#31 : Added configurable behaviour for bad model references from the …

…document template.

Options are, the module handler either throws an exception, ignores the match it's processing, or removes the match. Default is exception.

Examples/ConsoleApp/Program.cs

@@ -22,6 +22,7 @@ public class Program
     {
         public static string root = @"..\..\";
         public static bool debug = true;
+        public static HandleFailAction modelEntryFailAction = HandleFailAction.exception;
 
         static void Main(string[] args)
         {
@@ -40,7 +41,7 @@ static void Generate(string name, object model)
 
             Console.WriteLine("Generating " + name);
 
-            var doc = Templ.Load(file).Build(model, debug).SaveAs(output);
+            var doc = Templ.Load(file).Build(model, debug, modelEntryFailAction).SaveAs(output);
             if (debug) doc.Debugger.SaveAs(output);
         }
     }

Templ.NET/ModelEntry.cs

@@ -7,6 +7,22 @@
 
 namespace TemplNET
 {
+    public class ModelEntryException : Exception
+    {
+        public ModelEntryException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+    }
+
+    /// <summary>
+    /// List of ways in which an exception in a module handler can be handled
+    /// </summary>
+    /// Example:  {txt:user.name} // user.name is not a property in the model
+    public enum HandleFailAction
+    {
+        exception, ignore, remove
+    };
+
     /// <summary>
     /// Represents a reference-by-reflection to a Entry (a field/property/member) within an object. 
     /// The entry's nested Path is defined with a string.
@@ -189,23 +205,28 @@ private static MemberValue GetPrimitive(object model, string path)
         /// <param name="path"></param>
         public static TemplModelEntry Get(object model, string path)
         {
-            MemberValue propVal;
-            var primitive = GetPrimitive(model, path);
-            if (primitive == null)
-            {
-                propVal = MemberValue.FindPath(model, path.Trim());
+            try {
+                MemberValue propVal;
+                var primitive = GetPrimitive(model, path);
+                if (primitive == null)
+                {
+                    propVal = MemberValue.FindPath(model, path.Trim());
+                }
+                else
+                {
+                    propVal = primitive;
+                }
+                return new TemplModelEntry()
+                {
+                    Model = model,
+                    Path = path.Trim(),
+                    Info = propVal.Info,
+                    Value = propVal.Value
+                };
             }
-            else
-            {
-                propVal = primitive;
+            catch (Exception ex) {
+                throw new ModelEntryException($"Failed to retrieve entry from the model at path '{path}'", ex);
             }
-            return new TemplModelEntry()
-            {
-                Model = model,
-                Path = path.Trim(),
-                Info = propVal.Info,
-                Value = propVal.Value
-            };
         }
 
         /// <summary>

Templ.NET/Module.cs

@@ -65,7 +65,7 @@ protected TemplModule AddPrefix(string prefix)
         /// Applies all changes to the document.
         /// <see cref="Templ.Build"/> automatically executes it for all <see cref="Templ.ActiveModules"/>.
         /// </summary>
-        public abstract void Build(DocX doc, object model);
+        public abstract void Build(DocX doc, object model, HandleFailAction modelEntryFailAction);
     }
 
     /// <summary>
@@ -127,7 +127,6 @@ private bool RemoveExpired(T m)
         /// Verifies the number of fields in the supplied Match's placeholder is within the min/max expected for this Module.
         /// <para/> Throws exception if problems are found.
         /// </summary>
-        /// <param name="m"></param>
         private T CheckFieldCount(T m)
         {
             var l = m.Fields.Length;
@@ -141,10 +140,11 @@ private T CheckFieldCount(T m)
             }
             return m;
         }
+
         /// <summary>
         /// Handle and/or remove a collection of Matches from the document
         /// </summary>
-        public void BuildFromScope(DocX doc, object model, IEnumerable<T> scope)
+        public void BuildFromScope(DocX doc, object model, IEnumerable<T> scope, HandleFailAction modelEntryFailAction)
         {
             var watch = Stopwatch.StartNew();
             // Mark module instance as "used" if any matches are being processed
@@ -154,35 +154,51 @@ public void BuildFromScope(DocX doc, object model, IEnumerable<T> scope)
             // Note how we are constantly "committing" the changes using ToList().
             // This ensures order is preserved (e.g. all "finds" happen before all "handler"s)
             scope.Select( m => CheckFieldCount(m) ).ToList()
-                 .Select( m => Handler(doc, model, m)).ToList()
+                 .Select( m => TryHandler(doc, model, m, modelEntryFailAction)).ToList()
                  .Where(  m =>!RemoveExpired(m)).ToList()
                  .Select( m => CustomHandler(doc, model, m)).ToList()
                  .ForEach(m => RemoveExpired(m));
             Statistics.millis = watch.ElapsedMilliseconds;
         }
+
+        private T TryHandler(DocX doc, object model, T m, HandleFailAction modelEntryFailAction)
+        {
+            try
+            {
+                return Handler(doc, model, m);
+            }
+            catch (ModelEntryException)
+            {
+                switch (modelEntryFailAction)
+                {
+                    case HandleFailAction.exception:
+                        throw;
+                    case HandleFailAction.remove:
+                        m.Expired = true;
+                        break;
+                }
+                return m;
+            }
+        }
+
         /// <summary>
         /// Find and build all content from the document
         /// </summary>
-        public override void Build(DocX doc, object model)
+        public override void Build(DocX doc, object model, HandleFailAction modelEntryFailAction)
         {
-            BuildFromScope(doc, model, Regexes.SelectMany(rxp => FindAll(doc, rxp)));
+            BuildFromScope(doc, model, Regexes.SelectMany(rxp => FindAll(doc, rxp)), modelEntryFailAction);
         }
 
         /// <summary>
         /// Module-specific Match handler.
         /// Implementations should modify the Matched content, or mark expired to delete
         /// </summary>
-        /// <param name="doc"></param>
-        /// <param name="model"></param>
-        /// <param name="m"></param>
         public abstract T Handler(DocX doc, object model, T m);
 
         /// <summary>
         /// Module-specific finder.
         /// Implementations should retrieve all regex-matching content from the document.
         /// </summary>
-        /// <param name="doc"></param>
-        /// <param name="rxp"></param>
         public abstract IEnumerable<T> FindAll(DocX doc, TemplRegex rxp);
     }
 

Templ.NET/Modules.cs

@@ -64,7 +64,7 @@ public void BuildFromScope(DocX doc, object model, IEnumerable<Paragraph> paragr
         {
             Path = path;
             Paragraphs = paragraphs;
-            Build(doc, model);
+            Build(doc, model, HandleFailAction.exception);
             Path = "";
             paragraphs = new List<Paragraph>();
         }

Templ.NET/Templ.cs

@@ -127,15 +127,15 @@ public static Templ Load(string templatePath, bool useDefaultModules = true)
         /// </summary>
         /// <seealso cref="Debugger"/>
         /// 
-        public Templ Build(object model, bool debug = TemplConst.Debug)
+        public Templ Build(object model, bool debug = TemplConst.Debug, HandleFailAction modelEntryFailAction = HandleFailAction.exception)
         {
             if (debug)
             {
                 Debugger.AddState(Document, "Init");
             }
             ActiveModules.ForEach(module =>
             {
-                module.Build(Document.Docx, model);
+                module.Build(Document.Docx, model, modelEntryFailAction);
                 if (debug && module.Used)
                 {
                     Debugger.AddState(Document, module.Name);