[CALCITE-1241] Add a freemarker variable for adding non reserved keyw…

…ord list to Parser.jj template (Venki Korukanti)

Add a test to prevent unintentionally adding reserved keywords.

Close apache/calcite#233

src/main/codegen/config.fmpp

@@ -43,10 +43,15 @@ data: {
     imports: [
     ]
 
-    # List of new keywords. Example: "DATABASES", "TABLES".
+    # List of new keywords. Example: "DATABASES", "TABLES". If the keyword is not a reserved
+    # keyword add it to 'nonReservedKeywords' section.
     keywords: [
     ]
 
+    # List of keywords from "keywords" section that are not reserved.
+    nonReservedKeywords: [
+    ]
+
     # List of methods for parsing custom SQL statements.
     # Return type of method implementation should be 'SqlNode'.
     # Example: SqlShowDatabases(), SqlShowTables().

src/main/codegen/templates/Parser.jj

@@ -5619,6 +5619,9 @@ String CommonNonReservedKeyWord() :
         | <WRITE>
         | <XML>
         | <ZONE>
+      <#list parser.nonReservedKeywords as keyword>
+        | <${keyword}>
+      </#list>
     )
     {
         return unquotedIdentifier();