Prolog now completion only provides valid attributes

org.eclipse.lsp4xml/src/main/java/org/eclipse/lsp4xml/dom/DOMNode.java

@@ -370,6 +370,23 @@ public String getAttribute(String name) {
 		return value;
 	}
 
+	/**
+	 * Returns the attribute at the given index, the order is how the attributes
+	 * appear in the document.
+	 * @param index Starting at 0, index of attribute you want
+	 * @return
+	 */
+	public DOMAttr getAttributeAtIndex(int index) {
+		if(!hasAttributes()) {
+			return null;
+		}
+
+		if(index > attributeNodes.getLength() - 1) {
+			return null;
+		}
+		return attributeNodes.get(index);
+	}
+
 	public boolean hasAttribute(String name) {
 		return hasAttributes() && getAttributeNode(name) != null;
 	}

org.eclipse.lsp4xml/src/main/java/org/eclipse/lsp4xml/extensions/contentmodel/participants/XMLSyntaxErrorCode.java

@@ -51,7 +51,7 @@ public enum XMLSyntaxErrorCode implements IXMLErrorCode {
 	LessthanInAttValue, MarkupEntityMismatch, MarkupNotRecognizedInContent, NameRequiredInReference, OpenQuoteExpected,
 	PITargetRequired, PseudoAttrNameExpected, QuoteRequiredInXMLDecl, RootElementTypeMustMatchDoctypedecl,
 	SDDeclInvalid, SpaceRequiredBeforeEncodingInXMLDecl, SpaceRequiredBeforeStandalone, SpaceRequiredInPI,
-	VersionInfoRequired, VersionNotSupported, XMLDeclUnterminated, CustomETag, PrematureEOF, DoctypeNotAllowed;
+	VersionInfoRequired, VersionNotSupported, XMLDeclUnterminated, CustomETag, PrematureEOF, DoctypeNotAllowed, NoMorePseudoAttributes;
 
 	private final String code;
 
@@ -109,6 +109,7 @@ public static Range toLSPRange(XMLLocator location, XMLSyntaxErrorCode code, Obj
 			String attrName = getString(arguments[1]);
 			return XMLPositionUtility.selectAttributeNameFromGivenNameAt(attrName, offset, document);
 		}
+		case NoMorePseudoAttributes:
 		case EncodingDeclRequired:
 		case EqRequiredInXMLDecl:
 			return XMLPositionUtility.selectAttributeNameAt(offset, document);

org.eclipse.lsp4xml/src/main/java/org/eclipse/lsp4xml/extensions/prolog/PrologModel.java

@@ -39,6 +39,7 @@
 import org.eclipse.lsp4xml.settings.SharedSettings;
 import org.eclipse.lsp4xml.settings.XMLFormattingOptions;
 import org.eclipse.lsp4xml.utils.StringUtils;
+import org.w3c.dom.NamedNodeMap;
 
 /**
  * This class holds values that represent the XSI xsd. Can be seen at
@@ -144,17 +145,35 @@ public static void computeAttributeNameCompletionResponses(ICompletionRequest re
 			return;
 		}
 		boolean isSnippetsSupported = request.isCompletionSnippetsSupported();
-
-		if(!prolog.hasAttribute(VERSION_NAME)) {
+		int attrIndex = getAttributeCompletionPosition(offset, prolog);
+
+		if(attrIndex == 0) { // 1st attribute
+			if(isCurrentAttributeEqual(VERSION_NAME, prolog, 0)) {
+				return;
+			}
 			createCompletionItem(VERSION_NAME, isSnippetsSupported, true, editRange, VERSION_1, VERSION_VALUES, null, response, formattingsSettings);
+			return;
 		}
 
-		if(!prolog.hasAttribute(ENCODING_NAME)) {
-			createCompletionItem(ENCODING_NAME, isSnippetsSupported, true, editRange, UTF_8, ENCODING_VALUES, null, response, formattingsSettings);
+		if(attrIndex == 1) { // 2nd attribute
+			if(!isCurrentAttributeEqual(ENCODING_NAME, prolog, 1)) {
+				createCompletionItem(ENCODING_NAME, isSnippetsSupported, true, editRange, UTF_8, ENCODING_VALUES, null, response, formattingsSettings);
+			} else {
+				return;
+			}
+
+			if(!isCurrentAttributeEqual(STANDALONE_NAME, prolog, 1)) {
+				createCompletionItem(STANDALONE_NAME, isSnippetsSupported, true, editRange, YES, STANDALONE_VALUES, null, response, formattingsSettings);
+			}
+			return;
 		}
 
-		if(!prolog.hasAttribute(STANDALONE_NAME)) {
-			createCompletionItem(STANDALONE_NAME, isSnippetsSupported, true, editRange, YES, STANDALONE_VALUES, null, response, formattingsSettings);
+		if(attrIndex == 2) { // 3rd attribute
+			DOMAttr attrBefore = prolog.getAttributeAtIndex(1);
+			if(!STANDALONE_NAME.equals(attrBefore.getName()) && !isCurrentAttributeEqual(STANDALONE_NAME, prolog, 2)) {
+				createCompletionItem(STANDALONE_NAME, isSnippetsSupported, true, editRange, YES, STANDALONE_VALUES, null, response, formattingsSettings);
+			}
+			return;
 		}
 
 	}
@@ -201,4 +220,70 @@ private static void createCompletionItemsForValues(Collection<String> enumeratio
 		}
 	}
 
