Fix sourcesContent (#177)

* Fix sourcesContent

Author: non25

CHANGELOG.md

@@ -1,5 +1,9 @@
 # svelte-loader changelog
 
+## 3.1.1 (Unreleased)
+
+* Fix empty sourcesContent ([#177](https://github.com/sveltejs/svelte-loader/pull/177))
+
 ## 3.1.0
 
 * Pass preprocessor source maps to compiler ([#172](https://github.com/sveltejs/svelte-loader/pull/172))

index.js

@@ -50,6 +50,8 @@ module.exports = function(source, map) {
 		const compiled = compile(processed.toString(), compileOptions);
 		let { js, css, warnings } = compiled;
 
+		if (!js.map.sourcesContent) js.map.sourcesContent = [ source ];
+
 		warnings.forEach(
 			options.onwarn
 				? warning => options.onwarn(warning, handleWarning)