Add Deno support to the TypeScript AppHost toolchain resolver

src/Aspire.Cli/Projects/TypeScriptAppHostToolchainResolver.cs

@@ -15,7 +15,8 @@ internal enum TypeScriptAppHostToolchain
     Npm,
     Bun,
     Yarn,
-    Pnpm
+    Pnpm,
+    Deno
 }
 
 internal static class TypeScriptAppHostToolchainResolver
@@ -28,6 +29,9 @@ internal static class TypeScriptAppHostToolchainResolver
     private const string YarnConfigFileName = ".yarnrc.yml";
     private const string PackageLockFileName = "package-lock.json";
     private const string PnpmLockFileName = "pnpm-lock.yaml";
+    private const string DenoLockFileName = "deno.lock";
+    private const string DenoJsonFileName = "deno.json";
+    private const string DenoJsoncFileName = "deno.jsonc";
 
     public static bool IsTypeScriptLanguage(LanguageInfo? language)
     {
@@ -87,6 +91,21 @@ internal static TypeScriptAppHostToolchainResolution ResolveWithReason(Directory
                 return CreateLockFileResolution(TypeScriptAppHostToolchain.Yarn, YarnConfigFileName, candidateDirectory);
             }
 
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoLockFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoLockFileName, candidateDirectory);
+            }
+
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoJsonFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoJsonFileName, candidateDirectory);
+            }
+
+            if (File.Exists(Path.Combine(candidateDirectory.FullName, DenoJsoncFileName)))
+            {
+                return CreateLockFileResolution(TypeScriptAppHostToolchain.Deno, DenoJsoncFileName, candidateDirectory);
+            }
+
             if (File.Exists(Path.Combine(candidateDirectory.FullName, PackageLockFileName)))
             {
                 return CreateLockFileResolution(TypeScriptAppHostToolchain.Npm, PackageLockFileName, candidateDirectory);
@@ -113,6 +132,7 @@ public static string GetCommandName(TypeScriptAppHostToolchain toolchain)
             TypeScriptAppHostToolchain.Bun => "bun",
             TypeScriptAppHostToolchain.Yarn => "yarn",
             TypeScriptAppHostToolchain.Pnpm => "pnpm",
+            TypeScriptAppHostToolchain.Deno => "deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -130,6 +150,7 @@ public static string GetDisplayName(TypeScriptAppHostToolchain toolchain)
             TypeScriptAppHostToolchain.Bun => "Bun",
             TypeScriptAppHostToolchain.Yarn => "Yarn",
             TypeScriptAppHostToolchain.Pnpm => "pnpm",
+            TypeScriptAppHostToolchain.Deno => "Deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -198,6 +219,13 @@ private static CommandSpec[] CreatePreExecuteCommands(TypeScriptAppHostToolchain
                     Command = "pnpm",
                     Args = ["exec", "tsc", "--noEmit", "-p", tsConfigFileName]
                 },
+                // Deno type-checks with its own compiler and config (deno.json), so there is no
+                // tsc/tsconfig step. `deno check` is the native no-emit type-check over the AppHost graph.
+                TypeScriptAppHostToolchain.Deno => new CommandSpec
+                {
+                    Command = "deno",
+                    Args = ["check", "{appHostFile}"]
+                },
                 _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
             }
         ];
@@ -222,6 +250,15 @@ private static CommandSpec CreateExecuteCommand(TypeScriptAppHostToolchain toolc
                 Command = "pnpm",
                 Args = ["exec", "tsx", "--tsconfig", tsConfigFileName, "{appHostFile}"]
             },
+            // Deno runs the AppHost as its own runtime (no tsx transpiler). Unlike Node/Bun, Deno is
+            // not permissive for package.json projects: APIs like Deno.env/Deno.serve throw NotCapable
+            // without flags (and error non-interactively rather than prompting). The AppHost needs
+            // full host access, so `-A` grants all permissions, mirroring how Node/Bun run unrestricted.
+            TypeScriptAppHostToolchain.Deno => new CommandSpec
+            {
+                Command = "deno",
+                Args = ["run", "-A", "{appHostFile}"]
+            },
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -275,6 +312,14 @@ private static CommandSpec CreateWatchCommand(TypeScriptAppHostToolchain toolcha
                     "--exec", $"pnpm exec tsc --noEmit -p {tsConfigFileName} && pnpm exec tsx --tsconfig {tsConfigFileName} \"{{appHostFile}}\""
                 ]
             },
+            // Deno has a native file watcher, so nodemon is unnecessary. `--check` makes each restart
+            // type-check before running, matching the nodemon "tsc --noEmit && run" behavior other
+            // toolchains emulate. `-A` grants full permissions as on the non-watch execute command.
+            TypeScriptAppHostToolchain.Deno => new CommandSpec
+            {
+                Command = "deno",
+                Args = ["run", "-A", "--check", "--watch", "{appHostFile}"]
+            },
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }
@@ -344,6 +389,7 @@ private static bool TryParseToolchain(string packageManagerName, out TypeScriptA
             "bun" => TypeScriptAppHostToolchain.Bun,
             "yarn" => TypeScriptAppHostToolchain.Yarn,
             "pnpm" => TypeScriptAppHostToolchain.Pnpm,
+            "deno" => TypeScriptAppHostToolchain.Deno,
             _ => null
         };
 

