private async Task FixAllAsync(
string diagnosticId,
IOrderedEnumerable <Diagnostic> diagnostics,
Document document,
SemanticModel semanticModel,
SyntaxNode root,
SyntaxNode containingMemberDeclaration,
UnusedValuePreference preference,
bool removeAssignments,
UniqueVariableNameGenerator nameGenerator,
SyntaxEditor editor,
ISyntaxFactsService syntaxFacts,
CancellationToken cancellationToken)
{
switch (diagnosticId)
{
case IDEDiagnosticIds.ExpressionValueIsUnusedDiagnosticId:
FixAllExpressionValueIsUnusedDiagnostics(diagnostics, semanticModel, root,
preference, nameGenerator, editor, syntaxFacts, cancellationToken);
break;
case IDEDiagnosticIds.ValueAssignedIsUnusedDiagnosticId:
await FixAllValueAssignedIsUnusedDiagnosticsAsync(diagnostics, document, semanticModel, root, containingMemberDeclaration,
preference, removeAssignments, nameGenerator, editor, syntaxFacts, cancellationToken).ConfigureAwait(false);
break;
default:
throw ExceptionUtilities.Unreachable;
}
}
private async Task <SyntaxNode> PostProcessDocumentAsync(
Document document,
SyntaxNode currentRoot,
string diagnosticId,
UnusedValuePreference preference,
CancellationToken cancellationToken)
{
// If we added discard assignments, replace all discard variable declarations in
// this method with discard assignments, i.e. "var _ = M();" is replaced with "_ = M();"
// This is done to prevent compiler errors where the existing method has a discard
// variable declaration at a line following the one we added a discard assignment in our fix.
if (preference == UnusedValuePreference.DiscardVariable)
{
currentRoot = await PostProcessDocumentCoreAsync(
ReplaceDiscardDeclarationsWithAssignmentsAsync, currentRoot, document, cancellationToken).ConfigureAwait(false);
}
// If we added new variable declaration statements, move these as close as possible to their
// first reference site.
if (NeedsToMoveNewLocalDeclarationsNearReference(diagnosticId))
{
currentRoot = await PostProcessDocumentCoreAsync(
AdjustLocalDeclarationsAsync, currentRoot, document, cancellationToken).ConfigureAwait(false);
}
return(currentRoot);
}
private IEnumerable <IGrouping <SyntaxNode, Diagnostic> > GetDiagnosticsGroupedByMember(
ImmutableArray <Diagnostic> diagnostics,
ISyntaxFactsService syntaxFacts,
SyntaxNode root,
out string diagnosticId,
out UnusedValuePreference preference,
out bool removeAssignments)
{
diagnosticId = diagnostics[0].Id;
var success = AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.TryGetUnusedValuePreference(diagnostics[0], out preference);
Debug.Assert(success);
removeAssignments = AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.GetIsRemovableAssignmentDiagnostic(diagnostics[0]);
#if DEBUG
foreach (var diagnostic in diagnostics)
{
Debug.Assert(diagnosticId == diagnostic.Id);
Debug.Assert(AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.TryGetUnusedValuePreference(diagnostic, out var diagnosticPreference) &&
diagnosticPreference == preference);
Debug.Assert(removeAssignments == AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.GetIsRemovableAssignmentDiagnostic(diagnostic));
}
#endif
return(GetDiagnosticsGroupedByMember(diagnostics, syntaxFacts, root));
}
public static bool TryGetUnusedValuePreference(
Diagnostic diagnostic,
out UnusedValuePreference preference
)
{
if (
diagnostic.Properties != null &&
diagnostic.Properties.TryGetValue(
UnusedValuePreferenceKey,
out var preferenceString
)
)
{
switch (preferenceString)
{
case nameof(UnusedValuePreference.DiscardVariable):
preference = UnusedValuePreference.DiscardVariable;
return(true);
case nameof(UnusedValuePreference.UnusedLocalVariable):
preference = UnusedValuePreference.UnusedLocalVariable;
return(true);
}
}
preference = default;
return(false);
}
private void FixAllExpressionValueIsUnusedDiagnostics(
IOrderedEnumerable <Diagnostic> diagnostics,
SemanticModel semanticModel,
SyntaxNode root,
UnusedValuePreference preference,
UniqueVariableNameGenerator nameGenerator,
SyntaxEditor editor,
ISyntaxFactsService syntaxFacts,
CancellationToken cancellationToken)
{
// This method applies the code fix for diagnostics reported for expression statement dropping values.
