feat: Auto-detect and define build_type setting

Use the environment variables set by Cargo for the build scripts
to detect and define the `build_type` setting for Conan.

Build the example / test crate using both Debug and Release profiles.

.github/workflows/rust.yml

@@ -27,7 +27,9 @@ jobs:
     - name: Run tests
       run: cargo test --verbose -- --test-threads=1
     - name: Test build the example crates
-      run: cargo build -p example-build-script -vv
+      run: |
+        cargo build -p example-build-script -vv
+        cargo build -p example-build-script -vv --release
     - name: Test run the build script example
       run: cargo run -p example-build-script
   fmt:

.gitlab-ci.yml

@@ -42,4 +42,5 @@ runtests:
     script:
       - cargo test --verbose -- --test-threads=1
       - cargo build -p example-build-script -vv
+      - cargo build -p example-build-script -vv --release
       - cargo run -p example-build-script

README.md

@@ -40,6 +40,9 @@ fn main() {
 }
 ```
 
+The most commonly used `build_type` Conan setting will be defined automatically
+depending on the current Cargo build profile: Debug or Release.
+
 The Conan executable is assumed to be named `conan` unless
 the `CONAN` environment variable is set to override.
 

src/lib.rs

@@ -38,6 +38,9 @@
 //! ConanInstall::new().run().parse().emit();
 //! ```
 //!
+//! The most commonly used `build_type` Conan setting will be defined automatically
+//! depending on the current Cargo build profile: Debug or Release.
+//!
 //! The Conan executable is assumed to be named `conan` unless
 //! the `CONAN` environment variable is set to override.
 //!
@@ -181,12 +184,35 @@ impl ConanInstall {
             command.arg(build);
         }
 
+        // Use additional environment variables set by Cargo.
+        Self::add_settings_from_env(&mut command);
+
         let output = command
             .output()
             .expect("failed to run the Conan executable");
 
         ConanOutput(output)
     }
+
+    /// Adds automatic Conan settings arguments derived
+    /// from the environment variables set by Cargo.
+    ///
+    /// The following Conan settings are auto-detected and set:
+    ///
+    /// - `build_type`
+    fn add_settings_from_env(command: &mut Command) {
+        match std::env::var("PROFILE").as_deref() {
+            Ok("debug") => {
+                command.arg("-s");
+                command.arg("build_type=Debug");
+            }
+            Ok("release") => {
+                command.arg("-s");
+                command.arg("build_type=Release");
+            }
+            _ => (),
+        }
+    }
 }
 
 impl ConanOutput {