ProjectExplorer: Fix some corner cases in signal subscriptions

Handle cases where targets/projects are removed and then added again.

This is currently not done anywhere, but there should not be nasty
surprises when somebody decides to do that later.

Change-Id: I47f9b4a1577f2021bcee87ccdd5435e3628b2a95
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/projectexplorer/subscription.cpp

@@ -27,6 +27,7 @@
 
 #include "project.h"
 #include "projectconfiguration.h"
+#include "session.h"
 #include "target.h"
 
 #include <utils/qtcassert.h>
@@ -37,13 +38,8 @@ namespace Internal {
 Subscription::Subscription(const Subscription::Connector &s, const QObject *receiver, QObject *parent) :
     QObject(parent), m_subscriber(s)
 {
-    if (receiver != parent) {
-        connect(receiver, &QObject::destroyed, this, [this]() {
-            unsubscribeAll();
-            m_subscriber = Connector(); // Reset subscriber
-            deleteLater();
-        });
-    }
+    if (receiver != parent)
+        connect(receiver, &QObject::destroyed, this, &Subscription::destroy);
 }
 
 Subscription::~Subscription()
@@ -58,12 +54,7 @@ void Subscription::subscribe(ProjectConfiguration *pc)
 
     connectTo(pc);
 
-    if (auto p = qobject_cast<Project *>(pc)) {
-        for (Target *t : p->targets()) {
-            for (ProjectConfiguration *pc : t->projectConfigurations())
-                connectTo(pc);
-        }
-    } else if (auto t = qobject_cast<Target *>(pc)) {
+    if (auto t = qobject_cast<Target *>(pc)) {
         for (ProjectConfiguration *pc : t->projectConfigurations())
             connectTo(pc);
     }
@@ -73,14 +64,9 @@ void Subscription::unsubscribe(ProjectConfiguration *pc)
 {
     disconnectFrom(pc);
 
-    if (auto p = qobject_cast<Project *>(pc)) {
-        for (Target *t : p->targets()) {
-            for (ProjectConfiguration *pc : t->projectConfigurations())
-                unsubscribe(pc);
-        }
-    } else if (auto t = qobject_cast<Target *>(pc)) {
+    if (auto t = qobject_cast<Target *>(pc)) {
         for (ProjectConfiguration *pc : t->projectConfigurations())
-            unsubscribe(pc);
+            disconnectFrom(pc);
     }
 }
 
@@ -93,6 +79,9 @@ void Subscription::unsubscribeAll()
 
 void Subscription::connectTo(ProjectConfiguration *pc)
 {
+    if (!m_subscriber)
+        return; // May happen during shutdown of a subscription
+
     QTC_ASSERT(!m_connections.contains(pc), return);
 
     QMetaObject::Connection conn = m_subscriber(pc);
@@ -110,18 +99,27 @@ void Subscription::disconnectFrom(ProjectConfiguration *pc)
     m_connections.remove(pc);
 }
 
+void Subscription::destroy()
+{
+    unsubscribeAll();
+    m_subscriber = Connector(); // Reset subscriber
+    deleteLater();
+}
+
 ProjectSubscription::ProjectSubscription(const Subscription::Connector &s, const QObject *r,
                                          Project *p) :
     Subscription(s, r, p)
 {
-    if (m_subscriber) {
-        for (const Target *t : p->targets()) {
-            for (ProjectConfiguration *pc : t->projectConfigurations())
-                m_subscriber(pc);
-        }
-        connect(p, &Project::addedProjectConfiguration, this, &ProjectSubscription::subscribe);
-        connect(p, &Project::removedProjectConfiguration, this, &ProjectSubscription::unsubscribe);
-    }
+    QTC_ASSERT(m_subscriber, return);
+
+    for (Target *t : p->targets())
+        subscribe(t);
+
+    // Disconnect on removal of a project, to make it save to remove/add a project:
+    connect(SessionManager::instance(), &SessionManager::projectRemoved,
+            this, [this, p](Project *reported) { if (p == reported) { destroy(); } });
+    connect(p, &Project::addedProjectConfiguration, this, &ProjectSubscription::subscribe);
+    connect(p, &Project::removedProjectConfiguration, this, &ProjectSubscription::unsubscribe);
 }
 
 ProjectSubscription::~ProjectSubscription() = default;
@@ -130,8 +128,13 @@ TargetSubscription::TargetSubscription(const Subscription::Connector &s, const Q
                                        Target *t) :
     Subscription(s, r, t)
 {
-    for (ProjectConfiguration *pc : t->projectConfigurations())
-        m_subscriber(pc);
+    QTC_ASSERT(m_subscriber, return);
+
+    subscribe(t);
+
+    // Disconnect on removal of a target, to make it save to remove/add a target:
+    connect(t->project(), &Project::removedTarget, this,
+            [t, this](const Target *reportedTarget) { if (t == reportedTarget) { destroy(); } });
     connect(t, &Target::addedProjectConfiguration, this, &TargetSubscription::subscribe);
     connect(t, &Target::removedProjectConfiguration, this, &TargetSubscription::unsubscribe);
 }

src/plugins/projectexplorer/subscription.h

@@ -57,6 +57,8 @@ protected:
     void connectTo(ProjectConfiguration *pc);
     void disconnectFrom(ProjectConfiguration *pc);
 
+    void destroy();
+
     Connector m_subscriber;
     QHash<ProjectConfiguration *, QMetaObject::Connection> m_connections;
 };