feat: Improved completion sorting that takes into account the current word and prefix (strict then camel-hump)

src/main/java/com/redhat/devtools/lsp4ij/client/features/LSPCompletionFeature.java

@@ -97,7 +97,7 @@ public boolean isCompletionSupported(@NotNull PsiFile file) {
      * @param file the file.
      * @return true the file associated with a language server can support resolve completion and false otherwise.
      */
-    public boolean isResolveCompletionSupported(@Nullable PsiFile file) {
+    public boolean isResolveCompletionSupported(@NotNull PsiFile file) {
         return getCompletionCapabilityRegistry().isResolveCompletionSupported(file);
     }
 
@@ -182,7 +182,7 @@ public Icon getIcon(@NotNull CompletionItem item) {
     /**
      * Returns true if the IntelliJ lookup is strike out and false otherwise.
      *
-     * @param item
+     * @param item the completion item
      * @return true if the IntelliJ lookup is strike out and false otherwise.
      */
     public boolean isStrikeout(@NotNull CompletionItem item) {
@@ -215,12 +215,12 @@ public boolean isItemTextBold(@NotNull CompletionItem item) {
     /**
      * Don't override this method, we need to revisit the API and the prefix computation (to customize it).
      *
-     * @param context
-     * @param completionPrefix
-     * @param result
-     * @param lookupItem
-     * @param priority
-     * @param item
+     * @param context the completion context
+     * @param completionPrefix the completion prefix
+     * @param result the completion result set
+     * @param lookupItem the lookup item
+     * @param priority the completion priority
+     * @param item the completion item
      */
     @ApiStatus.Internal
     public void addLookupItem(@NotNull LSPCompletionContext context,
@@ -293,4 +293,15 @@ public void setServerCapabilities(@Nullable ServerCapabilities serverCapabilitie
             completionCapabilityRegistry.setServerCapabilities(serverCapabilities);
         }
     }
+
+    /**
+     * Determines whether or not client-side context-aware completion sorting should be used for the specified file.
+     *
+     * @param file the file
+     * @return true if client-side context-aware completion sorting should be used; otherwise false
+     */
+    public boolean useContextAwareSorting(@NotNull PsiFile file) {
+        // Default to disabled
+        return false;
+    }
 }

src/main/java/com/redhat/devtools/lsp4ij/features/completion/CompletionItemComparator.java

@@ -10,15 +10,30 @@
  ******************************************************************************/
 package com.redhat.devtools.lsp4ij.features.completion;
 
-import java.util.Comparator;
-
+import com.intellij.codeInsight.completion.PrefixMatcher;
+import com.intellij.openapi.util.text.StringUtil;
 import org.eclipse.lsp4j.CompletionItem;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.Comparator;
+
 /**
  * Compares {@link CompletionItem}s by their sortText property (falls back to comparing labels)
  */
 public class CompletionItemComparator implements Comparator<CompletionItem> {
+	private final PrefixMatcher prefixMatcher;
+	private final String currentWord;
+	private final boolean caseSensitive;
+
+	public CompletionItemComparator(@Nullable PrefixMatcher prefixMatcher,
+									@Nullable String currentWord,
+									boolean caseSensitive) {
+		this.prefixMatcher = prefixMatcher;
+		this.currentWord = currentWord;
+		this.caseSensitive = caseSensitive;
+	}
+
 	@Override
 	public int compare(CompletionItem item1, CompletionItem item2) {
 		if (item1 == item2) {
@@ -29,24 +44,100 @@ public int compare(CompletionItem item1, CompletionItem item2) {
 			return 1;
 		}
 
-		int comparison = compareNullable(item1.getSortText(), item2.getSortText());
+		// If one is a better match for the current word than the other, sort it higher
+		int comparison = compareAgainstCurrentWord(item1, item2);
+		if (comparison != 0) {
+			return comparison;
+		}
+
+		// If one is a better completion for the current prefix than the other, sort it higher
+		comparison = compareAgainstPrefix(item1, item2);
+		if (comparison != 0) {
+			return comparison;
+		}
+
+		// Order by language server-provided sort text
+		comparison = compare(item1.getSortText(), item2.getSortText());
+		if (comparison != 0) {
+			return comparison;
+		}
 