src/Aspire.Cli/Scaffolding/ScaffoldingService.cs

@@ -382,6 +382,9 @@ private static string CreateRootDelegateScript(TypeScriptAppHostToolchain toolch
             TypeScriptAppHostToolchain.Pnpm => $"pnpm --dir {relativeAppHostDirectory} run {scriptName}",
             TypeScriptAppHostToolchain.Yarn => $"yarn --cwd {relativeAppHostDirectory} run {scriptName}",
             TypeScriptAppHostToolchain.Bun => $"bun --cwd {relativeAppHostDirectory} run {scriptName}",
+            // Deno has no `run <script>` for package.json scripts; `deno task` runs them and `--cwd`
+            // scopes the task to the nested AppHost package, mirroring npm's `--prefix`.
+            TypeScriptAppHostToolchain.Deno => $"deno task --cwd {relativeAppHostDirectory} {scriptName}",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, null)
         };
     }

src/Aspire.Cli/Utils/CommandPathResolver.cs

@@ -14,7 +14,8 @@ internal static class CommandPathResolver
         ["npx"] = new("Node.js", "https://nodejs.org/en/download"),
         ["bun"] = new("Bun", "https://bun.sh/docs/installation"),
         ["yarn"] = new("Yarn", "https://yarnpkg.com/getting-started/install"),
-        ["pnpm"] = new("pnpm", "https://pnpm.io/installation")
+        ["pnpm"] = new("pnpm", "https://pnpm.io/installation"),
+        ["deno"] = new("Deno", "https://docs.deno.com/runtime/getting_started/installation/")
     };
 
     /// <summary>

src/Aspire.Cli/Utils/MissingJavaScriptToolWarning.cs

@@ -15,7 +15,8 @@ internal static class MissingJavaScriptToolWarning
         "npx is not installed or not found in PATH.",
         "bun is not installed or not found in PATH.",
         "yarn is not installed or not found in PATH.",
-        "pnpm is not installed or not found in PATH."
+        "pnpm is not installed or not found in PATH.",
+        "deno is not installed or not found in PATH."
     ];
 
     public static bool IsMatch(IEnumerable<(OutputLineStream Stream, string Line)> lines)

tests/Aspire.Cli.EndToEnd.Tests/Helpers/TypeScriptAppHostToolchainTestHelpers.cs

@@ -46,7 +46,7 @@ internal static void SetPackageManager(string projectRoot, string toolchain, boo
             return;
         }
 
