Issue3918 white space (#4664)

* Remove need for casts when using ConstraintExpression.Append

* Fix nullability of StringContraint.Matches

* Add `WhiteSpace` Constraint

* Add support for `.IgnoreWhiteSpace` modifier

to:
- AnyOfConstraint
- CollectionItemsEqualConstaint
- ContainsConstraint
- EqualConstraint
- UniqueItemsConstraint

Updates to Clip String
Requires individual clipping when white-space is ignored.
We then also need to show two different ^ to indicate the mismatched
location.

* Code review changes

* Make it clear that what the extra size is for when creating StringBuilder

nuget/framework/nunit.nuspec

@@ -33,6 +33,7 @@
     <dependencies>
       <group targetFramework="net462">
         <dependency id="System.Threading.Tasks.Extensions" version="4.5.4" exclude="Build,Analyzers" />
+        <dependency id="System.ValueTuple" version="4.5.0" exclude="Build,Analyzers" />
       </group>
       <group targetFramework="net6.0" />
     </dependencies>

src/NUnitFramework/framework/Constraints/AnyOfConstraint.cs

@@ -70,6 +70,18 @@ public AnyOfConstraint IgnoreCase
             }
         }
 
+        /// <summary>
+        /// Flag the constraint to ignore white space and return self.
+        /// </summary>
+        public AnyOfConstraint IgnoreWhiteSpace
+        {
+            get
+            {
+                _comparer.IgnoreWhiteSpace = true;
+                return this;
+            }
+        }
+
         /// <summary>
         /// Flag the constraint to use the supplied IComparer object.
         /// </summary>

src/NUnitFramework/framework/Constraints/CollectionItemsEqualConstraint.cs

@@ -40,6 +40,11 @@ protected CollectionItemsEqualConstraint(object? arg) : base(arg)
         /// </summary>
         protected bool IgnoringCase => _comparer.IgnoreCase;
 
+        /// <summary>
+        /// Get a flag indicating whether the user requested us to ignore white space.
+        /// </summary>
+        protected bool IgnoringWhiteSpace => _comparer.IgnoreWhiteSpace;
+
         /// <summary>
         /// Get a flag indicating whether any external comparers are in use.
         /// </summary>
@@ -61,6 +66,18 @@ public CollectionItemsEqualConstraint IgnoreCase
             }
         }
 
+        /// <summary>
+        /// Flag the constraint to ignore white space and return self.
+        /// </summary>
+        public CollectionItemsEqualConstraint IgnoreWhiteSpace
+        {
+            get
+            {
+                _comparer.IgnoreWhiteSpace = true;
+                return this;
+            }
+        }
+
         /// <summary>
         /// Flag the constraint to use the supplied IComparer object.
         /// </summary>

src/NUnitFramework/framework/Constraints/Comparers/StringsComparer.cs

@@ -17,9 +17,22 @@ public static EqualMethodResult Equal(object x, object y, ref Tolerance toleranc
             if (tolerance.HasVariance)
                 return EqualMethodResult.ToleranceNotSupported;
 
-            var stringComparison = equalityComparer.IgnoreCase ? StringComparison.CurrentCultureIgnoreCase : StringComparison.Ordinal;
-            return xString.Equals(yString, stringComparison) ?
-                EqualMethodResult.ComparedEqual : EqualMethodResult.ComparedNotEqual;
+            return Equals(xString, yString, equalityComparer.IgnoreCase, equalityComparer.IgnoreWhiteSpace) ?
+                EqualMethodResult.ComparedEqual :
+                EqualMethodResult.ComparedNotEqual;
+        }
+
+        public static bool Equals(string x, string y, bool ignoreCase, bool ignoreWhiteSpace)
+        {
+            if (ignoreWhiteSpace)
+            {
+                (int mismatchExpected, int mismatchActual) = MsgUtils.FindMismatchPosition(x, y, ignoreCase, true);
+                return mismatchExpected == -1 && mismatchActual == -1;
+            }
+            else
+            {
+                return x.Equals(y, ignoreCase ? StringComparison.CurrentCultureIgnoreCase : StringComparison.Ordinal);
+            }
         }
     }
 }