eslint-parser: ES2020 features (#11815)

* chore: update espree test on nullish coalescing

* feat: add optional chaining support

* fix: adapt to estree AST shape

* chore: update lockfile

* add estree optional-chaining test fixtures

* address review comments

* chore: simplify smoke test

* export * support

Co-authored-by: Brian Ng <bng412@gmail.com>

eslint/babel-eslint-parser/package.json

@@ -23,8 +23,8 @@
     "eslint": ">=6.0.0"
   },
   "dependencies": {
-    "eslint-scope": "5.0.0",
-    "eslint-visitor-keys": "^1.1.0",
+    "eslint-scope": "5.1.0",
+    "eslint-visitor-keys": "^1.3.0",
     "semver": "^6.3.0"
   },
   "devDependencies": {

eslint/babel-eslint-parser/src/convert/convertAST.js

@@ -1,4 +1,5 @@
 import { types as t, traverse } from "@babel/core";
+import VISITOR_KEYS from "../visitor-keys";
 
 function convertNodes(ast, code) {
   const astTransformVisitor = {
@@ -81,21 +82,28 @@ function convertNodes(ast, code) {
   };
   const state = { source: code };
 
-  // Monkey patch visitor keys in order to be able to traverse the estree nodes
-  t.VISITOR_KEYS.Property = t.VISITOR_KEYS.ObjectProperty;
-  t.VISITOR_KEYS.MethodDefinition = [
-    "key",
-    "value",
-    "decorators",
-    "returnType",
-    "typeParameters",
-  ];
+  const oldExportAllDeclarationKeys = t.VISITOR_KEYS.ExportAllDeclaration;
 
-  traverse(ast, astTransformVisitor, null, state);
+  try {
+    // Monkey patch visitor keys in order to be able to traverse the estree nodes
+    t.VISITOR_KEYS.ChainExpression = VISITOR_KEYS.ChainExpression;
+    t.VISITOR_KEYS.Property = VISITOR_KEYS.Property;
+    t.VISITOR_KEYS.MethodDefinition = VISITOR_KEYS.MethodDefinition;
 
-  // These can be safely deleted because they are not defined in the original visitor keys.
-  delete t.VISITOR_KEYS.Property;
-  delete t.VISITOR_KEYS.MethodDefinition;
+    // Make sure we visit `exported` key to remove `identifierName` from loc node
+    t.VISITOR_KEYS.ExportAllDeclaration = t.VISITOR_KEYS.ExportAllDeclaration.concat(
+      "exported",
+    );
+
+    traverse(ast, astTransformVisitor, null, state);
+  } finally {
+    // These can be safely deleted because they are not defined in the original visitor keys.
+    delete t.VISITOR_KEYS.ChainExpression;
+    delete t.VISITOR_KEYS.MethodDefinition;
+    delete t.VISITOR_KEYS.Property;
+
+    t.VISITOR_KEYS.ExportAllDeclaration = oldExportAllDeclarationKeys;
+  }
 }
 
 function convertProgramNode(ast) {

eslint/babel-eslint-parser/src/convert/convertTokens.js

@@ -115,7 +115,6 @@ function convertToken(token, source) {
     type === tt.incDec ||
     type === tt.colon ||
     type === tt.question ||
-    type === tt.questionDot ||
     type === tt.template ||
     type === tt.backQuote ||
     type === tt.dollarBraceL ||
@@ -173,6 +172,12 @@ function convertToken(token, source) {
   } else if (type === tt.bigint) {
     token.type = "Numeric";
     token.value = `${token.value}n`;
+  } else if (type === tt.questionDot) {
+    token.value = type.label;
+  }
+  if (typeof token.type !== "string") {
+    // Acorn does not have rightAssociative
+    delete token.type.rightAssociative;
   }
 
   return token;

eslint/babel-eslint-parser/src/visitor-keys.js

@@ -1,10 +1,13 @@
 import { types as t } from "@babel/core";
 import { KEYS as ESLINT_VISITOR_KEYS } from "eslint-visitor-keys";
 
-const { VISITOR_KEYS: BABEL_VISITOR_KEYS } = t;
+/*eslint no-unused-vars: ["error", { "ignoreRestSiblings": true }]*/
+const { ExportAllDeclaration, ...BABEL_VISITOR_KEYS } = t.VISITOR_KEYS;
 
 export default Object.assign(
   {
+    ChainExpression: ESLINT_VISITOR_KEYS.ChainExpression,
+    ExportAllDeclaration: ESLINT_VISITOR_KEYS.ExportAllDeclaration,
     Literal: ESLINT_VISITOR_KEYS.Literal,
     MethodDefinition: ["decorators"].concat(
       ESLINT_VISITOR_KEYS.MethodDefinition,

eslint/babel-eslint-parser/test/index.js

@@ -253,6 +253,10 @@ describe("Babel and Espree", () => {
     parseAndAssertSame('import "foo";');
   });
 
+  it("import meta", () => {
+    parseAndAssertSame("const url = import.meta.url");
+  });
+
   it("export default class declaration", () => {
     parseAndAssertSame("export default class Foo {}");
   });
@@ -273,15 +277,8 @@ describe("Babel and Espree", () => {
     parseAndAssertSame('export * from "foo";');
   });
 
-  // Espree doesn't support `export * as ns` yet
   it("export * as ns", () => {
-    const code = 'export * as Foo from "foo";';
-    const babylonAST = parseForESLint(code, {
-      eslintVisitorKeys: true,
-      eslintScopeManager: true,
-      babelOptions: BABEL_OPTIONS,
-    }).ast;
-    expect(babylonAST.tokens[1].type).toEqual("Punctuator");
+    parseAndAssertSame('export * as Foo from "foo";');
   });
 
   it("export named", () => {
@@ -292,26 +289,12 @@ describe("Babel and Espree", () => {
     parseAndAssertSame("var foo = 1;export { foo as bar };");
   });
 
-  // Espree doesn't support the optional chaining operator yet
-  it("optional chaining operator (token)", () => {
-    const code = "foo?.bar";
-    const babylonAST = parseForESLint(code, {
-      eslintVisitorKeys: true,
-      eslintScopeManager: true,
-      babelOptions: BABEL_OPTIONS,
-    }).ast;
-    expect(babylonAST.tokens[1].type).toEqual("Punctuator");
+  it("optional chaining operator", () => {
+    parseAndAssertSame("foo?.bar?.().qux()");
   });
 
-  // Espree doesn't support the nullish coalescing operator yet
-  it("nullish coalescing operator (token)", () => {
-    const code = "foo ?? bar";
-    const babylonAST = parseForESLint(code, {
-      eslintVisitorKeys: true,
-      eslintScopeManager: true,
-      babelOptions: BABEL_OPTIONS,
-    }).ast;
-    expect(babylonAST.tokens[1].type).toEqual("Punctuator");
+  it("nullish coalescing operator", () => {
+    parseAndAssertSame("foo ?? bar");
   });
 
   // Espree doesn't support the pipeline operator yet

eslint/babel-eslint-plugin/src/rules/no-unused-expressions.js

@@ -53,7 +53,8 @@ function isOptionalCallExpression(node) {
   return (
     !!node &&
     node.type === "ExpressionStatement" &&
-    node.expression.type === "OptionalCallExpression"
+    node.expression.type === "ChainExpression" &&
+    node.expression.expression.type === "CallExpression"
   );
 }