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(());
                 }
             };
-            highlighter_from_set
-                .highlighter
-                .highlight(&line, highlighter_from_set.syntax_set)
+            // 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 {

tests/examples/longline.json

@@ -0,0 +1,3 @@
+{"api":
+    {"ANGLE_instanced_arrays":{"__compat":{"mdn_url":"https://developer.mozilla.org/docs/Web/API/ANGLE_instanced_arrays","spec_url":"https://www.khronos.org/registry/webgl/extensions/ANGLE_instanced_arrays/","support":{"chrome":{"version_added":"32"},"chrome_android":{"version_added":"32"},"edge":{"version_added":"12"},"firefox":{"version_added":"47"},"firefox_android":{"version_added":true},"ie":{"version_added":"11"},"opera":{"version_added":"19"},"opera_android":{"version_added":"19"},"safari":{"version_added":"8"},"safari_ios":{"version_added":"8"},"samsunginternet_android":{"version_added":"2.0"},"webview_android":{"version_added":"4.4"}},"status":{"experimental":false,"standard_track":true,"deprecated":false}},"drawArraysInstancedANGLE":{"__compat":{"mdn_url":"https://developer.mozilla.org/docs/Web/API/ANGLE_instanced_arrays/drawArraysInstancedANGLE","spec_url":"https://www.khronos.org/registry/webgl/extensions/ANGLE_instanced_arrays/","support":{"chrome":{"version_added":"32"},"chrome_android":{"version_added":"32"},"edge":{"version_added":"12"},"firefox":{"version_added":"47"},"firefox_android":{"version_added":true},"ie":{"version_added":"11"},"opera":{"version_added":"19"},"opera_android":{"version_added":"19"},"safari":{"version_added":"8"},"safari_ios":{"version_added":"8"},"samsunginternet_android":{"version_added":"2.0"},"webview_android":{"version_added":"4.4"}},"status":{"experimental":false,"standard_track":true,"deprecated":false}}},"drawElementsInstancedANGLE":{"__compat":{"mdn_url":"https://developer.mozilla.org/docs/Web/API/ANGLE_instanced_arrays/drawElementsInstancedANGLE","spec_url":"https://www.khronos.org/registry/webgl/extensions/ANGLE_instanced_arrays/","support":{"chrome":{"version_added":"32"},"chrome_android":{"version_added":"32"},"edge":{"version_added":"12"},"firefox":{"version_added":"47"},"firefox_android":{"version_added":true},"ie":{"version_added":"11"},"opera":{"version_added":"19"},"opera_android":{"version_added":"19"},"safari":{"version_added":"8"},"safari_ios":{"version_added":"8"},"samsunginternet_android":{"version_added":"2.0"},"webview_android":{"version_added":"4.4"}},"status":{"experimental":false,"standard_track":true,"deprecated":false}}},"vertexAttribDivisorANGLE":{"__compat":{"mdn_url":"https://developer.mozilla.org/docs/Web/API/ANGLE_instanced_arrays/vertexAttribDivisorANGLE","spec_url":"https://www.khronos.org/registry/webgl/extensions/ANGLE_instanced_arrays/","support":{"chrome":{"version_added":"32"},"chrome_android":{"version_added":"32"},"edge":{"version_added":"12"},"firefox":{"version_added":"47"},"firefox_android":{"version_added":true},"ie":{"version_added":"11"},"opera":{"version_added":"19"},"opera_android":{"version_added":"19"},"safari":{"version_added":"8"},"safari_ios":{"version_added":"8"},"samsunginternet_android":{"version_added":"2.0"},"webview_android":{"version_added":"4.4"}},"status":{"experimental":false,"standard_track":true,"deprecated":false}}}},"AbortController":{"__compat":{"mdn_url":"https://developer.mozilla.org/docs/Web/API/AbortController","spec_url":"https://dom.spec.whatwg.org/#interface-abortcontroller","support":{"chrome":{"version_added":"66"},"chrome_android":{"version_added":"66"},"edge":{"version_added":"16"},"firefox":{"version_added":"57"},"firefox_android":{"version_added":"57"},"ie":{"version_added":false},"nodejs":{"version_added":"15.0.0"},"opera":{"version_added":"53"},"opera_android":{"version_added":"47"},"safari":[{"version_added":"12.1"},{"version_added":"11.1","partial_implementation":true,"notes":"Even though <code>window.AbortController</code> is defined, it doesn't really abort <code>fetch</code> requests. 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