Also ignore remap-path-prefix in metadata for cargo rustc.

src/cargo/core/compiler/context/compilation_files.rs

@@ -547,32 +547,36 @@ fn compute_metadata<'a, 'cfg>(
     // settings like debuginfo and whatnot.
     unit.profile.hash(&mut hasher);
     unit.mode.hash(&mut hasher);
-    if let Some(args) = bcx.extra_args_for(unit) {
-        args.hash(&mut hasher);
-    }
 
     // Throw in the rustflags we're compiling with.
     // This helps when the target directory is a shared cache for projects with different cargo configs,
     // or if the user is experimenting with different rustflags manually.
-    let mut flags = if unit.mode.is_doc() {
-        cx.bcx.rustdocflags_args(unit)
-    } else {
-        cx.bcx.rustflags_args(unit)
-    }
-    .iter();
-
-    // Ignore some flags. These may affect reproducible builds if they affect
-    // the path. The fingerprint will handle recompilation if these change.
-    while let Some(flag) = flags.next() {
-        if flag.starts_with("--remap-path-prefix=") {
-            continue;
-        }
-        if flag == "--remap-path-prefix" {
-            flags.next();
-            continue;
+    let mut hash_flags = |flags: &[String]| {
+        // Ignore some flags. These may affect reproducible builds if they affect
+        // the path. The fingerprint will handle recompilation if these change.
+        let mut iter = flags.iter();
+        while let Some(flag) = iter.next() {
+            if flag.starts_with("--remap-path-prefix=") {
+                continue;
+            }
+            if flag == "--remap-path-prefix" {
+                iter.next();
+                continue;
+            }
+            flag.hash(&mut hasher);
         }
-        flag.hash(&mut hasher);
+    };
+    if let Some(args) = bcx.extra_args_for(unit) {
+        // Arguments passed to `cargo rustc`.
+        hash_flags(args);
     }
+    // Arguments passed in via RUSTFLAGS env var.
+    let flags = if unit.mode.is_doc() {
+        bcx.rustdocflags_args(unit)
+    } else {
+        bcx.rustflags_args(unit)
+    };
+    hash_flags(flags);
 
     // Artifacts compiled for the host should have a different metadata
     // piece than those compiled for the target, so make sure we throw in

tests/testsuite/rustflags.rs

@@ -1361,7 +1361,7 @@ fn env_rustflags_misspelled_build_script() {
 }
 
 #[cargo_test]
-fn reamp_path_prefix_ignored() {
+fn remap_path_prefix_ignored() {
     // Ensure that --remap-path-prefix does not affect metadata hash.
     let p = project().file("src/lib.rs", "").build();
     p.cargo("build").run();
@@ -1372,15 +1372,24 @@ fn reamp_path_prefix_ignored() {
     assert_eq!(rlibs.len(), 1);
     p.cargo("clean").run();
 
+    let check_metadata_same = || {
+        let rlibs2 = p
+            .glob("target/debug/deps/*.rlib")
+            .collect::<Result<Vec<_>, _>>()
+            .unwrap();
+        assert_eq!(rlibs, rlibs2);
+    };
+
     p.cargo("build")
         .env(
             "RUSTFLAGS",
             "--remap-path-prefix=/abc=/zoo --remap-path-prefix /spaced=/zoo",
         )
         .run();
-    let rlibs2 = p
-        .glob("target/debug/deps/*.rlib")
-        .collect::<Result<Vec<_>, _>>()
-        .unwrap();
-    assert_eq!(rlibs, rlibs2);
+    check_metadata_same();
+
+    p.cargo("clean").run();
+    p.cargo("rustc -- --remap-path-prefix=/abc=/zoo --remap-path-prefix /spaced=/zoo")
+        .run();
+    check_metadata_same();
 }