Add PostAction for dotnet.config

src/Cli/Microsoft.TemplateEngine.Cli/Components.cs

@@ -14,7 +14,8 @@ public static class Components
                 (typeof(IPostActionProcessor), new ChmodPostActionProcessor()),
                 (typeof(IPostActionProcessor), new InstructionDisplayPostActionProcessor()),
                 (typeof(IPostActionProcessor), new ProcessStartPostActionProcessor()),
-                (typeof(IPostActionProcessor), new AddJsonPropertyPostActionProcessor())
+                (typeof(IPostActionProcessor), new AddJsonPropertyPostActionProcessor()),
+                (typeof(IPostActionProcessor), new CreateOrUpdateDotnetConfigPostActionProcessor()),
             };
     }
 }

src/Cli/Microsoft.TemplateEngine.Cli/LocalizableStrings.resx

@@ -953,4 +953,23 @@ The header is followed by the list of parameters and their errors (might be seve
   <data name="PostAction_ModifyJson_Verbose_AttemptingToFindJsonFile" xml:space="preserve">
     <value>Attempting to find json file '{0}' in '{1}'</value>
   </data>
+  <data name="PostAction_DotnetConfig_Error_ArgumentNotConfigured" xml:space="preserve">
+    <value>Post action argument '{0}' is mandatory, but not configured.</value>
+  </data>
+  <data name="PostAction_CreateDotnetConfig_Succeeded" xml:space="preserve">
+    <value>Successfully created 'dotnet.config' file.</value>
+    <comment>{Locked="dotnet.config"}</comment>
+  </data>
+  <data name="PostAction_CreateDotnetConfig_CreatedNewSection" xml:space="preserve">
+    <value>Created new section in 'dotnet.config' file</value>
+    <comment>{Locked="dotnet.config"}</comment>
+  </data>
+  <data name="PostAction_CreateDotnetConfig_ValueAlreadyExist" xml:space="preserve">
+    <value>The required value in 'dotnet.config' is already set.</value>
+    <comment>{Locked="dotnet.config"}</comment>
+  </data>
+  <data name="PostAction_CreateDotnetConfig_ManuallyUpdate" xml:space="preserve">
+    <value>Updating existing values in 'dotnet.config' is not yet supported. Please, manually update 'dotnet.config' to have '{0}' under section '{1}'.</value>
+    <comment>{Locked="dotnet.config"}</comment>
+  </data>
 </root>

src/Cli/Microsoft.TemplateEngine.Cli/Microsoft.TemplateEngine.Cli.csproj

@@ -16,6 +16,7 @@
     <PackageReference Include="Microsoft.TemplateEngine.Edge" />
     <PackageReference Include="Microsoft.TemplateSearch.Common" />
     <PackageReference Include="Microsoft.Extensions.Logging.Console" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Ini" />
     <PackageReference Include="Wcwidth.Sources" ExcludeAssets="all" GeneratePathProperty="true" />
     <PackageReference Include="System.CommandLine" />
   </ItemGroup>

src/Cli/Microsoft.TemplateEngine.Cli/PostActionProcessors/CreateOrUpdateDotnetConfigPostActionProcessor.cs

