Add msbuild task to generate binary runtimeconfig format

Directory.Build.props

@@ -70,6 +70,7 @@
     <WasmAppBuilderDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'WasmAppBuilder', 'Debug', '$(NetCoreAppToolCurrent)', 'publish'))</WasmAppBuilderDir>
     <WasmBuildTasksDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'WasmBuildTasks', 'Debug', '$(NetCoreAppToolCurrent)', 'publish'))</WasmBuildTasksDir>
     <MonoAOTCompilerDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'MonoAOTCompiler', 'Debug', '$(NetCoreAppToolCurrent)'))</MonoAOTCompilerDir>
+    <RuntimeConfigParserDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'RuntimeConfigParser', 'Debug', '$(NetCoreAppToolCurrent)', 'publish'))</RuntimeConfigParserDir>
 
     <InstallerTasksAssemblyPath Condition="'$(MSBuildRuntimeType)' == 'Core'">$([MSBuild]::NormalizePath('$(ArtifactsBinDir)', 'installer.tasks', 'Debug', '$(NetCoreAppToolCurrent)', 'installer.tasks.dll'))</InstallerTasksAssemblyPath>
     <InstallerTasksAssemblyPath Condition="'$(MSBuildRuntimeType)' != 'Core'">$([MSBuild]::NormalizePath('$(ArtifactsBinDir)', 'installer.tasks', 'Debug', 'net461', 'installer.tasks.dll'))</InstallerTasksAssemblyPath>
@@ -78,6 +79,7 @@
     <WasmAppBuilderTasksAssemblyPath>$([MSBuild]::NormalizePath('$(WasmAppBuilderDir)', 'WasmAppBuilder.dll'))</WasmAppBuilderTasksAssemblyPath>
     <WasmBuildTasksAssemblyPath>$([MSBuild]::NormalizePath('$(WasmBuildTasksDir)', 'WasmBuildTasks.dll'))</WasmBuildTasksAssemblyPath>
     <MonoAOTCompilerTasksAssemblyPath>$([MSBuild]::NormalizePath('$(MonoAOTCompilerDir)', 'MonoAOTCompiler.dll'))</MonoAOTCompilerTasksAssemblyPath>
+    <RuntimeConfigParserTasksAssemblyPath>$([MSBuild]::NormalizePath('$(RuntimeConfigParserDir)', 'RuntimeConfigParser.dll'))</RuntimeConfigParserTasksAssemblyPath>
   </PropertyGroup>
 
   <PropertyGroup Label="CalculateConfiguration">

src/tasks/RuntimeConfigParser/RuntimeConfigParser.cs

@@ -0,0 +1,108 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Reflection.Metadata;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+public class RuntimeConfigParserTask : Task
+{
+    /// <summary>
+    /// The path to runtimeconfig.json file.
+    /// </summary>
+    [Required]
+    public string RuntimeConfigFile { get; set; } = "";
+
+    /// <summary>
+    /// The path to the output binary file.
+    /// </summary>
+    [Required]
+    public string OutputFile { get; set; } = "";
+
+    /// <summary>
+    /// List of reserved properties.
+    /// </summary>
+    public ITaskItem[] ReservedProperties { get; set; } = Array.Empty<ITaskItem>();
+
+    public override bool Execute()
+    {
+        if (string.IsNullOrEmpty(RuntimeConfigFile))
+        {
+            throw new ArgumentException($"'{nameof(RuntimeConfigFile)}' is required.", nameof(RuntimeConfigFile));
+        }
+
+        if (string.IsNullOrEmpty(OutputFile))
+        {
+            throw new ArgumentException($"'{nameof(OutputFile)}' is required.", nameof(OutputFile));
+        }
+
+        Dictionary<string, string> configProperties = ConvertInputToDictionary(RuntimeConfigFile);
+
+        if (ReservedProperties.Length != 0)
+        {
+            checkDuplicateProperties(configProperties, ReservedProperties);
+        }
+
+        var blobBuilder = new BlobBuilder();
+        ConvertDictionaryToBlob(configProperties, blobBuilder);
+
+        using var stream = File.OpenWrite(OutputFile);
+        blobBuilder.WriteContentTo(stream);
+
+        return true;
+    }
+
+    /// Reads a json file from the given path and extracts the "configProperties" key (assumed to be a string to string dictionary)
+    private Dictionary<string, string> ConvertInputToDictionary(string inputFilePath)
+    {
+        var options = new JsonSerializerOptions {
+            AllowTrailingCommas = true,
+            ReadCommentHandling = JsonCommentHandling.Skip,
+        };
+
+        var jsonString = File.ReadAllText(inputFilePath);
+        var parsedJson = JsonSerializer.Deserialize<Root>(jsonString, options);
+
+        return parsedJson!.ConfigProperties;
+    }
+
+    /// Just write the dictionary out to a blob as a count followed by
+    /// a length-prefixed UTF8 encoding of each key and value
+    private void ConvertDictionaryToBlob(IReadOnlyDictionary<string, string> properties, BlobBuilder b)
+    {
+        int count = properties.Count;
+
+        b.WriteCompressedInteger(count);
+        foreach (var kvp in properties)
+        {
+            b.WriteSerializedString(kvp.Key);
+            b.WriteSerializedString(kvp.Value);
+        }
+    }
+
+    private void checkDuplicateProperties(IReadOnlyDictionary<string, string> properties, ITaskItem[] keys)
+    {
+        foreach (var key in keys)
+        {
+            if (properties.ContainsKey(key.ItemSpec))
+            {
+                throw new ArgumentException($"Property '{key}' can't be set by the user!");
+            }
+        }
+    }
+}
+
+public class Root
+{
+    // the configProperties key
+    [JsonPropertyName ("configProperties")]
+    public Dictionary<string, string> ConfigProperties {get; set;} = new Dictionary<string, string> ();
+    // everything other than configProperties
+    [JsonExtensionData]
+    public Dictionary<string, object> ExtensionData {get; set;} = new Dictionary<string, object> ();
+}

src/tasks/RuntimeConfigParser/RuntimeConfigParser.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>$(NetCoreAppToolCurrent)</TargetFramework>
+    <OutputType>Library</OutputType>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    <Nullable>enable</Nullable>
+    <NoWarn>$(NoWarn),CA1050</NoWarn>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Build" Version="$(RefOnlyMicrosoftBuildVersion)" />
+    <PackageReference Include="Microsoft.Build.Framework" Version="$(RefOnlyMicrosoftBuildFrameworkVersion)" />
+    <PackageReference Include="Microsoft.Build.Tasks.Core" Version="$(RefOnlyMicrosoftBuildTasksCoreVersion)" />
+    <PackageReference Include="Microsoft.Build.Utilities.Core" Version="$(RefOnlyMicrosoftBuildUtilitiesCoreVersion)" />
+    <PackageReference Include="System.Reflection.Metadata" Version="5.0.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="RuntimeConfigParser.cs" />
+  </ItemGroup>
+
+  <Target Name="PublishBuilder"
+          AfterTargets="Build"
+          DependsOnTargets="Publish" />
+
+  <Target Name="GetFilesToPackage" />
+
+</Project>