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

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 {

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());
@@ -1002,15 +1006,22 @@ 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.