fix(amazonq): clicking chat diff repeatedly only opens one tab instead of creating duplicates

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/AmazonQDiffVirtualFile.kt

@@ -0,0 +1,37 @@
+// Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.jetbrains.services.amazonq.lsp
+
+import com.intellij.diff.chains.SimpleDiffRequestChain
+import com.intellij.diff.editor.ChainDiffVirtualFile
+import com.intellij.diff.editor.DiffEditorTabFilesManager
+import com.intellij.diff.requests.SimpleDiffRequest
+import com.intellij.openapi.fileEditor.FileEditorManager
+import com.intellij.openapi.project.Project
+import software.aws.toolkits.resources.message
+
+/**
+ * A virtual file that represents an AmazonQ diff view.
+ * This class allows us to identify diff files created by AmazonQ.
+ */
+class AmazonQDiffVirtualFile(
+    diffChain: SimpleDiffRequestChain,
+    name: String,
+) : ChainDiffVirtualFile(diffChain, name) {
+    companion object {
+        fun openDiff(project: Project, diffRequest: SimpleDiffRequest) {
+            // Find any existing AmazonQ diff files
+            val fileEditorManager = FileEditorManager.getInstance(project)
+            val existingDiffFiles = fileEditorManager.openFiles.filterIsInstance<AmazonQDiffVirtualFile>()
+
+            // Close existing diff files
+            existingDiffFiles.forEach { fileEditorManager.closeFile(it) }
+
+            // Create and open the new diff file
+            val diffChain = SimpleDiffRequestChain(diffRequest)
+            val diffVirtualFile = AmazonQDiffVirtualFile(diffChain, diffRequest.title ?: message("aws.q.lsp.client.diff_message"))
+            DiffEditorTabFilesManager.getInstance(project).showDiffFile(diffVirtualFile, true)
+        }
+    }
+}

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/AmazonQLanguageClientImpl.kt

@@ -4,8 +4,6 @@
 package software.aws.toolkits.jetbrains.services.amazonq.lsp
 
 import com.intellij.diff.DiffContentFactory
-import com.intellij.diff.DiffManager
-import com.intellij.diff.DiffManagerEx
 import com.intellij.diff.requests.SimpleDiffRequest
 import com.intellij.openapi.application.ApplicationManager
 import com.intellij.openapi.fileChooser.FileChooserFactory
@@ -363,11 +361,12 @@
                             else -> "Modified"
                         }
                     )
-                    (DiffManager.getInstance() as DiffManagerEx).showDiffBuiltin(project, diffRequest)
+
+                    AmazonQDiffVirtualFile.openDiff(project, diffRequest)
                 } catch (e: Exception) {
                     LOG.warn { "Failed to open file diff: ${e.message}" }
                 } finally {
-                    // Clean up the temporary file
+                    // Clean up the temporary file used for syntax highlight
                     try {
                         tempPath?.let { Files.deleteIfExists(it) }
                     } catch (e: Exception) {