Make log of each separate child algorithm available for retrieval after

running model

python/PyQt6/core/auto_generated/processing/qgsprocessingcontext.sip.in

@@ -67,6 +67,20 @@ Returns the outputs generated by the child algorithm.
 Sets the ``outputs`` used for the child algorithm.
 
 .. seealso:: :py:func:`outputs`
+%End
+
+    QString htmlLog() const;
+%Docstring
+Returns the HTML formatted contents of logged messages which occurred while running the child.
+
+.. seealso:: :py:func:`setHtmlLog`
+%End
+
+    void setHtmlLog( const QString &log );
+%Docstring
+Sets the HTML formatted contents of logged messages which occurred while running the child.
+
+.. seealso:: :py:func:`htmlLog`
 %End
 
     bool operator==( const QgsProcessingModelChildAlgorithmResult &other ) const;

python/core/auto_generated/processing/qgsprocessingcontext.sip.in

@@ -67,6 +67,20 @@ Returns the outputs generated by the child algorithm.
 Sets the ``outputs`` used for the child algorithm.
 
 .. seealso:: :py:func:`outputs`
+%End
+
+    QString htmlLog() const;
+%Docstring
+Returns the HTML formatted contents of logged messages which occurred while running the child.
+
+.. seealso:: :py:func:`setHtmlLog`
+%End
+
+    void setHtmlLog( const QString &log );
+%Docstring
+Sets the HTML formatted contents of logged messages which occurred while running the child.
+
+.. seealso:: :py:func:`htmlLog`
 %End
 
     bool operator==( const QgsProcessingModelChildAlgorithmResult &other ) const;

src/core/processing/models/qgsprocessingmodelalgorithm.cpp

@@ -326,6 +326,7 @@ QVariantMap QgsProcessingModelAlgorithm::processAlgorithm( const QVariantMap &pa
   QVariantMap finalResults;
   QSet< QString > executed;
   bool executedAlg = true;
+  int previousHtmlLogLength = 0;
   while ( executedAlg && executed.count() < toExecute.count() )
   {
     executedAlg = false;
@@ -503,13 +504,8 @@ QVariantMap QgsProcessingModelAlgorithm::processAlgorithm( const QVariantMap &pa
       childResults.insert( childId, results );
       childResult.setOutputs( results );
 
-      context.modelChildResults().insert( childId, childResult );
+      if ( runResult )
-
-      if ( !runResult )
       {
-        throw QgsProcessingException( error );
-      }
-
         if ( feedback && !skipGenericLogging )
         {
           const QVariantMap displayOutputs = QgsProcessingUtils::removePointerValuesFromMap( results );
@@ -620,8 +616,31 @@ QVariantMap QgsProcessingModelAlgorithm::processAlgorithm( const QVariantMap &pa
         childAlg.reset( nullptr );
         modelFeedback.setCurrentStep( executed.count() );
         if ( feedback && !skipGenericLogging )
+        {
           feedback->pushInfo( QObject::tr( "OK. Execution took %1 s (%n output(s)).", nullptr, results.count() ).arg( childTime.elapsed() / 1000.0 ) );
         }
+      }
+
+      // trim out just the portion of the overall log which relates to this child
+      const QString thisAlgorithmHtmlLog = feedback->htmlLog().mid( previousHtmlLogLength );
+      previousHtmlLogLength = feedback->htmlLog().length();
+
+      if ( !runResult )
+      {
+        const QString formattedException = QStringLiteral( "<span style=\"color:red\">%1</span><br/>" ).arg( error.toHtmlEscaped() ).replace( '\n', QLatin1String( "<br>" ) );
+        const QString formattedRunTime = QStringLiteral( "<span style=\"color:red\">%1</span><br/>" ).arg( QObject::tr( "Failed after %1 s." ).arg( childTime.elapsed() / 1000.0 ).toHtmlEscaped() ).replace( '\n', QLatin1String( "<br>" ) );
+
+        childResult.setHtmlLog( thisAlgorithmHtmlLog + formattedException + formattedRunTime );
+        context.modelChildResults().insert( childId, childResult );
+
+        throw QgsProcessingException( error );
+      }
+      else
+      {
+        childResult.setHtmlLog( thisAlgorithmHtmlLog );
+        context.modelChildResults().insert( childId, childResult );
+      }
+    }
 
     if ( feedback && feedback->isCanceled() )
       break;

src/core/processing/qgsprocessingcontext.h

@@ -86,9 +86,24 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithmResult
      */
     void setOutputs( const QVariantMap &outputs ) { mOutputs = outputs; }
 
