Make sure that is_atom considers true, false, and null as atoms

bryanjos · bryanjos · commit dc00d1df1893 · 2017-08-11T16:19:22.000-05:00
diff --git a/src/javascript/lib/core/erlang_compat/erlang.js b/src/javascript/lib/core/erlang_compat/erlang.js
@@ -4,27 +4,39 @@ import lists from './lists';
 
 const selfPID = new ErlangTypes.PID();
 
-function atom_to_list(atom) {
-  return Symbol.keyFor(atom);
-}
-
 function atom_to_binary(atom, encoding = Symbol.for('utf8')) {
   if (encoding !== Symbol.for('utf8')) {
     throw new Error(`unsupported encoding ${encoding}`);
   }
 
-  if (atom.__MODULE__) {
+  if (atom === null) {
+    return 'nil';
+  } else if (is_boolean(atom)) {
+    return atom.toString();
+  } else if (atom.__MODULE__) {
     return Symbol.keyFor(atom.__MODULE__);
   }
 
   return Symbol.keyFor(atom);
 }
 
+function atom_to_list(atom) {
+  return atom_to_binary(atom);
+}
+
 function binary_to_atom(binary, encoding = Symbol.for('utf8')) {
   if (encoding !== Symbol.for('utf8')) {
     throw new Error(`unsupported encoding ${encoding}`);
   }
 
+  if (binary === 'nil') {
+    return null;
+  } else if (binary === 'true') {
+    return true;
+  } else if (binary === 'false') {
+    return false;
+  }
+
   return Symbol.for(binary);
 }
 
@@ -87,8 +99,16 @@ function bxor(left, right) {
 }
 
 function is_atom(value) {
+  if (value === null) {
+    return true;
+  } else if (is_boolean(value)) {
+    return true;
+  }
+
   return (
-    typeof value === 'symbol' || value instanceof Symbol || value.__MODULE__
+    typeof value === 'symbol' ||
+    value instanceof Symbol ||
+    value.__MODULE__ != null
   );
 }
 
diff --git a/src/javascript/tests/core/erlang_compat/erlang_spec.js b/src/javascript/tests/core/erlang_compat/erlang_spec.js
@@ -1,13 +1,26 @@
 import test from 'ava';
 import Core from '../../../lib/core';
 
+test('is_atom', t => {
+  t.is(Core.erlang.is_atom(null), true);
+  t.is(Core.erlang.is_atom(true), true);
+  t.is(Core.erlang.is_atom(false), true);
+  t.is(Core.erlang.is_atom(Symbol.for('error')), true);
+  t.is(Core.erlang.is_atom('Hello'), false);
+});
+
 test('atom_to_binary', t => {
   t.is(Core.erlang.atom_to_binary(Symbol.for('error')), 'error');
   t.is(
     Core.erlang.atom_to_binary(Symbol.for('error'), Symbol.for('utf8')),
     'error'
   );
 
+  t.is(Core.erlang.atom_to_binary(null, Symbol.for('utf8')), 'nil');
+
+  t.is(Core.erlang.atom_to_binary(true, Symbol.for('utf8')), 'true');
+  t.is(Core.erlang.atom_to_binary(false, Symbol.for('utf8')), 'false');
+
   t.throws(
     () => Core.erlang.atom_to_binary(Symbol.for('error'), Symbol.for('utf16')),
     Error
@@ -23,7 +36,7 @@ test('list_concatenation', t => {
     3,
     4,
     5,
-    6,
+    6
   ]);
 });
 
