From aaec25a798352fc222f86ab3b299384575f51dc8 Mon Sep 17 00:00:00 2001
From: Mitch Curtis <mitch.curtis@qt.io>
Date: Wed, 27 Nov 2019 11:00:59 +0100
Subject: StackView: fix crash when recursively removing items

This can happen when e.g. calling clear() in Component.onDestruction
in response to a pop() call.

The patch fixes the crash by warning and returning early.

If users really need to do this, the clear() call can be delayed:

    Component.onDestruction: {
        Qt.callLater(function() { stackView.clear(StackView.Immediate) })
    }

Change-Id: If3cf07495bb34b96089522f44c36976bd6c62492
Fixes: QTBUG-80353
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
---
 tests/auto/controls/data/tst_stackview.qml | 100 +++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)

(limited to 'tests/auto')

diff --git a/tests/auto/controls/data/tst_stackview.qml b/tests/auto/controls/data/tst_stackview.qml
index a9fbf874..c6515f77 100644
--- a/tests/auto/controls/data/tst_stackview.qml
+++ b/tests/auto/controls/data/tst_stackview.qml
@@ -1245,4 +1245,104 @@ TestCase {
         gc()
         verify(control.initialItem)
     }
+
+    // Need to use this specific structure in order to reproduce the crash.
+    Component {
+        id: clearUponDestructionContainerComponent
+
+        Item {
+            id: container
+            objectName: "container"
+
+            property alias control: stackView
+            property var onDestructionCallback
+
+            property Component clearUponDestructionComponent: Component {
+                id: clearUponDestructionComponent
+
+                Item {
+                    objectName: "clearUponDestructionItem"
+                    Component.onDestruction: container.onDestructionCallback(stackView)
+                }
+            }
+
+            StackView {
+                id: stackView
+                initialItem: Item {
+                    objectName: "initialItem"
+                }
+            }
+        }
+    }
+
+    // QTBUG-80353
+    // Tests that calling clear() in Component.onDestruction in response to that
+    // item being removed (e.g. via an earlier call to clear()) results in a warning and not a crash.
+    function test_recursiveClearClear() {
+        let container = createTemporaryObject(clearUponDestructionContainerComponent, testCase,
+            { onDestructionCallback: function(stackView) { stackView.clear(StackView.Immediate) }})
+        verify(container)
+
+        let control = container.control
+        control.push(container.clearUponDestructionComponent, StackView.Immediate)
+
+        // Shouldn't crash.
+        ignoreWarning(new RegExp(".*cannot clear while already in the process of removing elements"))
+        control.clear(StackView.Immediate)
+    }
+
+    function test_recursivePopClear() {
+        let container = createTemporaryObject(clearUponDestructionContainerComponent, testCase,
+            { onDestructionCallback: function(stackView) { stackView.clear(StackView.Immediate) }})
+        verify(container)
+
+        let control = container.control
+        control.push(container.clearUponDestructionComponent, StackView.Immediate)
+
+        // Pop all items except the first, removing the second item we pushed in the process.
+        // Shouldn't crash.
+        ignoreWarning(new RegExp(".*cannot clear while already in the process of removing elements"))
+        control.pop(null, StackView.Immediate)
+    }
+
+    function test_recursivePopPop() {
+        let container = createTemporaryObject(clearUponDestructionContainerComponent, testCase,
+            { onDestructionCallback: function(stackView) { stackView.pop(null, StackView.Immediate) }})
+        verify(container)
+
+        let control = container.control
+        // Push an extra item so that we can call pop(null) and reproduce the conditions for the crash.
+        control.push(component, StackView.Immediate)
+        control.push(container.clearUponDestructionComponent, StackView.Immediate)
+
+        // Pop the top item, then pop down to the first item in response.
+        ignoreWarning(new RegExp(".*cannot pop while already in the process of removing elements"))
+        control.pop(StackView.Immediate)
+    }
+
+    function test_recursiveReplaceClear() {
+        let container = createTemporaryObject(clearUponDestructionContainerComponent, testCase,
+            { onDestructionCallback: function(stackView) { stackView.clear(StackView.Immediate) }})
+        verify(container)
+
+        let control = container.control
+        control.push(container.clearUponDestructionComponent, StackView.Immediate)
+
+        // Replace the top item, then clear in response.
+        ignoreWarning(new RegExp(".*cannot clear while already in the process of removing elements"))
+        control.replace(component, StackView.Immediate)
+    }
+
+    function test_recursiveClearReplace() {
+        let container = createTemporaryObject(clearUponDestructionContainerComponent, testCase,
+            { onDestructionCallback: function(stackView) { stackView.replace(component, StackView.Immediate) }})
+        verify(container)
+
+        let control = container.control
+        control.push(container.clearUponDestructionComponent, StackView.Immediate)
+
+        // Replace the top item, then clear in response.
+        ignoreWarning(new RegExp(".*cannot replace while already in the process of removing elements"))
+        control.clear(StackView.Immediate)
+    }
 }
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