Merge branch 'develop' of https://github.com/tkouba/commandline into tkouba-develop

# Conflicts:
#	src/CommandLine/BaseAttribute.cs
#	src/CommandLine/CommandLine.csproj
#	tests/CommandLine.Tests.Properties/CommandLine.Tests.Properties.csproj
#	tests/CommandLine.Tests/CommandLine.Tests.csproj
Fix failed tests by seting HelpText default to string.empty

Author: moh-hassan

src/CommandLine/BaseAttribute.cs

@@ -12,8 +12,9 @@ public abstract class BaseAttribute : Attribute
         private int min;
         private int max;
         private object @default;
-        private string helpText;
+        private Infrastructure.LocalizableAttributeProperty helpText;
         private string metaValue;
+        private Type resourceType;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="CommandLine.BaseAttribute"/> class.
@@ -22,8 +23,9 @@ protected internal BaseAttribute()
         {
             min = -1;
             max = -1;
-            helpText = string.Empty;
+            helpText = new Infrastructure.LocalizableAttributeProperty(nameof(HelpText));
             metaValue = string.Empty;
+            resourceType = null;
         }
 
         /// <summary>
@@ -90,11 +92,8 @@ public object Default
         /// </summary>
         public string HelpText
         {
-            get { return helpText; }
-            set
-            {
-                helpText = value ?? throw new ArgumentNullException("value");
-            }
+            get => helpText.Value??string.Empty;
+            set => helpText.Value = value ?? throw new ArgumentNullException("value");
         }
 
         /// <summary>
@@ -105,7 +104,12 @@ public string MetaValue
             get { return metaValue; }
             set
             {
-                metaValue = value ?? throw new ArgumentNullException("value");
+                if (value == null)
+                {
+                    throw new ArgumentNullException("value");
+                }
+
+                metaValue = value;
             }
         }
 
@@ -117,5 +121,18 @@ public bool Hidden
             get;
             set;
         }
+
+        /// <summary>
+        /// Gets or sets the <see cref="System.Type"/> that contains the resources for <see cref="HelpText"/>.
+        /// </summary>
+        public Type ResourceType
+        {
+            get { return resourceType; }
+            set
+            {
+                resourceType =
+                helpText.ResourceType = value;
+            }
+        }
     }
 }

src/CommandLine/Infrastructure/LocalizableAttributeProperty.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+
+namespace CommandLine.Infrastructure
+{
+    internal class LocalizableAttributeProperty
+    {
+        private string _propertyName;
+        private string _value;
+        private Type _type;
+        private PropertyInfo _localizationPropertyInfo;
+
+        public LocalizableAttributeProperty(string propertyName)
+        {
+            _propertyName = propertyName;
+        }
+
+        public string Value
+        {
+            get { return GetLocalizedValue(); }
+            set
+            {
+                _localizationPropertyInfo = null;
+                _value = value;
+            }
+        }
+
+        public Type ResourceType
+        {
+            set
+            {
+                _localizationPropertyInfo = null;
+                _type = value;
+            }
+        }
+
+        private string GetLocalizedValue()
+        {
+            if (String.IsNullOrEmpty(_value) || _type == null)
+                return _value;
+            if (_localizationPropertyInfo == null)
+            {
+                // Static class IsAbstract 
+                if (!_type.IsVisible)
+                    throw new ArgumentException("Invalid resource type", _propertyName);
+                PropertyInfo propertyInfo = _type.GetProperty(_value, BindingFlags.Public | BindingFlags.GetProperty | BindingFlags.Static);
+                if (propertyInfo == null || !propertyInfo.CanRead || propertyInfo.PropertyType != typeof(string))
+                    throw new ArgumentException("Invalid resource property name", _propertyName);
+                _localizationPropertyInfo = propertyInfo;
+            }
+            return (string)_localizationPropertyInfo.GetValue(null, null);
+        }
+    }
+
+}

tests/CommandLine.Tests/Fakes/ResourceFakes.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace CommandLine.Tests.Fakes
+{
+    public static class StaticResource
+    {
+        public static string HelpText { get { return "Localized HelpText"; } }
+    }
+
+    public class NonStaticResource
+    {
+        public static string HelpText { get { return "Localized HelpText"; } }
+        public static string WriteOnlyText { set { value?.ToString(); } }
+        private static string PrivateHelpText { get { return "Localized HelpText"; } }
+    }
+
+    public class NonStaticResource_WithNonStaticProperty
+    {
+        public string HelpText { get { return "Localized HelpText"; } }
+    }
+
+    internal class InternalResource
+    {
+        public static string HelpText { get { return "Localized HelpText"; } }
+    }
+
+}

tests/CommandLine.Tests/Unit/BaseAttributeTests.cs

@@ -1,9 +1,5 @@
 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Threading.Tasks;
 using Xunit;
 
 namespace CommandLine.Tests.Unit
@@ -20,12 +16,44 @@ public static void Default(object defaultValue)
             Assert.Equal(defaultValue, baseAttribute.Default);
         }
 
+        [Theory]
+        [InlineData("", null, "")]
+        [InlineData("", typeof(Fakes.StaticResource), "")]
+        [InlineData("Help text", null, "Help text")]
+        [InlineData("HelpText", typeof(Fakes.StaticResource), "Localized HelpText")]
+        [InlineData("HelpText", typeof(Fakes.NonStaticResource), "Localized HelpText")]
+        public static void HelpText(string helpText, Type resourceType, string expected)
+        {
+            TestBaseAttribute baseAttribute = new TestBaseAttribute();
+            baseAttribute.HelpText = helpText;
+            baseAttribute.ResourceType = resourceType;
+            
+            Assert.Equal(expected, baseAttribute.HelpText);
+        }
+
+        [Theory]
+        [InlineData("HelpText", typeof(Fakes.NonStaticResource_WithNonStaticProperty))]
+        [InlineData("WriteOnlyText", typeof(Fakes.NonStaticResource))]
+        [InlineData("PrivateOnlyText", typeof(Fakes.NonStaticResource))]
+        [InlineData("HelpText", typeof(Fakes.InternalResource))]
+        public void ThrowsHelpText(string helpText, Type resourceType)
+        {
+            TestBaseAttribute baseAttribute = new TestBaseAttribute();
+            baseAttribute.HelpText = helpText;
+            baseAttribute.ResourceType = resourceType;
+
+            // Verify exception
+            Assert.Throws<ArgumentException>(() => baseAttribute.HelpText.ToString());
+        }
+
+
         private class TestBaseAttribute : BaseAttribute
         {
             public TestBaseAttribute()
             {
                 // Do nothing
             }
         }
+
     }
 }