Moved C Bridge from dotnet-sdk to core-sdk repo (#951)

Moved in Core C bridge from sdk-dotnet. Also fixed unused import warning in integration tests on Linux/ARM.

C bridge breaking changes:
- Renamed crate to `temporal_sdk_core_c_bridge`
- Renamed header file to `temporal-sdk-core-c-bridge.h`
- Added `temporal_core_` prefix to exported C functions and `TemporalCore` prefix to exported types
- Changed `TestServerOptions::download_ttl_ms` to `download_ttl_seconds`

Other:
- Upgraded to edition 2024, cleaned up dependencies
- Added missing RPC calls
- Added some smoke tests for the bridge
- Moved LTO profile to workspace root
- Added git diff check to CI
- Various lints and formatting

Author: maciejdudko

.github/workflows/per-pr.yml

@@ -34,6 +34,8 @@ jobs:
       - run: cargo doc --workspace --all-features --no-deps
       - run: cargo lint
       - run: cargo test-lint
+      - run: cargo check
+      - run: git diff --exit-code
 
   test:
     name: Unit Tests

AGENTS.md

@@ -8,6 +8,7 @@ document as your quick reference when submitting pull requests.
 - `core/` – implementation of the core SDK
 - `client/` – clients for communicating with Temporal clusters
 - `core-api/` – API definitions exposed by core
+- `core-c-bridge/` – C interface for core
 - `sdk/` – pre-alpha Rust SDK built on top of core (used mainly for tests)
 - `sdk-core-protos/` – protobuf definitions shared across crates
 - `fsm/` – state machine implementation and macros

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = ["core", "client", "core-api", "fsm", "test-utils", "sdk-core-protos", "sdk"]
+members = ["core", "client", "core-api", "fsm", "test-utils", "sdk-core-protos", "sdk", "core-c-bridge"]
 resolver = "2"
 
 [workspace.package]
@@ -18,3 +18,7 @@ prost-types = "0.13"
 
 [workspace.lints.rust]
 unreachable_pub = "warn"
+
+[profile.release-lto]
+inherits = "release"
+lto = true

README.md

@@ -26,13 +26,14 @@ installed to build Core.
 
 This repo is composed of multiple crates:
 
-- temporal-sdk-core-protos `./sdk-core-protos` - Holds the generated proto code and extensions
-- temporal-client `./client` - Defines client(s) for interacting with the Temporal gRPC service
-- temporal-sdk-core-api `./core-api` - Defines the API surface exposed by Core
-- temporal-sdk-core `./core` - The Core implementation
+- temporal-sdk-core-protos `./sdk-core-protos` - Holds the generated proto code and extensions.
+- temporal-client `./client` - Defines client(s) for interacting with the Temporal gRPC service.
+- temporal-sdk-core-api `./core-api` - Defines the API surface exposed by Core.
+- temporal-sdk-core `./core` - The Core implementation.
+- temporal-sdk-core-c-bridge `./core-c-bridge` - Provides C bindings for Core.
 - temporal-sdk `./sdk` - A (currently prototype) Rust SDK built on top of Core. Used for testing.
 - rustfsm `./fsm` - Implements a procedural macro used by core for defining state machines
-  (contains subcrates). It is temporal agnostic.
+  (contains subcrates). It is Temporal-agnostic.
 
 Visualized (dev dependencies are in blue):
 

core-c-bridge/Cargo.toml

@@ -0,0 +1,49 @@
+[package]
+name = "temporal-sdk-core-c-bridge"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+name = "temporal_sdk_core_c_bridge"
+crate-type = ["cdylib"]
+
+[dependencies]
+anyhow = "1.0"
+async-trait = "0.1"
+libc = "0.2"
+prost = { workspace = true }
+# We rely on Cargo semver rules not updating a 0.x to 0.y. Per the rand
+# documentation, before 1.0, minor 0.x updates _can_ break portability which can
+# cause non-determinism.
+rand = "0.8.5"
+rand_pcg = "0.3.1"
+serde_json = "1.0"
+tokio = "1.26"
+tokio-stream = "0.1"
+tokio-util = "0.7"
+tonic = { workspace = true }
+tracing = "0.1"
+url = "2.2"
+
+[dependencies.temporal-client]
+path = "../client"
+
+[dependencies.temporal-sdk-core]
+path = "../core"
+features = ["ephemeral-server"]
+
+[dependencies.temporal-sdk-core-api]
+path = "../core-api"
+
+[dependencies.temporal-sdk-core-protos]
+path = "../sdk-core-protos"
+
+[dev-dependencies]
+futures-util = "0.3"
+thiserror = { workspace = true }
+
+[dev-dependencies.temporal-sdk-core-test-utils]
+path = "../test-utils"
+
+[build-dependencies]
+cbindgen = { version = "0.29", default-features = false }

core-c-bridge/build.rs

@@ -0,0 +1,25 @@
+extern crate cbindgen;
+
+use std::env;
+
+fn main() {
+    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+
+    let changed = cbindgen::Builder::new()
+        .with_cpp_compat(true)
+        .with_crate(crate_dir)
+        .with_pragma_once(true)
+        .with_language(cbindgen::Language::C)
+        .with_item_prefix("TemporalCore")
+        .generate()
+        .expect("Unable to generate bindings")
+        .write_to_file("include/temporal-sdk-core-c-bridge.h");
+
+    // If this changed and an env var disallows change, error
+    if let Ok(env_val) = env::var("TEMPORAL_SDK_BRIDGE_DISABLE_HEADER_CHANGE") {
+        if changed && env_val == "true" {
+            println!("cargo:warning=bridge's header file changed unexpectedly from what's on disk");
+            std::process::exit(1);
+        }
+    }
+}