Ensure @charset statements are first

lib/parse-statements.js

@@ -66,6 +66,11 @@ function parseMedia(result, atRule) {
 }
 
 function parseCharset(result, atRule) {
+  if (atRule.prev()) {
+    return result.warn("@charset must precede all other statements", {
+      node: atRule,
+    })
+  }
   return {
     type: "charset",
     node: atRule,
@@ -74,19 +79,20 @@ function parseCharset(result, atRule) {
 }
 
 function parseImport(result, atRule) {
-  let prev = getPrev(atRule)
+  let prev = atRule.prev()
   if (prev) {
     do {
       if (
-        prev.type !== "atrule" ||
-        (prev.name !== "import" && prev.name !== "charset")
+        prev.type !== "comment" &&
+        (prev.type !== "atrule" ||
+          (prev.name !== "import" && prev.name !== "charset"))
       ) {
         return result.warn(
           "@import must precede all other statements (besides @charset)",
           { node: atRule }
         )
       }
-      prev = getPrev(prev)
+      prev = prev.prev()
     } while (prev)
   }
 
@@ -137,11 +143,3 @@ function parseImport(result, atRule) {
 
   return stmt
 }
-
-function getPrev(item) {
-  let prev = item.prev()
-  while (prev && prev.type === "comment") {
-    prev = prev.prev()
-  }
-  return prev
-}

test/lint.js

@@ -78,6 +78,23 @@ test("should not warn when @charset or @import statement before", t => {
   })
 })
 
+test("should warn when @charset is not first", t => {
+  return Promise.all([
+    processor.process(`a {} @charset "utf-8";`, { from: undefined }),
+    processor.process(`@media {} @charset "utf-8";`, { from: undefined }),
+    processor.process(`/* foo */ @charset "utf-8";`, { from: undefined }),
+    processor.process(`@import "bar.css"; @charset "utf-8";`, {
+      from: "test/fixtures/imports/foo.css",
+    }),
+  ]).then(results => {
+    results.forEach(result => {
+      const warnings = result.warnings()
+      t.is(warnings.length, 1)
+      t.is(warnings[0].text, "@charset must precede all other statements")
+    })
+  })
+})
+
 test("should warn when a user didn't close an import with ;", t => {
   return processor
     .process(`@import url('http://') :root{}`, { from: undefined })