Let reporters opt into fast path in RunContext::assertionStarting

The fast path allows `RunContext` to skip disabling output redirect,
and notifying the reporters, turning `RunContext::notifyAssertionStarted`
into a no-op. This improves the overall performance of assertion handling
significantly, and also prepares ground for future changes around
assertion handling and thread safety.

For simple 10M assertion run, this improves the running time by ~30%
in Debug build and ~40% in Release build.

For backwards-compatibility reasons, the fast path is disabled
by default. However, none of the first party reporters use the
`assertionStarting` event, so all first party reporters are opted-in.

Author: horenmar

src/catch2/interfaces/catch_interfaces_reporter.hpp

@@ -115,6 +115,11 @@ namespace Catch {
         //! Catch2 should call `Reporter::assertionEnded` even for passing
         //! assertions
         bool shouldReportAllAssertions = false;
+        //! Catch2 should call `Reporter::assertionStarting` for all assertions
+        // Defaults to true for backwards compatibility, but none of our current
+        // reporters actually want this, and it enables a fast path in assertion
+        // handling.
+        bool shouldReportAllAssertionStarts = true;
     };
 
     /**

src/catch2/internal/catch_run_context.cpp

@@ -172,6 +172,7 @@ namespace Catch {
         m_lastKnownLineInfo("DummyLocation", static_cast<size_t>(-1)),
         m_outputRedirect( makeOutputRedirect( m_reporter->getPreferences().shouldRedirectStdOut ) ),
         m_abortAfterXFailedAssertions( m_config->abortAfter() ),
+        m_reportAssertionStarting( m_reporter->getPreferences().shouldReportAllAssertionStarts ),
         m_includeSuccessfulResults( m_config->includeSuccessfulResults() || m_reporter->getPreferences().shouldReportAllAssertions ),
         m_shouldDebugBreak( m_config->shouldDebugBreak() )
     {
@@ -309,8 +310,10 @@ namespace Catch {
     }
 
     void RunContext::notifyAssertionStarted( AssertionInfo const& info ) {
-        auto _ = scopedDeactivate( *m_outputRedirect );
-        m_reporter->assertionStarting( info );
+        if (m_reportAssertionStarting) {
+            auto _ = scopedDeactivate( *m_outputRedirect );
+            m_reporter->assertionStarting( info );
+        }
     }
 
     bool RunContext::sectionStarted( StringRef sectionName,

src/catch2/internal/catch_run_context.hpp

@@ -159,6 +159,9 @@ namespace Catch {
         size_t m_abortAfterXFailedAssertions;
         bool m_lastAssertionPassed = false;
         bool m_shouldReportUnexpected = true;
+        // Caches whether `assertionStarting` events should be sent to the reporter.
+        bool m_reportAssertionStarting;
+        // Caches whether `assertionEnded` events for successful assertions should be sent to the reporter
         bool m_includeSuccessfulResults;
         // Caches m_config->shouldDebugBreak() to avoid vptr calls/allow inlining
         bool m_shouldDebugBreak;

src/catch2/reporters/catch_reporter_automake.hpp

@@ -19,9 +19,11 @@ namespace Catch {
     public:
         // GCC5 compat: we cannot use inherited constructor, because it
         //              doesn't implement backport of P0136
-        AutomakeReporter(ReporterConfig&& _config):
-            StreamingReporterBase(CATCH_MOVE(_config))
-        {}
+        AutomakeReporter( ReporterConfig&& _config ):
+            StreamingReporterBase( CATCH_MOVE( _config ) ) {
+            m_preferences.shouldReportAllAssertionStarts = false;
+        }
+
         ~AutomakeReporter() override;
 
         static std::string getDescription() {

src/catch2/reporters/catch_reporter_compact.hpp

@@ -16,7 +16,10 @@ namespace Catch {
 
     class CompactReporter final : public StreamingReporterBase {
     public:
-        using StreamingReporterBase::StreamingReporterBase;
+        CompactReporter( ReporterConfig&& _config ):
+            StreamingReporterBase( CATCH_MOVE( _config ) ) {
+            m_preferences.shouldReportAllAssertionStarts = false;
+        }
 
         ~CompactReporter() override;
 

src/catch2/reporters/catch_reporter_console.cpp

@@ -401,7 +401,10 @@ ConsoleReporter::ConsoleReporter(ReporterConfig&& config):
                 { "est run time high mean  high std dev", 14, Justification::Right }
             };
         }
-    }())) {}
+    }())) {
+    m_preferences.shouldReportAllAssertionStarts = false;
+}
+
 ConsoleReporter::~ConsoleReporter() = default;
 
 std::string ConsoleReporter::getDescription() {

src/catch2/reporters/catch_reporter_json.cpp

@@ -51,6 +51,8 @@ namespace Catch {
         //      not, but for machine-parseable reporters I think the answer
         //      should be yes.
         m_preferences.shouldReportAllAssertions = true;
+        // We only handle assertions when they end
+        m_preferences.shouldReportAllAssertionStarts = false;
 
         m_objectWriters.emplace( m_stream );
         m_writers.emplace( Writer::Object );

src/catch2/reporters/catch_reporter_junit.cpp

@@ -89,6 +89,7 @@ namespace Catch {
         {
             m_preferences.shouldRedirectStdOut = true;
             m_preferences.shouldReportAllAssertions = false;
+            m_preferences.shouldReportAllAssertionStarts = false;
             m_shouldStoreSuccesfulAssertions = false;
         }
 

src/catch2/reporters/catch_reporter_multi.cpp

@@ -19,6 +19,8 @@ namespace Catch {
             reporterish.getPreferences().shouldRedirectStdOut;
         m_preferences.shouldReportAllAssertions |=
             reporterish.getPreferences().shouldReportAllAssertions;
+        m_preferences.shouldReportAllAssertionStarts |=
+            reporterish.getPreferences().shouldReportAllAssertionStarts;
     }
 
     void MultiReporter::addListener( IEventListenerPtr&& listener ) {

src/catch2/reporters/catch_reporter_multi.hpp

@@ -29,6 +29,11 @@ namespace Catch {
         void updatePreferences(IEventListener const& reporterish);
 
     public:
+        MultiReporter( IConfig const* config ):
+            IEventListener( config ) {
+            m_preferences.shouldReportAllAssertionStarts = false;
+        }
+
         using IEventListener::IEventListener;
 
         void addListener( IEventListenerPtr&& listener );