absolute sourcemaps have source content

lib/map-generator.js

@@ -97,10 +97,17 @@ class MapGenerator {
           let from = node.source.input.from
           if (from && !already[from]) {
             already[from] = true
-            this.map.setSourceContent(
-              this.toUrl(this.path(from)),
-              node.source.input.css
-            )
+            let fromUrl = this.toUrl(this.path(from))
+            if (this.mapOpts.absolute) {
+              if (pathToFileURL) {
+                fromUrl = pathToFileURL(from).toString()
+              } else {
+                throw new Error(
+                  '`map.absolute` option is not available in this PostCSS build'
+                )
+              }
+            }
+            this.map.setSourceContent(fromUrl, node.source.input.css)
           }
         }
       })

test/map.test.ts

@@ -722,4 +722,15 @@ test('supports previous inline map with empty processor', () => {
   match((root3.source?.input.origin(1, 0) as any).file, 'a.css')
 })
 
+test('absolute sourcemaps have source contents', () => {
+  let result = postcss([() => {}]).process('a{}', {
+    from: '/dir/to/a.css',
+    map: {
+      inline: false,
+      absolute: true
+    }
+  })
+  equal(result.map.toJSON().sourcesContent, ['a{}'])
+})
+
 test.run()