Fixed merge for substitutions (#138)

* Added failing test

* Make substitution to use deep copy + fixed deep clone for some types

* NRE fix

* Fixed deep clone to take substitutions into account

Author: IgorFedchenko

src/Hocon.Configuration.Test/ConfigurationSpec.cs

@@ -8,6 +8,7 @@
 using System;
 using System.Configuration;
 using System.Linq;
+using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -273,6 +274,26 @@ public void CanEnumerateQuotedKeys()
 
             Assert.Equal("some quoted, key", enumerable.Select(kvp => kvp.Key).First());
         }
+        
+        [Fact]
+        public void CanSubstituteArrayCorrectly()
+        {
+            var hocon = @"
+ c: {
+    q: {
+        a: [2, 5]
+    }
+}
+c: {
+    m: ${c.q} {a: [6]}
+}
+";
+            var config = ConfigurationFactory.ParseString(hocon);
+            var unchanged = config.GetIntList("c.q.a");
+            unchanged.Should().Equal(new [] { 2, 5 });
+            var changed = config.GetIntList("c.m.a");
+            changed.Should().Equal(new [] { 6 });
+        }
 
         [Fact]
         public void CanParseSerializersAndBindings()

src/Hocon.Configuration.Test/Hocon.Configuration.Tests.csproj

@@ -6,6 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="FluentAssertions" Version="5.9.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="$(TestSdkVersion)" />
     <PackageReference Include="xunit" Version="$(XunitVersion)" />
     <DotNetCliToolReference Include="dotnet-xunit" Version="$(XunitCliVersion)" />

src/Hocon/Extensions/HoconElementExtensions.cs

@@ -0,0 +1,19 @@
+namespace Hocon.Extensions
+{
+    /// <summary>
+    /// HoconElementExtensions
+    /// </summary>
+    public static class HoconElementExtensions
+    {
+        /// <summary>
+        /// Performs deep clone of the element's value.
+        /// This is generally the same as <see cref="IHoconElement.Clone"/>, but
+        /// for substitutions it returns the substitution itself since it's value will be closed
+        /// during resolution process.
+        /// </summary>
+        public static IHoconElement CloneValue(this IHoconElement hoconElement, IHoconElement newParent)
+        {
+            return hoconElement is HoconSubstitution ? hoconElement : hoconElement.Clone(newParent);
+        }
+    }
+}

src/Hocon/Impl/HoconObject.cs

@@ -11,6 +11,7 @@
 using System.Linq;
 using System.Runtime.InteropServices.ComTypes;
 using System.Text;
+using Hocon.Extensions;
 
 namespace Hocon
 {
@@ -400,7 +401,7 @@ public IHoconElement Clone(IHoconElement newParent)
             var clone = new HoconObject(newParent);
             foreach (var kvp in this)
             {
-                clone.SetField(kvp.Key, kvp.Value);
+                clone.SetField(kvp.Key, kvp.Value.CloneValue(clone) as HoconField);
             }
             return clone;
         }

src/Hocon/Impl/HoconValue.cs

@@ -13,6 +13,7 @@
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
+using Hocon.Extensions;
 
 namespace Hocon
 {
@@ -706,7 +707,7 @@ public virtual IHoconElement Clone(IHoconElement newParent)
             var clone = new HoconValue(newParent);
             foreach (var element in this)
             {
-                clone.Add(element);
+                clone.Add(element.CloneValue(clone));
             }
             return clone;
         }

src/Hocon/Parser.cs

@@ -1,4 +1,4 @@
-//-----------------------------------------------------------------------
+//-----------------------------------------------------------------------
 // <copyright file="Parser.cs" company="Hocon Project">
 //     Copyright (C) 2009-2018 Lightbend Inc. <http://www.lightbend.com>
 //     Copyright (C) 2013-2018 .NET Foundation <https://github.com/akkadotnet/hocon>
@@ -184,7 +184,7 @@ private HoconValue ResolveSubstitution(HoconSubstitution sub)
 
             // third case, regular substitution
             _root.GetObject().TryGetValue(sub.Path, out var field);
-            return field;
+            return field?.Clone(field.Parent) as HoconValue;
         }
 
         private bool IsValueCyclic(HoconField field, HoconSubstitution sub)