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// 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.Collections.Immutable;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.RemoveAsyncModifier
{
internal abstract class AbstractRemoveAsyncModifierCodeFixProvider<TReturnStatementSyntax, TExpressionSyntax> : SyntaxEditorBasedCodeFixProvider
where TReturnStatementSyntax : SyntaxNode
where TExpressionSyntax : SyntaxNode
{
protected abstract bool IsAsyncSupportingFunctionSyntax(SyntaxNode node);
protected abstract SyntaxNode RemoveAsyncModifier(SyntaxGenerator generator, SyntaxNode methodLikeNode);
protected abstract SyntaxNode? ConvertToBlockBody(SyntaxNode node, TExpressionSyntax expressionBody);
public override async Task RegisterCodeFixesAsync(CodeFixContext context)
{
var document = context.Document;
var cancellationToken = context.CancellationToken;
var compilation = await document.Project.GetRequiredCompilationAsync(cancellationToken).ConfigureAwait(false);
var knownTypes = new KnownTypes(compilation);
var diagnostic = context.Diagnostics.First();
var token = diagnostic.Location.FindToken(cancellationToken);
var node = token.GetAncestor(IsAsyncSupportingFunctionSyntax);
if (node == null)
{
return;
}
var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var methodSymbol = GetMethodSymbol(node, semanticModel, cancellationToken);
if (methodSymbol == null)
{
return;
}
if (ShouldOfferFix(methodSymbol.ReturnType, knownTypes))
{
context.RegisterCodeFix(
CodeAction.Create(
CodeFixesResources.Remove_async_modifier,
GetDocumentUpdater(context),
nameof(CodeFixesResources.Remove_async_modifier)),
context.Diagnostics);
}
}
protected sealed override async Task FixAllAsync(
Document document, ImmutableArray<Diagnostic> diagnostics,
SyntaxEditor editor, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)
{
var solutionServices = document.Project.Solution.Services;
var generator = editor.Generator;
var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
var compilation = semanticModel.Compilation;
var knownTypes = new KnownTypes(compilation);
// For fix all we need to do nested locals or lambdas first, so order the diagnostics by location descending
foreach (var diagnostic in diagnostics.OrderByDescending(d => d.Location.SourceSpan.Start))
{
var token = diagnostic.Location.FindToken(cancellationToken);
var node = token.GetAncestor(IsAsyncSupportingFunctionSyntax);
if (node == null)
{
Debug.Fail("We should always be able to find the node from the diagnostic.");
continue;
}
var methodSymbol = GetMethodSymbol(node, semanticModel, cancellationToken);
if (methodSymbol == null)
{
Debug.Fail("We should always be able to find the method symbol for the diagnostic.");
continue;
}
// We might need to perform control flow analysis as part of the fix, so we need to do it on the original node
// so do it up front. Nothing in the fixer changes the reachability of the end of the method so this is safe
var controlFlow = GetControlFlowAnalysis(generator, semanticModel, node);
// If control flow couldn't be computed then its probably an empty block, which means we need to add a return anyway
var needsReturnStatementAdded = controlFlow == null || controlFlow.EndPointIsReachable;
editor.ReplaceNode(node,
(updatedNode, generator) => RemoveAsyncModifier(
solutionServices, syntaxFacts, generator, updatedNode, methodSymbol.ReturnType, knownTypes, needsReturnStatementAdded));
}
}
private static IMethodSymbol? GetMethodSymbol(SyntaxNode node, SemanticModel semanticModel, CancellationToken cancellationToken)
=> semanticModel.GetSymbolInfo(node, cancellationToken).Symbol as IMethodSymbol ??
semanticModel.GetDeclaredSymbol(node, cancellationToken) as IMethodSymbol;
private static bool ShouldOfferFix(ITypeSymbol returnType, KnownTypes knownTypes)
=> IsTaskType(returnType, knownTypes)
|| returnType.OriginalDefinition.Equals(knownTypes.TaskOfTType)
|| returnType.OriginalDefinition.Equals(knownTypes.ValueTaskOfTTypeOpt);
private static bool IsTaskType(ITypeSymbol returnType, KnownTypes knownTypes)
=> returnType.OriginalDefinition.Equals(knownTypes.TaskType)
|| returnType.OriginalDefinition.Equals(knownTypes.ValueTaskType);
private SyntaxNode RemoveAsyncModifier(
SolutionServices solutionServices,
ISyntaxFacts syntaxFacts,
SyntaxGenerator generator,
SyntaxNode node,
ITypeSymbol returnType,
KnownTypes knownTypes,
bool needsReturnStatementAdded)
{
node = RemoveAsyncModifier(generator, node);
var expression = generator.GetExpression(node);
if (expression is TExpressionSyntax expressionBody)
{
if (IsTaskType(returnType, knownTypes))
{
// We need to add a `return Task.CompletedTask;` so we have to convert to a block body
var blockBodiedNode = ConvertToBlockBody(node, expressionBody);
// Expression bodied members can't have return statements so if we can't convert to a block
// body then we've done all we can
if (blockBodiedNode != null)
{
node = AddReturnStatement(generator, blockBodiedNode);
}
}
else
{
