Do not create document links with zero length range

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/extensions/contentmodel/participants/ContentModelDocumentLinkParticipant.java

@@ -28,6 +28,7 @@
 import org.eclipse.lemminx.dom.XMLModel;
 import org.eclipse.lemminx.services.extensions.IDocumentLinkParticipant;
 import org.eclipse.lemminx.uriresolver.URIResolverExtensionManager;
+import org.eclipse.lemminx.utils.DOMUtils;
 import org.eclipse.lsp4j.DocumentLink;
 import org.w3c.dom.NamedNodeMap;
 
@@ -64,7 +65,7 @@ public void findDocumentLinks(DOMDocument document, List<DocumentLink> links) {
 			if (location != null) {
 				try {
 					DOMRange systemIdRange = docType.getSystemIdNode();
-					if (systemIdRange != null) {
+					if (DOMUtils.isNonEmptyRange(systemIdRange, true)) {
 						links.add(createDocumentLink(systemIdRange, location, true));
 					}
 				} catch (BadLocationException e) {
@@ -81,7 +82,7 @@ public void findDocumentLinks(DOMDocument document, List<DocumentLink> links) {
 				if (location != null) {
 					try {
 						DOMRange systemIdRange = entity.getSystemIdNode();
-						if (systemIdRange != null) {
+						if (DOMUtils.isNonEmptyRange(systemIdRange, true)) {
 							links.add(createDocumentLink(systemIdRange, location, true));
 						}
 					} catch (BadLocationException e) {
@@ -98,7 +99,7 @@ public void findDocumentLinks(DOMDocument document, List<DocumentLink> links) {
 			if (location != null) {
 				try {
 					DOMRange hrefRange = xmlModel.getHrefNode();
-					if (hrefRange != null) {
+					if (DOMUtils.isNonEmptyRange(hrefRange, true)) {
 						links.add(createDocumentLink(hrefRange, location, true));
 					}
 				} catch (BadLocationException e) {
@@ -115,7 +116,7 @@ public void findDocumentLinks(DOMDocument document, List<DocumentLink> links) {
 						noNamespaceSchemaLocation.getLocation());
 				if (location != null) {
 					DOMRange attrValue = noNamespaceSchemaLocation.getAttr().getNodeAttrValue();
-					if (attrValue != null) {
+					if (DOMUtils.isNonEmptyRange(attrValue, true)) {
 						links.add(createDocumentLink(attrValue, location, true));
 					}
 				}
@@ -132,7 +133,7 @@ public void findDocumentLinks(DOMDocument document, List<DocumentLink> links) {
 				String location;
 				for (SchemaLocationHint schemaLocationHint : schemaLocationHints) {
 					location = resolverManager.resolve(document.getDocumentURI(), null, schemaLocationHint.getHint());
-					if (location != null) {
+					if (DOMUtils.isNonEmptyRange(schemaLocationHint, false)) {
 						links.add(createDocumentLink(schemaLocationHint, location, false));
 					}
 				}

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/utils/DOMUtils.java

@@ -21,6 +21,7 @@
 import org.eclipse.lemminx.dom.DOMElement;
 import org.eclipse.lemminx.dom.DOMNode;
 import org.eclipse.lemminx.dom.DOMParser;
+import org.eclipse.lemminx.dom.DOMRange;
 import org.eclipse.lemminx.uriresolver.URIResolverExtensionManager;
 import org.xml.sax.InputSource;
 import org.xml.sax.SAXNotRecognizedException;
@@ -287,4 +288,18 @@ public static InputSource createInputSource(DOMDocument document) {
 		inputSource.setSystemId(uri);
 		return inputSource;
 	}
+
+	/**
+	 * Returns false if the range is zero-length, and true otherwise.
+	 * 
+	 * @param range the range to check
+	 * @param adjust true if the leading and trailing quotes should be removed before checking if it's zero-length, false otherwise
+	 * @return false if the range is zero-length, and true otherwise
+	 */
+	public static boolean isNonEmptyRange(DOMRange range, boolean adjust) {
+		if (range == null) {
+			return false;
+		}
+		return range.getEnd() - range.getStart() > (adjust ? 2 : 0);
+	}
 }

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/utils/XMLPositionUtility.java

@@ -1040,8 +1040,13 @@ public static Location createLocation(DOMRange target) {
 	public static DocumentLink createDocumentLink(DOMRange target, String location, boolean adjust)
 			throws BadLocationException {
 		DOMDocument document = target.getOwnerDocument();
-		Position start = document.positionAt(target.getStart() + (adjust ? 1 : 0));
-		Position end = document.positionAt(target.getEnd() - (adjust ? 1 : 0));
+		int startOffset = target.getStart() + (adjust ? 1 : 0);
+		int endOffset = target.getEnd() - (adjust ? 1 : 0);
+		if (startOffset == endOffset) {
+			throw new IllegalArgumentException("empty range");
+		}
+		Position start = document.positionAt(startOffset);
+		Position end = document.positionAt(endOffset);
 		return new DocumentLink(new Range(start, end), location);
 	}
 

