Add helper for markdown lists of projects

Author: mbg

csharp/autobuilder/Semmle.Autobuild.CSharp/CSharpAutobuilder.cs

@@ -3,6 +3,7 @@
 using Semmle.Autobuild.Shared;
 using Semmle.Util;
 using System.Linq;
+using System.Collections.Generic;
 
 namespace Semmle.Autobuild.CSharp
 {
@@ -141,7 +142,7 @@ protected override void AutobuildFailureDiagnostic()
                 var message = MakeDiagnostic("dotnet-incompatible-projects", "Some projects are incompatible with .NET Core");
                 message.MarkdownMessage =
                     "CodeQL found some projects which cannot be built with .NET Core:\n" +
-                    string.Join('\n', autoBuildRule.DotNetRule.NotDotNetProjects.Select(p => $"- `{p.FullPath}`"));
+                    autoBuildRule.DotNetRule.NotDotNetProjects.ToMarkdownList(5);
                 message.Severity = DiagnosticMessage.TspSeverity.Warning;
 
                 AddDiagnostic(message);
@@ -153,7 +154,7 @@ protected override void AutobuildFailureDiagnostic()
                 var message = MakeDiagnostic("dotnet-build-failure", "Some projects or solutions failed to build using .NET Core");
                 message.MarkdownMessage =
                     "CodeQL was unable to build the following projects using .NET Core:\n" +
-                    string.Join('\n', autoBuildRule.DotNetRule.FailedProjectsOrSolutions.Select(p => $"- `{p.FullPath}`")) +
+                    autoBuildRule.DotNetRule.FailedProjectsOrSolutions.ToMarkdownList(10) +
                     $"\nSet up a [manual build command]({buildCommandDocsUrl}).";
                 message.Severity = DiagnosticMessage.TspSeverity.Error;
 
@@ -166,7 +167,7 @@ protected override void AutobuildFailureDiagnostic()
                 var message = MakeDiagnostic("msbuild-build-failure", "Some projects or solutions failed to build using MSBuild");
                 message.MarkdownMessage =
                     "CodeQL was unable to build the following projects using MSBuild:\n" +
-                    string.Join('\n', autoBuildRule.MsBuildRule.FailedProjectsOrSolutions.Select(p => $"- `{p.FullPath}`")) +
+                    autoBuildRule.MsBuildRule.FailedProjectsOrSolutions.ToMarkdownList(10) +
                     $"\nSet up a [manual build command]({buildCommandDocsUrl}).";
                 message.Severity = DiagnosticMessage.TspSeverity.Error;
 

csharp/autobuilder/Semmle.Autobuild.Shared/MarkdownUtil.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Semmle.Autobuild.Shared
+{
+    public static class MarkdownUtil
+    {
+        /// <summary>
+        /// Formats items as markdown inline code.
+        /// </summary>
+        /// <returns>A function which formats items as markdown inline code.</returns>
+        public static readonly Func<string, string> CodeFormatter = item => $"`{item}`";
+
+        /// <summary>
+        /// Renders <see cref="projects" /> as a markdown list of the project paths.
+        /// </summary>
+        /// <param name="projects">
+        /// The list of projects whose paths should be rendered as a markdown list.
+        /// </param>
+        /// <param name="limit">The maximum number of items to include in the list.</param>
+        /// <returns>Returns the markdown list as a string.</returns>
+        public static string ToMarkdownList(this IEnumerable<IProjectOrSolution> projects, int? limit = null)
+        {
+            return projects.ToMarkdownList(p => $"`{p.FullPath}`", limit);
+        }
+
+        /// <summary>
+        /// Renders <see cref="items" /> as a markdown list.
+        /// </summary>
+        /// <typeparam name="T">The item type.</typeparam>
+        /// <param name="items">The list that should be formatted as a markdown list.</param>
+        /// <param name="formatter">A function which converts individual items into a string representation.</param>
+        /// <param name="limit">The maximum number of items to include in the list.</param>
+        /// <returns>Returns the markdown list as a string.</returns>
+        public static string ToMarkdownList<T>(this IEnumerable<T> items, Func<T, string> formatter, int? limit = null)
+        {
+            var sb = new StringBuilder();
+
+            // if there is a limit, take at most that many items from the  start of the list
+            var list = limit is not null ? items.Take(limit.Value) : items;
+            sb.Append(string.Join('\n', list.Select(item => $"- {formatter(item)}")));
+
+            // if there were more items than allowed in the list, add an extra item indicating
+            // how many more items there were
+            var length = items.Count();
+
+            if (limit is not null && length > limit)
+            {
+                sb.Append($"\n- and {length - limit} more. View the CodeQL logs for a full list.");
+            }
+
+            return sb.ToString();
+        }
+    }
+}