Refactored parts of AssertionScope into AssertionChain and used that …

…to improve the identifier in .Which constructs.

.editorconfig

@@ -199,6 +199,11 @@ dotnet_diagnostic.SA1116.severity = none
 dotnet_diagnostic.SA1117.severity = none
 # SA1200: Using directive should appear within a namespace declaration
 dotnet_diagnostic.SA1200.severity = none
+
+# Purpose: Use string. Empty for empty strings
+# Reason: There's no performance difference. See https://medium.com/@dk.kravtsov/string-empty-vs-in-c-70c64971161f 
+dotnet_diagnostic.SA1122.severity = none
+
 # SA1124: Do not use regions
 dotnet_diagnostic.SA1124.severity = none
 # SA1201: A property should not follow a method

Build/Build.cs

@@ -1,10 +1,6 @@
 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Net.Http;
-using System.Runtime.InteropServices;
 using LibGit2Sharp;
-using Microsoft.Build.Tasks;
 using Nuke.Common;
 using Nuke.Common.CI.GitHubActions;
 using Nuke.Common.Execution;

Build/_build.csproj

@@ -7,6 +7,7 @@
     <NukeRootDirectory>..\</NukeRootDirectory>
     <NukeScriptDirectory>..\</NukeScriptDirectory>
     <NukeVersion>8.1.0</NukeVersion>
+    <NukeTelemetryVersion>1</NukeTelemetryVersion>
   </PropertyGroup>
   <PropertyGroup Condition="$([MSBuild]::IsOSPlatform('Windows'))">
     <DefineConstants>OS_WINDOWS</DefineConstants>

FluentAssertions.sln.DotSettings

@@ -1,4 +1,4 @@
-<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
 	<s:Boolean x:Key="/Default/CodeEditing/Intellisense/CodeCompletion/AutoCompleteBasicCompletion/@EntryValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeEditing/Intellisense/LookupWindow/ShowSignatures/@EntryValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/CodeEditing/TypingAssist/FormatBlockOnRBrace/@EntryValue">False</s:Boolean>
@@ -143,7 +143,7 @@
 	<s:String x:Key="/Default/CodeStyle/Naming/XamlNaming/UserRules/=NAMESPACE_005FALIAS/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/XamlNaming/UserRules/=XAML_005FFIELD/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/XamlNaming/UserRules/=XAML_005FRESOURCE/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AaBb" /&gt;</s:String>
-
+	
 	<s:String x:Key="/Default/Environment/Editor/MatchingBraceHighlighting/Style/@EntryValue">OUTLINE</s:String>
 	<s:String x:Key="/Default/Environment/Hierarchy/PsiConfigurationSettingsKey/LocationType/@EntryValue">SOLUTION_FOLDER</s:String>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EFeature_002EServices_002EDaemon_002ESettings_002EMigration_002ESwaWarningsModeSettingsMigrate/@EntryIndexedValue">True</s:Boolean>
@@ -161,17 +161,17 @@
 	<s:Int64 x:Key="/Default/Environment/UnitTesting/ParallelProcessesCount/@EntryValue">4</s:Int64>
 	<s:Boolean x:Key="/Default/Environment/UnitTesting/ShadowCopy/@EntryValue">False</s:Boolean>
 	<s:Boolean x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/@KeyIndexDefined">True</s:Boolean>
-	<s:Boolean x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=behavior/@KeyIndexDefined">True</s:Boolean>
-	<s:Int64 x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=behavior/Order/@EntryValue">1</s:Int64>
-	<s:Boolean x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=scenario/@KeyIndexDefined">True</s:Boolean>
-	<s:Int64 x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=scenario/Order/@EntryValue">0</s:Int64>
+	<s:Boolean x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=behavior/@KeyIndexDefined">False</s:Boolean>
+
+	<s:Boolean x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Field/=scenario/@KeyIndexDefined">False</s:Boolean>
+
 	<s:String x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Shortcut/@EntryValue">aaa</s:String>
 	<s:String x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Description/@EntryValue">Arrange-Act-Assert</s:String>
 	<s:String x:Key="/Default/PatternsAndTemplates/LiveTemplates/Template/=012E3B0572DEF2448B0B5D9AA88E6210/Text/@EntryValue">[Fact]
 public void $END$()
 {
     // Arrange
-
+    
 
     // Act
 

Src/FluentAssertions/AndWhichConstraint.cs

@@ -2,45 +2,84 @@
 using System.Collections.Generic;
 using System.Linq;
 using FluentAssertions.Common;
+using FluentAssertions.Execution;
 using FluentAssertions.Formatting;
 
 namespace FluentAssertions;
 
 /// <summary>
-/// Constraint which can be returned from an assertion which matches a condition and which will allow
-/// further matches to be performed on the matched condition as well as the parent constraint.
+/// Provides a <see cref="Which"/> property that can be used in chained assertions where the prior assertions returns a
+/// single object that the assertion continues on.
 /// </summary>
-/// <typeparam name="TParentConstraint">The type of the original constraint that was matched</typeparam>
-/// <typeparam name="TMatchedElement">The type of the matched object which the parent constraint matched</typeparam>
-public class AndWhichConstraint<TParentConstraint, TMatchedElement> : AndConstraint<TParentConstraint>
+public class AndWhichConstraint<TParent, TSubject> : AndConstraint<TParent>
 {
-    private readonly Lazy<TMatchedElement> matchedConstraint;
+    private readonly AssertionChain assertionChain;
+    private readonly string pathPostfix;
+    private readonly Lazy<TSubject> getSubject;
 