+	/**
+	 * Returns the position the offset is in in relation to the attributes and their order
+	 * 
+	 * example:
+	 * 
+	 * <element a="1" b="2" | c="3">
+	 * 
+	 * This will return 2 since if you insert a new attribute there you can access
+	 * it from the list of attributes with this index.
+	 * @param completionOffset
+	 * @param element
+	 * @return
+	 */
+	private static int getAttributeCompletionPosition(int completionOffset, DOMNode element) {
+
+		NamedNodeMap attributeList = element.getAttributes();
+
+		if(attributeList == null) {
+			return 0;
+		}
+
+		int attributeListLength = attributeList.getLength();
+
+
+		if(attributeListLength == 0) {
+			return 0;
+		}
+
+		DOMAttr attr;
+
+		for (int i = 0; i < attributeListLength; i++) {
+			attr = element.getAttributeAtIndex(i);
+			if(completionOffset <= attr.getStart()) {
+				return i;
+			}
+		}
+
+		return attributeListLength;
+	}
+
+	/**
+	 * Returns true if the current attribute in the given position of the element's list of attributes
+	 * equals the provided attributeName
+	 * @param attributeName
+	 * @param element
+	 * @param position
+	 * @return
+	 */
+	private static boolean isCurrentAttributeEqual(String attributeName, DOMNode element, int index) {
+		NamedNodeMap attributeList = element.getAttributes();
+
+		if(attributeList == null) {
+			return false;
+		}
+
+		if(index >= attributeList.getLength()) {
+			return false;
+		}
+
+		if(attributeName.equals(element.getAttributeAtIndex(index).getName())) {
+			return true;
+		}
+
+		return false;
+	}
+
 }

org.eclipse.lsp4xml/src/test/java/org/eclipse/lsp4xml/extensions/contentmodel/XMLSyntaxDiagnosticsTest.java

@@ -164,6 +164,12 @@ public void testEqRequiredInXMLDecl() throws Exception {
 		testDiagnosticsFor(xml, d(0, 6, 0, 14, XMLSyntaxErrorCode.EqRequiredInXMLDecl));
 	}
 
+	@Test
+	public void testNoMorePseudoAttributes() throws Exception {
+		String xml = "<?xml version=\"1.0\" standalone=\"yes\" encoding=\"UTF-8\"?><a></a>";
+		testDiagnosticsFor(xml, d(0, 37, 0, 45, XMLSyntaxErrorCode.NoMorePseudoAttributes));
+	}
+
 	/**
 	 * ETagRequired tests
 	 * 

org.eclipse.lsp4xml/src/test/java/org/eclipse/lsp4xml/extensions/prolog/PrologCompletionExtensionsTest.java

@@ -40,27 +40,53 @@ public static void runOnceBeforeClass() {
 	}
 
 	@Test
-	public void completionVersion() throws BadLocationException {
+	public void completionVersionWithV() throws BadLocationException {
 		// completion on |
 		String xml = "<?xml v|?>\r\n" + //
 				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
-		testCompletionFor(xml, c("version", te(0, 6, 0, 7, "version=\"1.0\""), "version"));
+		testCompletionFor(xml, 1, c("version", te(0, 6, 0, 7, "version=\"1.0\""), "version"));
+	}
+
+	@Test
+	public void completionVersion() throws BadLocationException {
+		// completion on |
+		String xml = "<?xml |?>\r\n" + //
+				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
+		testCompletionFor(xml, c("version", te(0, 6, 0, 6, "version=\"1.0\""), "version"));
 	}
 
 	@Test
-	public void completionEncoding() throws BadLocationException {
+	public void completionEncodingAndStandalone() throws BadLocationException {
 		// completion on |
-		String xml = "<?xml e|?>\r\n" + //
+		String xml = "<?xml version=\"1.0\" |?>\r\n" + //
 				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
-		testCompletionFor(xml, c("encoding", te(0, 6, 0, 7, "encoding=\"UTF-8\""), "encoding"));
+		testCompletionFor(xml, 2, 
+			c("encoding", te(0, 20, 0, 20, "encoding=\"UTF-8\""), "encoding"), 
+			c("standalone", te(0, 20, 0, 20, "standalone=\"yes\""), "standalone"));
 	}
 
 	@Test
 	public void completionStandalone() throws BadLocationException {
 		// completion on |
-		String xml = "<?xml s|?>\r\n" + //
+		String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" |?>\r\n" + //
 				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
-		testCompletionFor(xml, c("standalone", te(0, 6, 0, 7, "standalone=\"yes\""), "standalone"));
+		testCompletionFor(xml, 1, c("standalone", te(0, 37, 0, 37, "standalone=\"yes\""), "standalone"));
+	}
+
+	@Test
+	public void noCompletionsAfterStandalone() throws BadLocationException {
+		// completion on |
+		String xml = "<?xml version=\"1.0\" standalone=\"yes\" |?>\r\n" + //
+				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
+		testCompletionFor(xml, 0, (CompletionItem []) null);
+	}
+
+	@Test
+	public void completionEncodingBeforeStandalone() throws BadLocationException {
+		// completion on |
+		String xml = "<?xml version=\"1.0\" | standalone=\"yes\" ?>\r\n" + //
+				"<project xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">";
+		testCompletionFor(xml, 1, c("encoding", te(0, 20, 0, 20, "encoding=\"UTF-8\""), "encoding"));
 	}
 
 	@Test
@@ -245,6 +271,10 @@ private void testCompletionFor(String xml, CompletionItem... expectedItems) thro
 		XMLAssert.testCompletionFor(xml, null, expectedItems);
 	}
 
+	private void testCompletionFor(String xml, int expectedCount, CompletionItem... expectedItems) throws BadLocationException {
+		XMLAssert.testCompletionFor(xml, expectedCount, expectedItems);
+	}
+
 	private void testCompletionFor(String xml, String fileURI, boolean autoCloseTags, boolean isSnippetsSupported,
 			CompletionItem... expectedItems) throws BadLocationException {
 		testCompletionFor(xml, fileURI, formattingSettings,