From 38212bf88f9bfbc5bd8c5745cf09400c0578aed2 Mon Sep 17 00:00:00 2001
From: Scott Wells <scott@illuminatedcloud.com>
Date: Sat, 30 Nov 2024 10:13:06 -0600
Subject: [PATCH] Issue 638 - This is a more comprehensive change to avoid
 adding duplicate completions. The real issue is that
 WordCompletionContributor is invoked automatically by
 TextMateCompletionContributor, and very often LSP languages are hosted in
 TextMate-based editors. Now we try to disable WordCompletionContributor by
 setting a process-level user data value temporarily while collecting
 completions from other contributors, and the original value is reliably
 restored (though since the process is transient, that's probably not
 necessary). If we're able to disable WordCompletionContributor, we just run
 all remaining completion contributors; if not, we run all remaining
 completion contributors filtering added completions to exclude duplicate
 lookup strings. That allow the behavior to degrade gracefully while still
 yielding an improved signal-to-noise ratio on added completions.

---
 .../completion/LSPCompletionContributor.java  | 52 ++++++++++++++-----
 1 file changed, 38 insertions(+), 14 deletions(-)

diff --git a/src/main/java/com/redhat/devtools/lsp4ij/features/completion/LSPCompletionContributor.java b/src/main/java/com/redhat/devtools/lsp4ij/features/completion/LSPCompletionContributor.java
index 53a70a274..163c47653 100644
--- a/src/main/java/com/redhat/devtools/lsp4ij/features/completion/LSPCompletionContributor.java
+++ b/src/main/java/com/redhat/devtools/lsp4ij/features/completion/LSPCompletionContributor.java
@@ -10,15 +10,14 @@
  ******************************************************************************/
 package com.redhat.devtools.lsp4ij.features.completion;
 
-import com.intellij.codeInsight.completion.CompletionContributor;
-import com.intellij.codeInsight.completion.CompletionParameters;
-import com.intellij.codeInsight.completion.CompletionResultSet;
+import com.intellij.codeInsight.completion.*;
 import com.intellij.codeInsight.lookup.*;
 import com.intellij.codeInsight.lookup.impl.LookupImpl;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.progress.ProcessCanceledException;
 import com.intellij.openapi.progress.ProgressManager;
+import com.intellij.openapi.util.UserDataHolder;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiFile;
 import com.intellij.util.containers.ContainerUtil;
@@ -142,20 +141,45 @@ private void addCompletionItems(@NotNull CompletionParameters parameters,
         }
 
         // If completions were added from LSP and this is auto-completion or the explicit completion trigger was typed
-        // only once, add completions from other contributors carefully to avoid duplicates, specifically from the word
-        // completion contributor
+        // only once, add completions from other all other contributors except for the word completion contributor.
+        // Note that the word completion contributor only really kicks in when LSP completions are added in the context
+        // of a TextMate file (see TextMateCompletionContributor), but that's going to be very common for LSP usage
+        // since it's often adding (pseudo-)language support when not already present in the host JetBrains IDE.
         if ((size > 0) && (parameters.getInvocationCount() < 2)) {
+            // Stop standard processing
             result.stopHere();
-            result.runRemainingContributors(parameters, completionResult -> {
-                LookupElement lookupElement = completionResult.getLookupElement();
-                if (lookupElement != null) {
-                    String lookupString = lookupElement.getLookupString();
-                    if (!addedLookupStrings.contains(lookupString)) {
-                        result.consume(lookupElement);
-                        addedLookupStrings.add(lookupString);
-                    }
+
+            // Try to disable word completion by temporarily setting FORBID_WORD_COMPLETION=true on the completion process
+            CompletionProcess completionProcess = parameters.getProcess();
+            UserDataHolder userDataHolder = completionProcess instanceof UserDataHolder ? (UserDataHolder) completionProcess : null;
+            boolean originalForbidWordCompletion = false;
+            if (userDataHolder != null) {
+                originalForbidWordCompletion = userDataHolder.getUserData(BaseCompletionService.FORBID_WORD_COMPLETION) == Boolean.TRUE;
+                userDataHolder.putUserData(BaseCompletionService.FORBID_WORD_COMPLETION, true);
+            }
+            try {
+                if (userDataHolder != null) {
+                    // If we disabled word completion, just run all remaining contributors
+                    result.runRemainingContributors(parameters, true);
+                } else {
+                    // If not, run all remaining contributors and only add results with distinct lookup strings
+                    result.runRemainingContributors(parameters, completionResult -> {
+                        LookupElement lookupElement = completionResult.getLookupElement();
+                        if (lookupElement != null) {
+                            String lookupString = lookupElement.getLookupString();
+                            if (!addedLookupStrings.contains(lookupString)) {
+                                result.consume(lookupElement);
+                                addedLookupStrings.add(lookupString);
+                            }
+                        }
+                    });
                 }
-            });
+            } finally {
+                // If appropriate, re-enable word completion
+                if (userDataHolder != null) {
+                    userDataHolder.putUserData(BaseCompletionService.FORBID_WORD_COMPLETION, originalForbidWordCompletion);
+                }
+            }
         }
     }