-        foreach (var lockFileName in new[] { "package-lock.json", "bun.lock", "bun.lockb", "pnpm-lock.yaml", "yarn.lock" })
+        foreach (var lockFileName in new[] { "package-lock.json", "bun.lock", "bun.lockb", "pnpm-lock.yaml", "yarn.lock", "deno.lock" })
         {
             var lockFilePath = Path.Combine(projectRoot, lockFileName);
             if (File.Exists(lockFilePath))
@@ -80,14 +80,33 @@ internal static string GetTypeCheckCommand(string toolchain, string tsConfigFile
             "yarn" => $"yarn run tsc --noEmit -p {tsConfigFileName}",
             "pnpm" => $"pnpm exec tsc --noEmit -p {tsConfigFileName}",
             "npm" => $"npx --no-install tsc --noEmit -p {tsConfigFileName}",
+            // Deno type-checks with its own compiler over the AppHost graph; there is no tsc/tsconfig step.
+            "deno" => "deno check apphost.mts",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
     /// <summary>
     /// Gets the script runner command for a toolchain.
     /// </summary>
     internal static string GetRunScriptCommand(string toolchain, string scriptName) =>
-        $"{GetCommandName(toolchain)} run {scriptName}";
+        NormalizeToolchain(toolchain) switch
+        {
+            // Deno runs package.json scripts via `deno task`, not `deno run` (which runs a file).
+            "deno" => $"deno task {scriptName}",
+            _ => $"{GetCommandName(toolchain)} run {scriptName}"
+        };
+
+    /// <summary>
+    /// Gets the console text that indicates watch mode is active for a toolchain.
+    /// The E2E path runs the scaffolded <c>aspire:dev</c> package script for every toolchain,
+    /// so readiness comes from <c>tsc --watch</c>.
+    /// </summary>
+    internal static string GetWatchModeReadyText(string toolchain)
+    {
+        _ = NormalizeToolchain(toolchain);
+
+        return "Watching for file changes.";
+    }
 
     /// <summary>
     /// Gets the primary lock file name a toolchain should produce after restore/install.
@@ -99,6 +118,7 @@ internal static string GetLockFileName(string toolchain) =>
             "yarn" => "yarn.lock",
             "pnpm" => "pnpm-lock.yaml",
             "npm" => "package-lock.json",
+            "deno" => "deno.lock",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -114,6 +134,7 @@ internal static string GetPackageManager(string toolchain) =>
             "yarn" => "yarn@4.14.1",
             "pnpm" => "pnpm@10.0.0",
             "npm" => "npm@10.0.0",
+            "deno" => "deno@2.9.0",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -132,6 +153,7 @@ internal static string GetDisplayName(string toolchain) =>
             "yarn" => "Yarn",
             "pnpm" => "pnpm",
             "npm" => "Node.js",
+            "deno" => "Deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -147,6 +169,7 @@ internal static string GetInstallationLink(string toolchain) =>
             "yarn" => "https://yarnpkg.com/getting-started/install",
             "pnpm" => "https://pnpm.io/installation",
             "npm" => "https://nodejs.org/en/download",
+            "deno" => "https://docs.deno.com/runtime/getting_started/installation/",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 
@@ -180,6 +203,7 @@ private static string GetCommandName(string toolchain) =>
             "yarn" => "yarn",
             "pnpm" => "pnpm",
             "npm" => "npm",
+            "deno" => "deno",
             _ => throw new ArgumentOutOfRangeException(nameof(toolchain), toolchain, "Unsupported TypeScript AppHost toolchain.")
         };
 

tests/Aspire.Cli.EndToEnd.Tests/TypeScriptAppHostToolchainTestHelpersTests.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Aspire.Cli.EndToEnd.Tests.Helpers;
+using Xunit;
+
+namespace Aspire.Cli.EndToEnd.Tests;
+
+public sealed class TypeScriptAppHostToolchainTestHelpersTests
+{
+    [Fact]
+    public void GetWatchModeReadyText_WhenToolchainIsDeno_ReturnsTypeScriptCompilerWatchText()
+    {
+        var watchModeReadyText = TypeScriptAppHostToolchainTestHelpers.GetWatchModeReadyText("deno");
+
+        Assert.Equal("Watching for file changes.", watchModeReadyText);
+    }
+}

tests/Aspire.Cli.EndToEnd.Tests/TypeScriptPolyglotTests.cs

@@ -22,7 +22,8 @@ public sealed class TypeScriptPolyglotTests(ITestOutputHelper output)
         "npm",
         "bun",
         "yarn",
-        "pnpm"
+        "pnpm",
+        "deno"
     };
 
