Facade to read GitVersionInformation injected by GitTools\GitVersion MSBuild task

ReadGitVersionInformation.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;

namespace ReadGitVersionInformation
{
    public interface IGitVersionInformation
    {
        string Major { get; }
        string Minor { get; }
        string Patch { get; }
        string PreReleaseTag { get; }
        string PreReleaseTagWithDash { get; }
        string PreReleaseLabel { get; }
        string PreReleaseNumber { get; }
        string BuildMetaData { get; }
        string BuildMetaDataPadded { get; }
        string FullBuildMetaData { get; }
        string MajorMinorPatch { get; }
        string SemVer { get; }
        string LegacySemVer { get; }
        string LegacySemVerPadded { get; }
        string AssemblySemVer { get; }
        string FullSemVer { get; }
        string InformationalVersion { get; }
        string BranchName { get; }
        string Sha { get; }
        string NuGetVersionV2 { get; }
        string NuGetVersion { get; }
        string CommitsSinceVersionSource { get; }
        string CommitsSinceVersionSourcePadded { get; }
        string CommitDate { get; }
    }

    public static class GitVersion
    {
        private static readonly Dictionary<string, IGitVersionInformation> _cache =
            new Dictionary<string, IGitVersionInformation>();

        public static IGitVersionInformation GetVersionInformation(bool fallbackToNormalVersion = true) =>
            GetVersionInformation(Assembly.GetCallingAssembly(), fallbackToNormalVersion);

        public static IGitVersionInformation GetVersionInformation(Assembly assembly, bool fallbackToNormalVersion = true)
        {
            var name = assembly.GetName();
            if (_cache.TryGetValue(name.FullName, out var cached))
                return cached;

            var assemblyName = name.Name;

            IGitVersionInformation result;

            var gitVersionInformationType = assembly.GetType(assemblyName + ".GitVersionInformation");
            if (gitVersionInformationType == null)
            {
                var informationalVersion = (AssemblyInformationalVersionAttribute)assembly
                    .GetCustomAttributes(typeof(AssemblyInformationalVersionAttribute), false)
                    .SingleOrDefault();
                if (informationalVersion == null)
                {
                    if (fallbackToNormalVersion)
                        result = new TransparentFallback(assembly);
                    else
                        throw new NotAGitVersionAssemblyException(assemblyName);
                }
                else
                    result = new GitVersionInformationFromInformationalVersion(informationalVersion.InformationalVersion);
            }
            else
                result = new GitVersionInformationFromClass(gitVersionInformationType.GetFields());

            _cache.Add(name.FullName, result);
            return result;
        }
    }

    public class NotAGitVersionAssemblyException : Exception
    {
        public NotAGitVersionAssemblyException(string assemblyName)
            : base($"The specified assembly '{assemblyName}' does not contain GitVersion information.") =>
            AssemblyName = assemblyName;

        public string AssemblyName { get; }
    }

    internal class GitVersionInformationFromClass : IGitVersionInformation
    {
        private readonly Dictionary<string, string> _values;

        public GitVersionInformationFromClass(IEnumerable<FieldInfo> fields)
        {
            if (fields == null)
                throw new ArgumentNullException(nameof(fields));
            _values = fields.ToDictionary(x => x.Name, x => (string)x.GetValue(null));
        }

        public string Major => GetFieldValue("Major");
        public string Minor => GetFieldValue("Minor");
        public string Patch => GetFieldValue("Patch");
        public string PreReleaseTag => GetFieldValue("PreReleaseTag");
        public string PreReleaseTagWithDash => GetFieldValue("PreReleaseTagWithDash");
        public string PreReleaseLabel => GetFieldValue("PreReleaseLabel");
        public string PreReleaseNumber => GetFieldValue("PreReleaseNumber");
        public string BuildMetaData => GetFieldValue("BuildMetaData");
        public string BuildMetaDataPadded => GetFieldValue("BuildMetaDataPadded");
        public string FullBuildMetaData => GetFieldValue("FullBuildMetaData");
        public string MajorMinorPatch => GetFieldValue("MajorMinorPatch");
        public string SemVer => GetFieldValue("SemVer");
        public string LegacySemVer => GetFieldValue("LegacySemVer");
        public string LegacySemVerPadded => GetFieldValue("LegacySemVerPadded");
        public string AssemblySemVer => GetFieldValue("AssemblySemVer");
        public string FullSemVer => GetFieldValue("FullSemVer");
        public string InformationalVersion => GetFieldValue("InformationalVersion");
        public string BranchName => GetFieldValue("BranchName");
        public string Sha => GetFieldValue("Sha");
        public string NuGetVersionV2 => GetFieldValue("NuGetVersionV2");
        public string NuGetVersion => GetFieldValue("NuGetVersion");
        public string CommitsSinceVersionSource => GetFieldValue("CommitsSinceVersionSource");
        public string CommitsSinceVersionSourcePadded => GetFieldValue("CommitsSinceVersionSourcePadded");
        public string CommitDate => GetFieldValue("CommitDate");

