Auto merge of #88363 - michaelwoerister:remapped-diagnostics, r=estebank

Path remapping: Make behavior of diagnostics output dependent on presence of --remap-path-prefix.

This PR fixes a regression (#87745) with `--remap-path-prefix` where the flag stopped causing diagnostic messages to be remapped as well. The regression was introduced in https://github.com/rust-lang/rust/pull/83813 where we erroneously assumed that remapping of diagnostic messages was not desired anymore (because #70642 partially undid that functionality with nobody objecting).

The issue is fixed by making `--remap-path-prefix` remap diagnostic messages again, including for paths that have been remapped in upstream crates (e.g. the standard library). This means that "sysroot-localization" (implemented in #70642) is also disabled if `rustc` is invoked with `--remap-path-prefix`. The assumption is that once someone starts explicitly remapping paths they also don't want paths to their local Rust installation in their build output.

In the future we might want to give more fine-grained control over this behavior via compiler flags (see https://github.com/rust-lang/rfcs/pull/3127 for a related RFC). For now this PR is intended as a regression fix.

This PR is an alternative to https://github.com/rust-lang/rust/pull/88191, which makes diagnostic messages be remapped unconditionally. That approach, however, would effectively revert #70642.

Fixes https://github.com/rust-lang/rust/issues/87745.

cc `@cbeuw`
r? `@ghost`

15 files changed, 83 insertions, 41 deletions

diff --git a/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs b/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
index 95216f1c3d7..cabe3e43b34 100644
--- a/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
@@ -66,7 +66,7 @@ impl<'tcx> DebugContext<'tcx> {
             rustc_interface::util::version_str().unwrap_or("unknown version"),
             cranelift_codegen::VERSION,
         );
-        let comp_dir = tcx.sess.opts.working_dir.to_string_lossy(false).into_owned();
+        let comp_dir = tcx.sess.opts.working_dir.to_string_lossy(FileNameDisplayPreference::Remapped).into_owned();
         let (name, file_info) = match tcx.sess.local_crate_source_file.clone() {
             Some(path) => {
                 let name = path.to_string_lossy().into_owned();
diff --git a/compiler/rustc_codegen_cranelift/src/lib.rs b/compiler/rustc_codegen_cranelift/src/lib.rs
index 4ef53663ca0..6c7c8cbc311 100644
--- a/compiler/rustc_codegen_cranelift/src/lib.rs
+++ b/compiler/rustc_codegen_cranelift/src/lib.rs
@@ -74,7 +74,7 @@ mod vtable;
 mod prelude {
     pub(crate) use std::convert::{TryFrom, TryInto};
 
-    pub(crate) use rustc_span::Span;
+    pub(crate) use rustc_span::{Span, FileNameDisplayPreference};
 
     pub(crate) use rustc_hir::def_id::{DefId, LOCAL_CRATE};
     pub(crate) use rustc_middle::bug;
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 8ff2f1cc652..346c51c5426 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -35,6 +35,7 @@ use rustc_middle::ty::{self, AdtKind, GeneratorSubsts, ParamEnv, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::{self, DebugInfo};
 use rustc_span::symbol::{Interner, Symbol};
+use rustc_span::FileNameDisplayPreference;
 use rustc_span::{self, SourceFile, SourceFileHash, Span};
 use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, LayoutOf, TagEncoding};
 use rustc_target::abi::{Int, Pointer, F32, F64};
@@ -771,7 +772,13 @@ pub fn file_metadata(cx: &CodegenCx<'ll, '_>, source_file: &SourceFile) -> &'ll
     let hash = Some(&source_file.src_hash);
     let file_name = Some(source_file.name.prefer_remapped().to_string());
     let directory = if source_file.is_real_file() && !source_file.is_imported() {
-        Some(cx.sess().opts.working_dir.to_string_lossy(false).to_string())
+        Some(
+            cx.sess()
+                .opts
+                .working_dir
+                .to_string_lossy(FileNameDisplayPreference::Remapped)
+                .to_string(),
+        )
     } else {
         // If the path comes from an upstream crate we assume it has been made
         // independent of the compiler's working directory one way or another.
@@ -999,7 +1006,7 @@ pub fn compile_unit_metadata(
     let producer = format!("clang LLVM ({})", rustc_producer);
 