     [Theory]
@@ -289,7 +290,7 @@ public async Task GeneratedAspireDevScript_StartsWatchMode_WithConfiguredToolcha
         await auto.TypeAsync(TypeScriptAppHostToolchainTestHelpers.GetRunScriptCommand(toolchain, "aspire:dev"));
         await auto.EnterAsync();
         await auto.WaitUntilAsync(
-            s => s.ContainsText("Watching for file changes."),
+            s => s.ContainsText(TypeScriptAppHostToolchainTestHelpers.GetWatchModeReadyText(toolchain)),
             timeout: TimeSpan.FromMinutes(2),
             description: $"{toolchain} watch mode to start");
 

tests/Aspire.Cli.Tests/Commands/TypeScriptAppHostToolingCheckTests.cs

@@ -25,6 +25,7 @@ public sealed class TypeScriptAppHostToolingCheckTests(ITestOutputHelper outputH
     [InlineData("bun@1.2.0", nameof(TypeScriptAppHostToolchain.Bun))]
     [InlineData("yarn@4.14.1", nameof(TypeScriptAppHostToolchain.Yarn))]
     [InlineData("pnpm@10.12.1", nameof(TypeScriptAppHostToolchain.Pnpm))]
+    [InlineData("deno@2.9.0", nameof(TypeScriptAppHostToolchain.Deno))]
     public async Task CheckAsync_ReturnsPass_WhenConfiguredToolchainIsAvailable(string packageManagerSpec, string toolchainName)
     {
         var toolchain = Enum.Parse<TypeScriptAppHostToolchain>(toolchainName);
@@ -54,6 +55,7 @@ public async Task CheckAsync_ReturnsPass_WhenConfiguredToolchainIsAvailable(stri
     [InlineData("bun@1.2.0", nameof(TypeScriptAppHostToolchain.Bun), "Bun", "https://bun.sh/docs/installation")]
     [InlineData("yarn@4.14.1", nameof(TypeScriptAppHostToolchain.Yarn), "Yarn", "https://yarnpkg.com/getting-started/install")]
     [InlineData("pnpm@10.12.1", nameof(TypeScriptAppHostToolchain.Pnpm), "pnpm", "https://pnpm.io/installation")]
+    [InlineData("deno@2.9.0", nameof(TypeScriptAppHostToolchain.Deno), "Deno", "https://docs.deno.com/runtime/getting_started/installation/")]
     public async Task CheckAsync_ReturnsFail_WhenConfiguredToolchainIsMissing(
         string packageManagerSpec,
         string toolchainName,

tests/Aspire.Cli.Tests/Projects/TypeScriptAppHostToolchainResolverTests.cs

@@ -22,6 +22,43 @@ public void Resolve_WhenPackageManagerIsBun_ReturnsBun()
         Assert.Equal(TypeScriptAppHostToolchain.Bun, toolchain);
     }
 
+    [Fact]
+    public void Resolve_WhenPackageManagerIsDeno_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"packageManager\": \"deno@2.9.0\" }");
+
+        var toolchain = TypeScriptAppHostToolchainResolver.Resolve(workspace.WorkspaceRoot, new TestEnvironment(), logger: null);
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, toolchain);
+    }
+
+    [Fact]
+    public void Resolve_WhenDenoLockExists_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"name\": \"apphost\" }");
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "deno.lock"), "{ \"version\": \"5\" }");
+
+        var resolution = TypeScriptAppHostToolchainResolver.ResolveWithReason(workspace.WorkspaceRoot, new TestEnvironment());
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, resolution.Toolchain);
+        Assert.Equal($"deno.lock found in {workspace.WorkspaceRoot.FullName}", resolution.Reason);
+    }
+
+    [Fact]
+    public void Resolve_WhenDenoJsonExists_ReturnsDeno()
+    {
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "package.json"), "{ \"name\": \"apphost\" }");
+        File.WriteAllText(Path.Combine(workspace.WorkspaceRoot.FullName, "deno.json"), "{}");
+
+        var resolution = TypeScriptAppHostToolchainResolver.ResolveWithReason(workspace.WorkspaceRoot, new TestEnvironment());
+
+        Assert.Equal(TypeScriptAppHostToolchain.Deno, resolution.Toolchain);
+        Assert.Equal($"deno.json found in {workspace.WorkspaceRoot.FullName}", resolution.Reason);
+    }
+
     [Fact]
     public void Resolve_WhenPnpmLockExists_ReturnsPnpm()
     {
@@ -346,6 +383,26 @@ public void ApplyToRuntimeSpec_WhenPnpmSelected_UsesPnpmTypeCheckCommands()
         Assert.Contains("pnpm exec tsc --noEmit -p tsconfig.apphost.json && pnpm exec tsx --tsconfig tsconfig.apphost.json \"{appHostFile}\"", runtimeSpec.WatchExecute?.Args ?? []);
     }
 
