feat: support postcss

Author: baseballyama

.changeset/silver-swans-build.md

@@ -0,0 +1,5 @@
+---
+"svelte-eslint-parser": patch
+---
+
+feat: support postcss

src/parser/style-context.ts

@@ -37,7 +37,7 @@ export interface StyleContextUnknownLang {
  */
 export function parseStyleContext(
   styleElement: SvelteStyleElement | undefined,
-  ctx: Context,
+  ctx: Context
 ): StyleContext {
   if (!styleElement || !styleElement.endTag) {
     return { status: "no-style-element" };
@@ -56,6 +56,7 @@ export function parseStyleContext(
   let parseFn: Parser<Root>, sourceAst: Root;
   switch (sourceLang) {
     case "css":
+    case "postcss":
       parseFn = postcss.parse;
       break;
     case "scss":
@@ -66,7 +67,7 @@ export function parseStyleContext(
   }
   const styleCode = ctx.code.slice(
     styleElement.startTag.range[1],
-    styleElement.endTag.range[0],
+    styleElement.endTag.range[0]
   );
   try {
     sourceAst = parseFn(styleCode, {
@@ -109,7 +110,7 @@ export function styleNodeLoc(node: Node): Partial<SourceLocation> {
  * Extracts a node range (like that of any ESLint node) from a parsed svelte style node.
  */
 export function styleNodeRange(
-  node: Node,
+  node: Node
 ): [number | undefined, number | undefined] {
   if (node.source === undefined) {
     return [undefined, undefined];

tests/fixtures/parser/ast/postcss-input.svelte

@@ -0,0 +1,6 @@
+<style lang="postcss">
+  body {
+    colour: white;
+    background-colour: grey;
+  }
+</style>