 		// If sortText is equal, fall back to comparing labels
-		if (comparison == 0) {
-			comparison = item1.getLabel().compareTo(item2.getLabel());
+		return compare(item1.getLabel(), item2.getLabel());
+	}
+
+	private int compare(@Nullable String string1, @Nullable String string2) {
+		return StringUtil.compare(string1, string2, !caseSensitive);
+	}
+
+	private boolean equals(@Nullable String string1, @Nullable String string2) {
+		return StringUtil.compare(string1, string2, !caseSensitive) == 0;
+	}
+
+	private boolean startsWith(@Nullable String string, @Nullable String prefix) {
+		if ((string == null) || (prefix == null)) {
+			return false;
 		}
+		return caseSensitive ? StringUtil.startsWith(string, prefix) : StringUtil.startsWithIgnoreCase(string, prefix);
+	}
+
+	private int compareAgainstCurrentWord(@NotNull CompletionItem item1, @NotNull CompletionItem item2) {
+		if (currentWord != null) {
+			String label1 = item1.getLabel();
+			String label2 = item2.getLabel();
+			// Don't do this for completion offerings that are quoted strings
+			if (((label1 == null) || !StringUtil.isQuotedString(label1)) &&
+				((label2 == null) || !StringUtil.isQuotedString(label2))) {
+				// Exact match
+				if (equals(currentWord, label1) &&
+					((label2 == null) || !equals(currentWord, label2))) {
+					return -1;
+				} else if (equals(currentWord, label2) &&
+						   ((label1 == null) || !equals(currentWord, label1))) {
+					return 1;
+				}
 
-		return comparison;
+				// Starts with
+				else if ((startsWith(currentWord, label1) || startsWith(label1, currentWord)) &&
+						 ((label2 == null) || !(startsWith(currentWord, label2) || startsWith(label2, currentWord)))) {
+					return -1;
+				} else if ((startsWith(currentWord, label2) || startsWith(label2, currentWord)) &&
+						   ((label1 == null) || !(startsWith(currentWord, label1) || startsWith(label1, currentWord)))) {
+					return 1;
+				}
+			}
+		}
+
+		return 0;
 	}
 
-	private int compareNullable(@Nullable String s1, @Nullable String s2) {
-		if (s1 == s2) {
-			return 0;
-		} else if (s1 == null) {
-			return -1;
-		} else if (s2 == null) {
-			return 1;
+	private int compareAgainstPrefix(@NotNull CompletionItem item1, @NotNull CompletionItem item2) {
+		if (prefixMatcher != null) {
+			String prefix = prefixMatcher.getPrefix();
+			String label1 = item1.getLabel();
+			String label2 = item2.getLabel();
+			// Don't do this for completion offerings that are quoted strings
+			if (((label1 == null) || !StringUtil.isQuotedString(label1)) &&
+				((label2 == null) || !StringUtil.isQuotedString(label2))) {
+				// Start starts with
+				if (startsWith(label1, prefix) &&
+					(!startsWith(label2, prefix))) {
+					return -1;
+				} else if (startsWith(label2, prefix) &&
+						   (!startsWith(label1, prefix))) {
+					return 1;
+				}
+				// Loose/camel-hump starts with
+				else if ((label1 != null) && prefixMatcher.isStartMatch(label1) &&
+						 ((label2 == null) || !prefixMatcher.isStartMatch(label2))) {
+					return -1;
+				} else if ((label2 != null) && prefixMatcher.isStartMatch(label2) &&
+						   ((label1 == null) || !prefixMatcher.isStartMatch(label1))) {
+					return 1;
+				}
+			}
 		}
-		return s1.compareTo(s2);
+
+		return 0;
 	}
 }

src/main/java/com/redhat/devtools/lsp4ij/features/completion/LSPCompletionContributor.java

