Use annotate-snippets for emitting errors (#3507)

Cargo.toml

@@ -58,6 +58,7 @@ unicode-width = "0.1.5"
 unicode_categories = "0.1.1"
 dirs = "1.0.4"
 ignore = "0.4.6"
+annotate-snippets = { version = "0.5.0", features = ["ansi_term"] }
 
 # A noop dependency that changes in the Rust repository, it's a bit of a hack.
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`

src/bin/main.rs

@@ -16,7 +16,7 @@ use getopts::{Matches, Options};
 
 use crate::rustfmt::{
     load_config, CliOptions, Color, Config, Edition, EmitMode, ErrorKind, FileLines, FileName,
-    Input, Session, Verbosity,
+    FormatReportFormatterBuilder, Input, Session, Verbosity,
 };
 
 fn main() {
@@ -310,19 +310,12 @@ fn format_and_emit_report<T: Write>(session: &mut Session<'_, T>, input: Input)
     match session.format(input) {
         Ok(report) => {
             if report.has_warnings() {
-                match term::stderr() {
-                    Some(ref t)
-                        if session.config.color().use_colored_tty()
-                            && t.supports_color()
-                            && t.supports_attr(term::Attr::Bold) =>
-                    {
-                        match report.fancy_print(term::stderr().unwrap()) {
-                            Ok(..) => (),
-                            Err(..) => panic!("Unable to write to stderr: {}", report),
-                        }
-                    }
-                    _ => eprintln!("{}", report),
-                }
+                eprintln!(
+                    "{}",
+                    FormatReportFormatterBuilder::new(&report)
+                        .enable_colors(should_print_with_colors(session))
+                        .build()
+                );
             }
         }
         Err(msg) => {
@@ -332,6 +325,19 @@ fn format_and_emit_report<T: Write>(session: &mut Session<'_, T>, input: Input)
     }
 }
 
+fn should_print_with_colors<T: Write>(session: &mut Session<'_, T>) -> bool {
+    match term::stderr() {
+        Some(ref t)
+            if session.config.color().use_colored_tty()
+                && t.supports_color()
+                && t.supports_attr(term::Attr::Bold) =>
+        {
+            true
+        }
+        _ => false,
+    }
+}
+
 fn print_usage_to_stdout(opts: &Options, reason: &str) {
     let sep = if reason.is_empty() {
         String::new()

