Add NotRouteConstraint implementation and associated tests

Implements a new route constraint that provides logical negation capabilities
for existing route constraints. This enables developers to create routes that
match when specific constraints do NOT match.

Key Features:
- Single constraint negation: not(int) matches non-integers
- Multiple constraint negation: not(int;bool) matches neither integers nor booleans
- Nested negation support: not(not(int)) for double negation (equivalent to int)
- Parameterized constraints: not(min(18)) for values under 18 or non-numeric
- File extension negation: not(file) for values without file extensions
- String pattern negation: not(alpha) for non-alphabetic values
and other patterns

Examples:
- /users/{id:not(int)} - matches /users/john but not /users/123
- /files/{name:not(file)} - matches /files/readme but not /files/doc.txt
- /ages/{age:not(min(18))} - matches /ages/16 but not /ages/25
- /values/{val:not(int;bool)} - matches /values/text but not /values/123 or /values/true

Implementation:
- Added NotRouteConstraint class with XML documentation
- Supports both IRouteConstraint and IParameterLiteralNodeMatchingPolicy
- Added to RouteOptions default constraint map with 'not' token

Testing:
- Tests for single/multiple constraints, nested negation, edge cases
- Integration tests with HttpContext and service provider scenarios
- Validation of argument null exceptions and error handling
- Performance tests for literal matching optimization

This enables more flexible route patterns by allowing inverse constraint logic.

It can also be used to escape internal implementation details when
building route templates.