@@ -17,6 +17,7 @@
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.progress.ProcessCanceledException;
 import com.intellij.openapi.progress.ProgressManager;
+import com.intellij.openapi.util.TextRange;
 import com.intellij.openapi.util.UserDataHolder;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiFile;
@@ -25,6 +26,7 @@
 import com.redhat.devtools.lsp4ij.LSPIJUtils;
 import com.redhat.devtools.lsp4ij.LanguageServerItem;
 import com.redhat.devtools.lsp4ij.client.ExecuteLSPFeatureStatus;
+import com.redhat.devtools.lsp4ij.client.features.LSPClientFeatures;
 import com.redhat.devtools.lsp4ij.client.features.LSPCompletionFeature;
 import com.redhat.devtools.lsp4ij.client.features.LSPCompletionProposal;
 import com.redhat.devtools.lsp4ij.client.indexing.ProjectIndexingManager;
@@ -102,8 +104,6 @@ public void fillCompletionVariants(@NotNull CompletionParameters parameters, @No
         }
     }
 
-    private static final CompletionItemComparator completionProposalComparator = new CompletionItemComparator();
-
     private void addCompletionItems(@NotNull CompletionParameters parameters,
                                     @NotNull CompletionPrefix completionPrefix,
                                     @NotNull Either<List<CompletionItem>, CompletionList> completion,
@@ -119,12 +119,19 @@ private void addCompletionItems(@NotNull CompletionParameters parameters,
             items.addAll(completionList.getItems());
         }
 
-        // Sort by item.sortText
-        items.sort(completionProposalComparator);
+        PsiFile originalFile = parameters.getOriginalFile();
+        LSPClientFeatures clientFeatures = languageServer.getClientFeatures();
+
+        // Sort the completions as appropriate based on client configuration
+        boolean useContextAwareSorting = clientFeatures.getCompletionFeature().useContextAwareSorting(originalFile);
+        PrefixMatcher prefixMatcher = useContextAwareSorting ? result.getPrefixMatcher() : null;
+        String currentWord = useContextAwareSorting ? getCurrentWord(parameters) : null;
+        boolean caseSensitive = clientFeatures.isCaseSensitive(originalFile);
+        items.sort(new CompletionItemComparator(prefixMatcher, currentWord, caseSensitive));
         int size = items.size();
 
         Set<String> addedLookupStrings = new HashSet<>();
-        var completionFeature = languageServer.getClientFeatures().getCompletionFeature();
+        var completionFeature = clientFeatures.getCompletionFeature();
         LSPCompletionFeature.LSPCompletionContext context = new LSPCompletionFeature.LSPCompletionContext(parameters, languageServer);
         // Items now sorted by priority, low index == high priority
         for (int i = 0; i < size; i++) {
@@ -186,6 +193,23 @@ private void addCompletionItems(@NotNull CompletionParameters parameters,
         }
     }
 
+    @Nullable
+    private static String getCurrentWord(@NotNull CompletionParameters parameters) {
+        PsiFile originalFile = parameters.getOriginalFile();
+        VirtualFile virtualFile = originalFile.getVirtualFile();
+        Document document = virtualFile != null ? LSPIJUtils.getDocument(virtualFile) : null;
+        if (document != null) {
+            int offset = parameters.getOffset();
+            TextRange wordTextRange = LSPIJUtils.getWordRangeAt(document, originalFile, offset);
+            if (wordTextRange != null) {
+                CharSequence documentChars = document.getCharsSequence();
+                CharSequence wordChars = documentChars.subSequence(wordTextRange.getStartOffset(), wordTextRange.getEndOffset());
+                return wordChars.toString();
+            }
+        }
+        return null;
+    }
+
     protected void updateWithItemDefaults(@NotNull CompletionItem item,
                                           @Nullable CompletionItemDefaults itemDefaults) {
         if (itemDefaults == null) {

src/main/java/com/redhat/devtools/lsp4ij/server/definition/launching/ClientConfigurationSettings.java

