dotnet · Copilot · Aug 22, 2025 · Aug 22, 2025 · Aug 22, 2025 · Aug 22, 2025
diff --git a/Microsoft.Maui.sln b/Microsoft.Maui.sln
@@ -4,6 +4,8 @@ VisualStudioVersion = 17.0.31410.414
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Core", "src\Core\src\Core.csproj", "{95BA42B5-B00E-4986-B9B5-517140378452}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Core.ConfigurationSourceGen", "src\Core\src\ConfigurationSourceGen\Core.ConfigurationSourceGen.csproj", "{2A1B3C4D-5E6F-7890-ABCD-EF1234567890}"
+EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Controls.Core", "src\Controls\src\Core\Controls.Core.csproj", "{AF64451F-E2BD-41C2-B083-F60C26AE2A9F}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Compatibility", "src\Compatibility\Core\src\Compatibility.csproj", "{00A11C2F-969F-4964-8557-91ADF4B1523D}"
@@ -38,6 +40,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TestUtils", "src\TestUtils\
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Core.UnitTests", "src\Core\tests\UnitTests\Core.UnitTests.csproj", "{92644F6F-5946-48FC-A21A-A3D6EE24E8B3}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Core.ConfigurationSourceGen.UnitTests", "src\Core\tests\ConfigurationSourceGen.UnitTests\Core.ConfigurationSourceGen.UnitTests.csproj", "{1F2E3D4C-5B6A-7890-CDEF-123456789ABC}"
+EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{E8AD265B-3C67-4640-AC58-A522F9FB3361}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "test", "test", "{C564DDD6-DE79-45CD-88EA-3F690481572A}"
@@ -259,6 +263,10 @@ Global
 		{95BA42B5-B00E-4986-B9B5-517140378452}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{95BA42B5-B00E-4986-B9B5-517140378452}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{95BA42B5-B00E-4986-B9B5-517140378452}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2A1B3C4D-5E6F-7890-ABCD-EF1234567890}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2A1B3C4D-5E6F-7890-ABCD-EF1234567890}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2A1B3C4D-5E6F-7890-ABCD-EF1234567890}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2A1B3C4D-5E6F-7890-ABCD-EF1234567890}.Release|Any CPU.Build.0 = Release|Any CPU
 		{AF64451F-E2BD-41C2-B083-F60C26AE2A9F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{AF64451F-E2BD-41C2-B083-F60C26AE2A9F}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{AF64451F-E2BD-41C2-B083-F60C26AE2A9F}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -301,6 +309,10 @@ Global
 		{92644F6F-5946-48FC-A21A-A3D6EE24E8B3}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{92644F6F-5946-48FC-A21A-A3D6EE24E8B3}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{92644F6F-5946-48FC-A21A-A3D6EE24E8B3}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1F2E3D4C-5B6A-7890-CDEF-123456789ABC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1F2E3D4C-5B6A-7890-CDEF-123456789ABC}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1F2E3D4C-5B6A-7890-CDEF-123456789ABC}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1F2E3D4C-5B6A-7890-CDEF-123456789ABC}.Release|Any CPU.Build.0 = Release|Any CPU
 		{F7F2B379-52CE-4802-9EC9-0D7967B6BFB7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{F7F2B379-52CE-4802-9EC9-0D7967B6BFB7}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{F7F2B379-52CE-4802-9EC9-0D7967B6BFB7}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -648,6 +660,7 @@ Global
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{95BA42B5-B00E-4986-B9B5-517140378452} = {E8AD265B-3C67-4640-AC58-A522F9FB3361}
+		{2A1B3C4D-5E6F-7890-ABCD-EF1234567890} = {E8AD265B-3C67-4640-AC58-A522F9FB3361}
 		{AF64451F-E2BD-41C2-B083-F60C26AE2A9F} = {50C758FE-4E10-409A-94F5-A75480960864}
 		{00A11C2F-969F-4964-8557-91ADF4B1523D} = {446EB407-57EB-441D-9ADB-1A006CBF672A}
 		{E1082E26-D700-4127-9329-66D673FD2D55} = {459BF674-83CB-46F6-881F-A2D2117DBF4D}
@@ -659,6 +672,7 @@ Global
 		{DAAC2822-63B6-4DE0-83AE-04873CD2F364} = {72397ADB-40A8-4B8E-8E08-2DBE2803C845}
