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Language Client FFI

engine/language_client_cffi/README.md

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Language Client FFI

Internal FFI for the language client.

Prerequisites

  • Cargo Make
    Install with: cargo install cargo-make
  • cbindgen
    Install with: cargo install cbindgen

Build Instructions

  1. Build the CFFI Layer for the Go SDK:

    bash
    cd engine/language_client_cffi
# default
cargo make go-sdk
# release build
RELEASE_MODE=1 cargo make go-sdk

    This command:

    1. Builds the CFFI layer for the Go SDK.
      • Generates the C header file baml_cffi_generated.h for go-sdk
    2. Builds baml-cli
    3. Runs baml-cli generate in integ tests

  2. Build integration tests:

    bash
    cd integ-tests/go
go build
./integ-tests

Local Development with Go Tests

When developing changes to the CFFI layer, Go tests will by default download and use a cached version of the library from GitHub releases. To test your local changes:

  1. Build the CFFI library (debug mode is faster for iteration):

    bash
    cd engine/language_client_cffi
cargo build  # or cargo build --release for optimized build

    This creates: engine/target/debug/libbaml_cffi.dylib (macOS) or libbaml_cffi.so (Linux)

  2. Run Go tests with your local library:

    bash
    cd engine/generators/languages/go/generated_tests/dynamic_types  # or any test directory
BAML_LIBRARY_PATH=/path/to/baml/engine/target/debug/libbaml_cffi.dylib go test -v

    The BAML_LIBRARY_PATH environment variable tells the Go SDK to use your locally built library instead of the cached version.

  3. Regenerate Go test code (if you've changed code generation):

    bash
    cd engine/generators/languages/go
cargo test --lib  # Regenerates all Go test projects

Quick Development Loop

bash
# 1. Make changes to Rust code
vim engine/language_client_cffi/src/ffi/functions.rs

# 2. Rebuild CFFI
cd engine/language_client_cffi && cargo build

# 3. Test with your changes
cd ../generators/languages/go/generated_tests/dynamic_types
BAML_LIBRARY_PATH=$PWD/../../../target/debug/libbaml_cffi.dylib go test -v

Note: Without setting BAML_LIBRARY_PATH, Go tests will use the cached library at ~/.cache/baml/libs/{VERSION}/ or download from GitHub releases, which won't reflect your local changes.

Note: The actual go-sdk lives in ../language_client_go. The CFFI layer is a thin wrapper around the go-sdk.

Additional Information

For further details on configuration and advanced usage, please refer to the corresponding cargo-make tasks defined in your project configuration files or the Go project documentation in the integ-tests/go directory.