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/catalog/XMLCatalogDocumentLinkTest.java

@@ -69,6 +69,20 @@ public void testCatalogWithCatalogDOCTYPE() {
 
 	}
 
+	@Test
+	public void testCatalogWithCatalogDOCTYPEZeroLength() {
+		String xml = "<!DOCTYPE catalog PUBLIC \"-//OASIS//DTD XML Catalogs V1.1//EN\" \"catalog.dtd\" >\n"
+				+ //
+				"<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
+				"  <uri\n" + //
+				"    id=\"\"\n" + //
+				"    uri=\"\" />\n" + //
+				"</catalog>";
+		testDocumentLinkFor(xml, CATALOG_PATH,
+				dl(r(0, 64, 0, 75), "src/test/resources/catalog.dtd"));
+
+	}
+
 	@Test
 	public void testSystemSuffixEntryDocumentLink() {
 		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
@@ -78,6 +92,14 @@ public void testSystemSuffixEntryDocumentLink() {
 				dl(r(1, 45, 1, 57), "src/test/resources/mySchema.xsd"));
 	}
 
+	@Test
+	public void testSystemSuffixEntryZeroLengthDocumentLink() {
+		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
+				"  <systemSuffix id=\"http://example.org\" uri=\"\"></systemSuffix>\n" + //
+				"</catalog>";
+		testDocumentLinkFor(xml, CATALOG_PATH);
+	}
+
 	@Test
 	public void testURISuffixEntryDocumentLink() {
 		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
@@ -87,6 +109,14 @@ public void testURISuffixEntryDocumentLink() {
 				dl(r(1, 42, 1, 54), "src/test/resources/mySchema.xsd"));
 	}
 
+	@Test
+	public void testURISuffixEntryZeroLengthDocumentLink() {
+		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
+				"  <uriSuffix id=\"\" uri=\"\"></uriSuffix>\n" + //
+				"</catalog>";
+		testDocumentLinkFor(xml, CATALOG_PATH);
+	}
+
 	@Test
 	public void testMustBeCatalog1() {
 		String xml = "<catalog><public url=\"document.xsd\" /></catalog>";
@@ -127,6 +157,14 @@ public void testDelegatePublicEntry() {
 				dl(r(1, 27, 1, 54), "src/test/resources/catalogs/catalog-public.xml"));
 	}
 
+	@Test
+	public void testDelegatePublicEntryZeroLength() {
+		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
+				"  <delegatePublic catalog=\"\" />\n" + //
+				"</catalog>";
+		testDocumentLinkFor(xml, CATALOG_PATH);
+	}
+
 	@Test
 	public void testDelegateSystemEntry() {
 		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
@@ -136,6 +174,14 @@ public void testDelegateSystemEntry() {
 				dl(r(1, 27, 1, 54), "src/test/resources/catalogs/catalog-public.xml"));
 	}
 
+	@Test
+	public void testDelegateSystemEntryZeroLength() {
+		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //
+				"  <delegateSystem catalog=\"\" />\n" + //
+				"</catalog>";
+		testDocumentLinkFor(xml, CATALOG_PATH);
+	}
+
 	@Test
 	public void testDelegateUriEntry() {
 		String xml = "<catalog xmlns=\"urn:oasis:names:tc:entity:xmlns:xml:catalog\">\n" + //

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/DTDDocumentLinkTest.java

@@ -36,6 +36,16 @@ public void docTypeSYSTEM() throws BadLocationException {
 				dl(r(1, 31, 1, 55), "src/test/resources/dtd/entities/base.dtd"));
 	}
 
+	@Test
+	public void docTypeSYSTEMZeroLengh() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\r\n" + //
+				"<!DOCTYPE root-element SYSTEM \"\" [\r\n" + //
+				"\r\n" + //
+				"]>\r\n" + //
+				"<root-element />";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xml/base.xml");
+	}
+
 	@Test
 	public void docTypePUBLIC() throws BadLocationException {
 		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\r\n" + //
@@ -47,6 +57,16 @@ public void docTypePUBLIC() throws BadLocationException {
 				dl(r(1, 38, 1, 62), "src/test/resources/dtd/entities/base.dtd"));
 	}
 
