Add feature toggle for completion word range fix

src/main/java/com/redhat/devtools/lsp4ij/LSPIJUtils.java

@@ -874,13 +874,38 @@ public static TextRange getWordRangeAt(@NotNull Document document,
     public static TextRange getWordRangeAt(@NotNull Document document,
                                            @Nullable PsiFile file,
                                            int offset) {
+        return getWordRangeAt(document, file, offset, false);
+    }
+
+    /**
+     * Returns the word range from the document at given offset and null otherwise.
+     *
+     * <code><pre>
+     *  - fo|o bar -> [foo]
+     *  - fo|o.bar() -> [foo]
+     *  - foo.b|ar() -> [bar]
+     *  - foo.bar(|) -> null
+     *  - foo  |  bar -> null
+     * </pre></code>
+     *
+     * @param document the document.
+     * @param file     the PsiFile or null otherwise.
+     * @param offset   the offset.
+     * @param excludeWhitespace if {@link PsiWhiteSpace whitespace} should not be returned
+     * @return the word range from the document at given offset and null otherwise.
+     */
+    @Nullable
+    public static TextRange getWordRangeAt(@NotNull Document document,
+                                           @Nullable PsiFile file,
+                                           int offset,
+                                           boolean excludeWhitespace) {
         if (offset > document.getTextLength()) {
             offset = document.getTextLength() - 1;
         }
         if (file != null && !SimpleLanguageUtils.isSupported(file.getLanguage())) {
             // It is not TextMate, TEXT file (since those language doesn't tokenize the file)
             // Try to use the PsiElement text range found at the given offset
-            TextRange textRange = findBestTextRangeAt(file, offset);
+            TextRange textRange = findBestTextRangeAt(file, offset, excludeWhitespace);
             if (textRange != null) {
                 return textRange;
             }
@@ -896,11 +921,11 @@ public static TextRange getWordRangeAt(@NotNull Document document,
         return (start < end) ? new TextRange(start, end) : null;
     }
 
-    private static TextRange findBestTextRangeAt(@Nullable PsiFile file, int offset) {
+    private static TextRange findBestTextRangeAt(@Nullable PsiFile file, int offset, boolean excludeWhitespace) {
         PsiElement element = file != null ? file.findElementAt(Math.max(offset - 1, 0)) : null;
         if (element != null) {
-            // When element is whitespace, completion should never replace it - that's not prefix
-            if (element instanceof PsiWhiteSpace) {
+            // When element is whitespace - exclude it if we need
+            if (excludeWhitespace && element instanceof PsiWhiteSpace) {
                 return null;
             }
             TextRange textRange = element.getTextRange();

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

@@ -335,4 +335,22 @@ public boolean isMultipleCaretsSupported(@NotNull PsiFile file) {
         // Default to enabled
         return true;
     }
+
+    /**
+     * Whether to exclude {@link com.intellij.psi.PsiWhiteSpace whitespace token} from completion prefix.
+     *
+     * <p>
+     * When disabled (the default), invoking a completion inside whitespace token
+     * will make this token a completion prefix, which means it will be replaced by {@code insertText}
+     * when user accept completion.
+     * When disabled, whitespace token will not be prefix, so when user accept completion,
+     * it will be just inserted at the caret, leaving whitespace as-is.
+     * </p>
+     * @param file the file
+     * @return {@code true} if {@link com.intellij.psi.PsiWhiteSpace whitespace token} should not be completion prefix
+     */
+    public boolean excludeWhitespaceFromCompletionPrefix(@NotNull PsiFile file) {
+        // Disabled by default to leave original behavior
+        return false;
+    }
 }

