Fix potential infinite loops in generators combined with section filter

The problem was that under specific circumstances, namely that none
of their children progressed, `GeneratorTracker` will not progress.
This was changed recently, to allow for code like this, where a
`SECTION` follows a `GENERATE` at the same level:

```cpp
SECTION("A") {}
auto a = GENERATE(1, 2);
SECTION("B") {}
```

However, this interacted badly with `SECTION` filters (`-c foo`),
as they could deactivate all `SECTION`s below a generator, and thus
stop it from progressing forever. This commit makes GeneratorTracker
check whether there are any filters active, and if they are, it checks
whether its section-children can ever run.

Fixes #2025

include/internal/catch_run_context.cpp

@@ -71,13 +71,53 @@ namespace Catch {
                 // `SECTION`s.
                 // **The check for m_children.empty cannot be removed**.
                 // doing so would break `GENERATE` _not_ followed by `SECTION`s.
-                const bool should_wait_for_child =
-                    !m_children.empty() &&
-                    std::find_if( m_children.begin(),
-                                  m_children.end(),
-                                  []( TestCaseTracking::ITrackerPtr tracker ) {
-                                      return tracker->hasStarted();
-                                  } ) == m_children.end();
+                const bool should_wait_for_child = [&]() {
+                    // No children -> nobody to wait for
+                    if ( m_children.empty() ) {
+                        return false;
+                    }
+                    // If at least one child started executing, don't wait
+                    if ( std::find_if(
+                             m_children.begin(),
+                             m_children.end(),
+                             []( TestCaseTracking::ITrackerPtr tracker ) {
+                                 return tracker->hasStarted();
+                             } ) != m_children.end() ) {
+                        return false;
+                    }
+
+                    // No children have started. We need to check if they _can_
+                    // start, and thus we should wait for them, or they cannot
+                    // start (due to filters), and we shouldn't wait for them
+                    auto* parent = m_parent;
+                    // This is safe: there is always at least one section
+                    // tracker in a test case tracking tree
+                    while ( !parent->isSectionTracker() ) {
+                        parent = &( parent->parent() );
+                    }
+                    assert( parent &&
+                            "Missing root (test case) level section" );
+
+                    auto const& parentSection =
+                        static_cast<SectionTracker&>( *parent );
+                    auto const& filters = parentSection.getFilters();
+                    // No filters -> no restrictions on running sections
+                    if ( filters.empty() ) {
+                        return true;
+                    }
+
+                    for ( auto const& child : m_children ) {
+                        if ( child->isSectionTracker() &&
+                             std::find( filters.begin(),
+                                        filters.end(),
+                                        static_cast<SectionTracker&>( *child )
+                                            .trimmedName() ) !=
+                                 filters.end() ) {
+                            return true;
+                        }
+                    }
+                    return false;
+                }();
 
                 // This check is a bit tricky, because m_generator->next()
                 // has a side-effect, where it consumes generator's current

include/internal/catch_test_case_tracker.cpp

@@ -233,6 +233,14 @@ namespace TestCaseTracking {
             m_filters.insert( m_filters.end(), filters.begin()+1, filters.end() );
     }
 
+    std::vector<std::string> const& SectionTracker::getFilters() const {
+        return m_filters;
+    }
+
+    std::string const& SectionTracker::trimmedName() const {
+        return m_trimmed_name;
+    }
+
 } // namespace TestCaseTracking
 
 using TestCaseTracking::ITracker;

include/internal/catch_test_case_tracker.h

@@ -163,6 +163,10 @@ namespace TestCaseTracking {
 
         void addInitialFilters( std::vector<std::string> const& filters );
         void addNextFilters( std::vector<std::string> const& filters );
+        //! Returns filters active in this tracker
+        std::vector<std::string> const& getFilters() const;
+        //! Returns whitespace-trimmed name of the tracked section
+        std::string const& trimmedName() const;
     };
 
 } // namespace TestCaseTracking