        private string GetFieldValue(string fieldName)
        {
            if (_values.TryGetValue(fieldName, out var value))
                return value;

            throw new UnknownGitVersionAssemblyVersion(fieldName);
        }
    }

    internal class GitVersionInformationFromInformationalVersion : IGitVersionInformation
    {
        private static readonly Regex _regex = new Regex(
            @"^(?<Major>\d?)\.(?<Minor>\d?)\.(?<Patch>\d?)-(?<PreReleaseLabel>[^.]+)\.(?<PreReleaseNumber>\d+)\+Branch\.(?<BranchName>[^.]+)\.Sha\.(?<Sha>[0-9a-z]+)$");

        public GitVersionInformationFromInformationalVersion(string informationalVersion)
        {
            InformationalVersion = informationalVersion;
            var match = _regex.Match(informationalVersion);
            Major = match.Groups["Major"].Value;
            Minor = match.Groups["Minor"].Value;
            Patch = match.Groups["Patch"].Value;
            PreReleaseLabel = match.Groups["PreReleaseLabel"].Value;
            PreReleaseNumber = match.Groups["PreReleaseNumber"].Value;
            BranchName = match.Groups["BranchName"].Value;
            Sha = match.Groups["Sha"].Value;
        }

        public string Major { get; }
        public string Minor { get; }
        public string Patch { get; }
        public string PreReleaseTag => $"{PreReleaseLabel}.{PreReleaseNumber}";
        public string PreReleaseTagWithDash => $"-{PreReleaseTag}";
        public string PreReleaseLabel { get; }
        public string PreReleaseNumber { get; }
        public string BuildMetaData => "";
        public string BuildMetaDataPadded => "";
        public string FullBuildMetaData => $"Branch.{BranchName}.Sha.{Sha}";
        public string MajorMinorPatch => $"{Major}.{Minor}.{Patch}";
        public string SemVer => $"{MajorMinorPatch}{PreReleaseTagWithDash}";
        public string LegacySemVer => $"{MajorMinorPatch}-{PreReleaseLabel}{PreReleaseNumber}";
        public string LegacySemVerPadded => $"{MajorMinorPatch}-{PreReleaseLabel}{CommitsSinceVersionSourcePadded}";
        public string AssemblySemVer => $"{MajorMinorPatch}.{PreReleaseNumber}";
        public string FullSemVer => SemVer;
        public string InformationalVersion { get; }
        public string BranchName { get; }
        public string Sha { get; }
        public string NuGetVersionV2 => LegacySemVerPadded;
        public string NuGetVersion => LegacySemVerPadded;
        public string CommitsSinceVersionSource => PreReleaseNumber;
        public string CommitsSinceVersionSourcePadded => $"{PreReleaseNumber.PadLeft(4, '0')}";
        public string CommitDate => new DateTime().ToString("yyyy-dd-MM");
    }

    internal class TransparentFallback : IGitVersionInformation
    {
        public TransparentFallback(Assembly assembly)
        {
            var version = assembly.GetName().Version;
            Major = version.Major.ToString();
            Minor = version.Minor.ToString();
            Patch = version.Revision.ToString();
            PreReleaseNumber = version.Build.ToString();
        }

        public string Major { get; }
        public string Minor { get; }
        public string Patch { get; }
        public string PreReleaseTag => "";
        public string PreReleaseTagWithDash => "";
        public string PreReleaseLabel => "";
        public string PreReleaseNumber { get; }
        public string BuildMetaData => "";
        public string BuildMetaDataPadded => "";
        public string FullBuildMetaData => SemVer;
        public string MajorMinorPatch => $"{Major}.{Minor}.{Patch}";
        public string SemVer => $"{MajorMinorPatch}{PreReleaseTagWithDash}";
        public string LegacySemVer => SemVer;
        public string LegacySemVerPadded => $"{MajorMinorPatch}{PreReleaseTagWithDash}{CommitsSinceVersionSourcePadded}";
        public string AssemblySemVer => $"{MajorMinorPatch}.{PreReleaseNumber}";
        public string FullSemVer => SemVer;
        public string InformationalVersion => SemVer;
        public string BranchName => "";
        public string Sha => "";
        public string NuGetVersionV2 => LegacySemVerPadded;
        public string NuGetVersion => LegacySemVerPadded;
        public string CommitsSinceVersionSource => PreReleaseNumber;
        public string CommitsSinceVersionSourcePadded => $"{PreReleaseNumber.PadLeft(4, '0')}";
        public string CommitDate => new DateTime().ToString("yyyy-dd-MM");
    }

    internal class UnknownGitVersionAssemblyVersion : Exception
    {
        public UnknownGitVersionAssemblyVersion(string fieldName)
            : base(
                $"The field '{fieldName}' is not a known property of the automatically generated GitVersionInformation class. This most likely hints at a version mismatch.") =>
            FieldName = fieldName;

        public string FieldName { get; }
    }
}