

I would not want to put a control-plane function in the data-plane client, unless there is really no way to put it in StorageControl.

Can you try putting this on StorageControl instead?

ccbcqbz · 2026-05-26T02:57:03Z

starting another impl block, say in control/client.rs

Hi @joshuatants , thanks for the comments. You're right, we can add new methods to handwritten control/client.rs via a separate impl block, but the blocker issue is that we cannot add new fields (like a REST HTTP client) to the StorageControl struct without causing compile-time failures in the auto-generated control/generated/client.rs, due to the fact that all fields of a struct must be declared inside the original struct definition block itself in Rust.

For example, compilation will fail for generated client when adding a new field to the handwritten client:

error[E0063]: missing field `test_field` in initializer of `control::client::StorageControl`
   --> src/storage/src/control/generated/client.rs:530:12
    |
530 |         Ok(Self { storage, control })
    |            ^^^^ missing `test_field`

And the project service account retrieval is a GCS JSON/REST-only feature (GET /storage/v1/projects/{project}/serviceAccount). It is not supported by the GCS gRPC control plane services. This is why get_service_account must reside on Storage, which already contains a fully initialized, handwritten REST engine.

This also likely explains why other language SDKs have implemented this feature in the storage client, despite it functionally being more of a control plane operation.

… bugs in tracing

…and add unit test coverage

…rs tests

coryan

i think it may be better to implement this function in the gRPC API and then let the generator do its job. @joshuatants this is your call.

coryan · 2026-05-26T12:50:54Z

 pub(crate) mod checksum;
 pub(crate) mod client;
 pub(crate) mod common_options;
+pub mod get_service_account;


That makes the module public, which you may not want to do.

Good catch. I've changed it to internal.

coryan · 2026-05-26T12:51:37Z

+    let project = project_id()?;
+
+    tracing::info!("testing get_service_account() for project: {project}");
+    let email = client.get_service_account(project).send().await?;


All the other APIs consume projects/_/buckets/{bucket_id} or anywhere cache names that are fully qualified. That is intentional, to keep the generated StorageControl working without a hand-written layer. Consider changing this to projects/{project}.

coryan · 2026-05-26T12:52:22Z

+    #[serde(flatten)]
+    pub unknown_fields: std::collections::HashMap<String, serde_json::Value>,


Why is this public?

coryan · 2026-05-26T12:53:44Z

+#[serde(default, rename_all = "camelCase")]
+pub(crate) struct ProjectServiceAccount {
+    pub kind: String,
+    #[serde(rename = "email_address")]


Maybe

Suggested change

#[serde(default, rename_all = "camelCase")]

pub(crate) struct ProjectServiceAccount {

pub kind: String,

#[serde(rename = "email_address")]

pub(crate) struct ProjectServiceAccount {

pub kind: String,

No sense in specifying the field name format and then overriding the format for the one field name where it matters?

coryan · 2026-05-26T12:55:08Z

+    /// Implements [crate::client::Storage::get_service_account].
+    fn get_service_account(
+        &self,
+        _project: String,


You want something like:

Suggested change

_project: String,

_request: GetServiceAccountRequest,

Because the thing may receive a request in the future.

coryan · 2026-05-26T12:55:49Z

+    /// # Design Note (Architectural Exception):
+    /// Logically, this administrative operation belongs to the control plane (`StorageControl`).
+    /// However, since the GCS gRPC control plane does not support project service account retrieval,
+    /// we place it here in the handwritten REST client to avoid altering machine-generated code.


This does not belong in the public documentation...

coryan · 2026-05-26T12:58:40Z

+    /// # Parameters
+    /// * `project` - the Project ID or project number.


Suggested change

/// # Parameters

/// * `project` - the Project ID or project number.

/// # Parameters

/// * `project` - the project name, either `projects/{projectId}` or `projects/{projectNumber}`.

/// See [The project resource] for more information about projects and their identifiers.

///

/// [The project resource]: https://docs.cloud.google.com/resource-manager/docs/cloud-platform-resource-hierarchy#projects

joshuatants · 2026-05-29T05:58:10Z

i think it may be better to implement this function in the gRPC API and then let the generator do its job. @joshuatants this is your call.

Thanks @coryan . Chatted with the rest of the SDK team. We agreed that we'll skip this API for now and try to get it implemented in the gRPC API.

Appreciate the work @ccbcqbz !

product-auto-label Bot added the api: storage Issues related to the Cloud Storage API. label May 26, 2026

gemini-code-assist Bot reviewed May 26, 2026

View reviewed changes

Comment thread src/storage/src/storage/get_service_account.rs

Comment thread src/storage/src/storage/get_service_account.rs

Comment thread src/storage/src/storage/get_service_account.rs

Chen Chen added 2 commits May 26, 2026 01:19

feat(storage): Support GCS Get Service Account

32ea9f4

docs(storage): Add GCS Get Service Account client example

4965ea4

ccbcqbz force-pushed the branch-get-service-account branch from f1af51a to 4965ea4 Compare May 26, 2026 01:19

Chen Chen added 3 commits May 26, 2026 03:09

refactor(storage): Import and reference X_GOOG_API_CLIENT_HEADER locally

8e9f03e

fix(storage): Normalize project string early to prevent double-prefix…

fd6416d

… bugs in tracing

fix(storage): Percent-encode project ID in GetServiceAccount request …

7071a98

…and add unit test coverage

ccbcqbz marked this pull request as ready for review May 26, 2026 04:25

ccbcqbz requested review from a team as code owners May 26, 2026 04:25

Chen Chen added 3 commits May 26, 2026 04:28

fix(storage): Remove unused import super::* from get_service_account.…

401bd76

…rs tests

style(storage): Apply cargo fmt standard formatting

8422799

style(storage): Apply cargo fmt formatting to integration tests

cfe6e6d

coryan reviewed May 26, 2026

View reviewed changes

refactor(storage): address code review feedback on get_service_account

466bba0

joshuatants closed this May 29, 2026

		#[serde(flatten)]
		pub unknown_fields: std::collections::HashMap<String, serde_json::Value>,

		/// # Parameters
		/// * `project` - the Project ID or project number.

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ccbcqbz commented May 26, 2026

Main changes:

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joshuatants commented May 29, 2026

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