Add do-nothing SQL kernel to the builtin kernels in order to enable SQL language coloring

src/Microsoft.DotNet.Interactive.SqlServer/MsSqlKernel.cs

@@ -36,7 +36,7 @@ public class MsSqlKernel :
         public MsSqlKernel(
             string name,
             string connectionString,
-            MsSqlServiceClient client) : base(name)
+            MsSqlServiceClient client) : base(name, "SQL")
         {
             if (string.IsNullOrWhiteSpace(connectionString))
             {

src/Microsoft.DotNet.Interactive.Tests/SqlKernelTests.cs

@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using FluentAssertions;
+using System.Threading.Tasks;
+using Microsoft.DotNet.Interactive.Commands;
+using Microsoft.DotNet.Interactive.Events;
+using Microsoft.DotNet.Interactive.Tests.Utility;
+using Xunit;
+
+namespace Microsoft.DotNet.Interactive.Tests
+{
+    public class SqlKernelTests
+    {
+        [Fact]
+        public async Task sql_kernel_emits_help_message_without_sql_server_extension_installed()
+        {
+            using var kernel = new CompositeKernel
+            {
+                new SqlKernel()
+            };
+
+            using var events = kernel.KernelEvents.ToSubscribedList();
+
+            var query = "select * from sys.databases";
+            await kernel.SendAsync(new SubmitCode($"#!sql\n\n{query}"));
+
+            var displayValue = events.Should()
+                .ContainSingle<DisplayedValueProduced>()
+                .Which;
+
+            var message = (string)displayValue.Value;
+
+            message.Should().NotContain(query);
+
+            // Should contain instructions for how to install SqlServer extension package
+            message.Should().Contain("#r Microsoft.DotNet.Interactive.SqlServer");
+
+            // Should contain instructions for how to get help message for MSSQL kernel
+            message.Should().Contain("#!connect mssql -h");
+        }
+    }
+}

src/Microsoft.DotNet.Interactive/Kernel.cs

@@ -35,7 +35,7 @@ public abstract partial class Kernel : IDisposable
         private FrontendEnvironment _frontendEnvironment;
         private ChooseKernelDirective _chooseKernelDirective;
 
-        protected Kernel(string name)
+        protected Kernel(string name, string language = null)
         {
             if (string.IsNullOrWhiteSpace(name))
             {
@@ -44,6 +44,8 @@ protected Kernel(string name)
 
             Name = name;
 
+            Language = language;
+
             SubmissionParser = new SubmissionParser(this);
 
             _disposables = new CompositeDisposable();
@@ -214,6 +216,8 @@ public FrontendEnvironment FrontendEnvironment
 
         public string Name { get; set; }
 
+        public string Language { get; private set; }
+
         public IReadOnlyCollection<ICommand> Directives => SubmissionParser.Directives;
 
         public void AddDirective(Command command) => SubmissionParser.AddDirective(command);

src/Microsoft.DotNet.Interactive/KernelExtensions.cs

@@ -45,6 +45,29 @@ public static Kernel FindKernel(this Kernel kernel, string name)
             };
         }
 
+        public static Kernel FindKernel(this Kernel kernel, Func<Kernel, bool> selector)
+        {
+            var root = kernel
+                       .RecurseWhileNotNull(k => k switch
+                       {
+                           { } kb => kb.ParentKernel,
+                           _ => null
+                       })
+                       .LastOrDefault();
+
+            return root switch
+            {
+                _ when selector(kernel) => kernel,
+                CompositeKernel c =>
+                c.Directives
+                 .OfType<ChooseKernelDirective>()
+                 .Where(d => selector(d.Kernel))
+                 .Select(d => d.Kernel)
+                 .SingleOrDefault(),
+                _ => null
+            };
+        }
+
         public static Task<KernelCommandResult> SendAsync(
             this Kernel kernel,
             KernelCommand command)

src/Microsoft.DotNet.Interactive/SqlKernel.cs

@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Threading.Tasks;
+using Microsoft.DotNet.Interactive.Commands;
+
+namespace Microsoft.DotNet.Interactive
+{
+    /* This kernel is used as a placeholder for the MSSQL kernel in order to enable SQL language coloring
+    * in the editor. Language grammars can only be defined for fixed kernel names, but MSSQL subkernels
+    * are user-defined via the #!connect magic command. So, this kernel is specified in addition to the
+    * user-defined kernel as a kind of "styling" kernel.
+    */
+    public class SqlKernel :
+        Kernel,
+        IKernelCommandHandler<SubmitCode>
+    {
+        public const string DefaultKernelName = "sql";
+
+        public SqlKernel() : base(DefaultKernelName)
+        {
+        }
+
+        public Task HandleAsync(SubmitCode command, KernelInvocationContext context)
+        {
+            var sqlKernel = this.FindKernel(kernel => kernel.Language?.ToUpper() == "SQL");
+            if (sqlKernel == null)
+            {
+                context.Display(@"
+A SQL kernel is not currently defined.
+
+SQL kernels are provided as part of the Microsoft.DotNet.Interactive.SqlServer package, which can be installed by using the following nuget command:
+#r Microsoft.DotNet.Interactive.SqlServer
+
+Once installed, you can find more info about creating a SQL kernel and running queries by running the following help command:
+#!connect mssql -h
+                ");
+            }
+            return Task.CompletedTask;
+        }
+    }
+}

