feat: optimize debug message formatting, #1065

docs: add impofration how to enable @debug output

README.md

@@ -756,6 +756,19 @@ module.exports = {
 };
 ```
 
+## How to enable `@debug` output
+
+Defaults, the output of `@debug` messages is disabled.
+To enable it, add to **webpack.config.js** following:
+```js
+module.exports = {
+  stats: {
+    loggingDebug: ['sass-loader'],
+  },
+  //...
+}
+```
+
 ## Examples
 
 ### Extracts CSS into separate files

src/utils.js

@@ -157,13 +157,15 @@ async function getSassOptions(
     const logger = loaderContext.getLogger("sass-loader");
     const formatSpan = (span) =>
       `${span.url || "-"}:${span.start.line}:${span.start.column}: `;
+    const formatDebugSpan = (span) => 
+      `[debug:${span.start.line}:${span.start.column}] `;
 
     options.logger = {
       debug(message, loggerOptions) {
         let builtMessage = "";
 
         if (loggerOptions.span) {
-          builtMessage = formatSpan(loggerOptions.span);
+          builtMessage = formatDebugSpan(loggerOptions.span);
         }
 
         builtMessage += message;