+	@Test
+	public void docTypePUBLICZeroLength() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\r\n" + //
+				"<!DOCTYPE root-element PUBLIC \"ABCD\" \"\" [\r\n" + //
+				"\r\n" + //
+				"]>\r\n" + //
+				"<root-element />";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xml/base.xml");
+	}
+
 	@Test
 	public void noLinks() throws BadLocationException {
 		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\r\n" + //

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/contentmodel/XMLModelDocumentLinkTest.java

@@ -35,4 +35,34 @@ public void xmlModelHref() throws BadLocationException {
 		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/Format.xml",
 				dl(r(1, 18, 1, 32), "src/test/resources/xsd/Format.xsd"));
 	}
+
+	@Test
+	public void xmlModelHrefZeroLength() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n" + //
+				"<?xml-model href=\"\" ?>\r\n" + //
+				"<Configuration>\r\n" + //
+				"  <ViewDefinitions>\r\n" + //
+				"    <View>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/Format.xml");
+	}
+
+	@Test
+	public void xmlModelHrefZeroLength2() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n" + //
+				"<?xml-model href= ?>\r\n" + //
+				"<Configuration>\r\n" + //
+				"  <ViewDefinitions>\r\n" + //
+				"    <View>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/Format.xml");
+	}
+
+	@Test
+	public void xmlModelHrefZeroLength3() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n" + //
+				"<?xml-model href ?>\r\n" + //
+				"<Configuration>\r\n" + //
+				"  <ViewDefinitions>\r\n" + //
+				"    <View>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/Format.xml");
+	}
 }

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/dtd/DTDDocumentLinkTest.java

@@ -31,4 +31,10 @@ public void entity() throws BadLocationException {
 		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xml/base.dtd",
 				dl(r(0, 28, 0, 43), "src/test/resources/document.ent"));
 	}
+
+	@Test
+	public void entityZeroLength() throws BadLocationException {
+		String xml = "<!ENTITY % document SYSTEM \"\">";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xml/base.dtd");
+	}
 }

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/relaxng/grammar/rng/RNGDocumentLinkingExtensionsTest.java

@@ -103,4 +103,55 @@ public void externalRef() throws BadLocationException {
 		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/relaxng/main.rng",
 				dl(r(11, 24, 11, 34), "src/test/resources/relaxng/inline.rng"));
 	}
+
+	@Test
+	public void emptyIncludeHref() throws BadLocationException {
+		String xml = "<grammar xmlns=\"http://relaxng.org/ns/structure/1.0\" >\n"
+				+ "	<include href=\"\">\n"
+				+ "		<define name=\"cardContent\">\n"
+				+ "			<element name=\"name\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "			<element name=\"emailAddress\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "		</define>\n"
+				+ "	</include>\n"
+				+ "</grammar>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/relaxng/main.rng");
+	}
+
+	@Test
+	public void emptyIncludeHref2() throws BadLocationException {
+		String xml = "<grammar xmlns=\"http://relaxng.org/ns/structure/1.0\" >\n"
+				+ "	<include href= >\n"
+				+ "		<define name=\"cardContent\">\n"
+				+ "			<element name=\"name\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "			<element name=\"emailAddress\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "		</define>\n"
+				+ "	</include>\n"
+				+ "</grammar>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/relaxng/main.rng");
+	}
+
+	@Test
+	public void emptyIncludeHref3() throws BadLocationException {
+		String xml = "<grammar xmlns=\"http://relaxng.org/ns/structure/1.0\" >\n"
+				+ "	<include href >\n"
+				+ "		<define name=\"cardContent\">\n"
+				+ "			<element name=\"name\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "			<element name=\"emailAddress\">\n"
+				+ "				<text />\n"
+				+ "			</element>\n"
+				+ "		</define>\n"
+				+ "	</include>\n"
+				+ "</grammar>";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/relaxng/main.rng");
+	}
 }

org.eclipse.lemminx/src/test/java/org/eclipse/lemminx/extensions/xinclude/XIncludeDocumentLinkTest.java

@@ -45,4 +45,15 @@ public void includeHrefInAnyLevel() throws BadLocationException {
 		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xinclude/main.xml",
 				dl(r(3, 22, 3, 35), "src/test/resources/xinclude/reference.xml"));
 	}
+
+	@Test
+	public void includeHrefZeroLength() throws BadLocationException {
+		String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + //
+				"<book xmlns:xi=\"http://www.w3.org/2001/XInclude\"> \n" + //
+				"  <author> \n" + //
+				"    <xi:include href=\"\" />\n" + // <-- documentLink
+				"  </author>\n" + //
+				"</book>\n";
+		XMLAssert.testDocumentLinkFor(xml, "src/test/resources/xinclude/main.xml");
+	}
 }