@@ -0,0 +1,131 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.Extensions.Configuration;
+using Microsoft.TemplateEngine.Abstractions;
+using Microsoft.TemplateEngine.Abstractions.PhysicalFileSystem;
+
+namespace Microsoft.TemplateEngine.Cli.PostActionProcessors
+{
+    internal sealed class CreateOrUpdateDotnetConfigPostActionProcessor : PostActionProcessorBase
+    {
+        private const string SectionArgument = "section";
+        private const string KeyArgument = "key";
+        private const string ValueArgument = "value";
+
+        public override Guid Id => ActionProcessorId;
+
+        internal static Guid ActionProcessorId { get; } = new Guid("597E7933-0D87-452C-B094-8FA0EEF7FD97");
+
+        protected override bool ProcessInternal(
+            IEngineEnvironmentSettings environment,
+            IPostAction action,
+            ICreationEffects creationEffects,
+            ICreationResult templateCreationResult,
+            string outputBasePath)
+        {
+            if (!action.Args.TryGetValue(SectionArgument, out string? sectionName))
+            {
+                Reporter.Error.WriteLine(string.Format(LocalizableStrings.PostAction_DotnetConfig_Error_ArgumentNotConfigured, SectionArgument));
+                return false;
+            }
+
+            if (!action.Args.TryGetValue(KeyArgument, out string? key))
+            {
+                Reporter.Error.WriteLine(string.Format(LocalizableStrings.PostAction_DotnetConfig_Error_ArgumentNotConfigured, KeyArgument));
+                return false;
+            }
+
+            if (!action.Args.TryGetValue(ValueArgument, out string? value))
+            {
+                Reporter.Error.WriteLine(string.Format(LocalizableStrings.PostAction_DotnetConfig_Error_ArgumentNotConfigured, ValueArgument));
+                return false;
+            }
+
+            var fileSystem = environment.Host.FileSystem;
+            var repoRoot = GetRootDirectory(fileSystem, outputBasePath);
+            var dotnetConfigFilePath = Path.Combine(repoRoot, "dotnet.config");
+            if (!fileSystem.FileExists(dotnetConfigFilePath))
+            {
+                fileSystem.WriteAllText(dotnetConfigFilePath, $"""
+                    [{sectionName}]
+                    {key} = "{value}"
+
+                    """);
+
+                Reporter.Output.WriteLine(LocalizableStrings.PostAction_CreateDotnetConfig_Succeeded);
+                return true;
+            }
+
+            var builder = new ConfigurationBuilder();
+            using var stream = fileSystem.OpenRead(dotnetConfigFilePath);
+            builder.AddIniStream(stream);
+            IConfigurationRoot config = builder.Build();
+            var section = config.GetSection(sectionName);
+
+            if (!section.Exists())
+            {
+                var existingContent = fileSystem.ReadAllText(dotnetConfigFilePath);
+                fileSystem.WriteAllText(dotnetConfigFilePath, $"""
+                    {existingContent}
+
+                    [{sectionName}]
+                    {key} = "{value}"
+
+                    """);
+
+                Reporter.Output.WriteLine(LocalizableStrings.PostAction_CreateDotnetConfig_CreatedNewSection);
+                return true;
+            }
+
+            string? existingValue = section[key];
+            if (string.IsNullOrEmpty(existingValue))
+            {
+                // The section exists, but the key/value pair does not.
+                Reporter.Error.WriteLine(string.Format(LocalizableStrings.PostAction_CreateDotnetConfig_ManuallyUpdate, $"{key} = \"{value}\"", $"[{sectionName}]"));
+                return false;
+            }
+
+            if (existingValue.Equals(value, StringComparison.Ordinal))
+            {
+                // The key already exists with the same value, nothing to do.
+                Reporter.Output.WriteLine(LocalizableStrings.PostAction_CreateDotnetConfig_ValueAlreadyExist);
+                return true;
+            }
+
+            Reporter.Error.WriteLine(string.Format(LocalizableStrings.PostAction_CreateDotnetConfig_ManuallyUpdate, $"{key} = \"{value}\"", $"[{sectionName}]"));
+            return false;
+        }
+
+        private static string GetRootDirectory(IPhysicalFileSystem fileSystem, string outputBasePath)
+        {
+            string? currentDirectory = outputBasePath;
+            string? directoryWithSln = null;
+            while (currentDirectory is not null)
+            {
+                if (fileSystem.FileExists(Path.Combine(currentDirectory, "dotnet.config")) ||
+                    fileSystem.DirectoryExists(Path.Combine(currentDirectory, ".git")))
+                {
+                    return currentDirectory;
+                }
+
+                // DirectoryExists here should always be true in practice, but for the way tests are mocking the file system, it's not.
+                // The check was added to prevent test failures similar to:
+                // System.IO.DirectoryNotFoundException : Could not find a part of the path '/Users/runner/work/1/s/artifacts/bin/Microsoft.TemplateEngine.Cli.UnitTests/Release/sandbox'.
+                // We get to this exception when doing `EnumerateFiles` on a directory that was virtually created in memory (not really available on disk).
+                // EnumerateFiles tries to access the physical file system, which then fails.
+                if (fileSystem.DirectoryExists(currentDirectory) &&
+                    (fileSystem.EnumerateFiles(currentDirectory, "*.sln", SearchOption.TopDirectoryOnly).Any() ||
+                    fileSystem.EnumerateFiles(currentDirectory, "*.slnx", SearchOption.TopDirectoryOnly).Any()))
+                {
+                    directoryWithSln = currentDirectory;
+                }
+
+                currentDirectory = Directory.GetParent(currentDirectory)?.FullName;
+            }
+
+            return directoryWithSln ?? outputBasePath;
+        }
+    }
+}