 		{FBB3270F-1924-4A72-845E-A6DF39C402F6} = {7AC28763-9C68-4BF9-A1BA-25CBFFD2D15C}
 		{92644F6F-5946-48FC-A21A-A3D6EE24E8B3} = {C564DDD6-DE79-45CD-88EA-3F690481572A}
+		{1F2E3D4C-5B6A-7890-CDEF-123456789ABC} = {C564DDD6-DE79-45CD-88EA-3F690481572A}
 		{E8AD265B-3C67-4640-AC58-A522F9FB3361} = {09C264E9-E3F3-4586-9151-DCBB1F6DA7AB}
 		{C564DDD6-DE79-45CD-88EA-3F690481572A} = {09C264E9-E3F3-4586-9151-DCBB1F6DA7AB}
 		{50C758FE-4E10-409A-94F5-A75480960864} = {459BF674-83CB-46F6-881F-A2D2117DBF4D}

diff --git a/src/Core/src/ConfigurationSourceGen/AppSettingsSourceGenerator.cs b/src/Core/src/ConfigurationSourceGen/AppSettingsSourceGenerator.cs
@@ -0,0 +1,186 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.Json;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.Maui.Core.ConfigurationSourceGen;
+
+[Generator]
+public class AppSettingsSourceGenerator : IIncrementalGenerator
+{
+    public void Initialize(IncrementalGeneratorInitializationContext context)
+    {
+        // Get additional files (like appsettings.json) and combine them
+        var appSettingsProvider = context.AdditionalTextsProvider
+            .Where(static file => Path.GetFileName(file.Path).Equals("appsettings.json", StringComparison.OrdinalIgnoreCase))
+            .Select(static (file, cancellationToken) => 
+            {
+                var content = file.GetText(cancellationToken)?.ToString();
+                return content;
+            })
+            .Where(static content => !string.IsNullOrEmpty(content))
+            .Collect(); // Collect all appsettings.json files into a single value
+
+        // Generate source when we have any appsettings.json files
+        context.RegisterSourceOutput(appSettingsProvider, static (context, contents) =>
+        {
+            try
+            {
+                if (contents.IsEmpty)
+                    return;
+
+                // Combine all appsettings files into one configuration
+                var allConfigurationEntries = new Dictionary<string, string>();
+
+                foreach (var content in contents)
+                {
+                    if (!string.IsNullOrEmpty(content))
+                    {
+                        var entries = ParseJsonToConfigurationEntries(content!);
+                        foreach (var entry in entries)
+                        {
+                            allConfigurationEntries[entry.Key] = entry.Value; // Later files override earlier ones
+                        }
+                    }
+                }
+
+                // Generate the extension method source code
+                var sourceCode = GenerateExtensionMethod(allConfigurationEntries);
+
+                // Add the generated source to the compilation
+                context.AddSource("LocalAppSettingsExtensions.g.cs", SourceText.From(sourceCode, Encoding.UTF8));
+            }
+            catch (Exception ex)
+            {
+                // Add diagnostic for any errors
+                context.ReportDiagnostic(Diagnostic.Create(
+                    new DiagnosticDescriptor(
+                        "MAS001",
+                        "AppSettings Source Generator Error",
+                        "Error generating app settings extension: {0}",
+                        "MauiAppSettings",
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true),
+                    Location.None,
+                    ex.Message));
+            }
+        });
+    }
+
+    private static Dictionary<string, string> ParseJsonToConfigurationEntries(string jsonContent)
+    {
+        var entries = new Dictionary<string, string>();
+
+        try
+        {
+            using var document = JsonDocument.Parse(jsonContent);
+            FlattenJsonElement(document.RootElement, entries, string.Empty);
+        }
+        catch (JsonException)
+        {
+            // If JSON parsing fails, return empty dictionary
+        }
+
+        return entries;
+    }
+
