From dbce7249a142a962e866d1d4ad3a2a4c1e46bc78 Mon Sep 17 00:00:00 2001
From: Kai Cataldo <kai@kaicataldo.com>
Date: Thu, 5 Dec 2019 23:30:33 -0500
Subject: [PATCH] WIP: eslint-parser supports BigInt Literal

---
 eslint/babel-eslint-parser/package.json       |  1 +
 .../src/babylon-to-espree/convertAST.js       |  1 -
 .../test/babel-eslint-parser.js               |  8 +++++-
 .../test/fixtures/config/babel.config.js      |  1 +
 packages/babel-parser/src/plugins/estree.js   | 28 +++++++++++++++++--
 5 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/eslint/babel-eslint-parser/package.json b/eslint/babel-eslint-parser/package.json
index e24970d36b8c..0205facb646d 100644
--- a/eslint/babel-eslint-parser/package.json
+++ b/eslint/babel-eslint-parser/package.json
@@ -34,6 +34,7 @@
     "@babel/plugin-proposal-nullish-coalescing-operator": "^7.0.0",
     "@babel/plugin-proposal-optional-chaining": "^7.0.0",
     "@babel/plugin-proposal-pipeline-operator": "^7.0.0",
+    "@babel/plugin-syntax-bigint": "^7.7.4",
     "@babel/plugin-syntax-dynamic-import": "^7.0.0",
     "@babel/plugin-syntax-export-default-from": "^7.0.0",
     "@babel/plugin-syntax-export-namespace-from": "^7.0.0",
diff --git a/eslint/babel-eslint-parser/src/babylon-to-espree/convertAST.js b/eslint/babel-eslint-parser/src/babylon-to-espree/convertAST.js
index 4acce5fb5036..50d472803a0b 100644
--- a/eslint/babel-eslint-parser/src/babylon-to-espree/convertAST.js
+++ b/eslint/babel-eslint-parser/src/babylon-to-espree/convertAST.js
@@ -70,7 +70,6 @@ const astTransformVisitor = {
     }
 
     // modules
-
     if (path.isImportDeclaration()) {
       delete node.isType;
     }
diff --git a/eslint/babel-eslint-parser/test/babel-eslint-parser.js b/eslint/babel-eslint-parser/test/babel-eslint-parser.js
index 37f15c03d310..d3aa67223b18 100644
--- a/eslint/babel-eslint-parser/test/babel-eslint-parser.js
+++ b/eslint/babel-eslint-parser/test/babel-eslint-parser.js
@@ -27,7 +27,7 @@ function parseAndAssertSame(code) {
     loc: true,
     range: true,
     comment: true,
-    ecmaVersion: 2018,
+    ecmaVersion: 2020,
     sourceType: "module",
   });
   const babylonAST = parseForESLint(code, {
@@ -518,5 +518,11 @@ describe("babylon-to-espree", () => {
         }
       `);
     });
+
+    it("BigInt", () => {
+      parseAndAssertSame(`
+        const a = 1n;
+      `);
+    });
   });
 });
diff --git a/eslint/babel-eslint-parser/test/fixtures/config/babel.config.js b/eslint/babel-eslint-parser/test/fixtures/config/babel.config.js
index 4d49158dba90..56a2f07d9707 100644
--- a/eslint/babel-eslint-parser/test/fixtures/config/babel.config.js
+++ b/eslint/babel-eslint-parser/test/fixtures/config/babel.config.js
@@ -17,5 +17,6 @@ module.exports = {
     "@babel/plugin-syntax-export-namespace-from",
     ["@babel/plugin-proposal-decorators", { decoratorsBeforeExport: false }],
     ["@babel/plugin-proposal-pipeline-operator", { proposal: "minimal" }],
+    "@babel/plugin-syntax-bigint",
   ],
 };
diff --git a/packages/babel-parser/src/plugins/estree.js b/packages/babel-parser/src/plugins/estree.js
index 60bc1effffa7..8692bb6e1d07 100644
--- a/packages/babel-parser/src/plugins/estree.js
+++ b/packages/babel-parser/src/plugins/estree.js
@@ -1,5 +1,7 @@
 // @flow
 
+/* global BigInt */
+
 import { types as tt, TokenType } from "../tokenizer/types";
 import type Parser from "../parser";
 import * as N from "../types";
@@ -31,6 +33,23 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return node;
     }
 
+    estreeParseBigIntLiteral(value: any): N.Node {
+      let bigInt = null;
+      try {
+        bigInt = BigInt(value);
+      } catch (e) {
+        // In environments that don't support BigInt, this value
+        // will be null.
+      }
+
+      // Espree creates a "Numeric" token for BigIntLiterals.
+      this.state.type = tt.num;
+      const node = this.estreeParseLiteral(bigInt);
+      node.bigint = String(node.value);
+
+      return node;
+    }
+
     estreeParseLiteral(value: any): N.Node {
       return this.parseLiteral(value, "Literal");
     }
@@ -244,13 +263,16 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
     parseExprAtom(refShorthandDefaultPos?: ?Pos): N.Expression {
       switch (this.state.type) {
-        case tt.regexp:
-          return this.estreeParseRegExpLiteral(this.state.value);
-
         case tt.num:
         case tt.string:
           return this.estreeParseLiteral(this.state.value);
 
+        case tt.regexp:
+          return this.estreeParseRegExpLiteral(this.state.value);
+
+        case tt.bigint:
+          return this.estreeParseBigIntLiteral(this.state.value);
+
         case tt._null:
           return this.estreeParseLiteral(null);