     let name_in_debuginfo = name_in_debuginfo.to_string_lossy();
-    let work_dir = tcx.sess.opts.working_dir.to_string_lossy(false);
+    let work_dir = tcx.sess.opts.working_dir.to_string_lossy(FileNameDisplayPreference::Remapped);
     let flags = "\0";
     let output_filenames = tcx.output_filenames(());
     let out_dir = &output_filenames.out_directory;
diff --git a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
index 2253007ce30..1eb497460e6 100644
--- a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
+++ b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
@@ -126,7 +126,7 @@ impl AnnotateSnippetEmitterWriter {
             }
             // owned: line source, line index, annotations
             type Owned = (String, usize, Vec<crate::snippet::Annotation>);
-            let filename = primary_lo.file.name.prefer_local();
+            let filename = source_map.filename_for_diagnostics(&primary_lo.file.name);
             let origin = filename.to_string_lossy();
             let annotated_files: Vec<Owned> = annotated_files
                 .into_iter()
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 25777f4133b..29f352ae585 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -1320,7 +1320,7 @@ impl EmitterWriter {
                         buffer_msg_line_offset,
                         &format!(
                             "{}:{}:{}",
-                            loc.file.name.prefer_local(),
+                            sm.filename_for_diagnostics(&loc.file.name),
                             sm.doctest_offset_line(&loc.file.name, loc.line),
                             loc.col.0 + 1,
                         ),
@@ -1334,7 +1334,7 @@ impl EmitterWriter {
                         0,
                         &format!(
                             "{}:{}:{}: ",
-                            loc.file.name.prefer_local(),
+                            sm.filename_for_diagnostics(&loc.file.name),
                             sm.doctest_offset_line(&loc.file.name, loc.line),
                             loc.col.0 + 1,
                         ),
@@ -1362,12 +1362,12 @@ impl EmitterWriter {
                     };
                     format!(
                         "{}:{}{}",
-                        annotated_file.file.name.prefer_local(),
+                        sm.filename_for_diagnostics(&annotated_file.file.name),
                         sm.doctest_offset_line(&annotated_file.file.name, first_line.line_index),
                         col
                     )
                 } else {
-                    format!("{}", annotated_file.file.name.prefer_local())
+                    format!("{}", sm.filename_for_diagnostics(&annotated_file.file.name))
                 };
                 buffer.append(buffer_msg_line_offset + 1, &loc, Style::LineAndColumn);
                 for _ in 0..max_line_num_len {
diff --git a/compiler/rustc_errors/src/json.rs b/compiler/rustc_errors/src/json.rs
index 1b6cd04cca6..dde978cd8c6 100644
--- a/compiler/rustc_errors/src/json.rs
+++ b/compiler/rustc_errors/src/json.rs
@@ -464,7 +464,7 @@ impl DiagnosticSpan {
         });
 
         DiagnosticSpan {
-            file_name: start.file.name.prefer_local().to_string(),
+            file_name: je.sm.filename_for_diagnostics(&start.file.name).to_string(),
             byte_start: start.file.original_relative_byte_pos(span.lo()).0,
             byte_end: start.file.original_relative_byte_pos(span.hi()).0,
             line_start: start.line,
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index a4b7bdd9155..1fd48309af9 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1113,7 +1113,7 @@ impl<'a> ExtCtxt<'a> {
                         span,
                         &format!(
                             "cannot resolve relative path in non-file source `{}`",
-                            other.prefer_local()
+                            self.source_map().filename_for_diagnostics(&other)
                         ),
                     ));
                 }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index d54933841fd..32150c7f4c6 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -1630,14 +1630,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 (TypeError::Sorts(values), extra) => {
                     let sort_string = |ty: Ty<'tcx>| match (extra, ty.kind()) {
                         (true, ty::Opaque(def_id, _)) => {
-                            let pos = self
-                                .tcx
-                                .sess
-                                .source_map()
-                                .lookup_char_pos(self.tcx.def_span(*def_id).lo());
+                            let sm = self.tcx.sess.source_map();
+                            let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
                             format!(
                                 " (opaque type at <{}:{}:{}>)",
-                                pos.file.name.prefer_local(),
+                                sm.filename_for_diagnostics(&pos.file.name),
                                 pos.line,
                                 pos.col.to_usize() + 1,
                             )
diff --git a/compiler/rustc_mir/src/interpret/eval_context.rs b/compiler/rustc_mir/src/interpret/eval_context.rs
index bfb3de04c59..c6003d87f3a 100644
--- a/compiler/rustc_mir/src/interpret/eval_context.rs
+++ b/compiler/rustc_mir/src/interpret/eval_context.rs
@@ -272,11 +272,12 @@ impl<'tcx> fmt::Display for FrameInfo<'tcx> {
                 write!(f, "inside `{}`", self.instance)?;
             }
             if !self.span.is_dummy() {
-                let lo = tcx.sess.source_map().lookup_char_pos(self.span.lo());
+                let sm = tcx.sess.source_map();
+                let lo = sm.lookup_char_pos(self.span.lo());
                 write!(
                     f,
                     " at {}:{}:{}",
-                    lo.file.name.prefer_local(),
+                    sm.filename_for_diagnostics(&lo.file.name),
                     lo.line,
                     lo.col.to_usize() + 1
                 )?;
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 73e05a35277..bf76dedd252 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -190,7 +190,7 @@ pub fn maybe_file_to_stream(
     let src = source_file.src.as_ref().unwrap_or_else(|| {
         sess.span_diagnostic.bug(&format!(
             "cannot lex `source_file` without source: {}",
-            source_file.name.prefer_local()
+            sess.source_map().filename_for_diagnostics(&source_file.name)
         ));
     });
 