+    private static void FlattenJsonElement(JsonElement element, Dictionary<string, string> entries, string prefix)
+    {
+        switch (element.ValueKind)
+        {
+            case JsonValueKind.Object:
+                foreach (var property in element.EnumerateObject())
+                {
+                    var key = string.IsNullOrEmpty(prefix) ? property.Name : $"{prefix}:{property.Name}";
+                    FlattenJsonElement(property.Value, entries, key);
+                }
+                break;
+
+            case JsonValueKind.Array:
+                var index = 0;
+                foreach (var item in element.EnumerateArray())
+                {
+                    var key = $"{prefix}:{index}";
+                    FlattenJsonElement(item, entries, key);
+                    index++;
+                }
+                break;
+
+            case JsonValueKind.String:
+                entries[prefix] = element.GetString() ?? string.Empty;
+                break;
+
+            case JsonValueKind.Number:
+                entries[prefix] = element.GetRawText();
+                break;
+
+            case JsonValueKind.True:
+            case JsonValueKind.False:
+                entries[prefix] = element.GetBoolean().ToString().ToLowerInvariant();
+                break;
+
+            case JsonValueKind.Null:
+                entries[prefix] = string.Empty;
+                break;
+        }
+    }
+
+    private static string GenerateExtensionMethod(Dictionary<string, string> configurationEntries)
+    {
+        var sourceBuilder = new StringBuilder();
+
+        sourceBuilder.AppendLine("//------------------------------------------------------------------------------");
+        sourceBuilder.AppendLine("// <auto-generated>");
+        sourceBuilder.AppendLine("//     This code was generated by the MAUI AppSettings source generator.");
+        sourceBuilder.AppendLine("//");
+        sourceBuilder.AppendLine("//     Changes to this file may cause incorrect behavior and will be lost if");
+        sourceBuilder.AppendLine("//     the code is regenerated.");
+        sourceBuilder.AppendLine("// </auto-generated>");
+        sourceBuilder.AppendLine("//------------------------------------------------------------------------------");
+        sourceBuilder.AppendLine();
+        sourceBuilder.AppendLine("using System.Collections.Generic;");
+        sourceBuilder.AppendLine("using Microsoft.Extensions.Configuration;");
+        sourceBuilder.AppendLine();
+        sourceBuilder.AppendLine("namespace Microsoft.Extensions.Configuration");
+        sourceBuilder.AppendLine("{");
+        sourceBuilder.AppendLine("    /// <summary>");
+        sourceBuilder.AppendLine("    /// Extension methods for IConfigurationBuilder to add local app settings.");
+        sourceBuilder.AppendLine("    /// </summary>");
+        sourceBuilder.AppendLine("    public static class LocalAppSettingsExtensions");
+        sourceBuilder.AppendLine("    {");
+        sourceBuilder.AppendLine("        /// <summary>");
+        sourceBuilder.AppendLine("        /// Adds configuration values from the local appsettings.json file as an in-memory collection.");
+        sourceBuilder.AppendLine("        /// </summary>");
+        sourceBuilder.AppendLine("        /// <param name=\"configurationBuilder\">The configuration builder.</param>");
+        sourceBuilder.AppendLine("        /// <returns>The configuration builder.</returns>");
+        sourceBuilder.AppendLine("        public static IConfigurationBuilder AddLocalAppSettings(this IConfigurationBuilder configurationBuilder)");
+        sourceBuilder.AppendLine("        {");
+        sourceBuilder.AppendLine("            var configurationData = new Dictionary<string, string>");
+        sourceBuilder.AppendLine("            {");
+
+        foreach (var entry in configurationEntries)
+        {
+            var escapedKey = EscapeStringLiteral(entry.Key);
+            var escapedValue = EscapeStringLiteral(entry.Value);
