feat: Color the error severity

codespan-reporting/examples/emit.rs

@@ -0,0 +1,25 @@
+extern crate codespan;
+extern crate codespan_reporting;
+
+use codespan::CodeMap;
+use codespan_reporting::termcolor::{ColorChoice, StandardStream};
+use codespan_reporting::{emit, Diagnostic, Label, Severity};
+
+fn main() {
+    let writer = StandardStream::stdout(ColorChoice::Auto);
+
+    let mut code_map = CodeMap::new();
+
+    let source = r##"
+(define test 123)
+(+ test "")
+"##;
+    let file_map = code_map.add_filemap("test".into(), source.to_string());
+
+    let diagnostic = Diagnostic::new(Severity::Error, "Unexpected type in `+` application")
+        .with_label(
+            Label::new_primary(file_map.line_span(2.into()).unwrap())
+                .with_message("Expected integer but got string"),
+        );
+    emit(&mut writer.lock(), &code_map, &diagnostic).unwrap();
+}

codespan-reporting/src/emitter.rs

@@ -1,23 +1,40 @@
+use std::io;
+
 use codespan::CodeMap;
 
+use termcolor::{ColorSpec, WriteColor};
+
 use Diagnostic;
 
-pub fn emit(codemap: &CodeMap, diagnostic: &Diagnostic) {
-    println!("{}: {}", diagnostic.severity, diagnostic.message);
+pub fn emit<W>(mut writer: W, codemap: &CodeMap, diagnostic: &Diagnostic) -> io::Result<()>
+where
+    W: WriteColor,
+{
+    writer.set_color(ColorSpec::new().set_fg(Some(diagnostic.severity.color())))?;
+    write!(writer, "{}", diagnostic.severity)?;
+    writer.reset()?;
+    writeln!(writer, ": {}", diagnostic.message)?;
     for label in &diagnostic.labels {
         match codemap.find_file(label.span.start()) {
             None => if let Some(ref message) = label.message {
-                println!("- {}", message)
+                writeln!(writer, "- {}", message)?
             },
             Some(file) => {
                 let (line, col) = file.location(label.span.start()).expect("location");
 
-                print!("- {}:{}:{}", file.name(), line.number(), col.number());
+                writeln!(
+                    writer,
+                    "- {}:{}:{}",
+                    file.name(),
+                    line.number(),
+                    col.number()
+                )?;
                 match label.message {
-                    None => println!(),
-                    Some(ref label) => println!(": {}", label),
+                    None => writeln!(writer)?,
+                    Some(ref label) => writeln!(writer, ": {}", label)?,
                 }
             },
         }
     }
+    Ok(())
 }

codespan-reporting/src/lib.rs

@@ -1,5 +1,5 @@
 extern crate codespan;
-extern crate termcolor;
+pub extern crate termcolor;
 
 use std::cmp::Ordering;
 use std::fmt;