Fix crash in kit's variable chooser if Qt version is removed

Currently the variable chooser cannot update itself if a sub-expander
changes or even is deleted, leading to inconsistencies and crashes if
that happens.
Make the Qt version sub-macroexpander be available for the kit even if
currently is no Qt version selected. For this we create a macro expander
that delegates to the kit's Qt version if possible at variable
substitution time, instead of taking the Qt version's expander directly.

Task-number: QTCREATORBUG-19900
Task-number: QTCREATORBUG-19901
Change-Id: I2bd9b3db60bf6e292abf2a29e0697dc5385709cd
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

1 files changed, 17 insertions, 5 deletions

diff --git a/src/plugins/qtsupport/qtkitinformation.cpp b/src/plugins/qtsupport/qtkitinformation.cpp
index 1653b48a16d..3e55fb3fd04 100644
--- a/src/plugins/qtsupport/qtkitinformation.cpp
+++ b/src/plugins/qtsupport/qtkitinformation.cpp
@@ -124,14 +124,26 @@ ProjectExplorer::IOutputParser *QtKitInformation::createOutputParser(const Proje
     return nullptr;
 }
 
+class QtMacroSubProvider
+{
+public:
+    QtMacroSubProvider(Kit *kit)
+        : expander(BaseQtVersion::createMacroExpander(
+              [kit] { return QtKitInformation::qtVersion(kit); }))
+    {}
+
+    MacroExpander *operator()() const
+    {
+        return expander.get();
+    }
+
+    std::shared_ptr<MacroExpander> expander;
+};
+
 void QtKitInformation::addToMacroExpander(Kit *kit, MacroExpander *expander) const
 {
     QTC_ASSERT(kit, return);
-    expander->registerSubProvider(
-                [kit]() -> MacroExpander * {
-                    BaseQtVersion *version = qtVersion(kit);
-                    return version ? version->macroExpander() : nullptr;
-                });
+    expander->registerSubProvider(QtMacroSubProvider(kit));
 
     expander->registerVariable("Qt:Name", tr("Name of Qt Version"),
                 [kit]() -> QString {