+    [Fact]
+    public void ApplyToRuntimeSpec_WhenDenoSelected_UsesDenoRunCommands()
+    {
+        var baseRuntimeSpec = CreateBaseRuntimeSpec();
+
+        var runtimeSpec = TypeScriptAppHostToolchainResolver.ApplyToRuntimeSpec(baseRuntimeSpec, TypeScriptAppHostToolchain.Deno);
+
+        Assert.Equal("TypeScript (Deno)", runtimeSpec.DisplayName);
+        Assert.Equal("deno", runtimeSpec.InstallDependencies?.Command);
+        Assert.Equal(["install"], runtimeSpec.InstallDependencies!.Args);
+        var preExecute = Assert.Single(runtimeSpec.PreExecute!);
+        Assert.Equal("deno", preExecute.Command);
+        Assert.Equal(["check", "{appHostFile}"], preExecute.Args);
+        Assert.Equal("deno", runtimeSpec.Execute.Command);
+        Assert.Equal(["run", "-A", "{appHostFile}"], runtimeSpec.Execute.Args);
+        Assert.Equal("deno", runtimeSpec.WatchExecute?.Command);
+        Assert.Equal(["run", "-A", "--check", "--watch", "{appHostFile}"], runtimeSpec.WatchExecute!.Args);
+        Assert.Equal("node", runtimeSpec.ExtensionLaunchCapability);
+    }
+
     private static RuntimeSpec CreateBaseRuntimeSpec()
     {
         return new RuntimeSpec

tests/Aspire.Cli.Tests/Utils/CommandPathResolverTests.cs

@@ -16,6 +16,7 @@ public class CommandPathResolverTests
     [InlineData("bun.cmd", "bun is not installed or not found in PATH. Please install Bun and try again.")]
     [InlineData("yarn", "yarn is not installed or not found in PATH. Please install Yarn and try again.")]
     [InlineData("pnpm", "pnpm is not installed or not found in PATH. Please install pnpm and try again.")]
+    [InlineData("deno", "deno is not installed or not found in PATH. Please install Deno and try again.")]
     public void TryResolveCommand_WhenJavaScriptCommandIsMissing_ReturnsToolSpecificInstallMessage(string command, string expectedMessage)
     {
         static string? MissingCommandResolver(string _) => null;
@@ -57,6 +58,7 @@ public void TryResolveCommand_WhenCommandExists_ReturnsResolvedPath()
     [InlineData("bun", "https://bun.sh/docs/installation")]
     [InlineData("yarn", "https://yarnpkg.com/getting-started/install")]
     [InlineData("pnpm", "https://pnpm.io/installation")]
+    [InlineData("deno", "https://docs.deno.com/runtime/getting_started/installation/")]
     public void GetInstallationLink_WhenJavaScriptCommandKnown_ReturnsExpectedLink(string command, string expectedLink)
     {
         Assert.Equal(expectedLink, CommandPathResolver.GetInstallationLink(command));

tests/Aspire.Cli.Tests/Utils/MissingJavaScriptToolWarningTests.cs

@@ -22,6 +22,7 @@ public class MissingJavaScriptToolWarningTests(ITestOutputHelper outputHelper)
     [InlineData("bun is not installed or not found in PATH. Please install Bun and try again.")]
     [InlineData("yarn is not installed or not found in PATH. Please install Yarn and try again.")]
     [InlineData("pnpm is not installed or not found in PATH. Please install pnpm and try again.")]
+    [InlineData("deno is not installed or not found in PATH. Please install Deno and try again.")]
     public void IsMatch_WhenJavaScriptToolIsMissing_ReturnsTrue(string message)
     {
         var lines = new[]