Author: sami-daniel

src/Http/Routing/src/Constraints/NotRouteConstraint.cs

@@ -0,0 +1,314 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !COMPONENTS
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing.Matching;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+#else
+using Microsoft.AspNetCore.Components.Routing;
+#endif
+
+namespace Microsoft.AspNetCore.Routing.Constraints;
+
+/// <summary>
+/// A route constraint that negates one or more inner constraints. The constraint matches
+/// when none of the inner constraints match the route value.
+/// </summary>
+/// <remarks>
+/// <para>
+/// The <see cref="NotRouteConstraint"/> implements logical negation for route constraints.
+/// It takes a semicolon-separated list of constraint names and returns <c>true</c> only
+/// when none of the specified constraints match the route value.
+/// </para>
+/// <para>
+/// <strong>Supported Features:</strong>
+/// </para>
+/// <list type="bullet">
+/// <item>
+/// <description>Basic type constraints: <c>int</c>, <c>bool</c>, <c>guid</c>, <c>datetime</c>, <c>decimal</c>, <c>double</c>, <c>float</c>, <c>long</c></description>
+/// </item>
+/// <item>
+/// <description>String constraints: <c>alpha</c>, <c>length(n)</c>, <c>minlength(n)</c>, <c>maxlength(n)</c></description>
+/// </item>
+/// <item>
+/// <description>Numeric constraints: <c>min(n)</c>, <c>max(n)</c>, <c>range(min,max)</c></description>
+/// </item>
+/// <item>
+/// <description>File constraints: <c>file</c>, <c>nonfile</c></description>
+/// </item>
+/// <item>
+/// <description>Special constraints: <c>required</c></description>
+/// </item>
+/// <item>
+/// <description>Multiple constraints with semicolon separation (logical AND of negations)</description>
+/// </item>
+/// <item>
+/// <description>Nested negation patterns (e.g., <c>not(not(int))</c>) - fully supported as recursive constraint evaluation</description>
+/// </item>
+/// </list>
+/// <para>
+/// <strong>Examples:</strong>
+/// </para>
+/// <list type="bullet">
+/// <item>
+/// <term><c>not(int)</c></term>
+/// <description>Matches any value that is NOT an integer (e.g., "abc", "12.5", "true")</description>
+/// </item>
+/// <item>
+/// <term><c>not(int;bool)</c></term>
+/// <description>Matches values that are neither integers nor booleans (e.g., "abc", "12.5")</description>
+/// </item>
+/// <item>
+/// <term><c>not(not(int))</c></term>
+/// <description>Double negation - matches integers (equivalent to just using <c>int</c> constraint)</description>
+/// </item>
+/// <item>
+/// <term><c>not(min(18))</c></term>
+/// <description>Matches integer values less than 18 or non-integer values</description>
+/// </item>
+/// <item>
+/// <term><c>not(alpha)</c></term>
+/// <description>Matches non-alphabetic values (e.g., "123", "test123")</description>
+/// </item>
+/// <item>
+/// <term><c>not(file)</c></term>
+/// <description>Matches values that don't contain file extensions</description>
+/// </item>
+/// </list>
+/// <para>
+/// <strong>Important Notes:</strong>
+/// </para>
+/// <list type="bullet">
+/// <item>
+/// <description>Unknown constraint names are ignored and always treated as non-matching, resulting in negation returning <c>true</c></description>
+/// </item>
+/// <item>
+/// <description>Nested negation patterns are fully supported and work recursively (e.g., <c>not(not(int))</c> = double negation)</description>
+/// </item>
+/// <item>
+/// <description>Multiple constraints are combined with logical AND - ALL inner constraints must fail for the negation to succeed</description>
+/// </item>
+/// <item>
+/// <description>Works with both route matching and literal parameter matching scenarios</description>
+/// </item>
+/// </list>
+/// </remarks>
+#if !COMPONENTS
+public class NotRouteConstraint : IRouteConstraint, IParameterLiteralNodeMatchingPolicy
+#else
+internal class NotRouteConstraint : IRouteConstraint
+#endif
+{
+    /// <summary>
+    /// Gets the array of inner constraint names to be negated.
+    /// </summary>
+    private string[] _inner { get; }
+
+    /// <summary>
+    /// Cached constraint map to avoid repeated reflection-based lookups.
+    /// </summary>
+    private static IDictionary<string, Type>? _cachedConstraintMap;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="NotRouteConstraint"/> class
+    /// with the specified inner constraints.
+    /// </summary>
+    /// <param name="constraints">
+    /// A semicolon-separated string containing the names of constraints to negate.
+    /// Can be a single constraint name (e.g., "int") or multiple constraints (e.g., "int;bool;guid").
+    /// Parameterized constraints are supported (e.g., "min(18);length(5)").
+    /// Unknown constraint names are treated as non-matching constraints.
+    /// </param>
+    /// <remarks>
+    /// <para>The constraints string is split by semicolons to create individual constraint checks.</para>
+    /// <para>Examples of valid constraint strings:</para>
+    /// <list type="bullet">
+    /// <item><description><c>"int"</c> - Single type constraint</description></item>
+    /// <item><description><c>"int;bool"</c> - Multiple type constraints</description></item>
+    /// <item><description><c>"min(18)"</c> - Parameterized constraint</description></item>
+    /// <item><description><c>"length(5);alpha"</c> - Mixed constraint types</description></item>
+    /// <item><description><c>""</c> - Empty string (always returns true)</description></item>
+    /// </list>
+    /// </remarks>
+    public NotRouteConstraint(string constraints)
+    {
+        _inner = constraints.Split(";");
+    }
+
+    private static IDictionary<string, Type> GetConstraintMap()
+    {
+        // Use cached map or fall back to default constraint map
+        return _cachedConstraintMap ??= GetDefaultConstraintMap();
+    }
+
+    private static Dictionary<string, Type> GetDefaultConstraintMap()
+    {
+        // FIXME: I'm not sure if this is a good thing to do because
+        // it requires weak spreading between the ConstraintMap and
+        // RouteOptions. It doesn't seem appropriate to create two
+        // identical variables for this...
+
+        var defaults = new Dictionary<string, Type>(StringComparer.OrdinalIgnoreCase)
+        {
+            // Type-specific constraints
+            ["int"] = typeof(IntRouteConstraint),
+            ["bool"] = typeof(BoolRouteConstraint),
+            ["datetime"] = typeof(DateTimeRouteConstraint),
+            ["decimal"] = typeof(DecimalRouteConstraint),
+            ["double"] = typeof(DoubleRouteConstraint),
+            ["float"] = typeof(FloatRouteConstraint),
+            ["guid"] = typeof(GuidRouteConstraint),
+            ["long"] = typeof(LongRouteConstraint),
+
+            // Length constraints
+            ["minlength"] = typeof(MinLengthRouteConstraint),
+            ["maxlength"] = typeof(MaxLengthRouteConstraint),
+            ["length"] = typeof(LengthRouteConstraint),
+
+            // Min/Max value constraints
+            ["min"] = typeof(MinRouteConstraint),
+            ["max"] = typeof(MaxRouteConstraint),
+            ["range"] = typeof(RangeRouteConstraint),
+
+            // Alpha constraint
+            ["alpha"] = typeof(AlphaRouteConstraint),
+
+#if !COMPONENTS
+            ["required"] = typeof(RequiredRouteConstraint),
+#endif
+
+            // File constraints
+            ["file"] = typeof(FileNameRouteConstraint),
+            ["nonfile"] = typeof(NonFileNameRouteConstraint),
+
+            // Not constraint
+            ["not"] = typeof(NotRouteConstraint)
+        };
+
+        return defaults;
+    }
+
+    /// <inheritdoc />
+    /// <remarks>
+    /// <para>
+    /// This method implements the core negation logic by:
+    /// </para>
+    /// <list type="number">
+    /// <item>Resolving each inner constraint name to its corresponding <see cref="IRouteConstraint"/> implementation</item>
+    /// <item>Testing each resolved constraint against the route value</item>
+    /// <item>Returning <c>false</c> immediately if any constraint matches (short-circuit evaluation)</item>
+    /// <item>Returning <c>true</c> only if no constraints match</item>
+    /// </list>
+    /// <para>
+    /// The method attempts to use the constraint map from <see cref="RouteOptions"/> if available via 
+    /// the HTTP context's service provider, falling back to the default constraint map if needed.
+    /// </para>
+    /// <para>
+    /// Unknown constraint names are ignored (treated as non-matching), which means they don't affect
+    /// the negation result.
+    /// </para>
+    /// </remarks>
+    public bool Match(
+#if !COMPONENTS
+        HttpContext? httpContext,
+        IRouter? route,
+        string routeKey,
+        RouteValueDictionary values,
+        RouteDirection routeDirection)
+#else
+        string routeKey,
+        RouteValueDictionary values)
+#endif
+    {
+        ArgumentNullException.ThrowIfNull(routeKey);
+        ArgumentNullException.ThrowIfNull(values);
+
+        // Try to get constraint map from HttpContext first, fallback to default map
+        IDictionary<string, Type> constraintMap;
+        IServiceProvider? serviceProvider = null;
+
+#if !COMPONENTS
+        if (httpContext?.RequestServices != null)
+        {
+            try
+            {
+                var routeOptions = httpContext.RequestServices.GetService<IOptions<RouteOptions>>();
+                if (routeOptions != null)
+                {
+                    constraintMap = routeOptions.Value.TrimmerSafeConstraintMap;
+                    serviceProvider = httpContext.RequestServices;
+                }
+                else
+                {
+                    constraintMap = GetConstraintMap();
+                }
+            }
+            catch
+            {
+                constraintMap = GetConstraintMap();
+            }
+        }
+        else
+        {
+            constraintMap = GetConstraintMap();
+        }
+#else
+        constraintMap = GetConstraintMap();
+#endif
+
+        foreach (var constraintText in _inner)
+        {
+            var resolvedConstraint = ParameterPolicyActivator.ResolveParameterPolicy<IRouteConstraint>(
+                constraintMap,
+                serviceProvider,
+                constraintText,
+                out _);
+
+            if (resolvedConstraint != null)
+            {
+                // If any inner constraint matches, return false (negation logic)
+#if !COMPONENTS
+                if (resolvedConstraint.Match(httpContext, route, routeKey, values, routeDirection))
+#else
+                if (resolvedConstraint.Match(routeKey, values))
+#endif
+                {
+                    return false;
+                }
+            }
+        }
+
+        // If no inner constraints matched, return true (all constraints were negated)
+        return true;
+    }
+
+#if !COMPONENTS
+    bool IParameterLiteralNodeMatchingPolicy.MatchesLiteral(string parameterName, string literal)
+    {
+        var constraintMap = GetConstraintMap();
+
+        foreach (var constraintText in _inner)
+        {
+            var resolvedConstraint = ParameterPolicyActivator.ResolveParameterPolicy<IRouteConstraint>(
+                constraintMap,
+                null,
+                constraintText,
+                out _);
+
+            if (resolvedConstraint is IParameterLiteralNodeMatchingPolicy literalPolicy)
+            {
+                // If any inner constraint matches the literal, return false (negation logic)
+                if (literalPolicy.MatchesLiteral(parameterName, literal))
+                {
+                    return false;
+                }
+            }
+        }
+
+        // If no inner constraints matched the literal, return true
+        return true;
+    }
+#endif
+}

