Fix some "nullable reference type" warnings

src/SolidGui/AppWritingSystems.cs

@@ -10,14 +10,8 @@ namespace SolidGui
 {
     public class AppWritingSystems
     {
-        private static IWritingSystemRepository _sWritingSystemsRepository;
+        private static Lazy<IWritingSystemRepository> _sWritingSystemsRepository = new(() => GlobalWritingSystemRepository.Initialize());
 
-        public static IWritingSystemRepository WritingSystems
-        {
-            get
-            {
-                return _sWritingSystemsRepository ?? (_sWritingSystemsRepository = GlobalWritingSystemRepository.Initialize());
-            }
-        }
+        public static IWritingSystemRepository WritingSystems => _sWritingSystemsRepository.Value;
     }
 }

src/SolidGui/DataShapesDialog.cs

@@ -18,7 +18,7 @@ namespace SolidGui
 {
     public partial class DataShapesDialog : Form
     {
-        private FindReplaceDialog _searchDialog;
+        private FindReplaceDialog? _searchDialog;
 
         public DataShapesDialog(FindReplaceDialog searchDialog, MainWindowPM mwp)
         {
@@ -34,9 +34,9 @@ public DataShapesDialog(FindReplaceDialog searchDialog, MainWindowPM mwp)
             _mainWindowPm = mwp;
         }
 
-        private MainWindowPM _mainWindowPm;
+        private MainWindowPM? _mainWindowPm;
 
-        private IEnumerable<SfmDictionary.DataShape> _shapes;
+        private IEnumerable<SfmDictionary.DataShape>? _shapes;
 
         private void _closeButton_Click(object sender, EventArgs e)
         {
@@ -166,7 +166,7 @@ except that dollars ($1$2) would need to be backslashes (\1\2).
 if any of the fields have hard-wrapped data.";
 
             RegexItem r = RegexItem.GetCustomRegex(sbFind.ToString(), sbReplace.ToString(), help, true);
-            _searchDialog.LaunchSearch(r);
+            _searchDialog?.LaunchSearch(r);
 
         }
 

src/SolidGui/DataValuesDialog.cs

@@ -20,7 +20,7 @@ public DataValuesDialog(MainWindowPM mwp)
             _mainWindowPm = mwp;
         }
 
-        private MainWindowPM _mainWindowPm;
+        private MainWindowPM? _mainWindowPm;
 
         private void _runButton_Click(object sender, EventArgs e)
         {
@@ -30,6 +30,7 @@ private void _runButton_Click(object sender, EventArgs e)
         private void Run()
         {
             if (String.IsNullOrEmpty(_markersTextBox.Text.Trim())) return;
+            if (_mainWindowPm == null) return;
 
             int max = (int)maxNumericUpDown.Value;
 

src/SolidGui/Engine/SfmField.cs

@@ -30,7 +30,7 @@ public SfmField()
         public string Trailing // (for trailing white space); added -JMC 2013-09
         {
             get { return String.IsNullOrEmpty(_trailing) ? DefaultTrailing : _trailing; }
-            set { _trailing = value.Contains("\n") ? value : null; } 
+            set { _trailing = value.Contains("\n") ? value : ""; }
         }
 
         // Set both the value and the trailing-space value using a single string

src/SolidGui/Engine/SolidReport.cs

@@ -43,6 +43,7 @@ public static bool IsDataWarning (EntryType et)
         public SolidReport()
         {
             Entries = new List<ReportEntry>();
+            FilePath = "";
         }
 
         public static SolidReport MakeCopy(SolidReport report)

src/SolidGui/Engine/SolidSettings.cs

@@ -33,6 +33,7 @@ public SolidSettings(List<SolidMarkerSetting> ms)
             _markerSettings = ms;
             _newlyAdded = new List<SolidMarkerSetting>();
             FileStatusReport = new SettingsFileReport();
+            FilePath = "";
         }
 
         public SolidSettings()
@@ -307,7 +308,7 @@ public static SolidSettings CreateSolidFileFromTemplate(string templateFilePath,
             {
                 ErrorReport.NotifyUserOfProblem(
                     "There was a problem opening that settings file.  The error was\r\n" + e.Message);
-                return null;
+                return new SolidSettings(); // Don't want to return null, so return default settings
             }
 
             return OpenSolidFile(outputFilePath);

src/SolidGui/MainWindowPM.cs

@@ -52,29 +52,21 @@ public class MainWindowPM :IDisposable
         private static Regex _cleanUpNewlinesNonLinux;
         */
 
-
-        public MainWindowPM() 
-        {
-            Initialize(new SfmDictionary()); // , new SolidSettings());
-        }
-
-        public override string ToString()
+        static MainWindowPM()
         {
-            return string.Format("{0} {1} {2} {3} {4} {5} {6}",
-                _workingDictionary, _markerSettingsModel, _recordFilters, _warningFilterChooserModel, 
-                _navigatorModel, _sfmEditorModel, GetHashCode());
-        }
-
-        private static String TempDictionaryPath()
-        {
-            return Path.Combine(Path.GetTempPath(), "TempDictionary.db");
+            RegexOptions options = RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.Multiline;
+            _cleanUpIndents = new Regex(@"^[ \t]+\\", options);  //any line-initial spaces or tabs
+            _cleanUpClosers = new Regex(@" ?\\\w+\* ?", options);  //any closing tag, and possibly one space buffer around it
+            _cleanUpInferred = new Regex(@"^[ \t]*\\\+.*(\r|\r?\n)", options);  //any inferred marker (\+mrkr) and its value and newline (any leading whitespace)
+            _cleanUpSeparators = new Regex(@"\t", options);  // one tab
+            _cleanUpNewlines = new Regex(@"(\r?\n|\r)", options);  // one newline (\r\n or \n or \r)
         }
 
