QbsProjectManager: Fix infinite loop on per-product build.

- Setting the QFuture result is not enough, we also need to emit the
  finished() signal.
- Never fail silently; use soft asserts for things that shouldn't happen
  and compile pane output for things that can.

Task-number: QBS-705
Change-Id: I4dad18c2ad573a92f2a0c5aa92b596851c56541e
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/qbsprojectmanager/qbsbuildstep.cpp

@@ -365,10 +365,12 @@ void QbsBuildStep::build()
     options.setFilesToConsider(m_changedFiles);
     options.setActiveFileTags(m_activeFileTags);
 
-    m_job = qbsProject()->build(options, m_products);
-
+    QString error;
+    m_job = qbsProject()->build(options, m_products, error);
     if (!m_job) {
+        emit addOutput(error, ErrorMessageOutput);
         m_fi->reportResult(false);
+        emit finished();
         return;
     }
 

src/plugins/qbsprojectmanager/qbscleanstep.cpp

@@ -105,6 +105,7 @@ void QbsCleanStep::run(QFutureInterface<bool> &fi)
 
     if (!m_job) {
         m_fi->reportResult(false);
+        emit finished();
         return;
     }
 

src/plugins/qbsprojectmanager/qbsinstallstep.cpp

@@ -98,6 +98,7 @@ void QbsInstallStep::run(QFutureInterface<bool> &fi)
 
     if (!m_job) {
         m_fi->reportResult(false);
+        emit finished();
         return;
     }
 

src/plugins/qbsprojectmanager/qbsproject.cpp

@@ -344,13 +344,15 @@ void QbsProject::invalidate()
     prepareForParsing();
 }
 
-qbs::BuildJob *QbsProject::build(const qbs::BuildOptions &opts, QStringList productNames)
+qbs::BuildJob *QbsProject::build(const qbs::BuildOptions &opts, QStringList productNames,
+                                 QString &error)
 {
-    if (!qbsProject().isValid() || isParsing())
-        return 0;
-    if (productNames.isEmpty()) {
+    QTC_ASSERT(qbsProject().isValid(), return 0);
+    QTC_ASSERT(!isParsing(), return 0);
+
+    if (productNames.isEmpty())
         return qbsProject().buildAllProducts(opts);
-    } else {
+
     QList<qbs::ProductData> products;
     foreach (const QString &productName, productNames) {
         bool found = false;
@@ -361,12 +363,13 @@ qbs::BuildJob *QbsProject::build(const qbs::BuildOptions &opts, QStringList prod
                 break;
             }
         }
-            if (!found)
+        if (!found) {
+            error = QLatin1String("Cannot build: Selected products do not exist anymore."); // TODO: Use tr() in 3.4
             return 0;
         }
+    }
 
     return qbsProject().buildSomeProducts(products, opts);
-    }
 }
 
 qbs::CleanJob *QbsProject::clean(const qbs::CleanOptions &opts)

src/plugins/qbsprojectmanager/qbsproject.h

@@ -84,7 +84,7 @@ public:
             const QString &newPath, const qbs::ProductData &productData,
             const qbs::GroupData &groupData);
 
-    qbs::BuildJob *build(const qbs::BuildOptions &opts, QStringList products = QStringList());
+    qbs::BuildJob *build(const qbs::BuildOptions &opts, QStringList products, QString &error);
     qbs::CleanJob *clean(const qbs::CleanOptions &opts);
     qbs::InstallJob *install(const qbs::InstallOptions &opts);