Add --format to dotnet sln list

src/Cli/dotnet/commands/dotnet-sln/LocalizableStrings.resx

@@ -177,4 +177,7 @@
   <data name="SolutionFolderHeader" xml:space="preserve">
     <value>Solution Folder(s)</value>
   </data>
-</root>
+  <data name="CmdFormatDescription" xml:space="preserve">
+    <value>The desired output format of the command</value>
+  </data>
+</root>

src/Cli/dotnet/commands/dotnet-sln/list/Program.cs

@@ -2,23 +2,29 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.CommandLine;
+using System.Text.Json;
 using Microsoft.DotNet.Cli;
 using Microsoft.DotNet.Cli.Sln.Internal;
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.DotNet.Tools.Common;
+using Microsoft.DotNet.Tools.Tool.List;
 
 namespace Microsoft.DotNet.Tools.Sln.List
 {
     internal class ListProjectsInSolutionCommand : CommandBase
     {
+        private readonly static JsonSerializerOptions s_noEscapeJsonSerializerOptions = new() { Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping };
+
         private readonly string _fileOrDirectory;
         private readonly bool _displaySolutionFolders;
+        private readonly SlnListReportOutputFormat _outputFormat;
 
         public ListProjectsInSolutionCommand(
             ParseResult parseResult) : base(parseResult)
         {
             _fileOrDirectory = parseResult.GetValue(SlnCommandParser.SlnArgument);
             _displaySolutionFolders = parseResult.GetValue(SlnListParser.SolutionFolderOption);
+            _outputFormat = parseResult.GetValue(SlnListParser.OutputFormatOption);
         }
 
         public override int Execute()
@@ -50,12 +56,23 @@ public override int Execute()
             {
                 Array.Sort(paths);
 
-                string header = _displaySolutionFolders ? LocalizableStrings.SolutionFolderHeader : LocalizableStrings.ProjectsHeader;
-                Reporter.Output.WriteLine($"{header}");
-                Reporter.Output.WriteLine(new string('-', header.Length));
-                foreach (string slnProject in paths)
+                switch (_outputFormat)
                 {
-                    Reporter.Output.WriteLine(slnProject);
+                    case SlnListReportOutputFormat.text:
+                        string header = _displaySolutionFolders ? LocalizableStrings.SolutionFolderHeader : LocalizableStrings.ProjectsHeader;
+                        Reporter.Output.WriteLine($"{header}");
+                        Reporter.Output.WriteLine(new string('-', header.Length));
+
+                        foreach (string slnProject in paths)
+                        {
+                            Reporter.Output.WriteLine(slnProject);
+                        }
+                        break;
+
+                    case SlnListReportOutputFormat.json:
+                        var jsonArray = JsonSerializer.Serialize(paths, s_noEscapeJsonSerializerOptions);
+                        Reporter.Output.WriteLine(jsonArray);
+                        break;
                 }
             }
             return 0;

src/Cli/dotnet/commands/dotnet-sln/list/SlnListParser.cs

@@ -7,10 +7,12 @@
 
 namespace Microsoft.DotNet.Cli
 {
-    public static class SlnListParser
+    internal static class SlnListParser
     {
         public static readonly CliOption<bool> SolutionFolderOption = new("--solution-folders") { Description = LocalizableStrings.ListSolutionFoldersArgumentDescription };
 
+        public static readonly CliOption<SlnListReportOutputFormat> OutputFormatOption = new("--format") { Description = LocalizableStrings.CmdFormatDescription };
+
         private static readonly CliCommand Command = ConstructCommand();
 
         public static CliCommand GetCommand()
@@ -23,6 +25,7 @@ private static CliCommand ConstructCommand()
             CliCommand command = new("list", LocalizableStrings.ListAppFullName);
 
             command.Options.Add(SolutionFolderOption);
+            command.Options.Add(OutputFormatOption);
             command.SetAction((parseResult) => new ListProjectsInSolutionCommand(parseResult).Execute());
 
             return command;

src/Cli/dotnet/commands/dotnet-sln/list/SlnListReportOutputFormat.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.DotNet.Tools.Sln.List
+{
+    internal enum SlnListReportOutputFormat
+    {
+        text = 0,
+        json = 1,
+    }
+}

test/dotnet-sln.Tests/GivenDotnetSlnList.cs

@@ -20,8 +20,9 @@ public class GivenDotnetSlnList : SdkTest
   <SLN_FILE>    The solution file to operate on. If not specified, the command will search the current directory for one. [default: {PathUtility.EnsureTrailingSlash(defaultVal)}]
 
 Options:
-  --solution-folders  Display solution folder paths.
-  -?, -h, --help    Show command line help.";
+  --solution-folders                           Display solution folder paths.
+  --format <console|console_with_header|json>  The desired output format of the command
+  -?, -h, --help                               Show command line help";
 
 
         public GivenDotnetSlnList(ITestOutputHelper log) : base(log)