Skip syntax highlighting for long lines (#2165)

* Skip highlighting for long lines

* Run cargo fmt, update changelog

CHANGELOG.md

@@ -12,6 +12,7 @@
 ## Other
 
 - Include info about custom assets in `--diagnostics` if used. See #2107, #2144 (@Enselic)
+- Skip syntax highlighting on long lines (> 16384 chars) to help improve performance. See #2165 (@keith-hall)
 
 ## Syntaxes
 

src/printer.rs

@@ -445,9 +445,18 @@ impl<'a> Printer for InteractivePrinter<'a> {
                     return Ok(());
                 }
             };
+            // skip syntax highlighting on long lines
+            if line.len() > 1024 * 16 {
+                let mut empty = highlighter_from_set
+                    .highlighter
+                    .highlight(&"\n", highlighter_from_set.syntax_set);
+                empty[0].1 = line.as_ref();
+                empty
+            } else {
                 highlighter_from_set
                     .highlighter
                     .highlight(&line, highlighter_from_set.syntax_set)
+            }
         };
 
         if out_of_range {