In GitLab CI, render Cake tasks as collapsible sections

src/Cake.GitLabCI.Module/AnsiEscapeCodes.cs

@@ -7,8 +7,10 @@ internal static class AnsiEscapeCodes
         public static readonly string ForegroundYellow = string.Format(FORMAT, 33);
         public static readonly string ForegroundLightGray = string.Format(FORMAT, 37);
         public static readonly string ForegroundDarkGray = string.Format(FORMAT, 90);
+        public static readonly string ForegroundBlue = string.Format(FORMAT, 34);
         public static readonly string BackgroundMagenta = string.Format(FORMAT, 45);
         public static readonly string BackgroundRed = string.Format(FORMAT, 41);
+        public static readonly string SectionMarker = "\u001B[0K";
 
         private const string FORMAT = "\u001B[{0}m";
     }

src/Cake.GitLabCI.Module/GitLabCIEngine.cs

@@ -0,0 +1,124 @@
+using System;
+using System.Collections.Generic;
+using System.Text.RegularExpressions;
+
+using Cake.Core;
+using Cake.Core.Diagnostics;
+using Cake.Module.Shared;
+
+using JetBrains.Annotations;
+
+namespace Cake.GitLabCI.Module
+{
+    /// <summary>
+    /// <see cref="ICakeEngine"/> implementation for GitLab CI.
+    /// </summary>
+    /// <remarks>
+    /// This engine emits additional console output to make GitLab CI render the output of the indiviudal Cake tasks as collapsible sections
+    /// (see <see href="https://docs.gitlab.com/ee/ci/yaml/script.html#custom-collapsible-sections">Custom collapsible sections (GitLab Docs)</see>).
+    /// </remarks>
+    [UsedImplicitly]
+    public sealed class GitLabCIEngine : CakeEngineBase
+    {
+        private readonly IConsole _console;
+        private readonly object _sectionNameLock = new object();
+        private readonly Dictionary<string, string> _taskSectionNames = new Dictionary<string, string>();
+        private readonly HashSet<string> _sectionNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GitLabCIEngine"/> class.
+        /// </summary>
+        /// <param name="dataService">Implementation of <see cref="ICakeDataService"/>.</param>
+        /// <param name="log">Implementation of <see cref="ICakeLog"/>.</param>
+        /// <param name="console">Implementation of <see cref="IConsole"/>.</param>
+        public GitLabCIEngine(ICakeDataService dataService, ICakeLog log, IConsole console)
+            : base(new CakeEngine(dataService, log))
+        {
+            _console = console;
+            _engine.BeforeSetup += OnBeforeSetup;
+            _engine.AfterSetup += OnAfterSetup;
+            _engine.BeforeTaskSetup += OnBeforeTaskSetup;
+            _engine.AfterTaskTeardown += OnAfterTaskTeardown;
+            _engine.BeforeTeardown += OnBeforeTeardown;
+            _engine.AfterTeardown += OnAfterTeardown;
+        }
+
+        private void OnBeforeSetup(object sender, BeforeSetupEventArgs e)
+        {
+            WriteSectionStart("setup", "Executing Setup");
+        }
+
+        private void OnAfterSetup(object sender, AfterSetupEventArgs e)
+        {
+            WriteSectionEnd("setup");
+        }
+
+        private void OnBeforeTaskSetup(object sender, BeforeTaskSetupEventArgs e)
+        {
+            WriteSectionStart(GetSectionNameForTask(e.TaskSetupContext.Task.Name), $"Executing task \"{e.TaskSetupContext.Task.Name}\"");
+        }
+
+        private void OnAfterTaskTeardown(object sender, AfterTaskTeardownEventArgs e)
+        {
+            WriteSectionEnd(GetSectionNameForTask(e.TaskTeardownContext.Task.Name));
+        }
+
+        private void OnBeforeTeardown(object sender, BeforeTeardownEventArgs e)
+        {
+            WriteSectionStart("teardown", "Executing Teardown");
+        }
+
+        private void OnAfterTeardown(object sender, AfterTeardownEventArgs e)
+        {
+            WriteSectionEnd("teardown");
+        }
+
+        private void WriteSectionStart(string sectionName, string sectionHeader)
+        {
+            _console.WriteLine("{0}", $"{AnsiEscapeCodes.SectionMarker}section_start:{DateTimeOffset.UtcNow.ToUnixTimeSeconds()}:{sectionName}\r{AnsiEscapeCodes.SectionMarker}{AnsiEscapeCodes.ForegroundBlue}{sectionHeader}{AnsiEscapeCodes.Reset}");
+        }
+
+        private void WriteSectionEnd(string sectionName)
+        {
+            _console.WriteLine("{0}", $"{AnsiEscapeCodes.SectionMarker}section_end:{DateTimeOffset.UtcNow.ToUnixTimeSeconds()}:{sectionName}\r{AnsiEscapeCodes.SectionMarker}");
+        }
+
+        /// <summary>
+        /// Computes a unique GitLab CI section name for a task name.
+        /// </summary>
+        /// <remarks>
+        /// GitLab CI requires a section name in both the "start" and "end" markers of a section.
+        /// The name can only be composed of letters, numbers, and the _, ., or - characters.
+        /// In Cake, each task corresponds to one section.
+        /// Since the task name may contain characters not allowed in the section name, unsupprted characters are removed from the task name.
+        /// Additionally, this method ensures that the section name is unique and the same task name will be mapped to the same section name for each call.
+        /// </remarks>
+        private string GetSectionNameForTask(string taskName)
+        {
+            lock (_sectionNameLock)
+            {
+                // If there is already a section name for the task, reuse the same name
+                if (_taskSectionNames.TryGetValue(taskName, out var sectionName))
+                {
+                    return sectionName;
+                }
+
+                // Remove unsuported characters from the task name (everything except letters, numbers or the _, ., and - characters
+                var normalizedTaskName = Regex.Replace(taskName, "[^A-Z|a-z|0-9|_|\\-|\\.]*", string.Empty).ToLowerInvariant();
+
+                // Normalizing the task name can cause multiple tasks to be mapped to the same section name
+                // To avoid name conflicts, append a number to the end to make the section name unique.
+                sectionName = normalizedTaskName;
+                var sectionCounter = 0;
+                while (!_sectionNames.Add(sectionName))
+                {
+                    sectionName = string.Concat(sectionName, "_", sectionCounter++);
+                }
+
+                // Save task name -> section name mapping for subsequent calls of GetSectionNameForTask()
+                _taskSectionNames.Add(taskName, sectionName);
+                return sectionName;
+            }
+        }
+    }
+}

src/Cake.GitLabCI.Module/GitLabCIModule.cs

@@ -1,5 +1,6 @@
 using System;
 
+using Cake.Core;
 using Cake.Core.Annotations;
 using Cake.Core.Composition;
 using Cake.Core.Diagnostics;
@@ -19,6 +20,7 @@ public void Register(ICakeContainerRegistrar registrar)
             if (StringComparer.OrdinalIgnoreCase.Equals(Environment.GetEnvironmentVariable("CI_SERVER"), "yes"))
             {
                 registrar.RegisterType<GitLabCILog>().As<ICakeLog>().Singleton();
+                registrar.RegisterType<GitLabCIEngine>().As<ICakeEngine>().Singleton();
             }
         }
     }