+            sourceBuilder.AppendLine($"                {{ \"{escapedKey}\", \"{escapedValue}\" }},");
+        }
+
+        sourceBuilder.AppendLine("            };");
+        sourceBuilder.AppendLine();
+        sourceBuilder.AppendLine("            return configurationBuilder.AddInMemoryCollection(configurationData);");
+        sourceBuilder.AppendLine("        }");
+        sourceBuilder.AppendLine("    }");
+        sourceBuilder.AppendLine("}");
+
+        return sourceBuilder.ToString();
+    }
+
+    private static string EscapeStringLiteral(string input)
+    {
+        return input.Replace("\\", "\\\\").Replace("\"", "\\\"").Replace("\r", "\\r").Replace("\n", "\\n").Replace("\t", "\\t");
+    }
+}
diff --git a/src/Core/src/ConfigurationSourceGen/Core.ConfigurationSourceGen.csproj b/src/Core/src/ConfigurationSourceGen/Core.ConfigurationSourceGen.csproj
@@ -0,0 +1,33 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>true</ImplicitUsings>
+    <LangVersion>Latest</LangVersion>
+    <AssemblyName>Microsoft.Maui.Core.ConfigurationSourceGen</AssemblyName>
+    <RootNamespace>Microsoft.Maui.Core.ConfigurationSourceGen</RootNamespace>
+    <PackageId>Microsoft.Maui.Core.ConfigurationSourceGen</PackageId>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <IncludeBuildOutput>false</IncludeBuildOutput>
+    <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+    <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
+    <IsRoslynComponent>true</IsRoslynComponent>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.12.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
+    <PackageReference Include="System.Text.Json" Version="8.0.0" PrivateAssets="all" />
+  </ItemGroup>
+
+  <Target Name="_CopyToBuildTasksDir" AfterTargets="Build">
+    <ItemGroup>
+      <_CopyItems Include="$(TargetDir)*.dll" Exclude="$(TargetDir)System.*.dll" />
+      <_CopyItems Include="$(TargetDir)*.pdb" Exclude="$(TargetDir)System.*.pdb" />
+    </ItemGroup>
+    <Copy SourceFiles="@(_CopyItems)" DestinationFolder="$(_MauiBuildTasksLocation)" ContinueOnError="true" Retries="0" />
+  </Target>
+</Project>
diff --git a/src/Core/src/Core.csproj b/src/Core/src/Core.csproj
@@ -28,6 +28,19 @@
 
   <Import Project="$(MauiSrcDirectory)MultiTargeting.targets" />
 
+  <ItemGroup>
+    <Compile Remove="ConfigurationSourceGen\**" />
+    <EmbeddedResource Remove="ConfigurationSourceGen\**" />
+    <None Remove="ConfigurationSourceGen\**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference
+      Include="ConfigurationSourceGen\Core.ConfigurationSourceGen.csproj"
+      OutputItemType="Analyzer"
+      ReferenceOutputAssembly="false" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="MemoryAnalyzers" />
     <PackageReference Include="Microsoft.Extensions.Configuration" />
@@ -69,6 +82,7 @@
     <None Remove="nuget\**" />
     <None Include="nuget\**" Exclude="nuget\**\*.in.*;nuget\**\net-windows\*" PackagePath="" Pack="true" />
     <None Include="nuget\buildTransitive\net-windows\**" PackagePath="buildTransitive\net$(_MauiMinimumSupportedDotNetTfm)-windows$(MinimumWindowsTargetFrameworkVersion)" Pack="true" />
+    <None Include="$(_MauiBuildTasksLocation)Microsoft.Maui.Core.ConfigurationSourceGen.dll" PackagePath="buildTransitive" Pack="true" />
   </ItemGroup>
 
   <!-- TypeScript compilation -->

diff --git a/src/Core/src/nuget/buildTransitive/Microsoft.Maui.Core.targets b/src/Core/src/nuget/buildTransitive/Microsoft.Maui.Core.targets
@@ -10,4 +10,9 @@
     <AfterMicrosoftNETSdkTargets>$(AfterMicrosoftNETSdkTargets);$(MSBuildThisFileDirectory)Microsoft.Maui.Core.After.targets</AfterMicrosoftNETSdkTargets>
   </PropertyGroup>
 
+  <!-- Enable Configuration Source Generator -->
+  <ItemGroup Condition=" '$(DisableMauiAnalyzers)' != 'true' ">
+    <Analyzer Include="$(MSBuildThisFileDirectory)Microsoft.Maui.Core.ConfigurationSourceGen.dll" IsImplicitlyDefined="true" />
+  </ItemGroup>
+
 </Project>