Extract RefitterRunner as shared generation workflow

src/Refitter.Core/Abstractions/IValidator.cs

@@ -0,0 +1,20 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Refitter.Core.Validation;
+
+namespace Refitter.Core;
+
+/// <summary>
+/// Validates an OpenAPI specification file and returns validation diagnostics and statistics.
+/// Each distribution form (CLI, MSBuild, Source Generator) can provide its own adapter.
+/// </summary>
+public interface IValidator
+{
+    /// <summary>
+    /// Validates the specified OpenAPI specification file.
+    /// </summary>
+    /// <param name="openApiPath">The path to the OpenAPI specification file.</param>
+    /// <param name="cancellationToken">A cancellation token.</param>
+    /// <returns>An <see cref="OpenApiValidationResult"/> containing diagnostics and element counts.</returns>
+    Task<OpenApiValidationResult> ValidateAsync(string openApiPath, CancellationToken cancellationToken = default);
+}

src/Refitter.Core/RefitterRunner.cs

@@ -0,0 +1,169 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Refitter.Core.Validation;
+
+namespace Refitter.Core;
+
+/// <summary>
+/// Encapsulates the shared generation workflow across all distribution forms (CLI, MSBuild, Source Generator).
+/// Handles generator creation, code generation, output planning, validation, warning detection, and file writing.
+/// </summary>
+public class RefitterRunner
+{
+    /// <summary>
+    /// Runs the complete generation workflow.
+    /// </summary>
+    /// <param name="settings">The generator settings.</param>
+    /// <param name="writer">Optional file writer for writing output files. When null, files are not written.</param>
+    /// <param name="validator">Optional validator for OpenAPI spec validation. When null, validation is skipped.</param>
+    /// <param name="settingsFilePath">Optional path to the .refitter settings file, used for resolving relative output paths.</param>
+    /// <param name="outputPath">Optional CLI output path override.</param>
+    /// <param name="cancellationToken">A cancellation token.</param>
+    /// <returns>A <see cref="RunResult"/> containing generated files, warnings, diagnostics, and the exit code.</returns>
+    public async Task<RunResult> RunAsync(
+        RefitGeneratorSettings settings,
+        IFileWriter? writer = null,
+        IValidator? validator = null,
+        string? settingsFilePath = null,
+        string? outputPath = null,
+        CancellationToken cancellationToken = default)
+    {
+        var stopwatch = Stopwatch.StartNew();
+        var warnings = new List<Warning>();
+        var diagnostics = new List<RunnerDiagnostic>();
+
+        try
+        {
+            var generator = await RefitGenerator.CreateAsync(
+                settings,
+                cancellationToken);
+
+            GeneratorOutput output;
+            if (settings.GenerateMultipleFiles)
+            {
+                output = generator.GenerateMultipleFiles();
+            }
+            else
+            {
+                var code = generator.Generate()
+                    .Replace("\r\n", "\n")
+                    .Replace("\r", "\n");
+                output = new GeneratorOutput(
+                    new List<GeneratedCode> { new(string.Empty, code) });
+            }
+
+            var planner = new OutputPlannerAdapter();
+            var plannedFiles = planner.Plan(
+                output,
+                settings,
+                settingsFilePath,
+                outputPath);
+
+            if (validator != null)
+            {
+                var openApiPaths = GetOpenApiPaths(settings);
+                foreach (var specPath in openApiPaths)
+                {
+                    if (!string.IsNullOrWhiteSpace(specPath))
+                    {
+                        var validationResult = await validator.ValidateAsync(
+                            specPath,
+                            cancellationToken);
+
+                        foreach (var error in validationResult.Diagnostics.Errors)
+                            diagnostics.Add(new RunnerDiagnostic(error.Message, IsError: true));
+
+                        foreach (var warning in validationResult.Diagnostics.Warnings)
+                            diagnostics.Add(new RunnerDiagnostic(warning.Message, IsError: false));
+
+                        validationResult.ThrowIfInvalid();
+                    }
+                }
+            }
+
+            if (writer != null)
+            {
+                foreach (var file in plannedFiles)
+                {
+                    await writer.WriteAsync(file, cancellationToken);
+                }
+            }
+
+            DetectWarnings(settings, warnings);
+
+            if (settings.IncludePathMatches.Length > 0 &&
+                generator.OpenApiDocument.Paths.Count == 0)
+            {
+                diagnostics.Add(new RunnerDiagnostic(
+                    $"All paths were filtered out by include path patterns: [{string.Join(", ", settings.IncludePathMatches)}]",
+                    IsError: false));
+            }
+
+            stopwatch.Stop();
+
+            return new RunResult(
+                plannedFiles,
+                warnings.AsReadOnly(),
+                diagnostics.AsReadOnly(),
+                stopwatch.Elapsed,
+                ExitCode: 0);
+        }
+        catch (Exception ex)
+        {
+            stopwatch.Stop();
+
+            var errorDiagnostics = new List<RunnerDiagnostic>(diagnostics)
+            {
+                new RunnerDiagnostic(ex.Message, IsError: true)
+            };
+
+            return new RunResult(
+                Array.Empty<PlannedFile>(),
+                warnings.AsReadOnly(),
+                errorDiagnostics.AsReadOnly(),
+                stopwatch.Elapsed,
+                ex.HResult,
+                ex);
+        }
+    }
+
+    private static string[] GetOpenApiPaths(RefitGeneratorSettings settings)
+    {
+        if (settings.OpenApiPaths is { Length: > 0 })
+            return settings.OpenApiPaths;
+
+        if (settings.OpenApiPath is not null)
+            return new[] { settings.OpenApiPath };
+
+        return Array.Empty<string>();
+    }
+
+    /// <summary>
+    /// Detects configuration warnings in the settings and adds them to the provided list.
+    /// </summary>
+    internal static void DetectWarnings(
+        RefitGeneratorSettings settings,
+        List<Warning> warnings)
+    {
+        if (settings is { UseIsoDateFormat: true, CodeGeneratorSettings.DateFormat: not null })
+        {
+            warnings.Add(
+                new Warning(
+                    "Date Format Override",
+                    "'codeGeneratorSettings.dateFormat' will be ignored due to 'useIsoDateFormat' set to true"));
+        }
+
+#pragma warning disable CS0618
+        if (settings.DependencyInjectionSettings?.UsePolly is true)
+#pragma warning restore CS0618
+        {
+            warnings.Add(
+                new Warning(
+                    "Deprecated Setting",
+                    "The 'usePolly' property is deprecated. Use 'transientErrorHandler: Polly' instead"));
+        }
+    }
+}