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

@@ -102,7 +102,11 @@ public LSPCompletionProposal(@NotNull CompletionItem item,
         this.editor = completionContext.getParameters().getEditor();
         this.completionContext = completionContext;
         this.completionOffset = completionContext.getParameters().getOffset();
-        this.prefixStartOffset = getPrefixStartOffset(editor.getDocument(), completionOffset);
+        this.prefixStartOffset = getPrefixStartOffset(
+            editor.getDocument(),
+            completionOffset,
+            completionFeature.excludeWhitespaceFromCompletionPrefix(completionContext.getParameters().getOriginalFile())
+        );
         this.completionFeature = completionFeature;
         putUserData(CodeCompletionHandlerBase.DIRECT_INSERTION, true);
     }
@@ -663,7 +667,7 @@ private boolean isSelectedCompletionItem() {
     // --------------- Prefix start offset
 
 
-    private int getPrefixStartOffset(@NotNull Document document, int completionOffset) {
+    private int getPrefixStartOffset(@NotNull Document document, int completionOffset, boolean excludeWhitespace) {
         Either<TextEdit, InsertReplaceEdit> textEdit = this.item.getTextEdit();
         if (textEdit != null) {
             // case 1: text edit is defined,
@@ -673,7 +677,7 @@ private int getPrefixStartOffset(@NotNull Document document, int completionOffse
 
         // case 2: text edit is undefined, try to compute the prefix start offset by using insertText
         String insertText = getInsertText();
-        Integer prefixStartOffset = computePrefixStartFromInsertText(document, file, completionOffset, insertText);
+        Integer prefixStartOffset = computePrefixStartFromInsertText(document, file, completionOffset, insertText, excludeWhitespace);
         return Objects.requireNonNullElse(prefixStartOffset, completionOffset);
     }
 

