Rollup merge of rust-lang#139507 - Zalathar:trim-env-name, r=jieyouxu

compiletest: Trim whitespace from environment variable names

When a test contains a directive like `//@ exec-env: FOO=bar`, compiletest currently includes that leading space in the name of the environment variable, so it is defined as ` FOO` instead of `FOO`.

This is an annoying footgun that is pretty much never intended, especially since most other directives *do* trim whitespace. So let's get rid of it by trimming the environment variable name.

Values remain untrimmed, since there could conceivably be a use-case for values with leading space, but perhaps we'll end up trimming values too in the future.

Recently observed in rust-lang#138603 (comment).

Fixes rust-lang#132990.
Supersedes rust-lang#133148.

r? jieyouxu

Author: Zalathar

src/tools/compiletest/src/header.rs

@@ -979,16 +979,13 @@ impl Config {
 
     fn parse_env(nv: String) -> (String, String) {
         // nv is either FOO or FOO=BAR
-        let mut strs: Vec<String> = nv.splitn(2, '=').map(str::to_owned).collect();
-
-        match strs.len() {
-            1 => (strs.pop().unwrap(), String::new()),
-            2 => {
-                let end = strs.pop().unwrap();
-                (strs.pop().unwrap(), end)
-            }
-            n => panic!("Expected 1 or 2 strings, not {}", n),
-        }
+        // FIXME(Zalathar): The form without `=` seems to be unused; should
+        // we drop support for it?
+        let (name, value) = nv.split_once('=').unwrap_or((&nv, ""));
+        // Trim whitespace from the name, so that `//@ exec-env: FOO=BAR`
+        // sees the name as `FOO` and not ` FOO`.
+        let name = name.trim();
+        (name.to_owned(), value.to_owned())
     }
 
     fn parse_pp_exact(&self, line: &str, testfile: &Path) -> Option<PathBuf> {

tests/ui/compiletest-self-test/env-trim-name.rs

@@ -0,0 +1,15 @@
+//@ edition: 2024
+//@ run-pass
+//@ rustc-env: MY_RUSTC_ENV = my-rustc-value
+//@ exec-env: MY_EXEC_ENV = my-exec-value
+
+// Check that compiletest trims whitespace from environment variable names
+// specified in `rustc-env` and `exec-env` directives, so that
+// `//@ exec-env: FOO=bar` sees the name as `FOO` and not ` FOO`.
+//
+// Values are currently not trimmed.
+
+fn main() {
+    assert_eq!(option_env!("MY_RUSTC_ENV"), Some(" my-rustc-value"));
+    assert_eq!(std::env::var("MY_EXEC_ENV").as_deref(), Ok(" my-exec-value"));
+}