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 10e9bde0d97..b4cc8b2b4a3 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -260,11 +260,12 @@ impl RealFileName {
         }
     }
 
-    pub fn to_string_lossy(&self, prefer_local: bool) -> Cow<'_, str> {
-        if prefer_local {
-            self.local_path_if_available().to_string_lossy()
-        } else {
-            self.remapped_path_if_available().to_string_lossy()
+    pub fn to_string_lossy(&self, display_pref: FileNameDisplayPreference) -> Cow<'_, str> {
+        match display_pref {
+            FileNameDisplayPreference::Local => self.local_path_if_available().to_string_lossy(),
+            FileNameDisplayPreference::Remapped => {
+                self.remapped_path_if_available().to_string_lossy()
+            }
         }
     }
 }
@@ -300,9 +301,15 @@ impl From<PathBuf> for FileName {
     }
 }
 
+#[derive(Clone, Copy, Eq, PartialEq, Hash, Debug)]
+pub enum FileNameDisplayPreference {
+    Remapped,
+    Local,
+}
+
 pub struct FileNameDisplay<'a> {
     inner: &'a FileName,
-    prefer_local: bool,
+    display_pref: FileNameDisplayPreference,
 }
 
 impl fmt::Display for FileNameDisplay<'_> {
@@ -310,7 +317,7 @@ impl fmt::Display for FileNameDisplay<'_> {
         use FileName::*;
         match *self.inner {
             Real(ref name) => {
-                write!(fmt, "{}", name.to_string_lossy(self.prefer_local))
+                write!(fmt, "{}", name.to_string_lossy(self.display_pref))
             }
             QuoteExpansion(_) => write!(fmt, "<quote expansion>"),
             MacroExpansion(_) => write!(fmt, "<macro expansion>"),
@@ -328,7 +335,7 @@ impl fmt::Display for FileNameDisplay<'_> {
 impl FileNameDisplay<'_> {
     pub fn to_string_lossy(&self) -> Cow<'_, str> {
         match self.inner {
-            FileName::Real(ref inner) => inner.to_string_lossy(self.prefer_local),
+            FileName::Real(ref inner) => inner.to_string_lossy(self.display_pref),
             _ => Cow::from(format!("{}", self)),
         }
     }
@@ -352,13 +359,17 @@ impl FileName {
     }
 
     pub fn prefer_remapped(&self) -> FileNameDisplay<'_> {
-        FileNameDisplay { inner: self, prefer_local: false }
+        FileNameDisplay { inner: self, display_pref: FileNameDisplayPreference::Remapped }
     }
 
     // This may include transient local filesystem information.
     // Must not be embedded in build outputs.
     pub fn prefer_local(&self) -> FileNameDisplay<'_> {
-        FileNameDisplay { inner: self, prefer_local: true }
+        FileNameDisplay { inner: self, display_pref: FileNameDisplayPreference::Local }
+    }
+
+    pub fn display(&self, display_pref: FileNameDisplayPreference) -> FileNameDisplay<'_> {
+        FileNameDisplay { inner: self, display_pref }
     }
 
     pub fn macro_expansion_source_code(src: &str) -> FileName {
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index c2de5ed2f58..9b8c8594ee8 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -427,7 +427,7 @@ impl SourceMap {
         }
     }
 
