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

src/catch2/internal/catch_run_context.cpp

@@ -82,13 +82,53 @@ 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 =
+                const bool should_wait_for_child = [&]() {
-                    !m_children.empty() &&
+                    // No children -> nobody to wait for
-                    std::find_if( m_children.begin(),
+                    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();
+                             } ) != 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

src/catch2/internal/catch_test_case_tracker.cpp

@@ -230,6 +230,14 @@ 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;

src/catch2/internal/catch_test_case_tracker.hpp

@@ -173,6 +173,10 @@ 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

tests/CMakeLists.txt

@@ -160,6 +160,32 @@ set_tests_properties(FilteredSection-1 PROPERTIES FAIL_REGULAR_EXPRESSION "No te
 add_test(NAME FilteredSection-2 COMMAND $<TARGET_FILE:SelfTest> \#1394\ nested -c NestedRunSection -c s1)
 set_tests_properties(FilteredSection-2 PROPERTIES FAIL_REGULAR_EXPRESSION "No tests ran")
 
+add_test(
+  NAME
+    FilteredSection::GeneratorsDontCauseInfiniteLoop-1
+  COMMAND
+    $<TARGET_FILE:SelfTest> "#2025: original repro" -c "fov_0"
+)
+set_tests_properties(FilteredSection::GeneratorsDontCauseInfiniteLoop-1
+  PROPERTIES
+    PASS_REGULAR_EXPRESSION "inside with fov: 0" # This should happen
+    FAIL_REGULAR_EXPRESSION "inside with fov: 1" # This would mean there was no filtering
+)
+
+# GENERATE between filtered sections (both are selected)
+add_test(
+  NAME
+    FilteredSection::GeneratorsDontCauseInfiniteLoop-2
+  COMMAND
+    $<TARGET_FILE:SelfTest> "#2025: same-level sections"
+    -c "A"
+    -c "B"
+)
+set_tests_properties(FilteredSection::GeneratorsDontCauseInfiniteLoop-2
+  PROPERTIES
+    PASS_REGULAR_EXPRESSION "All tests passed \\(4 assertions in 1 test case\\)"
+)
+
 # AppVeyor has a Python 2.7 in path, but doesn't have .py files as autorunnable
 add_test(NAME ApprovalTests COMMAND ${PYTHON_EXECUTABLE} ${CATCH_DIR}/tools/scripts/approvalTests.py $<TARGET_FILE:SelfTest>)
 set_tests_properties(ApprovalTests

tests/SelfTest/UsageTests/Tricky.tests.cpp

@@ -13,6 +13,8 @@
 #endif
 
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/generators/catch_generators.hpp>
+#include <catch2/generators/catch_generators_range.hpp>
 
 #include <cstdio>
 #include <sstream>
@@ -399,3 +401,28 @@ TEST_CASE("#1514: stderr/stdout is not captured in tests aborted by an exception
     // FAIL aborts the test by throwing a Catch exception
     FAIL("1514");
 }
+
+
+TEST_CASE( "#2025: -c shouldn't cause infinite loop", "[sections][generators][regression][.approvals]" ) {
+    SECTION( "Check cursor from buffer offset" ) {
+        auto bufPos = GENERATE_REF( range( 0, 44 ) );
+        WHEN( "Buffer position is " << bufPos ) { REQUIRE( 1 == 1 ); }
+    }
+}
+
+TEST_CASE("#2025: original repro", "[sections][generators][regression][.approvals]") {
+    auto fov = GENERATE(true, false);
+    DYNAMIC_SECTION("fov_" << fov) {
+        std::cout << "inside with fov: " << fov << '\n';
+    }
+}
+
+TEST_CASE("#2025: same-level sections", "[sections][generators][regression][.approvals]") {
+    SECTION("A") {
+        SUCCEED();
+    }
+    auto i = GENERATE(1, 2, 3);
+    SECTION("B") {
+        REQUIRE(i < 4);
+    }
+}