From 01153b6efaec26474cf13f6e337b27c37e2900c6 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Sat, 17 Feb 2024 20:58:47 -0800
Subject: [PATCH] Support switching Rust library backend with cargo features
 (#93)

---
 .github/workflows/build-rust.yml | 16 ++--------
 rust/Cargo.toml                  |  5 ++++
 rust/build.rs                    | 50 ++++++++++++++++++++------------
 3 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/.github/workflows/build-rust.yml b/.github/workflows/build-rust.yml
index 5de1d942..b817d014 100644
--- a/.github/workflows/build-rust.yml
+++ b/.github/workflows/build-rust.yml
@@ -70,23 +70,11 @@ jobs:
           version: latest
           platform: x64
 
-      - name: Select optimizer backend (non-macOS)
-        if: ${{ !startsWith(matrix.os, 'macOS') }}
-        run: |
-          sed -i 's/let optimizer_backend = "[a-z]\+"/let optimizer_backend = "${{ matrix.optimizer_backend }}"/' rust/build.rs
-          grep 'let optimizer_backend' rust/build.rs
-
-      - name: Select optimizer backend (macOS)
-        if: startsWith(matrix.os, 'macOS')
-        run: |
-          sed -i '' 's/let optimizer_backend = "[a-z]\+"/let optimizer_backend = "${{ matrix.optimizer_backend }}"/' rust/build.rs
-          grep 'let optimizer_backend' rust/build.rs
-
       - name: Build Rust
         working-directory: rust
-        run: cargo build --target ${{ matrix.rust-target }}
+        run: cargo build --target ${{ matrix.rust-target }} --features ${{ matrix.optimizer_backend }}
 
       - name: Run Rust
         if: matrix.rust-target != 'aarch64-apple-darwin' && matrix.rust-target != 'x86_64-pc-windows-gnu'
         working-directory: rust
-        run: cargo run --example swerve --target ${{ matrix.rust-target }}
+        run: cargo run --example swerve --target ${{ matrix.rust-target }} --features ${{ matrix.optimizer_backend }}
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index dcd65f59..b2f68114 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -16,5 +16,10 @@ cmake = "0.1"
 [lib]
 name = "trajoptlib"
 
+[features]
+default = []
+sleipnir = []
+casadi = []
+
 [[example]]
 name = "swerve"
diff --git a/rust/build.rs b/rust/build.rs
index 1558bcfa..b98259ba 100644
--- a/rust/build.rs
+++ b/rust/build.rs
@@ -2,15 +2,34 @@ use cmake::Config;
 
 fn main() -> miette::Result<()> {
     let mut cmake_config = Config::new("..");
-    let optimizer_backend = "casadi";
 
     cmake_config
         .profile("RelWithDebInfo")
-        .define("OPTIMIZER_BACKEND", optimizer_backend)
         .define("BUILD_TESTING", "OFF");
 
-    if cfg!(target_os = "windows") {
-        if optimizer_backend == "casadi" {
+    if cfg!(feature = "sleipnir") && cfg!(feature = "casadi") {
+        panic!("Only select one optimizer backend via cargo `--features sleipnir` or `--features casadi`.");
+    }
+
+    if cfg!(feature = "sleipnir") {
+        cmake_config
+            .define("OPTIMIZER_BACKEND", "sleipnir")
+            .define("BUILD_SHARED_LIBS", "OFF");
+
+        if cfg!(target_os = "windows") {
+            cmake_config
+                .generator("Visual Studio 17 2022")
+                .define("CMAKE_GENERATOR_PLATFORM", "x64")
+                .cxxflag("/EHsc");
+        } else if cfg!(target_os = "linux") {
+            cmake_config
+                .define("CMAKE_CXX_COMPILER", "g++")
+                .define("CMAKE_C_COMPILER", "gcc");
+        }
+    } else if cfg!(feature = "casadi") {
+        cmake_config.define("OPTIMIZER_BACKEND", "casadi");
+
+        if cfg!(target_os = "windows") {
             cmake_config
                 .generator("MinGW Makefiles")
                 .define("CMAKE_CXX_COMPILER", "x86_64-w64-mingw32-g++")
@@ -20,22 +39,15 @@ fn main() -> miette::Result<()> {
                     "-static-libgcc -static-libstdc++",
                 )
                 .define("CMAKE_EXE_LINKER_FLAGS", "-static-libgcc -static-libstdc++");
-        } else if optimizer_backend == "sleipnir" {
+        } else if cfg!(target_os = "linux") {
             cmake_config
-                .generator("Visual Studio 17 2022")
-                .define("CMAKE_GENERATOR_PLATFORM", "x64")
-                .cxxflag("/EHsc");
+                .define("CMAKE_CXX_COMPILER", "g++")
+                .define("CMAKE_C_COMPILER", "gcc");
         }
-    }
-
-    if cfg!(target_os = "linux") {
-        cmake_config
-            .define("CMAKE_CXX_COMPILER", "g++")
-            .define("CMAKE_C_COMPILER", "gcc");
-    }
-
-    if optimizer_backend == "sleipnir" {
-        cmake_config.define("BUILD_SHARED_LIBS", "OFF");
+    } else {
+        panic!(
+            "Select an optimizer backend via cargo `--features sleipnir` or `--features casadi`."
+        );
     }
 
     let dst = cmake_config.build();
@@ -43,7 +55,7 @@ fn main() -> miette::Result<()> {
     println!("cargo:rustc-link-search=native={}/bin", dst.display());
     println!("cargo:rustc-link-search=native={}/lib", dst.display());
     println!("cargo:rustc-link-lib=TrajoptLib");
-    if optimizer_backend == "sleipnir" {
+    if cfg!(feature = "sleipnir") {
         println!("cargo:rustc-link-lib=Sleipnir");
         println!("cargo:rustc-link-lib=fmt");
     }