src/Refitter.Core/RunResult.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+
+namespace Refitter.Core;
+
+/// <summary>
+/// Represents the result of a <see cref="RefitterRunner.RunAsync"/> invocation.
+/// </summary>
+/// <param name="GeneratedFiles">The list of planned output files with their paths and content.</param>
+/// <param name="Warnings">Configuration warnings detected during the run.</param>
+/// <param name="Diagnostics">Validation and error diagnostics collected during the run.</param>
+/// <param name="Elapsed">The elapsed time of the run.</param>
+/// <param name="ExitCode">The exit code (0 for success, non-zero for failure).</param>
+/// <param name="Exception">The original exception, if any, for form-specific error handling.</param>
+public record RunResult(
+    IReadOnlyList<PlannedFile> GeneratedFiles,
+    IReadOnlyList<Warning> Warnings,
+    IReadOnlyList<RunnerDiagnostic> Diagnostics,
+    TimeSpan Elapsed,
+    int ExitCode,
+    Exception? Exception = null);

src/Refitter.Core/RunnerDiagnostic.cs

@@ -0,0 +1,8 @@
+namespace Refitter.Core;
+
+/// <summary>
+/// Represents a diagnostic message from a generation run, such as a validation error or warning.
+/// </summary>
+/// <param name="Message">The diagnostic message text.</param>
+/// <param name="IsError">Whether this diagnostic represents an error (true) or a warning (false).</param>
+public record RunnerDiagnostic(string Message, bool IsError);