+    /**
+     * Returns the HTML formatted contents of logged messages which occurred while running the child.
+     *
+     * \see setHtmlLog()
+     */
+    QString htmlLog() const { return mHtmlLog; }
+
+    /**
+     * Sets the HTML formatted contents of logged messages which occurred while running the child.
+     *
+     * \see htmlLog()
+     */
+    void setHtmlLog( const QString &log ) { mHtmlLog = log; }
+
     bool operator==( const QgsProcessingModelChildAlgorithmResult &other ) const
     {
       return mExecutionStatus == other.mExecutionStatus
+             && mHtmlLog == other.mHtmlLog
              && mInputs == other.mInputs
              && mOutputs == other.mOutputs;
     }
@@ -102,6 +117,7 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithmResult
     Qgis::ProcessingModelChildAlgorithmExecutionStatus mExecutionStatus = Qgis::ProcessingModelChildAlgorithmExecutionStatus::NotExecuted;
     QVariantMap mInputs;
     QVariantMap mOutputs;
+    QString mHtmlLog;
 
 };
 

tests/src/analysis/testqgsprocessingmodelalgorithm.cpp

@@ -69,7 +69,7 @@ class DummyRaiseExceptionAlgorithm : public QgsProcessingAlgorithm
     QString displayName() const override { return mName; }
     QVariantMap processAlgorithm( const QVariantMap &, QgsProcessingContext &, QgsProcessingFeedback * ) override
     {
-      throw QgsProcessingException( QString() );
+      throw QgsProcessingException( QStringLiteral( "something bad happened" ) );
     }
     static bool postProcessAlgorithmCalled;
     QVariantMap postProcessAlgorithm( QgsProcessingContext &, QgsProcessingFeedback * ) final
@@ -2330,12 +2330,14 @@ void TestQgsProcessingModelAlgorithm::modelWithChildException()
 
   QgsProcessingModelChildAlgorithm algWhichRaisesException;
   algWhichRaisesException.setChildId( QStringLiteral( "raise" ) );
+  algWhichRaisesException.setDescription( QStringLiteral( "my second step" ) );
   algWhichRaisesException.setAlgorithmId( "dummy4:raise" );
   algWhichRaisesException.setDependencies( {QgsProcessingModelChildDependency( QStringLiteral( "buffer" ) )} );
   m.addChildAlgorithm( algWhichRaisesException );
 
   // run and check context details
   QgsProcessingContext context;
+  context.setLogLevel( Qgis::ProcessingLogLevel::ModelDebug );
   QgsProcessingFeedback feedback;
   QVariantMap params;
   QgsVectorLayer *layer3111 = new QgsVectorLayer( "Point?crs=epsg:3111", "v1", "memory" );
@@ -2359,9 +2361,13 @@ void TestQgsProcessingModelAlgorithm::modelWithChildException()
   QCOMPARE( context.modelChildResults().value( "buffer" ).executionStatus(), Qgis::ProcessingModelChildAlgorithmExecutionStatus::Success );
   QCOMPARE( context.modelChildResults().value( "buffer" ).inputs().value( "INPUT" ).toString(), QStringLiteral( "v1" ) );
   QCOMPARE( context.modelChildResults().value( "buffer" ).inputs().value( "OUTPUT" ).toString(), QStringLiteral( "memory:Buffered" ) );
+  QCOMPARE( context.modelChildResults().value( "buffer" ).htmlLog().left( 50 ), QStringLiteral( "<span style=\"color:#777\">Prepare algorithm: buffer" ) );
+  QCOMPARE( context.modelChildResults().value( "buffer" ).htmlLog().right( 21 ), QStringLiteral( "s (1 output(s)).<br/>" ) );
   QVERIFY( context.temporaryLayerStore()->mapLayer( context.modelChildResults().value( "buffer" ).outputs().value( "OUTPUT" ).toString() ) );
 
   QCOMPARE( context.modelChildResults().value( "raise" ).executionStatus(), Qgis::ProcessingModelChildAlgorithmExecutionStatus::Failed );
+  QCOMPARE( context.modelChildResults().value( "raise" ).htmlLog().left( 49 ), QStringLiteral( "<span style=\"color:#777\">Prepare algorithm: raise" ) );
+  QVERIFY( context.modelChildResults().value( "raise" ).htmlLog().contains( QStringLiteral( "Error encountered while running my second step: something bad happened" ) ) );
 }
 
 void TestQgsProcessingModelAlgorithm::modelDependencies()