Default allowHashBang to true when ecmaVersion >= 2023

FEATURE: Support hashbang comments by default in ECMAScript 2023 and later.

Closes #1134

Author: marijnh

acorn/README.md

@@ -54,10 +54,10 @@ required):
 
 - **ecmaVersion**: Indicates the ECMAScript version to parse. Must be
   either 3, 5, 6 (or 2015), 7 (2016), 8 (2017), 9 (2018), 10 (2019),
-  11 (2020), 12 (2021), 13 (2022, partial support)
-  or `"latest"` (the latest the library supports). This influences
-  support for strict mode, the set of reserved words, and support
-  for new syntax features.
+  11 (2020), 12 (2021), 13 (2022), 14 (2023), or `"latest"` (the
+  latest the library supports). This influences support for strict
+  mode, the set of reserved words, and support for new syntax
+  features.
 
   **NOTE**: Only 'stage 4' (finalized) ECMAScript features are being
   implemented by Acorn. Other proposed new features must be
@@ -104,9 +104,9 @@ required):
 - **allowSuperOutsideMethod**: By default, `super` outside a method
   raises an error. Set this to `true` to accept such code.
 
-- **allowHashBang**: When this is enabled (off by default), if the
-  code starts with the characters `#!` (as in a shellscript), the
-  first line will be treated as a comment.
+- **allowHashBang**: When this is enabled, if the code starts with the
+  characters `#!` (as in a shellscript), the first line will be
+  treated as a comment. Defaults to true when `ecmaVersion` >= 2023.
 
 - **locations**: When `true`, each node has a `loc` object attached
   with `start` and `end` subobjects, each of which contains the

acorn/src/options.js

@@ -7,10 +7,10 @@ import {SourceLocation} from "./locutil.js"
 export const defaultOptions = {
   // `ecmaVersion` indicates the ECMAScript version to parse. Must be
   // either 3, 5, 6 (or 2015), 7 (2016), 8 (2017), 9 (2018), 10
-  // (2019), 11 (2020), 12 (2021), 13 (2022), or `"latest"` (the
-  // latest version the library supports). This influences support
-  // for strict mode, the set of reserved words, and support for
-  // new syntax features.
+  // (2019), 11 (2020), 12 (2021), 13 (2022), 14 (2023), or `"latest"`
+  // (the latest version the library supports). This influences
+  // support for strict mode, the set of reserved words, and support
+  // for new syntax features.
   ecmaVersion: null,
   // `sourceType` indicates the mode the code should be parsed in.
   // Can be either `"script"` or `"module"`. This influences global
@@ -44,8 +44,9 @@ export const defaultOptions = {
   // When enabled, super identifiers are not constrained to
   // appearing in methods and do not raise an error when they appear elsewhere.
   allowSuperOutsideMethod: null,
-  // When enabled, hashbang directive in the beginning of file
-  // is allowed and treated as a line comment.
+  // When enabled, hashbang directive in the beginning of file is
+  // allowed and treated as a line comment. Enabled by default when
+  // `ecmaVersion` >= 2023.
   allowHashBang: false,
   // When `locations` is on, `loc` properties holding objects with
   // `start` and `end` properties in `{line, column}` form (with
@@ -120,6 +121,9 @@ export function getOptions(opts) {
   if (options.allowReserved == null)
     options.allowReserved = options.ecmaVersion < 5
 
+  if (opts.allowHashBang == null)
+    options.allowHashBang = options.ecmaVersion >= 14
+
   if (isArray(options.onToken)) {
     let tokens = options.onToken
     options.onToken = (token) => tokens.push(token)