src/Refitter.Core/Validation/OpenApiValidatorAdapter.cs

@@ -0,0 +1,16 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Refitter.Core.Validation;
+
+/// <summary>
+/// Adapts the static <see cref="OpenApiValidator"/> to the <see cref="IValidator"/> interface.
+/// </summary>
+public sealed class OpenApiValidatorAdapter : IValidator
+{
+    /// <inheritdoc />
+    public async Task<OpenApiValidationResult> ValidateAsync(string openApiPath, CancellationToken cancellationToken = default)
+    {
+        return await OpenApiValidator.Validate(openApiPath, cancellationToken);
+    }
+}

src/Refitter.Core/Warning.cs

@@ -0,0 +1,8 @@
+namespace Refitter.Core;
+
+/// <summary>
+/// Represents a user-facing configuration warning message.
+/// </summary>
+/// <param name="Title">The short title of the warning.</param>
+/// <param name="Description">The extended description of the warning.</param>
+public record Warning(string Title, string Description);

src/Refitter.MSBuild/RefitterGenerateTask.cs

@@ -71,65 +71,28 @@ private List<string> ProcessRefitterFile(string filePath)
         var settings = RefitterSettingsLoader.Load(json, baseDirectory);
         RefitterSettingsLoader.ApplyDefaults(filePath, settings);
 
-        var generator = RefitGenerator.CreateAsync(settings)
-            .GetAwaiter().GetResult();
-
-        var planner = new OutputPlannerAdapter();
         var writer = new MsBuildFileWriter();
+        IValidator? validator = SkipValidation
+            ? null
+            : new OpenApiValidatorAdapter();
 
-        var generatedFiles = new List<string>();
-
-        if (settings.GenerateMultipleFiles)
-        {
-            var output = generator.GenerateMultipleFiles();
-            var plannedFiles = planner.Plan(
-                output,
-                settings,
-                filePath,
-                cliOutputPath: null);
-
-            foreach (var plannedFile in plannedFiles)
-            {
-                writer.WriteAsync(plannedFile).GetAwaiter().GetResult();
-                generatedFiles.Add(Path.GetFullPath(plannedFile.Path));
-            }
-        }
-        else
-        {
-            var code = generator.Generate().Replace("\r\n", "\n");
-            var output = new GeneratorOutput(
-                new List<GeneratedCode> { new(string.Empty, code) });
-
-            var plannedFiles = planner.Plan(
-                output,
+        var runner = new RefitterRunner();
+        var result = runner.RunAsync(
                 settings,
-                filePath,
-                cliOutputPath: null);
-
-            writer.WriteAsync(plannedFiles[0]).GetAwaiter().GetResult();
-            generatedFiles.Add(Path.GetFullPath(plannedFiles[0].Path));
-        }
+                writer,
+                validator,
+                settingsFilePath: filePath,
+                outputPath: null,
+                CancellationToken.None)
+            .GetAwaiter().GetResult();
 
-        if (!SkipValidation)
-        {
-            var openApiPaths = settings.OpenApiPaths is { Length: > 0 }
-                ? settings.OpenApiPaths
-                : settings.OpenApiPath is not null
-                    ? [settings.OpenApiPath]
-                    : [];
+        if (result.ExitCode != 0)
+            throw result.Exception ?? new InvalidOperationException(
+                result.Diagnostics.FirstOrDefault()?.Message ?? "Unknown error");
 
-            foreach (var specPath in openApiPaths)
-            {
-                if (!string.IsNullOrWhiteSpace(specPath))
-                {
-                    var validationResult = OpenApiValidator.Validate(specPath)
-                        .GetAwaiter().GetResult();
-                    validationResult.ThrowIfInvalid();
-                }
-            }
-        }
-
-        return generatedFiles;
+        return result.GeneratedFiles
+            .Select(f => Path.GetFullPath(f.Path))
+            .ToList();
     }
 
     internal static string[] FilterFiles(string[] files, string includePatterns, string projectFileDirectory)