[WIP] Native Rust codegen: BAML IR to Rust types with Client Templates #2348

CeciliaZ030 · 2025-08-20T17:25:02Z

Summary

Adds first-pass native Rust code generation:

Converts BAML IR directly into idiomatic Rust types.
Integrates Askama templates for Rust emission.
Scaffolds function stubs and generator plumbing.

Repo: aomi-labs/baml

What's changed

Rust generator updates under engine/generators/languages/rust/src/** to emit native Rust types from IR.
IR→Rust pipelines for classes, enums, unions, and function stubs.
Integration hooks in generator library and CLI paths to enable Rust codegen.

Testing

Ran generator locally; emitted Rust builds for representative IR structures.
Smoke-tested function stubs and type shapes.

Next PR

Implement rust_language_client.
Decide process model to avoid FFI:
- Spawn client as a subprocess of the server, or
- Spawn server as a subprocess of the client.

Checklist

IR → native Rust type emission
Askama template integration
Integration tests + CI + docs
rust_language_client (next PR)
Subprocess orchestration + protocol (next PR)

Important

Adds Rust code generation for BAML IR using Askama templates, with support for classes, enums, unions, and function stubs.

Behavior:
- Converts BAML IR to Rust types using Askama templates in engine/generators/languages/rust/src/**.
- Adds generate_sdk_files in lib.rs to generate Rust SDK files.
- Supports classes, enums, unions, and function stubs.
Templates:
- Defines Cargo.toml and lib.rs templates for Rust client.
Integration:
- Prepares generate_sdk in generators_lib/src/lib.rs for Rust codegen (marked as todo).
CFFI:
- Updates cffi.pb.go for CFFI protocol buffer changes.

^{This description was created by}^{for 2309b48. You can customize this summary. It will automatically update as commits are pushed.}

- Add BAML-RUST.md: Comprehensive analysis of Rust client implementation approach - Add BAML-GO.md: Deep dive into Go client FFI architecture and performance - Document why OpenAPI-generated Rust clients are limited (~60% feature loss) - Outline implementation plan for native Rust client generator - Compare direct FFI clients vs HTTP-based clients 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]>

entelligence-ai-pr-reviews · 2025-08-20T17:25:05Z

🚀 Code Review Initiated

The review process for this pull request has started. Our system is analyzing the changes for:

Code quality, performance, and potential issues
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vercel · 2025-08-20T17:25:08Z

@CeciliaZ030 is attempting to deploy a commit to the Boundary Team on Vercel.

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ellipsis-dev

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Changes requested ❌

Reviewed everything up to 2309b48 in 6 minutes and 9 seconds. Click for details.

Reviewed 7760 lines of code in 30 files
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1. engine/baml-lib/baml-types/src/generator.rs:35

Draft comment:
The new Rust variant is added with default client mode set to Sync. Please double-check whether Sync is the desired default for Rust (vs. async) and document the rationale.
Reason this comment was not posted:
Comment did not seem useful. Confidence is useful = 0% <= threshold 50% The comment asks the PR author to double-check their choice and document the rationale, which violates the rule against asking for confirmation or explanation. It does not provide a specific suggestion or point out a clear issue with the code.

2. engine/generators/languages/rust/src/type.rs:305

Draft comment:
There is a duplicate implementation of safe_rust_identifier. Consolidate these into a single utility function to avoid maintenance issues.
Reason this comment was not posted:
Comment looked like it was already resolved.

3. engine/language_client_go/pkg/cffi/cffi.pb.go:328

Draft comment:
The generated protobuf code now omits the combined check for protoimpl.UnsafeEnabled && x != nil and always checks for x != nil. Ensure this change is intentional and document the rationale if it’s due to an update in protoc-gen-go.
Reason this comment was not posted:
Comment did not seem useful. Confidence is useful = 30% <= threshold 50% The comment is asking the author to ensure that a change is intentional and to document the rationale. This violates the rule against asking the author to confirm their intention or to update documentation. However, it does point out a specific change in behavior, which could be useful if it was framed differently.

