[pslql] ParseException when parsing ELSIF

Fixes #1731

docs/pages/release_notes.md

@@ -61,6 +61,8 @@ The designer will still be shipped with PMD's binaries.
     *   [#1701](https://github.com/pmd/pmd/issues/1701): \[java] UseTryWithResources does not handle multiple argument close methods
 *   java-codestyle
     *   [#1674](https://github.com/pmd/pmd/issues/1674): \[java] documentation of CommentDefaultAccessModifier is wrong
+*   plsql
+    *   [#1731](https://github.com/pmd/pmd/issues/1731): \[pslql] ParseException when parsing ELSIF
 
 ### API Changes
 

pmd-plsql/etc/grammar/PldocAST.jjt

@@ -2085,7 +2085,7 @@ ASTElseClause ElseClause()  :
 ASTElsifClause ElsifClause()  :
 {}
 {
-      <ELSIF>  Expression() <THEN> (Statement())+
+      <ELSIF>  Expression() <THEN> (LOOKAHEAD(1, {!(getToken(1).kind == ELSIF)}) Statement())+
       { return jjtThis ; }
 }
 
@@ -2280,7 +2280,7 @@ ASTWhileStatement WhileStatement()  :
 ASTIfStatement IfStatement()  :
 {}
 {
-	<IF> Expression() <THEN> (Statement())+
+	<IF> Expression() <THEN> (LOOKAHEAD(1, {!(getToken(1).kind == ELSIF)}) Statement())+
 	( ElsifClause() {jjtThis.setHasElse();} )*
 	[ ElseClause() {jjtThis.setHasElse();} ]
 	<END> <IF>
@@ -6095,7 +6095,6 @@ ASTID ID(): {}
 		//| <DISTINCT>  //RESERVED WORD
 		| <DO>
 		| <DROP>  //RESERVED WORD
-		//| <ELSE> //SYNTAX //RESERVED WORD
 		| <ELSIF> //SYNTAX
 
 		//| <END> |<CURRENT_USER>
@@ -6339,7 +6338,6 @@ ASTQualifiedID QualifiedID(): {}
 		//<DISTINCT>
 		| <DO>
 		//<DROP>
-		//<ELSE>
 		| <ELSIF>
 		//<END>
 		//<EXCEPTION>

pmd-plsql/src/test/java/net/sourceforge/pmd/lang/plsql/ast/IfStatementTest.java

@@ -0,0 +1,20 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.plsql.ast;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import net.sourceforge.pmd.lang.plsql.AbstractPLSQLParserTst;
+
+public class IfStatementTest extends AbstractPLSQLParserTst {
+
+    @Test
+    public void parseIfWithElseIf() throws Exception {
+        String code = "BEGIN\nIF 1 = 1 THEN null;\nELSIF (2 = 2) THEN null;\nELSE null;\nEND IF;\nEND;\n/\n";
+        ASTInput input = parsePLSQL(code);
+        Assert.assertNotNull(input);
+    }
+}