Update ecmaVersion to allow "latest"

package.json

@@ -61,14 +61,14 @@
         "mocha": "^9.0.0",
         "nyc": "^15.1.0",
         "prettier": "^2.0.5",
-        "semver": "^7.3.2",
         "ts-node": "^10.0.0",
         "typescript": "^4.0.0",
         "vue-eslint-parser": "^7.2.0"
     },
     "dependencies": {
         "eslint-utils": "^3.0.0",
         "eslint-visitor-keys": "^3.0.0",
-        "espree": "^6.0.0 || ^7.2.0"
+        "espree": "^6.0.0 || ^7.2.0",
+        "semver": "^6.3.0"
     }
 }

src/parser/espree.ts

@@ -10,6 +10,8 @@ export interface ESPree {
         // eslint-disable-next-line @typescript-eslint/no-explicit-any -- any
         options: any,
     ): AST.Program
+    latestEcmaVersion?: number
+    version: string
 }
 
 let espreeCache: ESPree | null = null

src/parser/parser.ts

@@ -1,5 +1,6 @@
 import type { ExpressionStatement, CallExpression } from "estree"
 import type { AST, SourceCode } from "eslint"
+import type { ESPree } from "./espree"
 import { getEspree } from "./espree"
 import {
     ParseError,
@@ -19,6 +20,9 @@ import {
 import type { ParserOptions } from "../types"
 import { TokenStore, isComma } from "./token-store"
 import type { JSONProgram } from "./ast"
+import { lte } from "semver"
+
+const DEFAULT_ECMA_VERSION = 2019
 
 /**
  * Parse source code
@@ -35,7 +39,7 @@ export function parseForESLint(
     }
 } {
     const parserOptions = Object.assign(
-        { filePath: "<input>", ecmaVersion: 2019 },
+        { filePath: "<input>", ecmaVersion: DEFAULT_ECMA_VERSION },
         options || {},
         {
             loc: true,
@@ -111,8 +115,12 @@ function parseJS(
     options: any,
 ): AST.Program {
     const espree = getEspree()
+    const ecmaVersion = normalizeEcmaVersion(espree, options.ecmaVersion)
     try {
-        return espree.parse(code, options)
+        return espree.parse(code, {
+            ...options,
+            ecmaVersion,
+        })
     } catch (err) {
         const perr = ParseError.normalize(err)
         if (perr) {
@@ -267,3 +275,37 @@ function getJSONSyntaxContext(str?: string | null): JSONSyntaxContext {
         escapeSequenceInIdentifier: true,
     }
 }
+
+/**
+ * Normalize ECMAScript version
+ */
+function normalizeEcmaVersion(
+    espree: ESPree,
+    version: number | "latest" | undefined,
+) {
+    if (version == null || version === "latest") {
+        return getLatestEcmaVersion(espree)
+    }
+    if (version > 5 && version < 2015) {
+        return version + 2009
+    }
+    return version
+}
+
+/**
+ * Get the latest ecma version from espree
+ */
+function getLatestEcmaVersion(espree: ESPree): number {
+    if (espree.latestEcmaVersion == null) {
+        for (const { v, latest } of [
+            { v: "6.1.0", latest: 2020 },
+            { v: "4.0.0", latest: 2019 },
+        ]) {
+            if (lte(v, espree.version)) {
+                return latest
+            }
+        }
+        return 2018
+    }
+    return normalizeEcmaVersion(espree, espree.latestEcmaVersion)
+}

tests/src/parser/parser-options.ts

@@ -0,0 +1,35 @@
+import assert from "assert"
+
+import { parseForESLint } from "../../../src/parser/parser"
+import { Linter } from "eslint"
+
+describe("Parser options.", () => {
+    for (const { code, parserOptions, errors } of [
+        {
+            code: "1_2_3",
+            parserOptions: {
+                ecmaVersion: "latest",
+            },
+            errors: [],
+        },
+    ]) {
+        it(`${JSON.stringify(code)} with parserOptions: ${JSON.stringify(
+            parserOptions,
+        )}`, () => {
+            const linter = new Linter()
+            linter.defineParser("jsonc-eslint-parser", {
+                parseForESLint: parseForESLint as never,
+            })
+
+            const result = linter.verify(
+                code,
+                {
+                    parser: "jsonc-eslint-parser",
+                    parserOptions: parserOptions as never,
+                },
+                "test.json",
+            )
+            assert.deepStrictEqual(result, errors)
+        })
+    }
+})