Support numeric separators

Author: goto-bus-stop

build.js

@@ -27,6 +27,7 @@ compile('acorn-import-meta', './lib/import-meta/index.js')
 compile('acorn-export-ns-from', './lib/export-ns-from/index.js')
 compile('acorn-class-fields', './lib/class-fields/index.js', privateClassElements)
 compile('acorn-static-class-features', './lib/static-class-features/index.js', privateClassElements)
+compile('acorn-numeric-separator', './lib/numeric-separator/index.js')
 compile('acorn-private-class-elements', './lib/private-class-elements/index.js', function (str) {
   return str.replace('class extends Parser', 'class Parser_ extends Parser')
 })

index.js

@@ -5,6 +5,7 @@ var CJSParser = acorn.Parser
   .extend(require('./lib/bigint'))
   .extend(require('./lib/class-fields'))
   .extend(require('./lib/static-class-features'))
+  .extend(require('./lib/numeric-separator'))
 var ESModulesParser = CJSParser
   .extend(require('./lib/export-ns-from'))
   .extend(require('./lib/import-meta'))

lib/numeric-separator/index.js

@@ -0,0 +1,61 @@
+/* Generated by `npm run build`, do not edit! */
+
+"use strict"
+
+module.exports = function(Parser) {
+  return /*@__PURE__*/(function (Parser) {
+    function anonymous () {
+      Parser.apply(this, arguments);
+    }
+
+    if ( Parser ) anonymous.__proto__ = Parser;
+    anonymous.prototype = Object.create( Parser && Parser.prototype );
+    anonymous.prototype.constructor = anonymous;
+
+    anonymous.prototype.readInt = function readInt (radix, len) {
+      // Hack: len is only != null for unicode escape sequences,
+      // where numeric separators are not allowed
+      if (len != null) { return Parser.prototype.readInt.call(this, radix, len) }
+
+      var start = this.pos, total = 0, acceptUnderscore = false
+      for (;;) {
+        var code = this.input.charCodeAt(this.pos), val = (void 0)
+        if (code >= 97) { val = code - 97 + 10 } // a
+        else if (code == 95) {
+          if (!acceptUnderscore) { this.raise(this.pos, "Invalid numeric separator") }
+          ++this.pos
+          acceptUnderscore = false
+          continue
+        } else if (code >= 65) { val = code - 65 + 10 } // A
+        else if (code >= 48 && code <= 57) { val = code - 48 } // 0-9
+        else { val = Infinity }
+        if (val >= radix) { break }
+        ++this.pos
+        total = total * radix + val
+        acceptUnderscore = true
+      }
+      if (this.pos === start) { return null }
+      if (!acceptUnderscore) { this.raise(this.pos - 1, "Invalid numeric separator") }
+
+      return total
+    };
+
+    anonymous.prototype.readNumber = function readNumber (startsWithDot) {
+      var token = Parser.prototype.readNumber.call(this, startsWithDot)
+      var octal = this.end - this.start >= 2 && this.input.charCodeAt(this.start) === 48
+      var stripped = this.getNumberInput(this.start, this.end)
+      if (stripped.length < this.end - this.start) {
+        if (octal) { this.raise(this.start, "Invalid number") }
+        this.value = parseFloat(stripped)
+      }
+      return token
+    };
+
+    // This is used by acorn-bigint
+    anonymous.prototype.getNumberInput = function getNumberInput (start, end) {
+      return this.input.slice(start, end).replace(/_/g, "")
+    };
+
+    return anonymous;
+  }(Parser))
+}

package.json

@@ -16,6 +16,7 @@
     "acorn-class-fields": "^0.3.1",
     "acorn-export-ns-from": "^0.1.0",
     "acorn-import-meta": "^1.0.0",
+    "acorn-numeric-separator": "^0.3.0",
     "acorn-private-class-elements": "^0.1.1",
     "acorn-static-class-features": "^0.2.0",
     "buble": "^0.19.8",

test/index.js

@@ -73,6 +73,13 @@ test('supports bigint', function (t) {
   t.end()
 })
 
+test('supports numeric separators', function (t) {
+  t.doesNotThrow(function () {
+    acorn.parse('50_000_000n ** 1n')
+  })
+  t.end()
+})
+
 test('supports import.meta with sourceType: module', function (t) {
   t.doesNotThrow(function () {
     acorn.parse('console.log(import.meta.url)', { sourceType: 'module' })