Add EVDP SDW if EVDP is not both

- Introduced new `emptyValueDelimiterPolicyWarning` enumeration in `dafext.xsd`.
- Implemented related validation logic in `ElementBaseGrammarMixin`.
- Added test cases to cover new behavior for `dfdl:emptyValueDelimiterPolicy`.

DAFFODIL-2205

Author: olabusayoT

daffodil-core/src/main/scala/org/apache/daffodil/core/grammar/ElementBaseGrammarMixin.scala

@@ -51,6 +51,7 @@ trait ElementBaseGrammarMixin
   with ElementBaseRuntime1Mixin { self: ElementBase =>
 
   requiredEvaluationsIfActivated(checkPrefixedLengthElementDecl)
+  requiredEvaluationsIfActivated(checkDelimitedLengthEVDP)
 
   private val context = this
 
@@ -81,6 +82,19 @@ trait ElementBaseGrammarMixin
     }
   }
 
+  final lazy val checkDelimitedLengthEVDP: Unit = {
+    if (
+      (hasInitiator || hasTerminator)
+      && emptyValueDelimiterPolicy != EmptyValueDelimiterPolicy.Both
+    ) {
+      SDW(
+        WarnID.EmptyValueDelimiterPolicyWarning,
+        "dfdl:emptyValueDelimiterPolicy='%s' will be ignored as it's only implemented for 'both'",
+        emptyValueDelimiterPolicy
+      )
+    }
+  }
+
   /**
    * true if padding will be inserted for this delimited element when unparsing.
    */

daffodil-propgen/src/main/resources/org/apache/daffodil/xsd/dafext.xsd

@@ -736,6 +736,7 @@
           <xs:enumeration value="discouragedDiscriminatorPlacement" />
           <xs:enumeration value="discouragedAssertPlacement" />
           <xs:enumeration value="emptyElementParsePolicyError" />
+          <xs:enumeration value="emptyValueDelimiterPolicyWarning"/>
           <xs:enumeration value="encodingErrorPolicyError" />
           <xs:enumeration value="escapeSchemeRefUndefined" />
           <xs:enumeration value="expressionCompilationSkipped" />

daffodil-test/src/test/resources/org/apache/daffodil/usertests/SepTests.tdml

@@ -609,4 +609,75 @@
     </tdml:infoset>
   </tdml:parserTestCase>
 
+  <tdml:defineSchema name="s7" elementFormDefault="unqualified">
+
+    <xs:include schemaLocation="/org/apache/daffodil/xsd/DFDLGeneralFormat.dfdl.xsd"/>
+    <dfdl:format
+      ref="ex:GeneralFormat"
+      emptyValueDelimiterPolicy="none"
+      lengthKind="delimited"
+      separatorPosition="infix"
+      separatorSuppressionPolicy="trailingEmpty"
+    />
+
+    <xs:element name="input">
+      <xs:complexType>
+        <xs:sequence
+          dfdl:separator=","
+          dfdl:separatorPosition="infix"
+          dfdl:separatorSuppressionPolicy="trailingEmpty">
+          <xs:element
+            name="FirstName"
+            type="xs:string"/>
+          <xs:element
+            name="MiddleName"
+            type="xs:string"
+            dfdl:initiator="("
+            dfdl:terminator=")"
+            dfdl:emptyValueDelimiterPolicy="none"/>
+          <xs:element
+            name="LastName"
+            type="xs:string"/>
+        </xs:sequence>
+      </xs:complexType>
+    </xs:element>
+  </tdml:defineSchema>
+
+  <tdml:parserTestCase name="test_sep_evdp_1" root="input" model="s7"
+    implementations="daffodil" roundTrip="onePass">
+    <tdml:document>
+      <tdml:documentPart type="text" replaceDFDLEntities="true">John,(),Doe</tdml:documentPart>
+    </tdml:document>
+    <tdml:infoset>
+      <tdml:dfdlInfoset>
+        <input>
+          <FirstName>John</FirstName>
+          <MiddleName></MiddleName>
+          <LastName>Doe</LastName>
+        </input>
+      </tdml:dfdlInfoset>
+    </tdml:infoset>
+    <tdml:warnings>
+      <tdml:warning>emptyValueDelimiterPolicyWarning</tdml:warning>
+      <tdml:warning>none</tdml:warning>
+      <tdml:warning>ignored</tdml:warning>
+      <tdml:warning>both</tdml:warning>
+    </tdml:warnings>
+  </tdml:parserTestCase>
+
+  <tdml:parserTestCase name="test_sep_evdp_2" root="input" model="s7"
+    implementations="daffodil">
+    <tdml:document>
+      <tdml:documentPart type="text" replaceDFDLEntities="true">John,,Doe</tdml:documentPart>
+    </tdml:document>
+    <tdml:infoset>
+      <tdml:dfdlInfoset>
+        <input>
+          <FirstName>John</FirstName>
+          <MiddleName></MiddleName>
+          <LastName>Doe</LastName>
+        </input>
+      </tdml:dfdlInfoset>
+    </tdml:infoset>
+  </tdml:parserTestCase>
 </tdml:testSuite>

daffodil-test/src/test/scala/org/apache/daffodil/usertests/TestSepTests.scala

@@ -20,6 +20,7 @@ package org.apache.daffodil.usertests
 import org.apache.daffodil.junit.tdml.TdmlSuite
 import org.apache.daffodil.junit.tdml.TdmlTests
 
+import org.junit.Ignore
 import org.junit.Test
 
 object TestSepTests extends TdmlSuite {
@@ -48,6 +49,10 @@ class TestSepTests extends TdmlTests {
   @Test def test_sep_ssp_never_6 = test
   @Test def test_sep_ssp_never_7 = test
 
+  // DAFFODIL-2205 - EmptyValueDelimiterPolicy only works with 'both'
+  @Test def test_sep_evdp_1 = test
+  @Ignore @Test def test_sep_evdp_2 = test
+
   // DAFFODIL-2791
   @Test def test_treatAsAbsent_occursIndex = test
 }