src/main/java/com/redhat/devtools/lsp4ij/internal/CompletionUtils.java

@@ -1,68 +1,77 @@
-/*******************************************************************************
- * Copyright (c) 2025 Red Hat, Inc.
- * Distributed under license by Red Hat, Inc. All rights reserved.
- * This program is made available under the terms of the
- * Eclipse Public License v2.0 which accompanies this distribution,
- * and is available at https://www.eclipse.org/legal/epl-v20.html
- *
- * Contributors:
- * Red Hat, Inc. - initial API and implementation
- *****************************************************************************/
-package com.redhat.devtools.lsp4ij.internal;
-
-import com.intellij.openapi.editor.Document;
-import com.intellij.openapi.util.TextRange;
-import com.intellij.psi.PsiFile;
-import com.redhat.devtools.lsp4ij.LSPIJUtils;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-/**
- * LSP/DAP Completion utilities.
- */
-public class CompletionUtils {
-
-    @Nullable
-    public static Integer computePrefixStartFromInsertText(@NotNull Document document,
-                                                           @Nullable PsiFile file,
-                                                           int completionOffset,
-                                                           String insertText) {
-
-        // case 2.1: first strategy, we collect word range at
-        // ex :
-        // insertText= '(let [${1:binding} ${2:value}])'
-        // document= le
-        // we have to return |le as prefix start offset
-
-        TextRange wordRange = LSPIJUtils.getWordRangeAt(document, file, completionOffset);
-        if (wordRange != null) {
-            return wordRange.getStartOffset();
-        }
-
-        // case 2.2: second strategy, we check if the left content of the completion offset
-        // matches the full insertText left content
-        // ex :
-        // insertText= 'foo.bar'
-        // document= {foo.b|}
-        // we have to return {| as prefix start offset
-
-        return getPrefixStartOffsetWhichMatchesLeftContent(document, completionOffset, insertText);
-    }
-
-    @Nullable
-    private static Integer getPrefixStartOffsetWhichMatchesLeftContent(@NotNull Document document,
-                                                                       int completionOffset,
-                                                                       @NotNull String insertText) {
-        int startOffset = Math.max(0, completionOffset - insertText.length());
-        int endOffset = startOffset + Math.min(insertText.length(), completionOffset);
-        String subDoc = document.getText(new TextRange(startOffset, endOffset)); // "".ch
-        for (int i = 0; i < insertText.length() && i < completionOffset; i++) {
-            String tentativeCommonString = subDoc.substring(i);
-            if (insertText.startsWith(tentativeCommonString)) {
-                return completionOffset - tentativeCommonString.length();
-            }
-        }
-        return null;
-    }
-
-}
+/*******************************************************************************
+ * Copyright (c) 2025 Red Hat, Inc.
+ * Distributed under license by Red Hat, Inc. All rights reserved.
+ * This program is made available under the terms of the
+ * Eclipse Public License v2.0 which accompanies this distribution,
+ * and is available at https://www.eclipse.org/legal/epl-v20.html
+ *
+ * Contributors:
+ * Red Hat, Inc. - initial API and implementation
+ *****************************************************************************/
+package com.redhat.devtools.lsp4ij.internal;
+
+import com.intellij.openapi.editor.Document;
+import com.intellij.openapi.util.TextRange;
+import com.intellij.psi.PsiFile;
+import com.redhat.devtools.lsp4ij.LSPIJUtils;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * LSP/DAP Completion utilities.
+ */
+public class CompletionUtils {
+
+    @Nullable
+    public static Integer computePrefixStartFromInsertText(@NotNull Document document,
+                                                           @Nullable PsiFile file,
+                                                           int completionOffset,
+                                                           String insertText) {
+        return computePrefixStartFromInsertText(document, file, completionOffset, insertText, false);
+    }
+
+    @Nullable
+    public static Integer computePrefixStartFromInsertText(@NotNull Document document,
+                                                           @Nullable PsiFile file,
+                                                           int completionOffset,
+                                                           String insertText,
+                                                           boolean excludeWhitespace) {
+
+        // case 2.1: first strategy, we collect word range at
+        // ex :
+        // insertText= '(let [${1:binding} ${2:value}])'
+        // document= le
+        // we have to return |le as prefix start offset
+
+        TextRange wordRange = LSPIJUtils.getWordRangeAt(document, file, completionOffset, excludeWhitespace);
+        if (wordRange != null) {
+            return wordRange.getStartOffset();
+        }
+
+        // case 2.2: second strategy, we check if the left content of the completion offset
+        // matches the full insertText left content
+        // ex :
+        // insertText= 'foo.bar'
+        // document= {foo.b|}
+        // we have to return {| as prefix start offset
+
+        return getPrefixStartOffsetWhichMatchesLeftContent(document, completionOffset, insertText);
+    }
+
+    @Nullable
+    private static Integer getPrefixStartOffsetWhichMatchesLeftContent(@NotNull Document document,
+                                                                       int completionOffset,
+                                                                       @NotNull String insertText) {
+        int startOffset = Math.max(0, completionOffset - insertText.length());
+        int endOffset = startOffset + Math.min(insertText.length(), completionOffset);
+        String subDoc = document.getText(new TextRange(startOffset, endOffset)); // "".ch
+        for (int i = 0; i < insertText.length() && i < completionOffset; i++) {
+            String tentativeCommonString = subDoc.substring(i);
+            if (insertText.startsWith(tentativeCommonString)) {
+                return completionOffset - tentativeCommonString.length();
+            }
+        }
+        return null;
+    }
+
+}

src/main/java/com/redhat/devtools/lsp4ij/usages/LSPUsageTargetProvider.java

@@ -143,7 +143,7 @@ public class LSPUsageTargetProvider implements UsageTargetProvider {
      */
     @NotNull
     private static UsageTarget[] getLSPTargets(@NotNull Editor editor, @NotNull PsiFile file) {
-        TextRange targetTextRange = LSPIJUtils.getWordRangeAt(editor.getDocument(), file, editor.getCaretModel().getOffset());
+        TextRange targetTextRange = LSPIJUtils.getWordRangeAt(editor.getDocument(), file, editor.getCaretModel().getOffset(), false);
         if (targetTextRange == null) {
             return UsageTarget.EMPTY_ARRAY;
         }