Add namespace statements

corpus/statements.txt

@@ -17,6 +17,32 @@ Import statements
   (import_statement (call_expression (function_name) (arguments (string_value))))
   (import_statement (string_value) (keyword_query)))
 
+==============================
+Namespace statements
+==============================
+
+/* Default namespace */
+@namespace url(XML-namespace-URL);
+@namespace "XML-namespace-URL";
+@namespace url(http://www.w3.org/1999/xhtml);
+@namespace svg url(http://www.w3.org/2000/svg);
+
+/* Prefixed namespace */
+@namespace prefix url(XML-namespace-URL);
+@namespace prefix "XML-namespace-URL";
+
+---
+
+(stylesheet
+  (comment)
+  (namespace_statement (call_expression (function_name) (arguments (plain_value))))
+  (namespace_statement (string_value))
+  (namespace_statement (call_expression (function_name) (arguments (plain_value))))
+  (namespace_statement (namespace_name) (call_expression (function_name) (arguments (plain_value))))
+  (comment)
+  (namespace_statement (namespace_name) (call_expression (function_name) (arguments (plain_value))))
+  (namespace_statement (namespace_name) (string_value)))
+
 ==============================
 Media statements
 ==============================

grammar.js

@@ -23,6 +23,7 @@ module.exports = grammar({
       $.import_statement,
       $.media_statement,
       $.charset_statement,
+      $.namespace_statement,
       $.at_rule
     ),
 
@@ -47,6 +48,13 @@ module.exports = grammar({
       ';'
     ),
 
+    namespace_statement: $ => seq(
+      '@namespace',
+      optional(alias($.identifier, $.namespace_name)),
+      choice($.string_value, $.call_expression),
+      ';'
+    ),
+
     at_rule: $ => seq(
       $.at_keyword,
       commaSep($._query),

src/grammar.json

@@ -27,6 +27,10 @@
           "type": "SYMBOL",
           "name": "charset_statement"
         },
+        {
+          "type": "SYMBOL",
+          "name": "namespace_statement"
+        },
         {
           "type": "SYMBOL",
           "name": "at_rule"
@@ -138,6 +142,49 @@
         }
       ]
     },
+    "namespace_statement": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "@namespace"
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "identifier"
+              },
+              "named": true,
+              "value": "namespace_name"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "string_value"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "call_expression"
+            }
+          ]
+        },
+        {
+          "type": "STRING",
+          "value": ";"
+        }
+      ]
+    },
     "at_rule": {
       "type": "SEQ",
       "members": [