src/dotnet-interactive-vscode/package.json

@@ -214,6 +214,13 @@
           "PowerShell (.NET Interactive)"
         ],
         "configuration": "./syntaxes/powershell.language-configuration.json"
+      },
+      {
+        "id": "dotnet-interactive.sql",
+        "aliases": [
+          "SQL (.NET Interactive)"
+        ],
+        "configuration": "./syntaxes/sql.language-configuration.json"
       }
     ],
     "grammars": [
@@ -256,6 +263,11 @@
         "language": "dotnet-interactive.pwsh",
         "scopeName": "source.dotnet-interactive.powershell",
         "path": "./syntaxes/source.dotnet-interactive.powershell.tmGrammar.json"
+      },
+      {
+        "language": "dotnet-interactive.sql",
+        "scopeName": "source.dotnet-interactive.sql",
+        "path": "./syntaxes/source.dotnet-interactive.sql.tmGrammar.json"
       }
     ]
   },

src/dotnet-interactive-vscode/src/interactiveNotebook.ts

@@ -13,7 +13,8 @@ export const notebookCellLanguages: Array<string> = [
     'dotnet-interactive.fsharp',
     'dotnet-interactive.html',
     'dotnet-interactive.javascript',
-    'dotnet-interactive.pwsh'
+    'dotnet-interactive.pwsh',
+    'dotnet-interactive.sql'
 ];
 
 const notebookLanguagePrefix = 'dotnet-interactive.';

src/dotnet-interactive-vscode/src/tests/unit/grammar.test.ts

@@ -88,7 +88,8 @@ describe('TextMate grammar tests', async () => {
             '#!markdown',
             '#!md',
             '#!powershell',
-            '#!pwsh'
+            '#!pwsh',
+            '#!sql'
         ];
         const tokens = await getTokens(text);
         expect(tokens).to.deep.equal([
@@ -157,6 +158,12 @@ describe('TextMate grammar tests', async () => {
                     tokenText: '#!pwsh',
                     scopes: ['source.dotnet-interactive', 'language.switch.powershell']
                 }
+            ],
+            [
+                {
+                    tokenText: '#!sql',
+                    scopes: ['source.dotnet-interactive', 'language.switch.sql']
+                }
             ]
         ]);
     });
@@ -207,7 +214,8 @@ describe('TextMate grammar tests', async () => {
         'html',
         'javascript',
         'markdown',
-        'powershell'
+        'powershell',
+        'sql'
     ];
 
     for (const language of allLanguages) {

src/dotnet-interactive-vscode/syntaxes/source.dotnet-interactive.magic-commands.tmGrammar.json

@@ -4,7 +4,7 @@
     "patterns": [
         {
             "name": "comment.line.magic-commands",
-            "begin": "^(#!)(?!([cf](#|s(harp)?)|powershell|pwsh|html|javascript|js|markdown|md))",
+            "begin": "^(#!)(?!([cf](#|s(harp)?)|powershell|pwsh|html|javascript|js|markdown|md|sql))",
             "end": "(?<=$)",
             "beginCaptures": {
                 "1": {
@@ -68,4 +68,4 @@
             ]
         }
     }
-}
+}

src/dotnet-interactive-vscode/syntaxes/source.dotnet-interactive.sql.tmGrammar.json

@@ -0,0 +1,14 @@
+{
+    "scopeName": "source.dotnet-interactive.sql",
+    "patterns": [
+        {
+            "include": "source.dotnet-interactive.magic-commands"
+        },
+        {
+            "include": "source.dotnet-interactive"
+        },
+        {
+            "include": "source.sql"
+        }
+    ]
+}

src/dotnet-interactive-vscode/syntaxes/source.dotnet-interactive.tmGrammar.json

@@ -3,7 +3,7 @@
     "patterns": [
         {
             "begin": "^#!cs(harp)?\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.csharp",
             "patterns": [
                 {
@@ -13,7 +13,7 @@
         },
         {
             "begin": "^#!fs(harp)?\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.fsharp",
             "patterns": [
                 {
@@ -23,7 +23,7 @@
         },
         {
             "begin": "^#!html\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.html",
             "patterns": [
                 {
@@ -33,7 +33,7 @@
         },
         {
             "begin": "^#!(javascript|js)\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.javascript",
             "patterns": [
                 {
@@ -43,7 +43,7 @@
         },
         {
             "begin": "^#!(markdown|md)\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.markdown",
             "patterns": [
                 {
@@ -53,13 +53,23 @@
         },
         {
             "begin": "^#!(powershell|pwsh)\\s+$",
-            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh)\\s+$)",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
             "name": "language.switch.powershell",
             "patterns": [
                 {
                     "include": "source.dotnet-interactive.powershell"
                 }
             ]
+        },
+        {
+            "begin": "^#!sql\\s+$",
+            "end": "(?=^#!(cs(harp)?|fs(harp)?|html|javascript|js|markdown|md|powershell|pwsh|sql)\\s+$)",
+            "name": "language.switch.sql",
+            "patterns": [
+                {
+                    "include": "source.dotnet-interactive.sql"
+                }
+            ]
         }
     ]
-}
+}