@@ -20,7 +20,17 @@
  */
 public class ClientConfigurationSettings {
     /**
-     * Client-side code workspace symbol settings.
+     * Client-side code completion settings.
+     */
+    public static class ClientConfigurationCompletionSettings {
+        /**
+         * Whether or not client-side context-aware completion sorting should be used. Defaults to false.
+         */
+        public boolean useContextAwareSorting = false;
+    }
+
+    /**
+     * Client-side workspace symbol settings.
      */
     public static class ClientConfigurationWorkspaceSymbolSettings {
         /**
@@ -35,7 +45,12 @@ public static class ClientConfigurationWorkspaceSymbolSettings {
     public boolean caseSensitive = false;
 
     /**
-     * Client-side code workspace symbol settings
+     * Client-side code completion settings
+     */
+    public @NotNull ClientConfigurationCompletionSettings completion = new ClientConfigurationCompletionSettings();
+
+    /**
+     * Client-side workspace symbol settings
      */
     public @NotNull ClientConfigurationWorkspaceSymbolSettings workspaceSymbol = new ClientConfigurationWorkspaceSymbolSettings();
 }

src/main/java/com/redhat/devtools/lsp4ij/server/definition/launching/UserDefinedClientFeatures.java

@@ -26,6 +26,7 @@ public UserDefinedClientFeatures() {
         super();
 
         // Use the extended feature implementations
+        setCompletionFeature(new UserDefinedCompletionFeature());
         setWorkspaceSymbolFeature(new UserDefinedWorkspaceSymbolFeature());
     }
 

src/main/java/com/redhat/devtools/lsp4ij/server/definition/launching/UserDefinedCompletionFeature.java

@@ -0,0 +1,31 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Red Hat Inc. and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+ * which is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+ *
+ * Contributors:
+ *     Red Hat Inc. - initial API and implementation
+ *******************************************************************************/
+package com.redhat.devtools.lsp4ij.server.definition.launching;
+
+import com.intellij.psi.PsiFile;
+import com.redhat.devtools.lsp4ij.client.features.LSPCompletionFeature;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Adds client-side code completion configuration features.
+ */
+public class UserDefinedCompletionFeature extends LSPCompletionFeature {
+
+    @Override
+    public boolean useContextAwareSorting(@NotNull PsiFile file) {
+        UserDefinedLanguageServerDefinition serverDefinition = (UserDefinedLanguageServerDefinition) getClientFeatures().getServerDefinition();
+        ClientConfigurationSettings clientConfiguration = serverDefinition.getLanguageServerClientConfiguration();
+        return clientConfiguration != null ? clientConfiguration.completion.useContextAwareSorting : super.useContextAwareSorting(file);
+    }
+}

src/main/resources/jsonSchema/clientSettings.schema.json

@@ -11,6 +11,19 @@
       "description": "Whether or not the language grammar is case-sensitive.",
       "default": false
     },
+    "completion": {
+      "type": "object",
+      "title": "Client-side completion configuration",
+      "additionalProperties": false,
+      "properties": {
+        "useContextAwareSorting": {
+          "type": "boolean",
+          "title": "Use context-aware completion sorting",
+          "description": "Whether or not client-side context-aware completion sorting should be used.",
+          "default": false
+        }
+      }
+    },
     "workspaceSymbol": {
       "type": "object",
       "title": "Client-side workspace symbol configuration",

src/test/java/com/redhat/devtools/lsp4ij/features/completion/CompletionItemComparatorTest.java

@@ -16,10 +16,11 @@
 import java.util.ArrayList;
 import java.util.List;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class CompletionItemComparatorTest {
-    private final CompletionItemComparator comparator = new CompletionItemComparator();
+    private final CompletionItemComparator comparator = new CompletionItemComparator(null, null, false);
 
     private final CompletionItem one = newItem("one", "1");
     private final CompletionItem nil = newItem("", null);