Remove Babylon plugins for features already merged to the ECMAScript …

…spec (#8448)

These are now enabled by default:
- objectRestSpread (2018)
- asyncGenerators (2018)
- optionalCatchBInding (2019)
- jsonStrings (2019)

TODO (after this commit):
- [ ] Deprecate the `@babel/plugin-syntax-*` packages.
- [ ] Deprecate the `@babel/plugin-proposal-*` packages.
- [ ] Create the `@babel/plugin-transform-*` packages.

packages/babel-core/src/transformation/util/missing-plugin-helper.js

@@ -1,16 +1,6 @@
 // @flow
 
 const pluginNameMap = {
-  asyncGenerators: {
-    syntax: {
-      name: "@babel/plugin-syntax-async-generators",
-      url: "https://git.io/vb4SY",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-async-generator-functions",
-      url: "https://git.io/vb4yp",
-    },
-  },
   classProperties: {
     syntax: {
       name: "@babel/plugin-syntax-class-properties",
@@ -143,26 +133,6 @@ const pluginNameMap = {
       url: "https://git.io/vb4yS",
     },
   },
-  objectRestSpread: {
-    syntax: {
-      name: "@babel/plugin-syntax-object-rest-spread",
-      url: "https://git.io/vb4y5",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-object-rest-spread",
-      url: "https://git.io/vb4Ss",
-    },
-  },
-  optionalCatchBinding: {
-    syntax: {
-      name: "@babel/plugin-syntax-optional-catch-binding",
-      url: "https://git.io/vb4Sn",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-optional-catch-binding",
-      url: "https://git.io/vb4SI",
-    },
-  },
   optionalChaining: {
     syntax: {
       name: "@babel/plugin-syntax-optional-chaining",
@@ -203,6 +173,41 @@ const pluginNameMap = {
       url: "https://git.io/vb4Sm",
     },
   },
+
+  // TODO: This plugins are now supported by default by @babel/parser: they can
+  // be removed from this list. Although removing them isn't a breaking change,
+  // it's better to keep a nice error message for users using older versions of
+  // the parser. They can be removed in Babel 8.
+  asyncGenerators: {
+    syntax: {
+      name: "@babel/plugin-syntax-async-generators",
+      url: "https://git.io/vb4SY",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-async-generator-functions",
+      url: "https://git.io/vb4yp",
+    },
+  },
+  objectRestSpread: {
+    syntax: {
+      name: "@babel/plugin-syntax-object-rest-spread",
+      url: "https://git.io/vb4y5",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-object-rest-spread",
+      url: "https://git.io/vb4Ss",
+    },
+  },
+  optionalCatchBinding: {
+    syntax: {
+      name: "@babel/plugin-syntax-optional-catch-binding",
+      url: "https://git.io/vb4Sn",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-optional-catch-binding",
+      url: "https://git.io/vb4SI",
+    },
+  },
 };
 
 const getNameURLCombination = ({ name, url }) => `${name} (${url})`;

packages/babel-core/test/api.js

@@ -769,10 +769,10 @@ describe("api", function() {
         options,
         function(err) {
           expect(err.message).toMatch(
-            "Support for the experimental syntax 'asyncGenerators' isn't currently enabled (1:15):",
+            "Support for the experimental syntax 'logicalAssignment' isn't currently enabled (1:3):",
           );
           expect(err.message).toMatch(
-            "Add @babel/plugin-proposal-async-generator-functions (https://git.io/vb4yp) to the " +
+            "Add @babel/plugin-proposal-logical-assignment-operators (https://git.io/vAlRe) to the " +
               "'plugins' section of your Babel config to enable transformation.",
           );
           done();

packages/babel-core/test/fixtures/api/parsing-errors/syntax-and-transform/file.js

@@ -1,4 +1 @@
-async function* agf() {
-  await 1;
-  yield 2;
-}
+a ||= 2;

packages/babel-generator/test/fixtures/edgecase/async-generator/options.json

@@ -1 +1 @@
-{ "plugins": ["asyncGenerators", "classProperties"] }
+{ "plugins": ["classProperties"] }

packages/babel-parser/src/parser/expression.js

@@ -1322,7 +1322,6 @@ export default class ExpressionParser extends LValParser {
       }
 
       if (this.match(tt.ellipsis)) {
-        this.expectPlugin("objectRestSpread");
         prop = this.parseSpread(isPattern ? { start: 0 } : undefined);
         if (isPattern) {
           this.toAssignable(prop, true, "object pattern");
@@ -1382,11 +1381,7 @@ export default class ExpressionParser extends LValParser {
           prop.computed = false;
         } else {
           isAsync = true;
-          if (this.match(tt.star)) {
-            this.expectPlugin("asyncGenerators");
-            this.next();
-            isGenerator = true;
-          }
+          isGenerator = this.eat(tt.star);
           this.parsePropertyName(prop);
         }
       } else {

packages/babel-parser/src/parser/statement.js

@@ -391,7 +391,6 @@ export default class StatementParser extends ExpressionParser {
 
     let forAwait = false;
     if (this.state.inAsync && this.isContextual("await")) {
-      this.expectPlugin("asyncGenerators");
       forAwait = true;
       this.next();
     }
@@ -556,7 +555,6 @@ export default class StatementParser extends ExpressionParser {
         this.checkLVal(clause.param, true, clashes, "catch clause");
         this.expect(tt.parenR);
       } else {
-        this.expectPlugin("optionalCatchBinding");
         clause.param = null;
       }
       clause.body = this.parseBlock();
@@ -853,9 +851,6 @@ export default class StatementParser extends ExpressionParser {
     this.initFunction(node, isAsync);
 
     if (this.match(tt.star)) {
-      if (node.async) {
-        this.expectPlugin("asyncGenerators");
-      }
       node.generator = true;
       this.next();
     }
@@ -1153,11 +1148,7 @@ export default class StatementParser extends ExpressionParser {
       }
     } else if (isSimple && key.name === "async" && !this.isLineTerminator()) {
       // an async method
-      const isGenerator = this.match(tt.star);
-      if (isGenerator) {
-        this.expectPlugin("asyncGenerators");
-        this.next();
-      }
+      const isGenerator = this.eat(tt.star);
 
       method.kind = "method";
       // The so-called parsed name would have been "async": get the real name.

packages/babel-parser/src/tokenizer/index.js

@@ -1070,7 +1070,6 @@ export default class Tokenizer extends LocationParser {
   readString(quote: number): void {
     let out = "",
       chunkStart = ++this.state.pos;
-    const hasJsonStrings = this.hasPlugin("jsonStrings");
     for (;;) {
       if (this.state.pos >= this.input.length) {
         this.raise(this.state.start, "Unterminated string constant");
@@ -1083,8 +1082,8 @@ export default class Tokenizer extends LocationParser {
         out += this.readEscapedChar(false);
         chunkStart = this.state.pos;
       } else if (
-        hasJsonStrings &&
-        (ch === charCodes.lineSeparator || ch === charCodes.paragraphSeparator)
+        ch === charCodes.lineSeparator ||
+        ch === charCodes.paragraphSeparator
       ) {
         ++this.state.pos;
         ++this.state.curLine;

packages/babel-parser/test/fixtures/experimental/class-private-methods/async-generator/options.json

@@ -1,3 +1,3 @@
 {
-  "plugins": ["classPrivateMethods", "asyncGenerators"]
+  "plugins": ["classPrivateMethods"]
 }