-        public void Initialize(SfmDictionary dict) // , SolidSettings settings)
+        public MainWindowPM()
         {
             _recordFilters = new RecordFilterSet();
-            _workingDictionary = dict;
-            // Settings = settings;
+            _workingDictionary = new SfmDictionary();
+            // Settings = new SolidSettings();
             _markerSettingsModel = new MarkerSettingsPM(this);
             _warningFilterChooserModel = new FilterChooserPM();
             _navigatorModel = new RecordNavigatorPM(this);
@@ -95,13 +87,18 @@ public void Initialize(SfmDictionary dict) // , SolidSettings settings)
             // and the choosers should listen to the nav so they can clear themselves as needed
             NavigatorModel.NavFilterChanged += WarningFilterChooserModel.OnNavFilterChanged;
             NavigatorModel.NavFilterChanged += MarkerSettingsModel.OnNavFilterChanged;
+        }
 
-            RegexOptions options = RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.Multiline;
-            _cleanUpIndents = new Regex(@"^[ \t]+\\", options);  //any line-initial spaces or tabs
-            _cleanUpClosers = new Regex(@" ?\\\w+\* ?", options);  //any closing tag, and possibly one space buffer around it
-            _cleanUpInferred = new Regex(@"^[ \t]*\\\+.*(\r|\r?\n)", options);  //any inferred marker (\+mrkr) and its value and newline (any leading whitespace)
-            _cleanUpSeparators = new Regex(@"\t", options);  // one tab
-            _cleanUpNewlines = new Regex(@"(\r?\n|\r)", options);  // one newline (\r\n or \n or \r)
+        public override string ToString()
+        {
+            return string.Format("{0} {1} {2} {3} {4} {5} {6}",
+                _workingDictionary, _markerSettingsModel, _recordFilters, _warningFilterChooserModel,
+                _navigatorModel, _sfmEditorModel, GetHashCode());
+        }
+
+        private static String TempDictionaryPath()
+        {
+            return Path.Combine(Path.GetTempPath(), "TempDictionary.db");
         }
 
         public MarkerSettingsPM MarkerSettingsModel
@@ -336,7 +333,7 @@ public bool ShouldAskForTemplateBeforeOpening(string filePath)
             // Check also that the setting file is valid.  If it's not allow true to be returned to pop up
             // the template chooser.
             // See http://projects.palaso.org/issues/show/180
-            SolidSettings solidSettings = null;
+            SolidSettings? solidSettings = null;
             try
             {
                 solidSettings = LoadSettingsFromExistingFile(solidFilePath);  // A dry run. If it succeeds, we'll reload later. -JMC

src/SolidGui/Processes/ProcessStructure.cs

@@ -321,7 +321,7 @@ private static void AddClosers(SfmLexEntry lexEntry)
 */
 
 
-        private static SfmFieldModel _appendTo;
+        private static SfmFieldModel? _appendTo;
 
         // Recursive
         private static void AddClosers(SfmFieldModel node)

src/SolidGui/QuickFixer.cs

@@ -187,7 +187,7 @@ private void PropagateField(string markerOfFieldToPropagate, string markerOfFiel
         {
             foreach (Record record in _dictionary.Records)
             {
-                SfmFieldModel fieldToCopy = null;
+                SfmFieldModel? fieldToCopy = null;
                 for (int i = 0; i < record.Fields.Count; i++)
                 {
                     SfmFieldModel field = record.Fields[i];
@@ -244,13 +244,13 @@ private void AddNewEntries(List<RecordAddition> additions, StringBuilder log)
             SolidSettings nullSettings = new SolidSettings();  // JMC: why a new bunch?
             foreach (RecordAddition addition in additions)
             {
-                string switchToCitationForm;
-                Record targetRecord = FindRecordByCitationFormOrLexemeForm(addition.targetHeadWord, out switchToCitationForm);
-                if (targetRecord == null)
+                string? switchToCitationForm;
+                Record? targetRecord = FindRecordByCitationFormOrLexemeForm(addition.targetHeadWord, out switchToCitationForm);
+                if (targetRecord is null)
                 {
                     targetRecord = FindRecordContainingVariantOrSubEntry(addition.targetHeadWord);
                 }
-                if (null == targetRecord)
+                if (targetRecord is null)
                 {
                     Record r = new Record();
                     var b = new StringBuilder();
@@ -309,7 +309,7 @@ private void SplitFieldsWithMultipleItems(List<string> markers, StringBuilder lo
         }
 
 
-        private Record FindRecordByCitationFormOrLexemeForm(string form, out string switchToCitationForm)
+        private Record? FindRecordByCitationFormOrLexemeForm(string form, out string? switchToCitationForm)
         {
             switchToCitationForm = null;
             form = form.Trim();
@@ -348,7 +348,7 @@ private Record FindRecordByCitationFormOrLexemeForm(string form, out string swit
 
             return null;
         }
-        private Record FindRecordContainingVariantOrSubEntry(string form)
+        private Record? FindRecordContainingVariantOrSubEntry(string form)
         {
 
             foreach (Record record in _dictionary.Records)