Workflow ID: wflow_nAH9TterNQA9PnWn

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ellipsis-dev · 2025-08-20T17:32:27Z

engine/generators/languages/rust/src/functions.rs

+}}
+
+"#,
+            func.name.to_lowercase(),


Using to_lowercase() on the function name may be insufficient if the original name isn’t already in snake_case. Consider applying a proper snake_case conversion (e.g. via the provided to_snake_case in utils) to ensure valid Rust identifiers.

ellipsis-dev · 2025-08-20T17:32:27Z

engine/generators/languages/rust/src/package.rs

+                path.push_str("crate::");
+            } else if i > 0 {
+                path.push_str(part);
+                path.push_str("::");


The module path built in relative_from appends '::' after each part. Consider trimming the trailing separator for a cleaner module path when concatenating with type names.

ellipsis-dev · 2025-08-20T17:32:27Z

BAML-GO.md

+    cFunctionName := C.CString(functionName)
+    defer C.free(unsafe.Pointer(cFunctionName))
+
+    result := C.WrapCallFunctionStreamFromC(runtime, cFunctionName, cEncodedArgs, C.uintptr_t(len(encodedArgs)), C.uint32_t(id))


Typo: The variable 'cEncodedArgs' is used here, but the function parameter is named 'encodedArgs'. This appears to be a lexicographical error and should be corrected.

Suggested change

result := C.WrapCallFunctionStreamFromC(runtime, cFunctionName, cEncodedArgs, C.uintptr_t(len(encodedArgs)), C.uint32_t(id))

result := C.WrapCallFunctionStreamFromC(runtime, cFunctionName, encodedArgs, C.uintptr_t(len(encodedArgs)), C.uint32_t(id))

ellipsis-dev · 2025-08-20T17:32:27Z

engine/language_client_codegen/src/version_check.rs

@@ -113,6 +113,9 @@ pub fn check_version(
                GeneratorOutputType::Go => {
                    format!("go install github.com/boundaryml/baml/go@{gen_version}")
                }
+                GeneratorOutputType::Rust => {
+                    format!("cargo install baml-py --version {gen_version}")


Typo note: The Rust branch command uses "cargo install baml-py --version {gen_version}". Is "baml-py" the intended package name for Rust, or should it be something like "baml-rs" to match the Rust target? Please verify.

Suggested change

format!("cargo install baml-py --version {gen_version}")

format!("cargo install baml-rs --version {gen_version}")

- Refactor Rust client generation templates for improved code structure - Remove redundant runtime.rs.j2 template - Update generator configuration to support Rust client output - Add Rust generator to BAML test configuration 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]>

➜ generators: ✗ cargo test --package generators-rust

CeciliaZ030 and others added 3 commits August 19, 2025 22:09

initial rust implementation

c1907a2

Add Rust client implementation and type aliases support

2309b48

CeciliaZ030 changed the title ~~Native Rust codegen: BAML IR to Rust types with Client Templates~~ [WIP] Native Rust codegen: BAML IR to Rust types with Client Templates Aug 20, 2025

add rust _templates

14b517c

ellipsis-dev bot reviewed Aug 20, 2025

View reviewed changes

CeciliaZ030 and others added 7 commits August 21, 2025 21:05

Add rust_language_client implementation

26bf190

update

b1b1c29

claude workflow

cac290b

generated correct test structure at

6d2af1b

➜ generators: ✗ cargo test --package generators-rust

update

eb09266

rlib from baml_cffi re-export in rust + integration tests compiles

7e0645e

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[WIP] Native Rust codegen: BAML IR to Rust types with Client Templates #2348

[WIP] Native Rust codegen: BAML IR to Rust types with Client Templates #2348

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	result := C.WrapCallFunctionStreamFromC(runtime, cFunctionName, cEncodedArgs, C.uintptr_t(len(encodedArgs)), C.uint32_t(id))
	result := C.WrapCallFunctionStreamFromC(runtime, cFunctionName, encodedArgs, C.uintptr_t(len(encodedArgs)), C.uint32_t(id))

	format!("cargo install baml-py --version {gen_version}")
	format!("cargo install baml-rs --version {gen_version}")

[WIP] Native Rust codegen: BAML IR to Rust types with Client Templates #2348

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[WIP] Native Rust codegen: BAML IR to Rust types with Client Templates #2348

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Summary

What's changed

Testing

Next PR

Checklist

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CeciliaZ030 commented Aug 20, 2025 •

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