Backport json emitter and stdin changes

src/bin/main.rs

@@ -74,14 +74,10 @@ pub enum OperationError {
     /// An io error during reading or writing.
     #[error("{0}")]
     IoError(IoError),
-    /// Attempt to use --check with stdin, which isn't currently
-    /// supported.
-    #[error("The `--check` option is not supported with standard input.")]
-    CheckWithStdin,
-    /// Attempt to use --emit=json with stdin, which isn't currently
-    /// supported.
-    #[error("Using `--emit` other than stdout is not supported with standard input.")]
-    EmitWithStdin,
+    /// Attempt to use --emit with a mode which is not currently
+    /// supported with stdandard input.
+    #[error("Emit mode {0} not supported with standard output.")]
+    StdinBadEmit(EmitMode),
 }
 
 impl From<IoError> for OperationError {
@@ -255,15 +251,20 @@ fn format_string(input: String, options: GetOptsOptions) -> Result<i32> {
     let (mut config, _) = load_config(Some(Path::new(".")), Some(options.clone()))?;
 
     if options.check {
-        return Err(OperationError::CheckWithStdin.into());
-    }
-    if let Some(emit_mode) = options.emit_mode {
-        if emit_mode != EmitMode::Stdout {
-            return Err(OperationError::EmitWithStdin.into());
+        config.set().emit_mode(EmitMode::Diff);
+    } else {
+        match options.emit_mode {
+            // Emit modes which work with standard input
+            // None means default, which is Stdout.
+            None | Some(EmitMode::Stdout) | Some(EmitMode::Checkstyle) | Some(EmitMode::Json) => {}
+            Some(emit_mode) => {
+                return Err(OperationError::StdinBadEmit(emit_mode).into());
+            }
         }
+        config
+            .set()
+            .emit_mode(options.emit_mode.unwrap_or(EmitMode::Stdout));
     }
-    // emit mode is always Stdout for Stdin.
-    config.set().emit_mode(EmitMode::Stdout);
     config.set().verbose(Verbosity::Quiet);
 
     // parse file_lines

src/config/file_lines.rs

@@ -39,7 +39,7 @@ impl fmt::Display for FileName {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             FileName::Real(p) => write!(f, "{}", p.to_str().unwrap()),
-            FileName::Stdin => write!(f, "stdin"),
+            FileName::Stdin => write!(f, "<stdin>"),
         }
     }
 }

src/emitter/checkstyle.rs

@@ -2,7 +2,6 @@ use self::xml::XmlEscaped;
 use super::*;
 use crate::rustfmt_diff::{make_diff, DiffLine, Mismatch};
 use std::io::{self, Write};
-use std::path::Path;
 
 mod xml;
 
@@ -30,7 +29,6 @@ impl Emitter for CheckstyleEmitter {
         }: FormattedFile<'_>,
     ) -> Result<EmitterResult, io::Error> {
         const CONTEXT_SIZE: usize = 0;
-        let filename = ensure_real_path(filename);
         let diff = make_diff(original_text, formatted_text, CONTEXT_SIZE);
         output_checkstyle_file(output, filename, diff)?;
         Ok(EmitterResult::default())
@@ -39,13 +37,13 @@ impl Emitter for CheckstyleEmitter {
 
 pub(crate) fn output_checkstyle_file<T>(
     mut writer: T,
-    filename: &Path,
+    filename: &FileName,
     diff: Vec<Mismatch>,
 ) -> Result<(), io::Error>
 where
     T: Write,
 {
-    write!(writer, r#"<file name="{}">"#, filename.display())?;
+    write!(writer, r#"<file name="{}">"#, filename)?;
     for mismatch in diff {
         let begin_line = mismatch.line_number;
         let mut current_line;
@@ -77,7 +75,11 @@ mod tests {
     fn emits_empty_record_on_file_with_no_mismatches() {
         let file_name = "src/well_formatted.rs";
         let mut writer = Vec::new();
-        let _ = output_checkstyle_file(&mut writer, &PathBuf::from(file_name), vec![]);
+        let _ = output_checkstyle_file(
+            &mut writer,
+            &FileName::Real(PathBuf::from(file_name)),
+            vec![],
+        );
         assert_eq!(
             &writer[..],
             format!(r#"<file name="{}"></file>"#, file_name).as_bytes()

src/emitter/diff.rs

@@ -28,7 +28,7 @@ impl Emitter for DiffEmitter {
 
         if has_diff {
             if self.config.print_misformatted_file_names() {
-                writeln!(output, "{}", ensure_real_path(filename).display())?;
+                writeln!(output, "{}", filename)?;
             } else {
                 print_diff(
                     mismatch,
@@ -40,8 +40,7 @@ impl Emitter for DiffEmitter {
             // This occurs when the only difference between the original and formatted values
             // is the newline style. This happens because The make_diff function compares the
             // original and formatted values line by line, independent of line endings.
-            let file_path = ensure_real_path(filename);
-            writeln!(output, "Incorrect newline style in {}", file_path.display())?;
+            writeln!(output, "Incorrect newline style in {}", filename)?;
             return Ok(EmitterResult { has_diff: true });
         }