-    fn span_to_string(&self, sp: Span, prefer_local: bool) -> String {
+    fn span_to_string(&self, sp: Span, filename_display_pref: FileNameDisplayPreference) -> String {
         if self.files.borrow().source_files.is_empty() || sp.is_dummy() {
             return "no-location".to_string();
         }
@@ -436,7 +436,7 @@ impl SourceMap {
         let hi = self.lookup_char_pos(sp.hi());
         format!(
             "{}:{}:{}: {}:{}",
-            if prefer_local { lo.file.name.prefer_local() } else { lo.file.name.prefer_remapped() },
+            lo.file.name.display(filename_display_pref),
             lo.line,
             lo.col.to_usize() + 1,
             hi.line,
@@ -446,20 +446,24 @@ impl SourceMap {
 
     /// Format the span location suitable for embedding in build artifacts
     pub fn span_to_embeddable_string(&self, sp: Span) -> String {
-        self.span_to_string(sp, false)
+        self.span_to_string(sp, FileNameDisplayPreference::Remapped)
     }
 
     /// Format the span location to be printed in diagnostics. Must not be emitted
     /// to build artifacts as this may leak local file paths. Use span_to_embeddable_string
     /// for string suitable for embedding.
     pub fn span_to_diagnostic_string(&self, sp: Span) -> String {
-        self.span_to_string(sp, true)
+        self.span_to_string(sp, self.path_mapping.filename_display_for_diagnostics)
     }
 
     pub fn span_to_filename(&self, sp: Span) -> FileName {
         self.lookup_char_pos(sp.lo()).file.name.clone()
     }
 
+    pub fn filename_for_diagnostics<'a>(&self, filename: &'a FileName) -> FileNameDisplay<'a> {
+        filename.display(self.path_mapping.filename_display_for_diagnostics)
+    }
+
     pub fn is_multiline(&self, sp: Span) -> bool {
         let lo = self.lookup_source_file_idx(sp.lo());
         let hi = self.lookup_source_file_idx(sp.hi());
@@ -1013,15 +1017,22 @@ impl SourceMap {
 #[derive(Clone)]
 pub struct FilePathMapping {
     mapping: Vec<(PathBuf, PathBuf)>,
+    filename_display_for_diagnostics: FileNameDisplayPreference,
 }
 
 impl FilePathMapping {
     pub fn empty() -> FilePathMapping {
-        FilePathMapping { mapping: vec![] }
+        FilePathMapping::new(Vec::new())
     }
 
     pub fn new(mapping: Vec<(PathBuf, PathBuf)>) -> FilePathMapping {
-        FilePathMapping { mapping }
+        let filename_display_for_diagnostics = if mapping.is_empty() {
+            FileNameDisplayPreference::Local
+        } else {
+            FileNameDisplayPreference::Remapped
+        };
+
+        FilePathMapping { mapping, filename_display_for_diagnostics }
     }
 
     /// Applies any path prefix substitution as defined by the mapping.
diff --git a/src/test/ui/remap-path-prefix.rs b/src/test/ui/remap-path-prefix.rs
new file mode 100644
index 00000000000..2eef9709977
--- /dev/null
+++ b/src/test/ui/remap-path-prefix.rs
@@ -0,0 +1,9 @@
+// compile-flags: --remap-path-prefix={{src-base}}=remapped
+
+fn main() {
+    // We cannot actually put an ERROR marker here because
+    // the file name in the error message is not what the
+    // test framework expects (since the filename gets remapped).
+    // We still test the expected error in the stderr file.
+    ferris
+}
diff --git a/src/test/ui/remap-path-prefix.stderr b/src/test/ui/remap-path-prefix.stderr
new file mode 100644
index 00000000000..ad6a35d1256
--- /dev/null
+++ b/src/test/ui/remap-path-prefix.stderr
@@ -0,0 +1,9 @@
+error[E0425]: cannot find value `ferris` in this scope
+  --> remapped/remap-path-prefix.rs:8:5
+   |
+LL |     ferris
+   |     ^^^^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.
diff --git a/src/tools/clippy/clippy_lints/src/macro_use.rs b/src/tools/clippy/clippy_lints/src/macro_use.rs
index a371f8bbd3c..39f7ade3f81 100644
--- a/src/tools/clippy/clippy_lints/src/macro_use.rs
+++ b/src/tools/clippy/clippy_lints/src/macro_use.rs
@@ -47,11 +47,8 @@ pub struct MacroRefData {
 
 impl MacroRefData {
     pub fn new(name: String, callee: Span, cx: &LateContext<'_>) -> Self {
-        let mut path = cx
-            .sess()
-            .source_map()
-            .span_to_filename(callee)
-            .prefer_local()
+        let sm = cx.sess().source_map();
+        let mut path = sm.filename_for_diagnostics(&sm.span_to_filename(callee))
             .to_string();
 
         // std lib paths are <::std::module::file type>