-    public AndWhichConstraint(TParentConstraint parentConstraint, TMatchedElement matchedConstraint)
-        : base(parentConstraint)
+    /// <summary>
+    /// Creates an object that allows continuing an assertion executed through <paramref name="parent"/> and
+    /// which resulted in a single <paramref name="subject"/>.
+    /// </summary>
+    public AndWhichConstraint(TParent parent, TSubject subject)
+        : base(parent)
+    {
+        getSubject = new Lazy<TSubject>(() => subject);
+    }
+
+    /// <summary>
+    /// Creates an object that allows continuing an assertion executed through <paramref name="parent"/> and
+    /// which resulted in a single <paramref name="subject"/> on an existing <paramref name="assertionChain"/>, but where
+    /// the previous caller identifier is post-fixed with <paramref name="pathPostfix"/>.
+    /// </summary>
+    public AndWhichConstraint(TParent parent, TSubject subject, AssertionChain assertionChain, string pathPostfix = "")
+        : base(parent)
     {
-        this.matchedConstraint =
-            new Lazy<TMatchedElement>(() => matchedConstraint);
+        getSubject = new Lazy<TSubject>(() => subject);
+
+        this.assertionChain = assertionChain;
+        this.pathPostfix = pathPostfix;
     }
 
-    public AndWhichConstraint(TParentConstraint parentConstraint, IEnumerable<TMatchedElement> matchedConstraint)
-        : base(parentConstraint)
+    /// <summary>
+    /// Creates an object that allows continuing an assertion executed through <paramref name="parent"/> and
+    /// which resulted in a potential collection of objects through <paramref name="subjects"/>.
+    /// </summary>
+    /// <remarks>
+    /// If <paramref name="subjects"/> contains more than one object, a clear exception is thrown.
+    /// </remarks>
+    public AndWhichConstraint(TParent parent, IEnumerable<TSubject> subjects)
+        : base(parent)
     {
-        this.matchedConstraint =
-            new Lazy<TMatchedElement>(
-                () => SingleOrDefault(matchedConstraint));
+        getSubject = new Lazy<TSubject>(() => SingleOrDefault(subjects));
     }
 
-    private static TMatchedElement SingleOrDefault(
-        IEnumerable<TMatchedElement> matchedConstraint)
+    /// <summary>
+    /// Creates an object that allows continuing an assertion executed through <paramref name="parent"/> and
+    /// which resulted in a potential collection of objects through <paramref name="subjects"/> on an
+    /// existing <paramref name="assertionChain"/>, but where
+    /// the previous caller identifier is post-fixed with <paramref name="pathPostfix"/>.
+    /// </summary>
+    /// <remarks>
+    /// If <paramref name="subjects"/> contains more than one object, a clear exception is thrown.
+    /// </remarks>
+    public AndWhichConstraint(TParent parent, IEnumerable<TSubject> subjects, AssertionChain assertionChain, string pathPostfix)
+        : base(parent)
     {
-        TMatchedElement[] matchedElements = matchedConstraint.ToArray();
+        getSubject = new Lazy<TSubject>(() => SingleOrDefault(subjects));
+
+        this.assertionChain = assertionChain;
+        this.pathPostfix = pathPostfix;
+    }
+
+    private static TSubject SingleOrDefault(IEnumerable<TSubject> subjects)
+    {
+        TSubject[] matchedElements = subjects.ToArray();
 
         if (matchedElements.Length > 1)
         {
             string foundObjects = string.Join(Environment.NewLine,
-                matchedElements.Select(
-                    ele => "\t" + Formatter.ToString(ele)));
+                matchedElements.Select(ele => "\t" + Formatter.ToString(ele)));
 
             string message = "More than one object found.  FluentAssertions cannot determine which object is meant."
                 + $"  Found objects:{Environment.NewLine}{foundObjects}";
@@ -54,13 +93,24 @@ private static TMatchedElement SingleOrDefault(
     /// <summary>
     /// Returns the single result of a prior assertion that is used to select a nested or collection item.
     /// </summary>
-    public TMatchedElement Which => matchedConstraint.Value;
+    /// <remarks>
+    /// Just a convenience property that returns the same value as <see cref="Which"/>.
+    /// </remarks>
+    public TSubject Subject => Which;
 
     /// <summary>
     /// Returns the single result of a prior assertion that is used to select a nested or collection item.
     /// </summary>
-    /// <remarks>
-    /// Just a convenience property that returns the same value as <see cref="Which"/>.
-    /// </remarks>
-    public TMatchedElement Subject => Which;
+    public TSubject Which
+    {
+        get
+        {
+            if (pathPostfix is not null and not "")
+            {
+                assertionChain.WithCallerPostfix(pathPostfix).ReuseOnce();
+            }
+
+            return getSubject.Value;
+        }
+    }
 }