src/format_report_formatter.rs

@@ -0,0 +1,173 @@
+use crate::config::FileName;
+use crate::formatting::FormattingError;
+use crate::{ErrorKind, FormatReport};
+use annotate_snippets::display_list::DisplayList;
+use annotate_snippets::formatter::DisplayListFormatter;
+use annotate_snippets::snippet::{Annotation, AnnotationType, Slice, Snippet, SourceAnnotation};
+use std::fmt::{self, Display};
+
+/// A builder for [`FormatReportFormatter`].
+pub struct FormatReportFormatterBuilder<'a> {
+    report: &'a FormatReport,
+    enable_colors: bool,
+}
+
+impl<'a> FormatReportFormatterBuilder<'a> {
+    /// Creates a new [`FormatReportFormatterBuilder`].
+    pub fn new(report: &'a FormatReport) -> Self {
+        Self {
+            report,
+            enable_colors: false,
+        }
+    }
+
+    /// Enables colors and formatting in the output.
+    pub fn enable_colors(self, enable_colors: bool) -> Self {
+        Self {
+            enable_colors,
+            ..self
+        }
+    }
+
+    /// Creates a new [`FormatReportFormatter`] from the settings in this builder.
+    pub fn build(self) -> FormatReportFormatter<'a> {
+        FormatReportFormatter {
+            report: self.report,
+            enable_colors: self.enable_colors,
+        }
+    }
+}
+
+/// Formats the warnings/errors in a [`FormatReport`].
+///
+/// Can be created using a [`FormatReportFormatterBuilder`].
+pub struct FormatReportFormatter<'a> {
+    report: &'a FormatReport,
+    enable_colors: bool,
+}
+
+impl<'a> Display for FormatReportFormatter<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let formatter = DisplayListFormatter::new(self.enable_colors);
+        let errors_by_file = &self.report.internal.borrow().0;
+
+        for (file, errors) in errors_by_file {
+            for error in errors {
+                let snippet = formatting_error_to_snippet(file, error);
+                writeln!(f, "{}\n", formatter.format(&DisplayList::from(snippet)))?;
+            }
+        }
+
+        if !errors_by_file.is_empty() {
+            let snippet = formatting_failure_snippet(self.report.warning_count());
+            writeln!(f, "{}", formatter.format(&DisplayList::from(snippet)))?;
+        }
+
+        Ok(())
+    }
+}
+
+fn formatting_failure_snippet(warning_count: usize) -> Snippet {
+    Snippet {
+        title: Some(Annotation {
+            id: None,
+            label: Some(format!(
+                "rustfmt has failed to format. See previous {} errors.",
+                warning_count
+            )),
+            annotation_type: AnnotationType::Warning,
+        }),
+        footer: Vec::new(),
+        slices: Vec::new(),
+    }
+}
+
+fn formatting_error_to_snippet(file: &FileName, error: &FormattingError) -> Snippet {
+    let slices = vec![snippet_code_slice(file, error)];
+    let title = Some(snippet_title(error));
+    let footer = snippet_footer(error).into_iter().collect();
+
+    Snippet {
+        title,
+        footer,
+        slices,
+    }
+}
+
+fn snippet_title(error: &FormattingError) -> Annotation {
+    let annotation_type = error_kind_to_snippet_annotation_type(&error.kind);
+
+    Annotation {
+        id: title_annotation_id(error),
+        label: Some(error.kind.to_string()),
+        annotation_type,
+    }
+}
+
+fn snippet_footer(error: &FormattingError) -> Option<Annotation> {
+    let message_suffix = error.msg_suffix();
+
+    if !message_suffix.is_empty() {
+        Some(Annotation {
+            id: None,
+            label: Some(message_suffix.to_string()),
+            annotation_type: AnnotationType::Note,
+        })
+    } else {
+        None
+    }
+}
+
+fn snippet_code_slice(file: &FileName, error: &FormattingError) -> Slice {
+    let annotations = slice_annotation(error).into_iter().collect();
+    let origin = Some(format!("{}:{}", file, error.line));
+    let source = error.line_buffer.clone();
+
+    Slice {
+        source,
+        line_start: error.line,
+        origin,
+        fold: false,
+        annotations,
+    }
+}
+
+fn slice_annotation(error: &FormattingError) -> Option<SourceAnnotation> {
+    let (range_start, range_length) = error.format_len();
+    let range_end = range_start + range_length;
+
+    if range_length > 0 {
+        Some(SourceAnnotation {
+            annotation_type: AnnotationType::Error,
+            range: (range_start, range_end),
+            label: String::new(),
+        })
+    } else {
+        None
+    }
+}
+
+fn title_annotation_id(error: &FormattingError) -> Option<String> {
+    const INTERNAL_ERROR_ID: &str = "internal";
+
+    if error.is_internal() {
+        Some(INTERNAL_ERROR_ID.to_string())
+    } else {
+        None
+    }
+}
+
+fn error_kind_to_snippet_annotation_type(error_kind: &ErrorKind) -> AnnotationType {
+    match error_kind {
+        ErrorKind::LineOverflow(..)
+        | ErrorKind::TrailingWhitespace
+        | ErrorKind::IoError(_)
+        | ErrorKind::ParseError
+        | ErrorKind::LostComment
+        | ErrorKind::LicenseCheck
+        | ErrorKind::BadAttr
+        | ErrorKind::InvalidGlobPattern(_)
+        | ErrorKind::VersionMismatch => AnnotationType::Error,
+        ErrorKind::BadIssue(_) | ErrorKind::DeprecatedAttr => AnnotationType::Warning,
+    }
+}

src/formatting.rs

@@ -275,18 +275,14 @@ impl FormattingError {
         }
     }
 
-    pub(crate) fn msg_prefix(&self) -> &str {
+    pub(crate) fn is_internal(&self) -> bool {
         match self.kind {
             ErrorKind::LineOverflow(..)
             | ErrorKind::TrailingWhitespace
             | ErrorKind::IoError(_)
             | ErrorKind::ParseError
-            | ErrorKind::LostComment => "internal error:",
-            ErrorKind::LicenseCheck
-            | ErrorKind::BadAttr
-            | ErrorKind::InvalidGlobPattern(..)
-            | ErrorKind::VersionMismatch => "error:",
-            ErrorKind::BadIssue(_) | ErrorKind::DeprecatedAttr => "warning:",
+            | ErrorKind::LostComment => true,
+            _ => false,
         }
     }
 

src/git-rustfmt/main.rs

@@ -11,7 +11,7 @@ use env_logger;
 use getopts::{Matches, Options};
 use rustfmt_nightly as rustfmt;
 
-use crate::rustfmt::{load_config, CliOptions, Input, Session};
+use crate::rustfmt::{load_config, CliOptions, FormatReportFormatterBuilder, Input, Session};
 
 fn prune_files(files: Vec<&str>) -> Vec<&str> {
     let prefixes: Vec<_> = files
@@ -67,7 +67,7 @@ fn fmt_files(files: &[&str]) -> i32 {
     for file in files {
         let report = session.format(Input::File(PathBuf::from(file))).unwrap();
         if report.has_warnings() {
-            eprintln!("{}", report);
+            eprintln!("{}", FormatReportFormatterBuilder::new(&report).build());
         }
         if !session.has_no_errors() {
             exit_code = 1;