Fix interpolated at-rule parsing (#133)

Closes #131

lib/scss-parser.js

@@ -162,6 +162,23 @@ class ScssParser extends Parser {
     }
   }
 
+  atrule(token) {
+    let name = token[1]
+    let prev = token
+    while (!this.tokenizer.endOfFile()) {
+      let next = this.tokenizer.nextToken()
+      if (next[0] === 'word' && next[2] === prev[3] + 1) {
+        name += next[1]
+        prev = next
+      } else {
+        this.tokenizer.back(next)
+        break
+      }
+    }
+
+    super.atrule(['at-word', name, token[2], prev[3]])
+  }
+
   raw(node, prop, tokens) {
     super.raw(node, prop, tokens)
     if (node.raws[prop]) {

test/parse.test.js

@@ -100,8 +100,33 @@ it('parses interpolation inside interpolation', () => {
   expect(root.first.value).toEqual('#{"#{&}__column"}')
 })
 
+it("parses interpolation that's the entire at-rule", () => {
+  let root = parse('@#{$var} param { }')
+  expect(root.first.name).toEqual('#{$var}')
+  expect(root.first.params).toEqual('param')
+})
+
+it('parses interpolation at the beginning of at-rule', () => {
+  let root = parse('@#{$var}suffix param { }')
+  expect(root.first.name).toEqual('#{$var}suffix')
+  expect(root.first.params).toEqual('param')
+})
+
+it('parses interpolation within at-rule', () => {
+  let root = parse('@before#{$var}after param { }')
+  expect(root.first.name).toEqual('before#{$var}after')
+  expect(root.first.params).toEqual('param')
+})
+
 it('parses interpolation right after at-rule', () => {
   let root = parse('@media#{$var} { }')
+  expect(root.first.name).toEqual('media#{$var}')
+  expect(root.first.params).toEqual('')
+})
+
+it('parses interpolation in at-rule value', () => {
+  let root = parse('@media #{$var} { }')
+  expect(root.first.name).toEqual('media')
   expect(root.first.params).toEqual('#{$var}')
 })