PT 159667257 - Fixed sorting issue with proposals

Boot LS  proposals sorting fixed by wrapping LSP4E proposals with
IJavaCompletionProposal and setting relevance value.

eclipse-language-servers/org.springframework.tooling.boot.ls/src/org/springframework/tooling/boot/ls/jdt/SpringBootJavaCompletionProposalComputer.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2017, 2018 Pivotal, Inc.
+ * Copyright (c) 2017, 2019 Pivotal, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -20,10 +20,14 @@ import java.util.concurrent.TimeoutException;
 
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.jdt.ui.text.java.ContentAssistInvocationContext;
+import org.eclipse.jdt.ui.text.java.IJavaCompletionProposal;
 import org.eclipse.jdt.ui.text.java.IJavaCompletionProposalComputer;
+import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.contentassist.ICompletionProposal;
 import org.eclipse.jface.text.contentassist.IContextInformation;
 import org.eclipse.lsp4e.operations.completion.LSContentAssistProcessor;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.graphics.Point;
 
 /**
  * @author Martin Lippert
@@ -52,13 +56,46 @@ public class SpringBootJavaCompletionProposalComputer implements IJavaCompletion
 		});
 		
 		try {
-			return Arrays.asList(future.get(TIMEOUT_LENGTH, TIMEOUT_UNIT));
+			return Arrays.asList(asJavaProposals(future));
 		} catch (InterruptedException | ExecutionException | TimeoutException e) {
 			e.printStackTrace();
 			return Collections.emptyList();
 		}
 	}
 
+	/**
+	 * PT 159667257 - Strange sorting order
+	 * 
+	 * In order for boot LS proposals to appear in the right order by JDT, we need to return IJavaCompletionProposal
+	 * . the LSPCompletionProposal that LSP4E computes is NOT IJavaCompletionProposal, and as a consequence JDT
+	 * will by default sort any non Java  proposals by display value, which is  why  we get  strange sorting order,  even if our boot  LS
+	 * and  LSP4E both return  a proposal list  in the right order.
+	 * 
+	 * This method wraps around the LSCompletionProposal with  a  IJavaCompletionProposal,  and it sets the relevance
+	 * number that JDT uses to sort proposals in a desired order.
+	 * @param future
+	 * @return
+	 * @throws InterruptedException
+	 * @throws ExecutionException
+	 * @throws TimeoutException
+	 */
+	private ICompletionProposal[] asJavaProposals(CompletableFuture<ICompletionProposal[]> future)
+			throws InterruptedException, ExecutionException, TimeoutException {
+		ICompletionProposal[] originalProposals = future.get(TIMEOUT_LENGTH, TIMEOUT_UNIT);
+		
+		// We assume that the original proposals are in the correct order, so we set relevance
+		// based on this existing order. Note  that based  on  IJavaCompletionProposal  javadoc,
+		// relevance values are [0,1000] so we start at 1000
+		int relevance = 1000;
+		ICompletionProposal[] javaProposals = new ICompletionProposal[originalProposals.length];
+		
+		for (int i = 0; i < originalProposals.length; i++) {
+			javaProposals[i] = new LSJavaProposal(originalProposals[i], relevance--);
+		}
+		 
+		return javaProposals;
+	}
+
 	@Override
 	public List<IContextInformation> computeContextInformation(ContentAssistInvocationContext context,
 			IProgressMonitor monitor) {
@@ -74,5 +111,52 @@ public class SpringBootJavaCompletionProposalComputer implements IJavaCompletion
 	@Override
 	public void sessionEnded() {
 	}
+	
+	class LSJavaProposal implements IJavaCompletionProposal {
+		
+		private ICompletionProposal delegate;
+		private int relevance;
+
+		public LSJavaProposal(ICompletionProposal delegate,  int relevance) {
+			this.delegate = delegate;
+			this.relevance = relevance;
+		}
+
+		@Override
+		public void apply(IDocument document) {
+			delegate.apply(document);	
+		}
+
+		@Override
+		public String getAdditionalProposalInfo() {
+			return delegate.getAdditionalProposalInfo();
+		}
+
+		@Override
+		public IContextInformation getContextInformation() {
+			return delegate.getContextInformation();
+		}
+
+		@Override
+		public String getDisplayString() {
+			return delegate.getDisplayString();
+		}
+
+		@Override
+		public Image getImage() {
+			return delegate.getImage();
+		}
+
+		@Override
+		public Point getSelection(IDocument document) {
+			return delegate.getSelection(document);
+		}
+
+		@Override
+		public int getRelevance() {
+			return relevance;
+		}
+		
+	}
 
 }