Merge pull request #56 from cuviper/wrappers

Support `RUSTC_WRAPPER` and `RUSTC_WORKSPACE_WRAPPER`

src/lib.rs

@@ -83,6 +83,8 @@ mod tests;
 pub struct AutoCfg {
     out_dir: PathBuf,
     rustc: PathBuf,
+    rustc_wrapper: Option<PathBuf>,
+    rustc_workspace_wrapper: Option<PathBuf>,
     rustc_version: Version,
     target: Option<OsString>,
     no_std: bool,
@@ -168,6 +170,8 @@ impl AutoCfg {
 
         let mut ac = AutoCfg {
             rustflags: rustflags(&target, &dir),
+            rustc_wrapper: get_rustc_wrapper(false),
+            rustc_workspace_wrapper: get_rustc_wrapper(true),
             out_dir: dir,
             rustc: rustc,
             rustc_version: rustc_version,
@@ -234,7 +238,18 @@ impl AutoCfg {
         static ID: AtomicUsize = ATOMIC_USIZE_INIT;
 
         let id = ID.fetch_add(1, Ordering::Relaxed);
-        let mut command = Command::new(&self.rustc);
+
+        // Build the command with possible wrappers.
+        let mut rustc = self
+            .rustc_wrapper
+            .iter()
+            .chain(self.rustc_workspace_wrapper.iter())
+            .chain(Some(&self.rustc));
+        let mut command = Command::new(rustc.next().unwrap());
+        for arg in rustc {
+            command.arg(arg);
+        }
+
         command
             .arg("--crate-name")
             .arg(format!("probe{}", id))
@@ -478,3 +493,27 @@ fn rustflags(target: &Option<OsString>, dir: &Path) -> Vec<String> {
 
     Vec::new()
 }
+
+fn get_rustc_wrapper(workspace: bool) -> Option<PathBuf> {
+    // We didn't really know whether the workspace wrapper is applicable until Cargo started
+    // deliberately setting or unsetting it in rust-lang/cargo#9601. We'll use the encoded
+    // rustflags as a proxy for that change for now, but we could instead check version 1.55.
+    if workspace && env::var_os("CARGO_ENCODED_RUSTFLAGS").is_none() {
+        return None;
+    }
+
+    let name = if workspace {
+        "RUSTC_WORKSPACE_WRAPPER"
+    } else {
+        "RUSTC_WRAPPER"
+    };
+
+    if let Some(wrapper) = env::var_os(name) {
+        // NB: `OsStr` didn't get `len` or `is_empty` until 1.9.
+        if wrapper != OsString::new() {
+            return Some(wrapper.into());
+        }
+    }
+
+    None
+}

tests/wrappers.rs

@@ -0,0 +1,51 @@
+extern crate autocfg;
+
+use std::env;
+
+/// Tests that autocfg uses the RUSTC_WRAPPER and/or RUSTC_WORKSPACE_WRAPPER
+/// environment variables when running rustc.
+#[test]
+#[cfg(unix)] // we're using system binaries as wrappers
+fn test_wrappers() {
+    fn set(name: &str, value: Option<bool>) {
+        match value {
+            Some(true) => env::set_var(name, "/usr/bin/env"),
+            Some(false) => env::set_var(name, "/bin/false"),
+            None => env::remove_var(name),
+        }
+    }
+
+    // Use the same path as this test binary.
+    let dir = env::current_exe().unwrap().parent().unwrap().to_path_buf();
+    env::set_var("OUT_DIR", &format!("{}", dir.display()));
+
+    // This is used as a heuristic to detect rust-lang/cargo#9601.
+    env::set_var("CARGO_ENCODED_RUSTFLAGS", "");
+
+    // No wrapper, a good pass-through wrapper, and a bad wrapper.
+    let variants = [None, Some(true), Some(false)];
+
+    for &workspace in &variants {
+        for &rustc in &variants {
+            set("RUSTC_WRAPPER", rustc);
+            set("RUSTC_WORKSPACE_WRAPPER", workspace);
+
+            let ac = autocfg::AutoCfg::new().unwrap();
+            if rustc == Some(false) || workspace == Some(false) {
+                // Everything should fail with bad wrappers.
+                assert!(!ac.probe_type("usize"));
+            } else {
+                // Try known good and bad types for the wrapped rustc.
+                assert!(ac.probe_type("usize"));
+                assert!(!ac.probe_type("mesize"));
+            }
+        }
+    }
+
+    // Finally, make sure that `RUSTC_WRAPPER` is applied outermost
+    // by using something that doesn't pass through at all.
+    env::set_var("RUSTC_WRAPPER", "/bin/true");
+    env::set_var("RUSTC_WORKSPACE_WRAPPER", "/bin/false");
+    let ac = autocfg::AutoCfg::new().unwrap();
+    assert!(ac.probe_type("mesize")); // anything goes!
+}