Fixing unnamed root ParameterExpression translation / Try+Catching visualizer translation exceptions, re: #100

Author: SteveWilkes

ReadableExpressions.UnitTests/WhenTranslatingVariableNames.cs

@@ -24,6 +24,17 @@ public void ShouldNameAnUnnamedVariable()
             translated.ShouldBe("@int = default(int)");
         }
 
+        // See https://github.com/agileobjects/ReadableExpressions/issues/100
+        [Fact]
+        public void ShouldNameARootUnnamedVariable()
+        {
+            var intVariable = Variable(typeof(int));
+
+            var translated = intVariable.ToReadableString();
+
+            translated.ShouldBe("@int");
+        }
+
         [Fact]
         public void ShouldNameAnUnnamedParameter()
         {

ReadableExpressions.Visualizers.ObjectSource/ExpressionVisualizerObjectSource.cs

@@ -17,7 +17,34 @@ public static void GetData(
             Stream outgoingData,
             Action<Stream, string> serializer)
         {
-            var translated = GetTranslationFor(target) ?? "default(void)";
+            string translated;
+
+            try
+            {
+                translated = GetTranslationFor(target) ?? "default(void)";
+            }
+            catch (Exception ex)
+            {
+                translated = $@"</pre>
+<h1>Ut-oh</h1>
+<p>
+    An exception occurred translating that 
+    <span class=""tn"">{target?.GetType().Name ?? "target"}</span>.
+</p>
+<p>
+    Please report this error with the stack trace below using 
+    <a href=""https://github.com/agileobjects/ReadableExpressions/issues/new"" target=""_blank"">
+    https://github.com/agileobjects/ReadableExpressions/issues/new
+    </a>.
+</p>
+
+<p>Thanks! (and sorry about that)<br />Steve</p>
+
+<hr />
+
+<p>{ex}</p>
+<pre>".TrimStart();
+            }
 
             serializer.Invoke(outgoingData, translated);
         }
@@ -54,7 +81,7 @@ internal static string GetTranslationFor(object target)
         private static string Translate(Type type)
             => type.ToReadableString(ApplyDialogSettings);
 
-        private static ITranslationSettings ApplyDialogSettings(ITranslationSettings settings) 
+        private static ITranslationSettings ApplyDialogSettings(ITranslationSettings settings)
             => GetDialogSettings().Update(settings.FormatUsing(_htmlFormatter));
 
         private static VisualizerDialogSettings GetDialogSettings()

ReadableExpressions/ExpressionAnalysis.cs

@@ -80,7 +80,7 @@ protected virtual void Analyse(Expression expression)
             {
                 case DebugInfo:
                 case Default:
-                case Parameter:
+                case Parameter when ((ParameterExpression)expression).IsNamed():
                 case RuntimeVariables:
                     ResultExpression = expression;
                     break;
@@ -234,8 +234,8 @@ public bool IsPartOfMethodCallChain(MethodCallExpression methodCall)
         /// </summary>
         /// <param name="variable">The variable for which to get the 1-based index.</param>
         /// <returns>
-        /// The 1-based index of the given <paramref name="variable"/>, or null if only variable of
-        /// this Type is declared.
+        /// The 1-based index of the given <paramref name="variable"/>, or null if only one variable
+        /// of this Type is declared.
         /// </returns>
         public int? GetUnnamedVariableNumberOrNull(ParameterExpression variable)
         {

ReadableExpressions/Extensions/InternalExpressionExtensions.cs

@@ -16,6 +16,9 @@
 
     internal static class InternalExpressionExtensions
     {
+        public static bool IsNamed(this ParameterExpression parameter)
+            => !parameter.Name.IsNullOrWhiteSpace();
+
         public static bool HasReturnType(this Expression expression)
             => expression.Type != typeof(void);
 

ReadableExpressions/Translations/ParameterTranslation.cs

@@ -14,7 +14,7 @@ internal static class ParameterTranslation
     {
         public static ITranslation For(ParameterExpression parameter, ITranslationContext context)
         {
-            if (parameter.Name.IsNullOrWhiteSpace())
+            if (!parameter.IsNamed())
             {
                 return new UnnamedParameterTranslation(parameter, context);
             }