Decorators Stage 2 Parsing

src/index.js

@@ -47,6 +47,11 @@ const parserClassCache: { [key: string]: Class<Parser> } = {};
 
 /** Get a Parser class with plugins applied. */
 function getParserClass(pluginsFromOptions: $ReadOnlyArray<string>): Class<Parser> {
+
+  if (pluginsFromOptions.indexOf("decorators") >= 0 && pluginsFromOptions.indexOf("decoratorsStage2") >= 0) {
+    throw new Error("Cannot use decorators and decoratorsStage2 plugin together");
+  }
+
   // Filter out just the plugins that have an actual mixin associated with them.
   let pluginList = pluginsFromOptions.filter((p) => p === "estree" || p === "flow" || p === "jsx");
 

src/parser/expression.js

@@ -857,8 +857,16 @@ export default class ExpressionParser extends LValParser {
         if (this.eat(tt.braceR)) break;
       }
 
-      while (this.match(tt.at)) {
-        decorators.push(this.parseDecorator());
+      if (this.match(tt.at)) {
+        if (this.hasPlugin("decoratorsStage2")) {
+          this.raise(this.state.start, "Stage 2 decorators disallow object literal property decorators");
+        } else {
+          // we needn't check if decorators (stage 0) plugin is enabled since it's checked by
+          // the call to this.parseDecorator
+          while (this.match(tt.at)) {
+            decorators.push(this.parseDecorator());
+          }
+        }
       }
 
       let prop = this.startNode(), isGenerator = false, isAsync = false, startPos, startLoc;

src/parser/lval.js

@@ -187,6 +187,9 @@ export default class LValParser extends NodeUtils {
         break;
       } else {
         const decorators = [];
+        if (this.match(tt.at) && this.hasPlugin("decoratorsStage2")) {
+          this.raise(this.state.start, "Stage 2 decorators cannot be used to decorate parameters");
+        }
         while (this.match(tt.at)) {
           decorators.push(this.parseDecorator());
         }

src/parser/statement.js

@@ -157,6 +157,10 @@ export default class StatementParser extends ExpressionParser {
   }
 
   parseDecorators(allowExport?: boolean): void {
+    if (this.hasPlugin("decoratorsStage2")) {
+      allowExport = false;
+    }
+
     while (this.match(tt.at)) {
       const decorator = this.parseDecorator();
       this.state.decorators.push(decorator);
@@ -172,12 +176,38 @@ export default class StatementParser extends ExpressionParser {
   }
 
   parseDecorator(): N.Decorator {
-    if (!this.hasPlugin("decorators")) {
+    if (!(this.hasPlugin("decorators") || this.hasPlugin("decoratorsStage2"))) {
       this.unexpected();
     }
+
     const node = this.startNode();
     this.next();
-    node.expression = this.parseMaybeAssign();
+
+    if (this.hasPlugin("decoratorsStage2")) {
+      const startPos = this.state.start;
+      const startLoc = this.state.startLoc;
+      let expr = this.parseIdentifier(false);
+
+      while (this.eat(tt.dot)) {
+        const node = this.startNodeAt(startPos, startLoc);
+        node.object = expr;
+        node.property = this.parseIdentifier(true);
+        node.computed = false;
+        expr = this.finishNode(node, "MemberExpression");
+      }
+
+      if (this.eat(tt.parenL)) {
+        const node = this.startNodeAt(startPos, startLoc);
+        node.callee = expr;
+        node.arguments = this.parseCallExpressionArguments(tt.parenR, false);
+        expr = this.finishNode(node, "CallExpression");
+        this.toReferencedList(expr.arguments);
+      }
+
+      node.expression = expr;
+    } else {
+      node.expression = this.parseMaybeAssign();
+    }
     return this.finishNode(node, "Decorator");
   }
 
@@ -683,6 +713,10 @@ export default class StatementParser extends ExpressionParser {
       }
 
       this.parseClassMember(classBody, member, state);
+
+      if (this.hasPlugin("decoratorsStage2") && member.kind != "method" && member.decorators && member.decorators.length > 0) {
+        this.raise(member.start, "Stage 2 decorators may only be used with a class or a class method");
+      }
     }
 
     if (decorators.length) {
@@ -750,6 +784,7 @@ export default class StatementParser extends ExpressionParser {
     if (!methodOrProp.computed && methodOrProp.static && (methodOrProp.key.name === "prototype" || methodOrProp.key.value === "prototype")) {
       this.raise(methodOrProp.key.start, "Classes may not have static property named prototype");
     }
+
     if (this.isClassMethod()) {
       // a normal method
       if (this.isNonstaticConstructor(method)) {

test/fixtures/experimental/decorators-stage-2/class-decorator-call-expr/actual.js

@@ -0,0 +1,2 @@
+@foo('bar')
+class Foo {}

test/fixtures/experimental/decorators-stage-2/class-decorator-call-expr/expected.json

@@ -0,0 +1,154 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 24,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 2,
+      "column": 12
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 24,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 2,
+        "column": 12
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 12,
+        "end": 24,
+        "loc": {
+          "start": {
+            "line": 2,
+            "column": 0
+          },
+          "end": {
+            "line": 2,
+            "column": 12
+          }
+        },
+        "decorators": [
+          {
+            "type": "Decorator",
+            "start": 0,
+            "end": 11,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 0
+              },
+              "end": {
+                "line": 1,
+                "column": 11
+              }
+            },
+            "expression": {
+              "type": "CallExpression",
+              "start": 1,
+              "end": 11,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 1
+                },
+                "end": {
+                  "line": 1,
+                  "column": 11
+                }
+              },
+              "callee": {
+                "type": "Identifier",
+                "start": 1,
+                "end": 4,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 1
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 4
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "arguments": [
+                {
+                  "type": "StringLiteral",
+                  "start": 5,
+                  "end": 10,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 5
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 10
+                    }
+                  },
+                  "extra": {
+                    "rawValue": "bar",
+                    "raw": "'bar'"
+                  },
+                  "value": "bar"
+                }
+              ]
+            }
+          }
+        ],
+        "id": {
+          "type": "Identifier",
+          "start": 18,
+          "end": 21,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 6
+            },
+            "end": {
+              "line": 2,
+              "column": 9
+            },
+            "identifierName": "Foo"
+          },
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 22,
+          "end": 24,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 10
+            },
+            "end": {
+              "line": 2,
+              "column": 12
+            }
+          },
+          "body": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/decorators-stage-2/class-decorator/actual.js

@@ -0,0 +1,4 @@
+@abc
+class Foo {
+
+}

test/fixtures/experimental/decorators-stage-2/class-decorator/expected.json

@@ -0,0 +1,117 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 19,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 19,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 5,
+        "end": 19,
+        "loc": {
+          "start": {
+            "line": 2,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "decorators": [
+          {
+            "type": "Decorator",
+            "start": 0,
+            "end": 4,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 0
+              },
+              "end": {
+                "line": 1,
+                "column": 4
+              }
+            },
+            "expression": {
+              "type": "Identifier",
+              "start": 1,
+              "end": 4,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 1
+                },
+                "end": {
+                  "line": 1,
+                  "column": 4
+                },
+                "identifierName": "abc"
+              },
+              "name": "abc"
+            }
+          }
+        ],
+        "id": {
+          "type": "Identifier",
+          "start": 11,
+          "end": 14,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 6
+            },
+            "end": {
+              "line": 2,
+              "column": 9
+            },
+            "identifierName": "Foo"
+          },
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 15,
+          "end": 19,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 10
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}