GeneratedCodeTestHelper.cs

namespace EasySourceGenerators.Tests;

internal static class GeneratedCodeTestHelper
{
    private const char UnicodeBom = '\uFEFF';

    internal static string ReadGeneratedCode(string generatedFileName)
    {
        string rawCode = ReadGeneratedCodeRaw(generatedFileName);
        return StripGeneratedPreamble(rawCode);
    }

    internal static string ReadGeneratedCodeRaw(string generatedFileName)
    {
        string generatedCodePath = GetGeneratedCodePath(generatedFileName);
        return File.ReadAllText(generatedCodePath).TrimStart(UnicodeBom).ReplaceLineEndings("\n").TrimEnd();
    }

    private static string StripGeneratedPreamble(string generatedCode)
    {
        string[] lines = generatedCode.Split('\n');
        int index = 0;

        while (index < lines.Length)
        {
            string currentLine = lines[index];
            bool isGeneratedPreambleLine = currentLine.StartsWith("//", StringComparison.Ordinal)
                || currentLine.StartsWith("#pragma warning disable", StringComparison.Ordinal)
                || string.IsNullOrWhiteSpace(currentLine);

            if (!isGeneratedPreambleLine)
            {
                break;
            }

            index++;
        }

        return string.Join('\n', lines[index..]).TrimEnd();
    }

    private static string GetGeneratedCodePath(string generatedFileName)
    {
        string projectDirectory = FindProjectDirectory();
        string[] generatedFiles = Directory.GetFiles(projectDirectory, generatedFileName, SearchOption.AllDirectories);

        if (generatedFiles.Length == 0)
        {
            throw new AssertionException($"Could not find expected generated file '{generatedFileName}' under {projectDirectory}{Path.DirectorySeparatorChar}**");
        }

        return generatedFiles[0];
    }

    private static string FindProjectDirectory()
    {
        string? currentDirectory = TestContext.CurrentContext.TestDirectory;

        while (currentDirectory is not null)
        {
            string projectFilePath = Path.Combine(currentDirectory, "EasySourceGenerators.Tests.csproj");
            if (File.Exists(projectFilePath))
            {
                return currentDirectory;
            }

            currentDirectory = Directory.GetParent(currentDirectory)?.FullName;
        }

        throw new DirectoryNotFoundException("Could not locate EasySourceGenerators.Tests project directory.");
    }
}