fix(parser): allow true, false, null as identifiers

Fix #1

parser.js

@@ -146,12 +146,7 @@ class KdlParser extends EmbeddedActionsParser {
     })
 
     this.RULE('node', () => {
-      const name = this.OR([
-        { ALT: () => this.CONSUME(Identifier).image },
-        { ALT: () => this.SUBRULE(this.string) },
-        { ALT: () => this.SUBRULE(this.rawString) }
-      ])
-
+      const name = this.SUBRULE(this.identifier)
       const properties = {}
       const values = []
 
@@ -201,11 +196,18 @@ class KdlParser extends EmbeddedActionsParser {
       return { name, properties, values, children }
     })
 
-    this.RULE('property', () => {
-      const key = this.OR([
+    this.RULE('identifier', () => {
+      return this.OR([
         { ALT: () => this.CONSUME(Identifier).image },
-        { ALT: () => this.SUBRULE(this.string) }
+        { ALT: () => this.SUBRULE(this.string) },
+        { ALT: () => this.SUBRULE(this.rawString) },
+        { ALT: () => this.CONSUME(Boolean).image },
+        { ALT: () => this.CONSUME(Null).image }
       ])
+    })
+
+    this.RULE('property', () => {
+      const key = this.SUBRULE(this.identifier)
       this.CONSUME(Equals)
       const value = this.SUBRULE(this.value)
       return [key, value]

test/kdl/identifier_boolean_null.kdl

@@ -0,0 +1,3 @@
+true
+false
+null

test/suite.json

@@ -38,5 +38,10 @@
     { "name": "node", "values": [true] },
     { "name": "node", "values": [false] },
     { "name": "node", "values": [null] }
+  ],
+  "identifier_boolean_null": [
+    { "name": "true" },
+    { "name": "false" },
+    { "name": "null" }
   ]
 }