Semantic Snippets - using snippet (#77214)

Adds snippet provider for the using snippet.

Author: akhera99

src/Features/CSharp/Portable/Completion/CompletionProviders/SnippetCompletionProvider.cs

@@ -51,6 +51,7 @@ internal sealed class SnippetCompletionProvider : LSPCompletionProvider
         CSharpSnippetIdentifiers.StaticIntMain,
         CSharpSnippetIdentifiers.Struct,
         CSharpSnippetIdentifiers.StaticVoidMain,
+        CSharpSnippetIdentifiers.Using,
         CSharpSnippetIdentifiers.While
     ];
 

src/Features/CSharp/Portable/Snippets/CSharpSnippetIdentifiers.cs

@@ -25,5 +25,6 @@ internal static class CSharpSnippetIdentifiers
     public const string StaticIntMain = "sim";
     public const string Struct = "struct";
     public const string StaticVoidMain = "svm";
+    public const string Using = "using";
     public const string While = "while";
 }

src/Features/CSharp/Portable/Snippets/CSharpUsingSnippetProvider.cs

@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Snippets;
+using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets;
+
+[ExportSnippetProvider(nameof(ISnippetProvider), LanguageNames.CSharp), Shared]
+[method: ImportingConstructor]
+[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+internal sealed class CSharpUsingSnippetProvider() : AbstractUsingSnippetProvider<UsingStatementSyntax>
+{
+    public override string Identifier => CSharpSnippetIdentifiers.Using;
+
+    public override string Description => CSharpFeaturesResources.using_statement;
+
+    protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsList(UsingStatementSyntax node, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
+    {
+        var expression = node.Expression!;
+        return [new SnippetPlaceholder(expression.ToString(), expression.SpanStart)];
+    }
+
+    protected override int GetTargetCaretPosition(UsingStatementSyntax usingStatement, SourceText sourceText)
+        => CSharpSnippetHelpers.GetTargetCaretPositionInBlock(
+            usingStatement,
+            static s => (BlockSyntax)s.Statement,
+            sourceText);
+
+    protected override Task<Document> AddIndentationToDocumentAsync(Document document, UsingStatementSyntax usingStatement, CancellationToken cancellationToken)
+        => CSharpSnippetHelpers.AddBlockIndentationToDocumentAsync(
+            document,
+            usingStatement,
+            static s => (BlockSyntax)s.Statement,
+            cancellationToken);
+}

src/Features/CSharpTest/Snippets/CSharpUsingSnippetProviderTests.cs

@@ -0,0 +1,202 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests.Snippets;
+
+[Trait(Traits.Feature, Traits.Features.Snippets)]
+public sealed class CSharpUsingSnippetProviderTests : AbstractCSharpSnippetProviderTests
+{
+    protected override string SnippetIdentifier => "using";
+
+    [Fact]
+    public async Task InsertUsingSnippetInMethodTest()
+    {
+        await VerifySnippetAsync("""
+            class Program
+            {
+                public void Method()
+                {
+                    $$
+                }
+            }
+            """, """
+            class Program
+            {
+                public void Method()
+                {
+                    using ({|0:resource|})
+                    {
+                        $$
+                    }
+                }
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task InsertUsingSnippetInGlobalContextTest()
+    {
+        await VerifySnippetAsync("""
+            $$
+            """, """
+            using ({|0:resource|})
+            {
+                $$
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task NoUsingSnippetInBusingNamespaceTest()
+    {
+        await VerifySnippetIsAbsentAsync("""
+            namespace Namespace
+            {
+                $$
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task NoUsingSnippetInFileScopedNamespaceTest()
+    {
+        await VerifySnippetIsAbsentAsync("""
+            namespace Namespace;
+            $$
+            """);
+    }
+
+    [Fact]
+    public async Task InsertUsingSnippetInConstructorTest()
+    {
+        await VerifySnippetAsync("""
+            class Program
+            {
+                public Program()
+                {
+                    $$
+                }
+            }
+            """, """
+            class Program
+            {
+                public Program()
+                {
+                    using ({|0:resource|})
+                    {
+                        $$
+                    }
+                }
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task NoUsingSnippetInTypeBodyTest()
+    {
+        await VerifySnippetIsAbsentAsync("""
+            class Program
+            {
+                $$
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task InsertUsingSnippetInLocalFunctionTest()
+    {
+        await VerifySnippetAsync("""
+            class Program
+            {
+                public void Method()
+                {
+                    void LocalFunction()
+                    {
+                        $$
+                    }
+                }
+            }
+            """, """
+            class Program
+            {
+                public void Method()
+                {
+                    void LocalFunction()
+                    {
+                        using ({|0:resource|})
+                        {
+                            $$
+                        }
+                    }
+                }
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task InsertUsingSnippetInAnonymousFunctionTest()
+    {
+        await VerifySnippetAsync("""
+            class Program
+            {
+                public void Method()
+                {
+                    var action = delegate()
+                    {
+                        $$
+                    };
+                }
+            }
+            """, """
+            class Program
+            {
+                public void Method()
+                {
+                    var action = delegate()
+                    {
+                        using ({|0:resource|})
+                        {
+                            $$
+                        }
+                    };
+                }
+            }
+            """);
+    }
+
+    [Fact]
+    public async Task InsertUsingSnippetInParenthesizedLambdaExpressionTest()
+    {
+        await VerifySnippetAsync("""
+            class Program
+            {
+                public void Method()
+                {
+                    var action = () =>
+                    {
+                        $$
+                    };
+                }
+            }
+            """, """
+            class Program
+            {
+                public void Method()
+                {
+                    var action = () =>
+                    {
+                        using ({|0:resource|})
+                        {
+                            $$
+                        }
+                    };
+                }
+            }
+            """);
+    }
+}

src/Features/Core/Portable/Snippets/SnippetProviders/AbstractUsingSnippetProvider.cs

@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.Utilities;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+
+internal abstract class AbstractUsingSnippetProvider<TUsingStatementSyntax> : AbstractStatementSnippetProvider<TUsingStatementSyntax>
+    where TUsingStatementSyntax : SyntaxNode
+{
+    protected sealed override async Task<TextChange> GenerateSnippetTextChangeAsync(Document document, int position, CancellationToken cancellationToken)
+    {
+        var generator = SyntaxGenerator.GetGenerator(document);
+        var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+        var identifierName = NameGenerator.GenerateUniqueName("resource",
+            n => semanticModel.LookupSymbols(position, name: n).IsEmpty);
+        var statement = generator.UsingStatement(generator.IdentifierName(identifierName), statements: []);
+        return new TextChange(TextSpan.FromBounds(position, position), statement.NormalizeWhitespace().ToFullString());
+    }
+}