Parse enum unions in config

In particular, `HttpProtocols` and `SslProtocols`.  This should be more forward compatible than adding an explicit enum member for each combination of values.

For #58088

Author: amcasey

src/Servers/Kestrel/Core/src/Internal/ConfigurationReader.cs

@@ -175,37 +175,91 @@ private static Dictionary<string, SniConfig> ReadSni(IConfigurationSection sniCo
 
     private static HttpProtocols? ParseProtocols(string? protocols)
     {
-        if (Enum.TryParse<HttpProtocols>(protocols, ignoreCase: true, out var result))
+        if (protocols is null)
+        {
+            return null;
+        }
+
+        if (protocols.Contains('|'))
+        {
+            var split = protocols.Split('|');
+            var result = HttpProtocols.None;
+            foreach (var protocol in split)
+            {
+                // Enum.TryParse handles trimming
+                if (!TryParseProtocol(protocol, out var parsed))
+                {
+                    return null;
+                }
+                result |= parsed;
+            }
+            return result;
+        }
+        else if (TryParseProtocol(protocols, out var result))
         {
             return result;
         }
 
         return null;
+
+        static bool TryParseProtocol(string protocol, [NotNullWhen(true)] out HttpProtocols result)
+        {
+            if (Enum.TryParse<HttpProtocols>(protocol, ignoreCase: true, out var parsed))
+            {
+                result = parsed;
+                return true;
+            }
+            result = default;
+            return false;
+        }
     }
 
     private static SslProtocols? ParseSslProcotols(IConfigurationSection sslProtocols)
     {
         // Avoid trimming warning from IConfigurationSection.Get<string[]>()
-        string[]? stringProtocols = null;
         var childrenSections = sslProtocols.GetChildren().ToArray();
-        if (childrenSections.Length > 0)
+        if (childrenSections.Length == 0)
+        {
+            return null;
+        }
+
+        var result = SslProtocols.None;
+
+        foreach (var childrenSection in childrenSections)
         {
-            stringProtocols = new string[childrenSections.Length];
-            for (var i = 0; i < childrenSections.Length; i++)
+            var stringProtocols = childrenSection.Value!;
+            if (stringProtocols.Contains('|'))
             {
-                stringProtocols[i] = childrenSections[i].Value!;
+                var split = stringProtocols.Split('|');
+                foreach (var stringProtocol in split)
+                {
+                    // Enum.TryParse handles trimming
+                    if (!TryParseSslProtocol(stringProtocol, out var parsed))
+                    {
+                        // A bad value in any list clobbers all lists
+                        return SslProtocols.None;
+                    }
+                    result |= parsed;
+                }
+            }
+            else if (TryParseSslProtocol(stringProtocols, out var parsed))
+            {
+                result |= parsed;
             }
         }
 
-        return stringProtocols?.Aggregate(SslProtocols.None, (acc, current) =>
+        return result;
+
+        static bool TryParseSslProtocol(string protocol, [NotNullWhen(true)] out SslProtocols result)
         {
-            if (Enum.TryParse(current, ignoreCase: true, out SslProtocols parsed))
+            if (Enum.TryParse<SslProtocols>(protocol, ignoreCase: true, out var parsed))
             {
-                return acc | parsed;
+                result = parsed;
+                return true;
             }
-
-            return acc;
-        });
+            result = default;
+            return false;
+        }
     }
 
     internal static void ThrowIfContainsHttpsOnlyConfiguration(EndpointConfig endpoint)

src/Servers/Kestrel/Kestrel/test/ConfigurationReaderTests.cs

@@ -218,6 +218,62 @@ public void ReadEndpointsSection_ReturnsCollection()
         Assert.True(cert4.AllowInvalid);
     }
 
+    [Fact]
+    public void ReadEndpointWithSingleHttpProtocolSet_ReturnsCorrectValue()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:Protocols", "Http1"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Equal(HttpProtocols.Http1, endpoint.Protocols);
+    }
+
+    [Fact]
+    public void ReadEndpointWithMultipleHttpProtocolsSet_ReturnsCorrectValue()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:Protocols", "Http1AndHttp2"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Equal(HttpProtocols.Http1AndHttp2, endpoint.Protocols);
+    }
+
+    [Fact]
+    public void ReadEndpointWithUnionHttpProtocolsSet_ReturnsCorrectValue()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:Protocols", "Http2 | Http1"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Equal(HttpProtocols.Http1AndHttp2, endpoint.Protocols);
+    }
+
+    [Fact]
+    public void ReadEndpointWithUnionHttpProtocolsSet_ReturnsNullForBadPart()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:Protocols", "Http2 | Http0"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Null(endpoint.Protocols);
+    }
+
     [Fact]
     public void ReadEndpointWithSingleSslProtocolSet_ReturnsCorrectValue()
     {
@@ -251,6 +307,51 @@ public void ReadEndpointWithMultipleSslProtocolsSet_ReturnsCorrectValue()
 #pragma warning restore SYSLIB0039
     }
 
+    [Fact]
+    public void ReadEndpointWithUnionSslProtocolSet_ReturnsCorrectValue()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:SslProtocols:0", "Tls12 | Tls11"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+#pragma warning disable SYSLIB0039 // TLS 1.0 and 1.1 are obsolete
+        Assert.Equal(SslProtocols.Tls11 | SslProtocols.Tls12, endpoint.SslProtocols);
+#pragma warning restore SYSLIB0039
+    }
+
+    [Fact]
+    public void ReadEndpointWithUnionSslProtocolSet_ReturnsNoneForBadPart()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:SslProtocols:0", "Tls12 | Tls0"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Equal(SslProtocols.None, endpoint.SslProtocols);
+    }
+
+    [Fact]
+    public void ReadEndpointWithUnionSslProtocolSet_ReturnsNoneForBadPartInAnyChild()
+    {
+        var config = new ConfigurationBuilder().AddInMemoryCollection(new[]
+        {
+            new KeyValuePair<string, string>("Endpoints:End1:Url", "http://*:5001"),
+            new KeyValuePair<string, string>("Endpoints:End1:SslProtocols:0", "Tls11"),
+            new KeyValuePair<string, string>("Endpoints:End1:SslProtocols:1", "Tls12 | Tls0"),
+        }).Build();
+        var reader = new ConfigurationReader(config);
+
+        var endpoint = reader.Endpoints.First();
+        Assert.Equal(SslProtocols.None, endpoint.SslProtocols);
+    }
+
     [Fact]
     public void ReadEndpointWithSslProtocolSet_ReadsCaseInsensitive()
     {