Added testing for CARGO_ENCODED_RUSTFLAGS

cargo/cargo_build_script_runner/bin.rs

@@ -103,7 +103,10 @@ fn run_buildrs() -> Result<(), String> {
     // Bazel does not support byte strings so in order to correctly represent `CARGO_ENCODED_RUSTFLAGS`
     // the escaped `\x1f` sequences need to be unescaped
     if let Ok(encoded_rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
-        command.env("CARGO_ENCODED_RUSTFLAGS", encoded_rustflags.replace("\\x1f", "\x1f"));
+        command.env(
+            "CARGO_ENCODED_RUSTFLAGS",
+            encoded_rustflags.replace("\\x1f", "\x1f"),
+        );
     }
 
     if let Some(ar_path) = env::var_os("AR") {

test/cargo_build_script/BUILD.bazel

@@ -8,6 +8,8 @@ cargo_build_script(
     name = "tools_exec_build_rs",
     srcs = ["build.rs"],
     build_script_env = {"TOOL": "$(execpath :tool)"},
+    # Add a flag to test that they're exposed to the build script
+    rustc_flags = ["--verbose"],
     tools = [":tool"],
 )
 

test/cargo_build_script/build.rs

@@ -1,4 +1,24 @@
+//! A Cargo build script binary used in unit tests for the Bazel `cargo_build_script` rule
+
+/// `cargo_build_script` should always set `CARGO_ENCODED_RUSTFLAGS`
+fn test_encoded_rustflags() {
+    let encoded_rustflags = std::env::var("CARGO_ENCODED_RUSTFLAGS").unwrap();
+
+    let flags: Vec<String> = encoded_rustflags
+        .split('\x1f')
+        .map(str::to_string)
+        .collect();
+    assert_eq!(flags.len(), 2);
+
+    assert!(flags[0].starts_with("--sysroot"));
+    assert!(flags[1].starts_with("--verbose"));
+}
+
 fn main() {
+
+    // Perform some unit testing
+    test_encoded_rustflags();
+
     // Pass the TOOL_PATH along to the rust_test so we can assert on it.
     println!(
         "cargo:rustc-env=TOOL_PATH={}",