Fix: not greedy match the frontmatter in postcss parser (#4457)

src/language-css/parser-postcss.js

@@ -439,7 +439,7 @@ function parseNestedCSS(node) {
 
 function parseWithParser(parser, text) {
   let result;
-  const frontMatterMatches = text.match(/^---(\n[\s\S]*)?\n---/);
+  const frontMatterMatches = text.match(/^---(\n[\s\S]*?)?\n---/);
   const frontMatter = frontMatterMatches && frontMatterMatches[0];
   const normalizedText = frontMatter ? text.substr(frontMatter.length) : text;
 

tests/css_yaml/__snapshots__/jsfmt.spec.js.snap

@@ -53,6 +53,33 @@ a {
 
 `;
 
+exports[`malformed-2.css 1`] = `
+---
+foo: bar
+---
+
+a {
+color:blue
+}
+
+---
+
+.b {
+color:red
+}~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+---
+foo: bar
+---
+
+a {
+  color: blue;
+}
+--- .b {
+  color: red;
+}
+
+`;
+
 exports[`only_comments.css 1`] = `
 ---
 # comment 1

tests/css_yaml/malformed-2.css

@@ -0,0 +1,13 @@
+---
+foo: bar
+---
+
+a {
+color:blue
+}
+
+---
+
+.b {
+color:red
+}