add support for class decorators

src/state.js

@@ -51,6 +51,8 @@ export function Parser(options, input, startPos) {
   // Labels in scope.
   this.labels = []
 
+  this.decorators = []
+
   // If enabled, skip leading hashbang line.
   if (this.pos === 0 && this.options.allowHashBang && this.input.slice(0, 2) === '#!')
     this.skipLineComment(2)

src/statement.js

@@ -51,9 +51,23 @@ pp.parseStatement = function(declaration, topLevel) {
   case tt._function:
     if (!declaration && this.options.ecmaVersion >= 6) this.unexpected()
     return this.parseFunctionStatement(node)
+
+  case tt.at:
+    while (this.type === tt.at) {
+      this.decorators.push(this.parseDecorator());
+    }
+    if (this.type !== tt._class) {
+      this.raise(this.start, "Leading decorators must be attached to a class declaration");
+    }
+
   case tt._class:
     if (!declaration) this.unexpected()
+    if (this.decorators.length) {
+      node.decorators = this.decorators
+      this.decorators = []
+    }
     return this.parseClass(node, true)
+
   case tt._if: return this.parseIfStatement(node)
   case tt._return: return this.parseReturnStatement(node)
   case tt._switch: return this.parseSwitchStatement(node)
@@ -99,6 +113,13 @@ pp.parseStatement = function(declaration, topLevel) {
   }
 }
 
+pp.parseDecorator = function() {
+  let node = this.startNode()
+  this.next()
+  node.expression = this.parseMaybeAssign()
+  return this.finishNode(node, "Decorator")
+}
+
 pp.parseBreakContinueStatement = function(node, keyword) {
   let isBreak = keyword == "break"
   this.next()
@@ -423,52 +444,6 @@ pp.parseFunctionParams = function(node) {
 // Parse a class declaration or literal (depending on the
 // `isStatement` parameter).
 
-pp.parseClass = function(node, isStatement) {
-  this.next()
-  node.id = this.type === tt.name ? this.parseIdent() : isStatement ? this.unexpected() : null
-  node.superClass = this.eat(tt._extends) ? this.parseExprSubscripts() : null
-  let classBody = this.startNode()
-  classBody.body = []
-  this.expect(tt.braceL)
-  while (!this.eat(tt.braceR)) {
-    if (this.eat(tt.semi)) continue
-    let method = this.startNode()
-    let isGenerator = this.eat(tt.star)
-    this.parsePropertyName(method)
-    if (this.type !== tt.parenL && !method.computed && method.key.type === "Identifier" &&
-        method.key.name === "static") {
-      if (isGenerator) this.unexpected()
-      method['static'] = true
-      isGenerator = this.eat(tt.star)
-      this.parsePropertyName(method)
-    } else {
-      method['static'] = false
-    }
-    if (this.options.features["es7.asyncFunctions"] && this.type !== tt.parenL &&
-        !method.computed && method.key.type === "Identifier" && method.key.name === "async") {
-      isAsync = true;
-      this.parsePropertyName(method);
-    }
-    method.kind = "method"
-    if (!method.computed && !isGenerator) {
-      if (method.key.type === "Identifier") {
-        if (this.type !== tt.parenL && (method.key.name === "get" || method.key.name === "set")) {
-          method.kind = method.key.name
-          this.parsePropertyName(method)
-        } else if (!method['static'] && method.key.name === "constructor") {
-          method.kind = "constructor"
-        }
-      } else if (!method['static'] && method.key.type === "Literal" && method.key.value === "constructor") {
-        method.kind = "constructor"
-      }
-    }
-    method.value = this.parseMethod(isGenerator)
-    classBody.body.push(this.finishNode(method, "MethodDefinition"))
-  }
-  node.body = this.finishNode(classBody, "ClassBody")
-  return this.finishNode(node, isStatement ? "ClassDeclaration" : "ClassExpression")
-}
-
 pp.parseClass = function(node, isStatement) {
   this.next()
   this.parseClassId(node, isStatement)
@@ -476,8 +451,13 @@ pp.parseClass = function(node, isStatement) {
   var classBody = this.startNode()
   classBody.body = []
   this.expect(tt.braceL)
+  var decorators = []
   while (!this.eat(tt.braceR)) {
     if (this.eat(tt.semi)) continue
+    if (this.options.features["es7.decorators"] && this.type === tt.at) {
+      decorators.push(this.parseDecorator());
+      continue;
+    }
     var method = this.startNode()
     var isGenerator = this.eat(tt.star), isAsync = false
     this.parsePropertyName(method)
@@ -508,8 +488,15 @@ pp.parseClass = function(node, isStatement) {
         method.kind = "constructor"
       }
     }
+    if (this.options.features["es7.decorators"] && decorators.length) {
+      method.decorators = decorators
+      decorators = []
+    }
     this.parseClassMethod(classBody, method, isGenerator, isAsync)
   }
+  if (decorators.length) {
+    raise(this.start, "You have trailing decorators with no method");
+  }
   node.body = this.finishNode(classBody, "ClassBody")
   return this.finishNode(node, isStatement ? "ClassDeclaration" : "ClassExpression")
 }
@@ -540,11 +527,11 @@ pp.parseExport = function(node) {
   }
   if (this.eat(tt._default)) { // export default ...
     let expr = this.parseMaybeAssign()
-    let needsSemi = false
+    let needsSemi = true
     if (expr.id) switch (expr.type) {
       case "FunctionExpression": expr.type = "FunctionDeclaration"; break
       case "ClassExpression": expr.type = "ClassDeclaration"; break
-      default: needsSemi = true
+      default: needsSemi = false
     }
     node.declaration = expr
     if (needsSemi) this.semicolon()

src/tokenize.js

@@ -322,6 +322,7 @@ pp.getTokenFromCode = function(code) {
   case 125: ++this.pos; return this.finishToken(tt.braceR)
   case 58: ++this.pos; return this.finishToken(tt.colon)
   case 63: ++this.pos; return this.finishToken(tt.question)
+  case 64: ++this.pos; return this.finishToken(tt.at)
 
   case 96: // '`'
     if (this.options.ecmaVersion < 6) break

src/tokentype.js

@@ -61,6 +61,7 @@ export const types = {
   ellipsis: new TokenType("...", beforeExpr),
   backQuote: new TokenType("`", startsExpr),
   dollarBraceL: new TokenType("${", {beforeExpr: true, startsExpr: true}),
+  at: new TokenType("@"),
 
   // Operators. These carry several kinds of properties to help the
   // parser use them properly (the presence of these properties is

test/tests-babel.js

@@ -2056,3 +2056,5 @@ test('export async function foo(){}', {
   sourceType: "module",
   features: { "es7.asyncFunctions": true }
 });
+
+// ES7 decorators