Add ESLint 8 support to @babel/eslint-parser

babel.config.js

@@ -58,6 +58,7 @@ module.exports = function (api) {
   let ignoreLib = true;
   let includeRegeneratorRuntime = false;
   let needsPolyfillsForOldNode = false;
+  let dynamicESLintVersionCheck = false;
 
   let transformRuntimeOptions;
 
@@ -99,6 +100,8 @@ module.exports = function (api) {
       needsPolyfillsForOldNode = true;
       break;
     case "test-legacy": // In test-legacy environment, we build babel on latest node but test on minimum supported legacy versions
+      dynamicESLintVersionCheck = true;
+    // fall through
     case "production":
       // Config during builds before publish.
       targets = { node: nodeVersion };
@@ -107,10 +110,12 @@ module.exports = function (api) {
     case "test":
       targets = { node: "current" };
       needsPolyfillsForOldNode = true;
+      dynamicESLintVersionCheck = true;
       break;
     case "development":
       envOpts.debug = true;
       targets = { node: "current" };
+      dynamicESLintVersionCheck = true;
       break;
   }
 
@@ -218,6 +223,10 @@ module.exports = function (api) {
         exclude: /regenerator-runtime/,
         plugins: [["@babel/transform-runtime", transformRuntimeOptions]],
       },
+      dynamicESLintVersionCheck && {
+        test: ["./eslint/*/src"].map(normalize),
+        plugins: [pluginDynamicESLintVersionCheck],
+      },
     ].filter(Boolean),
   };
 
@@ -654,3 +663,30 @@ function pluginBabelParserTokenType({
     tokenTypesMapping.set(tokenTypesDefinition[i].key.name, i);
   }
 })();
+
+// Transforms
+//    ESLINT_VERSION
+// to
+//    process.env.ESLINT_VERSION_FOR_BABEL
+//      ? parseInt(process.env.ESLINT_VERSION_FOR_BABEL, 10)
+//      : ESLINT_VERSION
+function pluginDynamicESLintVersionCheck({ template }) {
+  const transformed = new WeakSet();
+
+  return {
+    visitor: {
+      ReferencedIdentifier(path) {
+        if (path.node.name !== "ESLINT_VERSION") return;
+
+        if (transformed.has(path.node)) return;
+        transformed.add(path.node);
+
+        path.replaceWith(template.expression.ast`
+          process.env.ESLINT_VERSION_FOR_BABEL
+            ? parseInt(process.env.ESLINT_VERSION_FOR_BABEL, 10)
+            : ${path.node}
+        `);
+      },
+    },
+  };
+}

eslint/babel-eslint-parser/package.json

@@ -28,7 +28,7 @@
   },
   "peerDependencies": {
     "@babel/core": ">=7.11.0",
-    "eslint": ">=7.5.0"
+    "eslint": "^7.5.0 || ^8.0.0"
   },
   "dependencies": {
     "eslint-scope": "^5.1.1",
@@ -38,6 +38,7 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "dedent": "^0.7.0",
-    "eslint": "^7.27.0"
+    "eslint": "^7.27.0",
+    "eslint-8": "npm:eslint@^8.0.0"
   }
 }

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

@@ -1,3 +1,5 @@
+const ESLINT_VERSION = require("../utils/eslint-version.cjs");
+
 function* it(children) {
   if (Array.isArray(children)) yield* children;
   else yield children;
@@ -40,7 +42,7 @@ const convertNodesVisitor = {
       delete node.extra;
     }
 
-    if (node?.loc.identifierName) {
+    if (node.loc.identifierName) {
       delete node.loc.identifierName;
     }
 
@@ -89,6 +91,15 @@ const convertNodesVisitor = {
         } else {
           q.loc.end.column += 2;
         }
+
+        if (ESLINT_VERSION >= 8) {
+          q.start -= 1;
+          if (q.tail) {
+            q.end += 1;
+          } else {
+            q.end += 2;
+          }
+        }
       }
     }
   },
@@ -117,6 +128,10 @@ function convertProgramNode(ast) {
         ast.range[1] = lastToken.end;
         ast.loc.end.line = lastToken.loc.end.line;
         ast.loc.end.column = lastToken.loc.end.column;
+
+        if (ESLINT_VERSION >= 8) {
+          ast.end = lastToken.end;
+        }
       }
     }
   } else {
@@ -129,6 +144,10 @@ function convertProgramNode(ast) {
   if (ast.body && ast.body.length > 0) {
     ast.loc.start.line = ast.body[0].loc.start.line;
     ast.range[0] = ast.body[0].start;
+
+    if (ESLINT_VERSION >= 8) {
+      ast.start = ast.body[0].start;
+    }
   }
 }
 

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

@@ -1,3 +1,5 @@
+const ESLINT_VERSION = require("../utils/eslint-version.cjs");
+
 function convertTemplateType(tokens, tl) {
   let curlyBrace = null;
   let templateTokens = [];
@@ -190,12 +192,45 @@ function convertToken(token, source, tl) {
     // Acorn does not have rightAssociative
     delete token.type.rightAssociative;
   }
-
-  return token;
 }
 
 module.exports = function convertTokens(tokens, code, tl) {
-  return convertTemplateType(tokens, tl)
-    .filter(t => t.type !== "CommentLine" && t.type !== "CommentBlock")
-    .map(t => convertToken(t, code, tl));
+  const result = [];
+
+  const withoutComments = convertTemplateType(tokens, tl).filter(
+    t => t.type !== "CommentLine" && t.type !== "CommentBlock",
+  );
+  for (let i = 0, { length } = withoutComments; i < length; i++) {
+    const token = withoutComments[i];
+
+    if (!process.env.BABEL_8_BREAKING) {
+      // Babel 8 already produces a single token
+
+      if (
+        ESLINT_VERSION >= 8 &&
+        i + 1 < length &&
+        token.type.label === tl.hash
+      ) {
+        const nextToken = withoutComments[i + 1];
+
+        // We must disambiguate private identifier from the hack pipes topic token
+        if (nextToken.type.label === tl.name && token.end === nextToken.start) {
+          i++;
+
+          nextToken.type = "PrivateIdentifier";
+          nextToken.start -= 1;
+          nextToken.loc.start.column -= 1;
+          nextToken.range = [nextToken.start, nextToken.end];
+
+          result.push(nextToken);
+          continue;
+        }
+      }
+    }
+
+    convertToken(token, code, tl);
+    result.push(token);
+  }
+
+  return result;
 };

eslint/babel-eslint-parser/src/utils/eslint-version.cjs

@@ -0,0 +1 @@
+module.exports = parseInt(require("eslint/package.json").version, 10);

eslint/babel-eslint-parser/src/worker/configuration.cjs

@@ -1,4 +1,5 @@
 const babel = require("./babel-core.cjs");
+const ESLINT_VERSION = require("../utils/eslint-version.cjs");
 
 /**
  * Merge user supplied estree plugin options to default estree plugin options
@@ -8,8 +9,7 @@ const babel = require("./babel-core.cjs");
  */
 function getParserPlugins(babelOptions) {
   const babelParserPlugins = babelOptions.parserOpts?.plugins ?? [];
-  // todo: enable classFeatures when it is supported by ESLint
-  const estreeOptions = { classFeatures: false };
+  const estreeOptions = { classFeatures: ESLINT_VERSION >= 8 };
   for (const plugin of babelParserPlugins) {
     if (Array.isArray(plugin) && plugin[0] === "estree") {
       Object.assign(estreeOptions, plugin[1]);