src/Http/Routing/src/PublicAPI.Unshipped.txt

@@ -1,3 +1,6 @@
 #nullable enable
 Microsoft.AspNetCore.Builder.ValidationEndpointConventionBuilderExtensions
+Microsoft.AspNetCore.Routing.Constraints.NotRouteConstraint
+Microsoft.AspNetCore.Routing.Constraints.NotRouteConstraint.Match(Microsoft.AspNetCore.Http.HttpContext? httpContext, Microsoft.AspNetCore.Routing.IRouter? route, string! routeKey, Microsoft.AspNetCore.Routing.RouteValueDictionary! values, Microsoft.AspNetCore.Routing.RouteDirection routeDirection) -> bool
+Microsoft.AspNetCore.Routing.Constraints.NotRouteConstraint.NotRouteConstraint(string! constraints) -> void
 static Microsoft.AspNetCore.Builder.ValidationEndpointConventionBuilderExtensions.DisableValidation<TBuilder>(this TBuilder builder) -> TBuilder

src/Http/Routing/src/RouteOptions.cs

@@ -141,6 +141,8 @@ private static IDictionary<string, Type> GetDefaultConstraintMap()
         AddConstraint<FileNameRouteConstraint>(defaults, "file");
         AddConstraint<NonFileNameRouteConstraint>(defaults, "nonfile");
 
+        // Not constraint
+        AddConstraint<NotRouteConstraint>(defaults, "not");
         return defaults;
     }