Update: Upgrade Acorn to support ES2017 (fixes #287) (#290)

Author: xjamundx

README.md

@@ -41,7 +41,7 @@ var ast = espree.parse(code, {
     // create a top-level tokens array containing all tokens
     tokens: true,
 
-    // specify the language version (3, 5, 6, or 7, default is 5)
+    // specify the language version (3, 5, 6, 7, or 8, default is 5)
     ecmaVersion: 5,
 
     // specify which type of script you're parsing (script or module, default is script)
@@ -130,10 +130,17 @@ We are building on top of Acorn, however, so that we can contribute back and hel
 
 All of them.
 
-### What ECMAScript 7 features do you support?
+### What ECMAScript 7/2016 features do you support?
 
 There is only one ECMAScript 7 syntax change: the exponentiation operator. Espree supports this.
 
+### What ECMAScript 2017 features do you support?
+
+Because ECMAScript 2017 is still under development, we are implementing features as they are finalized. Currently, Espree supports:
+
+* `async` functions
+* Trailing commas in function declarations and calls (including arrow functions and concise methods)
+
 ### How do you determine which experimental features to support?
 
 In general, we do not support experimental JavaScript features. We may make exceptions from time to time depending on the maturity of the features.

espree.js

@@ -340,6 +340,7 @@ acorn.plugins.espree = function(instance) {
 
             var prop = this.startNode(),
                 isGenerator,
+                isAsync,
                 startPos,
                 startLoc;
 
@@ -369,8 +370,22 @@ acorn.plugins.espree = function(instance) {
                 }
             }
 
-            this.parsePropertyName(prop);
-            this.parsePropertyValue(prop, isPattern, isGenerator, startPos, startLoc, refShorthandDefaultPos);
+            // grab the property name or "async"
+            this.parsePropertyName(prop/* , refDestructuringErrors */);
+            if (this.options.ecmaVersion >= 8 &&
+                !isPattern &&
+                !isGenerator &&
+                !prop.computed &&
+                prop.key.type === "Identifier" &&
+                prop.key.name === "async" &&
+                this.type !== tt.parenL &&
+                !this.canInsertSemicolon()
+            ) {
+                this.parsePropertyName(prop/* , refDestructuringErrors */);
+                isAsync = true;
+            }
+
+            this.parsePropertyValue(prop, isPattern, isGenerator, isAsync, startPos, startLoc, refShorthandDefaultPos);
             this.checkPropClash(prop, propHash);
             node.properties.push(this.finishNode(prop, "Property"));
         }
@@ -506,12 +521,13 @@ function tokenize(code, options) {
             case 5:
             case 6:
             case 7:
+            case 8:
                 acornOptions.ecmaVersion = options.ecmaVersion;
                 extra.ecmaVersion = options.ecmaVersion;
                 break;
 
             default:
-                throw new Error("ecmaVersion must be 3, 5, 6, or 7.");
+                throw new Error("ecmaVersion must be 3, 5, 6, 7, or 8.");
         }
     }
 
@@ -643,12 +659,13 @@ function parse(code, options) {
                 case 5:
                 case 6:
                 case 7:
+                case 8:
                     acornOptions.ecmaVersion = options.ecmaVersion;
                     extra.ecmaVersion = options.ecmaVersion;
                     break;
 
                 default:
-                    throw new Error("ecmaVersion must be 3, 5, 6, or 7.");
+                    throw new Error("ecmaVersion must be 3, 5, 6, 7, or 8.");
             }
         }
 

package.json

@@ -18,7 +18,7 @@
   },
   "license": "BSD-2-Clause",
   "dependencies": {
-    "acorn": "^3.3.0",
+    "acorn": "^4.0.1",
     "acorn-jsx": "^3.0.0"
   },
   "devDependencies": {

tests/fixtures/ecma-version/6/destructuring-and-spread/error-complex-destructured-spread-first.result.js

@@ -1,6 +1,6 @@
 module.exports = {
-    "index": 4,
+    "index": 5,
     "lineNumber": 1,
-    "column": 5,
+    "column": 6,
     "message": "Comma is not permitted after the rest element"
 };

tests/fixtures/ecma-version/6/destructuring-and-spread/invalid-not-final-array-empty.result.js

@@ -1,6 +1,6 @@
 module.exports = {
-    "index": 4,
+    "index": 5,
     "lineNumber": 1,
-    "column": 5,
+    "column": 6,
     "message": "Comma is not permitted after the rest element"
 };

tests/fixtures/ecma-version/6/destructuring-and-spread/not-final-array.result.js

@@ -1,6 +1,6 @@
 module.exports = {
-    "index": 4,
+    "index": 5,
     "lineNumber": 1,
-    "column": 5,
+    "column": 6,
     "message": "Comma is not permitted after the rest element"
 };