From ec9135b658e18e80c621a63d86df24ff983794be Mon Sep 17 00:00:00 2001
From: Magne Sjaastad <magne.sjaastad@ceetronsolutions.com>
Date: Sun, 11 Oct 2026 15:49:28 +0200
Subject: [PATCH] #14903: Ignore empty restart files in opm-common reader

---
 .../FileInterface/RifReaderOpmCommon.cpp      |  5 +++-
 .../UnitTests/RifReaderOpmCommon-Test.cpp     | 26 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/ApplicationLibCode/FileInterface/RifReaderOpmCommon.cpp b/ApplicationLibCode/FileInterface/RifReaderOpmCommon.cpp
index eb9d45b262..f433c9158f 100644
--- a/ApplicationLibCode/FileInterface/RifReaderOpmCommon.cpp
+++ b/ApplicationLibCode/FileInterface/RifReaderOpmCommon.cpp
@@ -911,6 +911,9 @@ void RifReaderOpmCommon::setupInitAndRestartAccess()
 
             m_restartFile = std::make_unique<EclIO::ERst>( m_restartFileName );
 
+            // An empty restart file, e.g. while the simulation is starting, reports step 0 without any arrays
+            if ( m_restartFile->size() == 0 ) m_restartFile = nullptr;
+
             const bool isLoggingEnabled = RiaPreferencesSystem::current()->isLoggingActivatedForKeyword( "RifReaderOpmCommon" );
             if ( isLoggingEnabled ) RiaLogging::logElapsedTime( "Import of meta data from " + m_restartFileName, startTime );
         }
@@ -1096,7 +1099,7 @@ void RifReaderOpmCommon::buildMetaData( RigEclipseCaseData* eclipseCaseData, caf
     }
 
     auto task = progress.task( "Handling well information", 10 );
-    if ( loadWellDataEnabled() && !m_restartFileName.empty() )
+    if ( loadWellDataEnabled() && m_restartFile != nullptr )
     {
         auto startTime = RiaLogging::currentTime();
 
diff --git a/ApplicationLibCode/UnitTests/RifReaderOpmCommon-Test.cpp b/ApplicationLibCode/UnitTests/RifReaderOpmCommon-Test.cpp
index 395254df27..4b90e1d2f6 100644
--- a/ApplicationLibCode/UnitTests/RifReaderOpmCommon-Test.cpp
+++ b/ApplicationLibCode/UnitTests/RifReaderOpmCommon-Test.cpp
@@ -23,8 +23,13 @@
 #include "RiaEclipseUnitTools.h"
 #include "RiaTestDataDirectory.h"
 
+#include "RigEclipseCaseData.h"
+
 #include "opm/io/eclipse/ERst.hpp"
 
+#include <QFile>
+#include <QTemporaryDir>
+
 #include <filesystem>
 #include <stdexcept>
 
@@ -91,3 +96,24 @@ TEST( RifReaderOpmCommon, RestartDataSize )
     EXPECT_EQ( 0, RifReaderOpmCommon::restartDataSize( restartFile, "XXXX", reportStep ) );
     EXPECT_THROW( RifReaderOpmCommon::restartDataSize( restartFile, "PRESSURE", 99 ), std::invalid_argument );
 }
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+TEST( RifReaderOpmCommon, EmptyRestartFile )
+{
+    QTemporaryDir tempDir;
+    ASSERT_TRUE( tempDir.isValid() );
+
+    const QString sourceGrid = QString( TEST_MODEL_DIR ) + "/TEST10K_FLT_LGR_NNC/TEST10K_FLT_LGR_NNC.EGRID";
+    const QString gridFile   = tempDir.filePath( "EMPTY_RESTART.EGRID" );
+    ASSERT_TRUE( QFile::copy( sourceGrid, gridFile ) );
+
+    QFile restartFile( tempDir.filePath( "EMPTY_RESTART.UNRST" ) );
+    ASSERT_TRUE( restartFile.open( QIODevice::WriteOnly ) );
+    restartFile.close();
+
+    cvf::ref<RigEclipseCaseData> caseData = new RigEclipseCaseData( nullptr );
+    cvf::ref<RifReaderOpmCommon> reader   = new RifReaderOpmCommon;
+    EXPECT_TRUE( reader->open( gridFile, caseData.p() ) );
+}