fix(rust): Fix broken module tree for nested proto packages

[dashed]

Summary

The sentry_protos v0.8.3 Rust crate on crates.io is broken — it fails to compile due to invalid super::super::super:: references in billing.v1.services.usage.v1.rs. This breaks Rust CI in all downstream consumers (e.g., sentry-kafka-schemas PR #476).

Root cause

The build_rust/src/main.rs code generator flattened all proto packages into 2-level name::version modules, discarding intermediate path segments. For example, sentry_protos.billing.v1.services.usage.v1 was mapped to a flat usage::v1 module at the crate root instead of being nested under billing::v1::services::usage::v1.

Prost generates super:: paths based on the full proto package hierarchy. From billing.v1.services.usage.v1, referencing a type in billing.v1 produces super::super::super::DataCategory (3 levels up). But the flat usage::v1 module is only 2 levels deep — so the super:: paths escape above the crate root, causing E0433 compilation errors.

Changes

• build_rust/src/main.rs: Replaced the custom ModuleTree code generation with prost-build's built-in include_file(), which generates properly nested module declarations matching the proto package hierarchy. A thin lib.rs re-exports the inner sentry_protos module to maintain the existing public API.
• rust/src/_include.rs: New prost-generated file with correctly nested pub mod declarations.
• rust/src/lib.rs: Simplified to 2 lines — includes the generated module file and re-exports.
• .github/workflows/ci.yml: Added cargo check && cargo clippy verification step after code generation and before auto-commit, so broken codegen is caught on the PR (this was the gap that allowed v0.8.3 to ship broken).
• rust/tests/codegen_test.rs: New integration tests — compile-time module importability checks, cross-package type reference roundtrips (the exact v0.8.3 bug scenario), and protobuf encode/decode verification.

Generated proto .rs files: unchanged

All sentry_protos.*.rs files are identical between this branch and main. Only the module structure changed.

Public API comparison

Module	main	This PR	Notes
billing::v1	crate::billing::v1	crate::billing::v1	Same (re-exported)
conduit::v1alpha	crate::conduit::v1alpha	crate::conduit::v1alpha	Same
seer::v1	crate::seer::v1	crate::seer::v1	Same
sentry::v1	crate::sentry::v1	crate::sentry::v1	Same
snuba::v1	crate::snuba::v1	crate::snuba::v1	Same
taskbroker::v1	crate::taskbroker::v1	crate::taskbroker::v1	Same
contract::v1	crate::contract::v1	crate::billing::v1::services::contract::v1	Path changed
usage::v1	crate::usage::v1 (broken)	crate::billing::v1::services::usage::v1	Fixed

Breaking change

contract::v1 moved from crate::contract::v1 to crate::billing::v1::services::contract::v1. The usage::v1 path change is not a regression since it never compiled.

Test plan

• cargo check passes
• cargo clippy passes (no warnings)
• cargo test passes — 5 integration tests covering cross-package roundtrips, contract types, and default messages
• All generated .rs proto files are unchanged vs main
• Verify sentry-kafka-schemas CI passes with this fix released

[github-actions]

The latest Buf updates on your PR. Results from workflow ci / buf-checks (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	⏩ skipped	✅ passed	✅ passed	Mar 13, 2026, 9:21 PM

[krithikravi]

lgtm, i was also running into this issue. i'd wait for someone else to chime in on this too though

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Unused regex dependency left in Cargo.toml
  • Removed the unused regex dependency from build_rust/Cargo.toml after confirming no code references it.

Or push these changes by commenting:

@cursor push 3af2bb227c

Preview (3af2bb227c)

diff --git a/build_rust/Cargo.toml b/build_rust/Cargo.toml
--- a/build_rust/Cargo.toml
+++ b/build_rust/Cargo.toml
@@ -13,7 +13,6 @@
 glob = "0.3.1"
 prost = "0.14"
 prost-types = "0.14"
-regex = "1.10.5"
 tokio = { version = "1.0", features = ["macros", "rt-multi-thread"] }
 tonic = "0.14"
 tonic-prost-build = "0.14"

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}

[evanh]

Thanks for adding all this!