Add cargo runner support in order to work with cross

README.md

@@ -33,6 +33,7 @@ Other crates that might be useful in testing command line programs.
 * [`assert_fs`][assert_fs] for filesystem fixtures and assertions.
   * or [tempfile][tempfile] for scratchpad directories.
 * [dir-diff][dir-diff] for testing file side-effects.
+* [cross][cross] for cross-platform testing.
 
 [escargot]: http://docs.rs/escargot
 [rexpect]: https://crates.io/crates/rexpect
@@ -41,6 +42,7 @@ Other crates that might be useful in testing command line programs.
 [duct]: https://crates.io/crates/duct
 [assert_fs]: https://crates.io/crates/assert_fs
 [commandspec]: https://crates.io/crates/commandspec
+[cross]: https://github.com/cross-rs/cross
 
 ## License
 
@@ -58,13 +60,13 @@ fitzgen
 >
 > bravo bravo WG-cli
 
-passcod 
+passcod
 > Running commands and dealing with output can be complex in many many ways, so assert_cmd smoothing that is excellent, very much welcome, and improves ergonomics significantly.
 
-volks73 
+volks73
 >  I have used [assert_cmd] in other projects and I am extremely pleased with it
 
-coreyja 
+coreyja
 > [assert_cmd] pretty much IS my testing strategy so far, though my app under test is pretty small.
 >
 > This library has made it really easy to add some test coverage to my project, even when I am just learning how to write Rust!

build.rs

@@ -0,0 +1,16 @@
+use std::env;
+use std::fs;
+use std::io::Write;
+use std::path;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    // env::ARCH doesn't include full triplet, and AFAIK there isn't a nicer way of getting the full triplet
+    // (see lib.rs for the rest of this hack)
+    let out = path::PathBuf::from(env::var_os("OUT_DIR").expect("run within cargo"))
+        .join("current_target.txt");
+    let default_target = env::var("TARGET").expect("run as cargo build script");
+    let mut file = fs::File::create(out).unwrap();
+    file.write_all(default_target.as_bytes()).unwrap();
+}

src/cargo.rs

@@ -89,6 +89,12 @@ where
     ///
     /// See the [`cargo` module documentation][crate::cargo] for caveats and workarounds.
     ///
+    /// The [`Command`] created with this method may run the binary through a runner, as configured
+    /// in the `CARGO_TARGET_<TRIPLET>_RUNNER` environment variable.  This is useful for running
+    /// binaries that can't be launched directly, such as cross-compiled binaries. When using
+    /// this method with [cross](https://github.com/cross-rs/cross), no extra configuration is
+    /// needed.
+    ///
     /// # Examples
     ///
     /// ```rust,no_run
@@ -132,12 +138,27 @@ impl CommandCargoExt for process::Command {
 pub(crate) fn cargo_bin_cmd<S: AsRef<str>>(name: S) -> Result<process::Command, CargoError> {
     let path = cargo_bin(name);
     if path.is_file() {
-        Ok(process::Command::new(path))
+        if let Some(runner) = cargo_runner() {
+            let mut cmd = process::Command::new(&runner[0]);
+            cmd.args(&runner[1..]).arg(path);
+            Ok(cmd)
+        } else {
+            Ok(process::Command::new(path))
+        }
     } else {
         Err(CargoError::with_cause(NotFoundError { path }))
     }
 }
 
+pub(crate) fn cargo_runner() -> Option<Vec<String>> {
+    let runner_env = format!(
+        "CARGO_TARGET_{}_RUNNER",
+        CURRENT_TARGET.replace('-', "_").to_uppercase()
+    );
+    let runner = std::env::var(runner_env).ok()?;
+    Some(runner.split(' ').map(str::to_string).collect())
+}
+
 /// Error when finding crate binary.
 #[derive(Debug)]
 pub struct CargoError {
@@ -206,3 +227,6 @@ fn cargo_bin_str(name: &str) -> path::PathBuf {
         .map(|p| p.into())
         .unwrap_or_else(|| target_dir().join(format!("{}{}", name, env::consts::EXE_SUFFIX)))
 }
+
+/// The current process' target triplet.
+const CURRENT_TARGET: &str = include_str!(concat!(env!("OUT_DIR"), "/current_target.txt"));

tests/cargo.rs

@@ -2,6 +2,7 @@ use std::process;
 use std::process::Command;
 
 use assert_cmd::prelude::*;
+use escargot::CURRENT_TARGET;
 
 #[test]
 fn cargo_binary() {
@@ -19,15 +20,23 @@ fn cargo_binary_with_empty_env() {
 
 #[test]
 fn mod_example() {
-    let bin_under_test = escargot::CargoBuild::new()
-        .bin("bin_fixture")
-        .current_release()
-        .current_target()
-        .run()
-        .unwrap();
-    let mut cmd = bin_under_test.command();
-    let output = cmd.unwrap();
-    println!("{:?}", output);
+    let runner_env = format!(
+        "CARGO_TARGET_{}_RUNNER",
+        CURRENT_TARGET.replace('-', "_").to_uppercase()
+    );
+    if std::env::var(runner_env).is_ok() {
+        // not running this test on cross because escargot doesn't support the cargo target runner yet
+    } else {
+        let bin_under_test = escargot::CargoBuild::new()
+            .bin("bin_fixture")
+            .current_release()
+            .current_target()
+            .run()
+            .unwrap();
+        let mut cmd = bin_under_test.command();
+        let output = cmd.unwrap();
+        println!("{:?}", output);
+    }
 }
 
 #[test]