fix: make sourceMaps relative to the CSS output file (#274)

Co-authored-by: Ward Peeters <[email protected]>

Author: coxmi

src/index.js

@@ -204,7 +204,7 @@ export default (options = {}) => {
             'utf8'
           ).toString('base64')}*/`
         } else if (sourceMap === true) {
-          code += `\n/*# sourceMappingURL=${fileName}.map */`
+          code += `\n/*# sourceMappingURL=${path.basename(fileName)}.map */`
         }
 
         return {

test/__snapshots__/index.test.js.snap

@@ -183,7 +183,7 @@ body {
   color: red;
 }
 
-/*# sourceMappingURL=this/is/extracted.css.map */"
+/*# sourceMappingURL=extracted.css.map */"
 `;
 
 exports[`extract custom-path: css map 1`] = `"{\\"version\\":3,\\"sources\\":[\\"foo.css\\",\\"bar.css\\",\\"test/fixtures/simple/style.styl\\",\\"style.styl\\",\\"style.sass\\",\\"test/fixtures/simple/style.less\\",\\"style.less\\",\\"style.pcss\\"],\\"names\\":[],\\"mappings\\":\\"AAAA;EACE,UAAU;AACZ;;ACFA;EACE,UAAU;AACZ;;ACFA;EACE,WAAO;EACP,gBAAY;ACCd;AACA,yDAAyD;ACJzD;EACE,UAAU;EACV,sBAAsB,EAAE;;ACC1B;EACE,cAAA;ACFF;;ACFA;EACE,UAAU;AACZ\\",\\"file\\":\\"this/is/extracted.css\\",\\"sourcesContent\\":[\\"body {\\\\n  color: red;\\\\n}\\\\n\\",\\".bar {\\\\n  color: red;\\\\n}\\\\n\\",null,null,\\"#sidebar {\\\\n  width: 30%;\\\\n  background-color: #faa; }\\\\n\\",null,null,\\".pcss {\\\\n  color: red;\\\\n}\\\\n\\"]}"`;
@@ -281,7 +281,7 @@ body {
   color: red;
 }
 
-/*# sourceMappingURL=this/is/extracted.css.map */"
+/*# sourceMappingURL=extracted.css.map */"
 `;
 
 exports[`extract relative-path: css map 1`] = `"{\\"version\\":3,\\"sources\\":[\\"foo.css\\",\\"bar.css\\",\\"test/fixtures/simple/style.styl\\",\\"style.styl\\",\\"style.sass\\",\\"test/fixtures/simple/style.less\\",\\"style.less\\",\\"style.pcss\\"],\\"names\\":[],\\"mappings\\":\\"AAAA;EACE,UAAU;AACZ;;ACFA;EACE,UAAU;AACZ;;ACFA;EACE,WAAO;EACP,gBAAY;ACCd;AACA,yDAAyD;ACJzD;EACE,UAAU;EACV,sBAAsB,EAAE;;ACC1B;EACE,cAAA;ACFF;;ACFA;EACE,UAAU;AACZ\\",\\"file\\":\\"this/is/extracted.css\\",\\"sourcesContent\\":[\\"body {\\\\n  color: red;\\\\n}\\\\n\\",\\".bar {\\\\n  color: red;\\\\n}\\\\n\\",null,null,\\"#sidebar {\\\\n  width: 30%;\\\\n  background-color: #faa; }\\\\n\\",null,null,\\".pcss {\\\\n  color: red;\\\\n}\\\\n\\"]}"`;