Prefer public IDs when comparing grammar descriptors

src/main/java/org/dita/dost/util/XMLGrammarPoolImplUtils.java

@@ -68,7 +68,11 @@ public int hashCode(final XMLGrammarDescription desc) {
             // return -1 for XSD grammar hashcode because we want to disable XSD grammar caching
             return -1;
         } else {
-            return desc.hashCode();
+            if (desc.getPublicId() != null) {
+                return desc.getPublicId().hashCode();
+            } else {
+                return desc.hashCode();
+            }
         }
     }
 
@@ -94,7 +98,11 @@ public boolean equals(final XMLGrammarDescription desc1,
             // always return false for XSD grammar to disable XSD grammar caching
             return false;
         } else {
-            return desc1.equals(desc2);
+            if (desc1.getPublicId() != null && desc2.getPublicId() != null) {
+                return desc1.getPublicId().equals(desc2.getPublicId());
+            } else {
+                return desc1.equals(desc2);
+            }
         }
     }
 

src/test/java/org/dita/dost/util/XMLGrammarPoolImplUtilsTest.java

@@ -0,0 +1,83 @@
+/*
+ * This file is part of the DITA Open Toolkit project.
+ *
+ * Copyright 2020 Radu Coravu
+ *
+ * See the accompanying LICENSE file for applicable license.
+ */
+package org.dita.dost.util;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.io.File;
+
+import org.apache.xerces.impl.dtd.DTDGrammar;
+import org.apache.xerces.impl.dtd.XMLDTDDescription;
+import org.apache.xerces.xni.grammars.Grammar;
+import org.junit.Before;
+import org.junit.Test;
+
+
+public class XMLGrammarPoolImplUtilsTest {
+
+	private XMLGrammarPoolImplUtils utils;
+
+	@Before
+	public void setUp() {
+		utils = new XMLGrammarPoolImplUtils();
+	}
+
+	@Test
+	public void testCompareDescriptorsByPublicID_same() {
+		final XMLDTDDescription desc1 = getXmldtdDescription("file:/foo/abc.xml", "file:/foo/abc.dtd", "publicID");
+		final DTDGrammar exp = new DTDGrammar(null, desc1);
+		utils.putGrammar(exp);
+
+		final XMLDTDDescription desc2 = getXmldtdDescription("file:/abc.xml", "file:/abc.dtd", "publicID");
+		final Grammar act = utils.getGrammar(desc2);
+
+		assertEquals(exp, act);
+	}
+
+	@Test
+    public void testCompareDescriptorsByPublicID_different() {
+		final XMLDTDDescription desc1 = getXmldtdDescription("file:/foo/abc.xml", "file:/foo/abc.dtd", "publicID");
+		final DTDGrammar exp = new DTDGrammar(null, desc1);
+    	utils.putGrammar(exp);
+
+		final XMLDTDDescription desc2 = getXmldtdDescription("file:/abc.xml", "file:/abc.dtd", "differentId");
+		final Grammar act = utils.getGrammar(desc2);
+
+		assertNull(act);
+    }
+
+	@Test
+	public void testCompareDescriptorsBySystemID_same() {
+		final XMLDTDDescription desc1 = getXmldtdDescription("file:/foo/abc.xml", "file:/foo/abc.dtd", null);
+		final DTDGrammar exp = new DTDGrammar(null, desc1);
+		utils.putGrammar(exp);
+
+		final XMLDTDDescription desc2 = getXmldtdDescription("file:/abc.xml", "file:/foo/abc.dtd", null);
+		final Grammar act = utils.getGrammar(desc2);
+
+		assertEquals(exp, act);
+	}
+
+	@Test
+    public void testCompareDescriptorsBySystemID_different() {
+		final XMLDTDDescription desc1 = getXmldtdDescription("file:/foo/abc.xml", "file:/foo/abc.dtd", null);
+		final DTDGrammar exp = new DTDGrammar(null, desc1);
+    	utils.putGrammar(exp);
+
+		final XMLDTDDescription desc2 = getXmldtdDescription("file:/abc.xml", "file:/abc.dtd", null);
+		final Grammar act = utils.getGrammar(desc2);
+
+    	assertNull(act);
+    }
+
+	private XMLDTDDescription getXmldtdDescription(String base, String systemId, String publicId) {
+		return new XMLDTDDescription(publicId, "topic.dtd", base, systemId, "topic");
+	}
+
+}