// For Task<T> returning expression bodied methods we can just wrap the whole expression
var newExpressionBody = WrapExpressionWithTaskFromResult(generator, expressionBody, returnType, knownTypes);
node = generator.WithExpression(node, newExpressionBody);
}
}
else
{
if (IsTaskType(returnType, knownTypes))
{
// If the end of the method isn't reachable, or there were no statements to analyze, then we
// need to add an explicit return
if (needsReturnStatementAdded)
{
node = AddReturnStatement(generator, node);
}
}
}
return ChangeReturnStatements(solutionServices, syntaxFacts, generator, node, returnType, knownTypes);
}
private static ControlFlowAnalysis? GetControlFlowAnalysis(SyntaxGenerator generator, SemanticModel semanticModel, SyntaxNode node)
{
var statements = generator.GetStatements(node);
if (statements.Count > 0)
{
return semanticModel.AnalyzeControlFlow(statements[0], statements[statements.Count - 1]);
}
return null;
}
private static SyntaxNode AddReturnStatement(SyntaxGenerator generator, SyntaxNode node)
=> generator.WithStatements(node, generator.GetStatements(node).Concat(generator.ReturnStatement()));
private SyntaxNode ChangeReturnStatements(
SolutionServices solutionServices,
ISyntaxFacts syntaxFacts,
SyntaxGenerator generator,
SyntaxNode node,
ITypeSymbol returnType,
KnownTypes knownTypes)
{
var editor = new SyntaxEditor(node, solutionServices);
// Look for all return statements, but if we find a new node that can have the async modifier we stop
// because that will have its own diagnostic and fix, if applicable
var returns = node.DescendantNodes(n => n == node || !IsAsyncSupportingFunctionSyntax(n)).OfType<TReturnStatementSyntax>();
foreach (var returnSyntax in returns)
{
var returnExpression = syntaxFacts.GetExpressionOfReturnStatement(returnSyntax);
if (returnExpression is null)
{
// Convert return; into return Task.CompletedTask;
var returnTaskCompletedTask = GetReturnTaskCompletedTaskStatement(generator, returnType, knownTypes);
editor.ReplaceNode(returnSyntax, returnTaskCompletedTask);
}
else
{
// Convert return <expr>; into return Task.FromResult(<expr>);
var newExpression = WrapExpressionWithTaskFromResult(generator, returnExpression, returnType, knownTypes);
editor.ReplaceNode(returnExpression, newExpression);
}
}
return editor.GetChangedRoot();
}
private static SyntaxNode GetReturnTaskCompletedTaskStatement(SyntaxGenerator generator, ITypeSymbol returnType, KnownTypes knownTypes)
{
SyntaxNode invocation;
if (returnType.OriginalDefinition.Equals(knownTypes.TaskType))
{
var taskTypeExpression = TypeExpressionForStaticMemberAccess(generator, knownTypes.TaskType);
invocation = generator.MemberAccessExpression(taskTypeExpression, nameof(Task.CompletedTask));
}
else
{
invocation = generator.ObjectCreationExpression(knownTypes.ValueTaskType!);
}
var statement = generator.ReturnStatement(invocation);
return statement;
}
private static SyntaxNode WrapExpressionWithTaskFromResult(SyntaxGenerator generator, SyntaxNode expression, ITypeSymbol returnType, KnownTypes knownTypes)
{
if (returnType.OriginalDefinition.Equals(knownTypes.TaskOfTType))
{
var taskTypeExpression = TypeExpressionForStaticMemberAccess(generator, knownTypes.TaskType!);
var unwrappedReturnType = returnType.GetTypeArguments()[0];
var memberName = generator.GenericName(nameof(Task.FromResult), unwrappedReturnType);
var taskFromResult = generator.MemberAccessExpression(taskTypeExpression, memberName);
return generator.InvocationExpression(taskFromResult, expression.WithoutTrivia()).WithTriviaFrom(expression);
}
else
{
return generator.ObjectCreationExpression(returnType, expression);
}
}
// Workaround for https://github.com/dotnet/roslyn/issues/43950
// Copied from https://github.com/dotnet/roslyn-analyzers/blob/f24a5b42c85be6ee572f3a93bef223767fbefd75/src/Utilities/Workspaces/SyntaxGeneratorExtensions.cs#L68-L74
private static SyntaxNode TypeExpressionForStaticMemberAccess(SyntaxGenerator generator, INamedTypeSymbol typeSymbol)
{
var qualifiedNameSyntaxKind = generator.QualifiedName(generator.IdentifierName("ignored"), generator.IdentifierName("ignored")).RawKind;
var memberAccessExpressionSyntaxKind = generator.MemberAccessExpression(generator.IdentifierName("ignored"), "ignored").RawKind;
var typeExpression = generator.TypeExpression(typeSymbol);
return QualifiedNameToMemberAccess(qualifiedNameSyntaxKind, memberAccessExpressionSyntaxKind, typeExpression, generator);
// Local function
static SyntaxNode QualifiedNameToMemberAccess(int qualifiedNameSyntaxKind, int memberAccessExpressionSyntaxKind, SyntaxNode expression, SyntaxGenerator generator)
{
if (expression.RawKind == qualifiedNameSyntaxKind)
{
var left = QualifiedNameToMemberAccess(qualifiedNameSyntaxKind, memberAccessExpressionSyntaxKind, expression.ChildNodes().First(), generator);
var right = expression.ChildNodes().Last();
return generator.MemberAccessExpression(left, right);
}
return expression;
}
}
}
}
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