Rollup merge of rust-lang#139834 - ChrisDenton:spf, r=WaffleLapkin

Don't canonicalize crate paths

When printing paths in diagnostic we should favour printing the paths that were passed in rather than resolving all symlinks.

This PR changes the form of the crate path but it should only really affect diagnostics as filesystem functions won't care which path is used. The uncanonicalized path was already used as a fallback for when canonicalization failed.

This is a partial alternative to rust-lang#139823.

Author: matthiaskrgr

Diff for: compiler/rustc_metadata/src/locator.rs

@@ -427,12 +427,21 @@ impl<'a> CrateLocator<'a> {
 
                         let (rlibs, rmetas, dylibs) =
                             candidates.entry(hash.to_string()).or_default();
-                        let path =
-                            try_canonicalize(&spf.path).unwrap_or_else(|_| spf.path.to_path_buf());
-                        if seen_paths.contains(&path) {
-                            continue;
-                        };
-                        seen_paths.insert(path.clone());
+                        {
+                            // As a perforamnce optimisation we canonicalize the path and skip
+                            // ones we've already seeen. This allows us to ignore crates
+                            // we know are exactual equal to ones we've already found.
+                            // Going to the same crate through different symlinks does not change the result.
+                            let path = try_canonicalize(&spf.path)
+                                .unwrap_or_else(|_| spf.path.to_path_buf());
+                            if seen_paths.contains(&path) {
+                                continue;
+                            };
+                            seen_paths.insert(path);
+                        }
+                        // Use the original path (potentially with unresolved symlinks),
+                        // filesystem code should not care, but this is nicer for diagnostics.
+                        let path = spf.path.to_path_buf();
                         match kind {
                             CrateFlavor::Rlib => rlibs.insert(path, search_path.kind),
                             CrateFlavor::Rmeta => rmetas.insert(path, search_path.kind),

Diff for: tests/run-make/crate-loading-multiple-candidates/crateresolve1-1.rs

@@ -0,0 +1,6 @@
+#![crate_name = "crateresolve1"]
+#![crate_type = "lib"]
+
+pub fn f() -> isize {
+    10
+}

Diff for: tests/run-make/crate-loading-multiple-candidates/crateresolve1-2.rs

@@ -0,0 +1,6 @@
+#![crate_name = "crateresolve1"]
+#![crate_type = "lib"]
+
+pub fn f() -> isize {
+    20
+}

Diff for: tests/run-make/crate-loading-multiple-candidates/multiple-candidates.rs

@@ -0,0 +1,3 @@
+extern crate crateresolve1;
+
+fn main() {}

Diff for: tests/run-make/crate-loading-multiple-candidates/multiple-candidates.stderr

@@ -0,0 +1,12 @@
+error[E0464]: multiple candidates for `rlib` dependency `crateresolve1` found
+  --> multiple-candidates.rs:1:1
+   |
+LL | extern crate crateresolve1;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: candidate #1: ./mylibs/libcrateresolve1-1.rlib
+   = note: candidate #2: ./mylibs/libcrateresolve1-2.rlib
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0464`.

Diff for: tests/run-make/crate-loading-multiple-candidates/rmake.rs

@@ -0,0 +1,34 @@
+//@ needs-symlink
+//@ ignore-cross-compile
+
+// Tests that the multiple candidate dependencies diagnostic prints relative
+// paths if a relative library path was passed in.
+
+use run_make_support::{bare_rustc, diff, rfs, rustc};
+
+fn main() {
+    // Check that relative paths are preserved in the diagnostic
+    rfs::create_dir("mylibs");
+    rustc().input("crateresolve1-1.rs").out_dir("mylibs").extra_filename("-1").run();
+    rustc().input("crateresolve1-2.rs").out_dir("mylibs").extra_filename("-2").run();
+    check("./mylibs");
+
+    // Check that symlinks aren't followed when printing the diagnostic
+    rfs::rename("mylibs", "original");
+    rfs::symlink_dir("original", "mylibs");
+    check("./mylibs");
+}
+
+fn check(library_path: &str) {
+    let out = rustc()
+        .input("multiple-candidates.rs")
+        .library_search_path(library_path)
+        .ui_testing()
+        .run_fail()
+        .stderr_utf8();
+    diff()
+        .expected_file("multiple-candidates.stderr")
+        .normalize(r"\\", "/")
+        .actual_text("(rustc)", &out)
+        .run();
+}