Fix profile selection errors and EDT threading violations

Fixes #6039

This commit addresses two related issues:

1. IllegalStateException: "You don't have access to the resource"
   - Modified listRegionProfiles() to return null for empty profiles
     instead of throwing an IllegalStateException
   - Updated callers to handle null/empty profiles gracefully

2. EDT Threading Violation when selecting Q profile
   - Wrapped QRegionProfileDialog.show() in runInEdt to ensure
     dialog is shown on Event Dispatch Thread
   - Made AsyncComboBox.repaint() calls EDT-safe using invokeLater

Files changed:
- QRegionProfileManager.kt: Return null for empty profiles
- ChatCommunicationManager.kt: Add runInEdt wrapper for dialog
- CodeWhispererModelConfigurator.kt: Handle null profiles gracefully
- QRegionProfileDialog.kt: Handle empty profiles with telemetry
- AsyncComboBox.kt: EDT-safe repaint calls

Author: amit-lulla

.changes/next-release/bugfix-115a739a-007b-4bf6-9f07-6e50cfbfa029.json

@@ -0,0 +1,4 @@
+{
+  "type" : "bugfix",
+  "description" : "Amazon Q: Fix profile selection errors and EDT threading violations (#6039)"
+}

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

@@ -5,6 +5,7 @@ package software.aws.toolkits.jetbrains.services.amazonq.lsp.flareChat
 
 import com.google.gson.Gson
 import com.google.gson.JsonObject
+import com.intellij.openapi.application.runInEdt
 import com.intellij.openapi.components.Service
 import com.intellij.openapi.components.service
 import com.intellij.openapi.project.Project
@@ -203,10 +204,13 @@ class ChatCommunicationManager(private val project: Project, private val cs: Cor
                         project.messageBus.syncPublisher(QRegionProfileSelectedListener.TOPIC)
                             .onProfileSelected(project, QRegionProfileManager.getInstance().activeProfile(project))
                     } else {
-                        QRegionProfileDialog(
-                            project,
-                            selectedProfile = null
-                        ).show()
+                        // Wrap in runInEdt to ensure dialog is shown on Event Dispatch Thread
+                        runInEdt {
+                            QRegionProfileDialog(
+                                project,
+                                selectedProfile = null
+                            ).show()
+                        }
                     }
 
                     return

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/profile/QRegionProfileDialog.kt

@@ -75,10 +75,21 @@ class QRegionProfileDialog(
 
             combo.proposeModelUpdate { model ->
                 try {
-                    QRegionProfileManager.getInstance().listRegionProfiles(project)?.forEach {
-                        model.addElement(it)
-                    } ?: error("Attempted to fetch profiles while there does not exist")
-
+                    val profiles = QRegionProfileManager.getInstance().listRegionProfiles(project)
+                    // Handle empty/null profiles gracefully instead of throwing
+                    if (profiles.isNullOrEmpty()) {
+                        val conn = ToolkitConnectionManager.getInstance(project).activeConnectionForFeature(QConnection.getInstance()) as? AwsBearerTokenConnection
+                        Telemetry.amazonq.didSelectProfile.use { span ->
+                            span.source(QProfileSwitchIntent.User.value)
+                                .amazonQProfileRegion("not-set")
+                                .ssoRegion(conn?.region)
+                                .credentialStartUrl(conn?.startUrl)
+                                .result(MetricResult.Failed)
+                                .reason("No profiles available")
+                        }
+                        return@proposeModelUpdate
+                    }
+                    profiles.forEach { model.addElement(it) }
                     model.selectedItem = selectedProfile
                 } catch (e: Exception) {
                     val conn = ToolkitConnectionManager.getInstance(project).activeConnectionForFeature(QConnection.getInstance()) as? AwsBearerTokenConnection

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/profile/QRegionProfileManager.kt

@@ -110,9 +110,11 @@ class QRegionProfileManager : PersistentStateComponent<QProfileState>, Disposabl
             if (mappedProfiles.size == 1) {
                 switchProfile(project, mappedProfiles.first(), intent = QProfileSwitchIntent.Update)
             }
-            mappedProfiles.takeIf { it.isNotEmpty() }?.also {
-                connectionIdToProfileCount[connection.id] = it.size
-            } ?: error("You don't have access to the resource")
+            // Return null for empty profiles instead of throwing, let callers handle gracefully
+            if (mappedProfiles.isNotEmpty()) {
+                connectionIdToProfileCount[connection.id] = mappedProfiles.size
+            }
+            mappedProfiles.takeIf { it.isNotEmpty() }
         } catch (e: Exception) {
             if (e is AccessDeniedException) {
                 LOG.warn { "Failed to list region profiles: ${e.message}" }

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/codewhisperer/customization/CodeWhispererModelConfigurator.kt

@@ -130,7 +130,10 @@ class DefaultCodeWhispererModelConfigurator(
         calculateIfIamIdentityCenterConnection(project) {
             // 1. fetch all profiles, invoke fetch customizations API and get result for each profile and aggregate all the results
             val profiles = QRegionProfileManager.getInstance().listRegionProfiles(project)
-                ?: error("Attempted to fetch profiles while there does not exist")
+            // Return empty list when no profiles available instead of throwing
+            if (profiles.isNullOrEmpty()) {
+                return@calculateIfIamIdentityCenterConnection emptyList()
+            }
 
             val customizations = profiles.flatMap { profile ->
                 runCatching {

plugins/core/jetbrains-community/src/software/aws/toolkits/jetbrains/ui/AsyncComboBox.kt

@@ -4,6 +4,7 @@
 package software.aws.toolkits.jetbrains.ui
 
 import com.intellij.openapi.Disposable
+import com.intellij.openapi.application.ApplicationManager
 import com.intellij.openapi.application.ModalityState
 import com.intellij.openapi.progress.EmptyProgressIndicator
 import com.intellij.openapi.progress.ProgressIndicator
@@ -92,7 +93,8 @@ class AsyncComboBox<T> private constructor(
         currentIndicator?.cancel()
         loading.set(true)
         removeAllItems()
-        repaint()
+        // Ensure repaint happens on EDT for thread safety
+        ApplicationManager.getApplication().invokeLater { repaint() }
         val indicator = EmptyProgressIndicator(ModalityState.any()).also {
             currentIndicator = it
         }
@@ -105,7 +107,8 @@ class AsyncComboBox<T> private constructor(
                             newModel.invoke(delegatedComboBoxModel(indicator))
                         }.invokeOnCompletion {
                             loading.set(false)
-                            repaint()
+                            // Ensure repaint happens on EDT for thread safety
+                            ApplicationManager.getApplication().invokeLater { repaint() }
                         }
                     },
                     indicator