Atomically swap config data (dotnet/extensions#1202)

Swap the configuration providers' data atomically, rather than directly changing the property, so that any enumeration of the dictionary running during the reload operation does not throw an InvalidOperationException due to the collection being modified.
Relates to dotnet/extensions#1189.


Commit migrated from dotnet/extensions@192abfd

src/libraries/Microsoft.Extensions.Configuration.EnvironmentVariables/src/EnvironmentVariablesConfigurationProvider.cs

@@ -48,7 +48,7 @@ public override void Load()
 
         internal void Load(IDictionary envVariables)
         {
-            Data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+            var data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
 
             var filteredEnvVariables = envVariables
                 .Cast<DictionaryEntry>()
@@ -58,8 +58,10 @@ internal void Load(IDictionary envVariables)
             foreach (var envVariable in filteredEnvVariables)
             {
                 var key = ((string)envVariable.Key).Substring(_prefix.Length);
-                Data[key] = (string)envVariable.Value;
+                data[key] = (string)envVariable.Value;
             }
+
+            Data = data;
         }
 
         private static string NormalizeKey(string key)

src/libraries/Microsoft.Extensions.Configuration.EnvironmentVariables/tests/EnvironmentVariablesTest.cs

@@ -1,7 +1,11 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.Extensions.Configuration.Test;
 using Xunit;
 
@@ -148,5 +152,48 @@ public void ReplaceDoubleUnderscoreInEnvironmentVariables()
             Assert.Equal("connection", envConfigSrc.Get("data:ConnectionString"));
             Assert.Equal("System.Data.SqlClient", envConfigSrc.Get("ConnectionStrings:_db1_ProviderName"));
         }
+
+        [Fact]
+        public void BindingDoesNotThrowIfReloadedDuringBinding()
+        {
+            var dic = new Dictionary<string, string>
+            {
+                {"Number", "-2"},
+                {"Text", "Foo"}
+            };
+            var configurationBuilder = new ConfigurationBuilder();
+            configurationBuilder.AddInMemoryCollection(dic);
+            configurationBuilder.AddEnvironmentVariables();
+            var config = configurationBuilder.Build();
+
+            MyOptions options = null;
+
+            using (var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(250)))
+            {
+                void ReloadLoop()
+                {
+                    while (!cts.IsCancellationRequested)
+                    {
+                        config.Reload();
+                    }
+                }
+
+                _ = Task.Run(ReloadLoop);
+
+                while (!cts.IsCancellationRequested)
+                {
+                    options = config.Get<MyOptions>();
+                }
+            }
+
+            Assert.Equal(-2, options.Number);
+            Assert.Equal("Foo", options.Text);
+        }
+
+        private sealed class MyOptions
+        {
+            public int Number { get; set; }
+            public string Text { get; set; }
+        }
     }
 }

src/libraries/Microsoft.Extensions.Configuration/tests/FunctionalTests/ConfigurationTests.cs

@@ -5,13 +5,13 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Testing;
 using Microsoft.AspNetCore.Testing.xunit;
 using Microsoft.Extensions.Configuration.Ini;
 using Microsoft.Extensions.Configuration.Json;
-using Microsoft.Extensions.Configuration.Xml;
 using Microsoft.Extensions.Configuration.UserSecrets;
+using Microsoft.Extensions.Configuration.Xml;
 using Microsoft.Extensions.FileProviders;
 using Microsoft.Extensions.Primitives;
 using Xunit;
@@ -944,6 +944,48 @@ await WaitForChange(
             Assert.True(token.HasChanged);
         }
 
+        [Fact]
+        public void BindingDoesNotThrowIfReloadedDuringBinding()
+        {
+            WriteTestFiles();
+
+            var configurationBuilder = CreateBuilder();
+            configurationBuilder.Add(new TestIniSourceProvider(_iniFile));
+            configurationBuilder.Add(new TestJsonSourceProvider(_jsonFile));
+            configurationBuilder.Add(new TestXmlSourceProvider(_xmlFile));
+            configurationBuilder.AddEnvironmentVariables();
+            configurationBuilder.AddCommandLine(new[] { "--CmdKey1=CmdValue1" });
+            configurationBuilder.AddInMemoryCollection(_memConfigContent);
+
+            var config = configurationBuilder.Build();
+
+            using (var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(250)))
+            {
+                void ReloadLoop()
+                {
+                    while (!cts.IsCancellationRequested)
+                    {
+                        config.Reload();
+                    }
+                }
+
+                _ = Task.Run(ReloadLoop);
+
+                MyOptions options = null;
+
+                while (!cts.IsCancellationRequested)
+                {
+                    options = config.Get<MyOptions>();
+                }
+
+                Assert.Equal("CmdValue1", options.CmdKey1);
+                Assert.Equal("IniValue1", options.IniKey1);
+                Assert.Equal("JsonValue1", options.JsonKey1);
+                Assert.Equal("MemValue1", options.MemKey1);
+                Assert.Equal("XmlValue1", options.XmlKey1);
+            }
+        }
+
         public void Dispose()
         {
             _fileProvider.Dispose();
@@ -966,5 +1008,18 @@ private async Task WaitForChange(
                 await Task.Delay(_msDelay);
             }
         }
+
+        private sealed class MyOptions
+        {
+            public string CmdKey1 { get; set; }
+
+            public string IniKey1 { get; set; }
+
+            public string JsonKey1 { get; set; }
+
+            public string MemKey1 { get; set; }
+
+            public string XmlKey1 { get; set; }
+        }
     }
 }

src/libraries/Microsoft.Extensions.Configuration/tests/FunctionalTests/Microsoft.Extensions.Configuration.Functional.Tests.csproj

@@ -9,6 +9,9 @@
   </ItemGroup>
 
   <ItemGroup>
+    <Reference Include="Microsoft.Extensions.Configuration.Binder" />
+    <Reference Include="Microsoft.Extensions.Configuration.CommandLine" />
+    <Reference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" />
     <Reference Include="Microsoft.Extensions.Configuration.Ini" />
     <Reference Include="Microsoft.Extensions.Configuration.Json" />
     <Reference Include="Microsoft.Extensions.Configuration.Xml" />