// We replace each flagged expression statement with an assignment to a discard variable or a new unused local,
// based on the user's preference.
foreach (var diagnostic in diagnostics)
{
var expressionStatement = root.FindNode(diagnostic.Location.SourceSpan).FirstAncestorOrSelf <TExpressionStatementSyntax>();
if (expressionStatement == null)
{
continue;
}
var expression = syntaxFacts.GetExpressionOfExpressionStatement(expressionStatement);
switch (preference)
{
case UnusedValuePreference.DiscardVariable:
Debug.Assert(semanticModel.Language != LanguageNames.VisualBasic);
var discardAssignmentExpression = (TExpressionSyntax)editor.Generator.AssignmentStatement(
left: editor.Generator.IdentifierName(AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.DiscardVariableName),
right: expression.WithoutTrivia())
.WithTriviaFrom(expression)
.WithAdditionalAnnotations(Simplifier.Annotation, Formatter.Annotation);
editor.ReplaceNode(expression, discardAssignmentExpression);
break;
case UnusedValuePreference.UnusedLocalVariable:
// Add Simplifier annotation so that 'var'/explicit type is correctly added based on user options.
var localDecl = editor.Generator.LocalDeclarationStatement(
name: nameGenerator.GenerateUniqueNameAtSpanStart(expressionStatement),
initializer: expression.WithoutLeadingTrivia())
.WithTriviaFrom(expressionStatement)
.WithAdditionalAnnotations(Simplifier.Annotation, Formatter.Annotation);
editor.ReplaceNode(expressionStatement, localDecl);
break;
}
}
}
public Options(
UnusedValuePreference unusedValueExpressionStatementPreference,
ReportDiagnostic unusedValueExpressionStatementSeverity,
UnusedValuePreference unusedValueAssignmentPreference,
ReportDiagnostic unusedValueAssignmentSeverity,
UnusedParametersPreference unusedParametersPreference,
ReportDiagnostic unusedParametersSeverity)
{
Debug.Assert(unusedValueExpressionStatementSeverity != ReportDiagnostic.Suppress ||
unusedValueAssignmentSeverity != ReportDiagnostic.Suppress ||
unusedParametersSeverity != ReportDiagnostic.Suppress);
UnusedValueExpressionStatementPreference = unusedValueExpressionStatementPreference;
UnusedValueExpressionStatementSeverity = unusedValueExpressionStatementSeverity;
UnusedValueAssignmentPreference = unusedValueAssignmentPreference;
UnusedValueAssignmentSeverity = unusedValueAssignmentSeverity;
_unusedParametersPreference = unusedParametersPreference;
_unusedParametersSeverity = unusedParametersSeverity;
}
private async Task FixAllValueAssignedIsUnusedDiagnosticsAsync(
IOrderedEnumerable <Diagnostic> diagnostics,
Document document,
SemanticModel semanticModel,
SyntaxNode root,
SyntaxNode containingMemberDeclaration,
UnusedValuePreference preference,
bool removeAssignments,
UniqueVariableNameGenerator nameGenerator,
SyntaxEditor editor,
ISyntaxFactsService syntaxFacts,
CancellationToken cancellationToken)
{
// This method applies the code fix for diagnostics reported for unused value assignments to local/parameter.
// The actual code fix depends on whether or not the right hand side of the assignment has side effects.
// For example, if the right hand side is a constant or a reference to a local/parameter, then it has no side effects.
// The lack of side effects is indicated by the "removeAssignments" parameter for this function.
// If the right hand side has no side effects, then we can replace the assignments with variable declarations that have no initializer
// or completely remove the statement.
// If the right hand side does have side effects, we replace the identifier token for unused value assignment with
// a new identifier token (either discard '_' or new unused local variable name).
// For both the above cases, if the original diagnostic was reported on a local declaration, i.e. redundant initialization
// at declaration, then we also add a new variable declaration statement without initializer for this local.
var nodeReplacementMap = PooledDictionary <SyntaxNode, SyntaxNode> .GetInstance();
var nodesToRemove = PooledHashSet <SyntaxNode> .GetInstance();
var nodesToAdd = PooledHashSet <(TLocalDeclarationStatementSyntax declarationStatement, SyntaxNode node)> .GetInstance();
// Indicates if the node's trivia was processed.
var processedNodes = PooledHashSet <SyntaxNode> .GetInstance();
var candidateDeclarationStatementsForRemoval = PooledHashSet <TLocalDeclarationStatementSyntax> .GetInstance();
var hasAnyUnusedLocalAssignment = false;
try
{
foreach (var(node, isUnusedLocalAssignment) in GetNodesToFix())
{
hasAnyUnusedLocalAssignment |= isUnusedLocalAssignment;
var declaredLocal = semanticModel.GetDeclaredSymbol(node, cancellationToken) as ILocalSymbol;
if (declaredLocal == null && node.Parent is TCatchStatementSyntax)
{
declaredLocal = semanticModel.GetDeclaredSymbol(node.Parent, cancellationToken) as ILocalSymbol;
}
string newLocalNameOpt = null;
if (removeAssignments)
{
// Removable assignment or initialization, such that right hand side has no side effects.
if (declaredLocal != null)
{
// Redundant initialization.
// For example, "int a = 0;"
var variableDeclarator = node.FirstAncestorOrSelf <TVariableDeclaratorSyntax>();
Debug.Assert(variableDeclarator != null);
nodesToRemove.Add(variableDeclarator);
// Local declaration statement containing the declarator might be a candidate for removal if all its variables get marked for removal.
candidateDeclarationStatementsForRemoval.Add(variableDeclarator.GetAncestor <TLocalDeclarationStatementSyntax>());
}
else
{
// Redundant assignment or increment/decrement.
if (syntaxFacts.IsOperandOfIncrementOrDecrementExpression(node))
{
// For example, C# increment operation "a++;"
Debug.Assert(node.Parent.Parent is TExpressionStatementSyntax);
nodesToRemove.Add(node.Parent.Parent);
}
else
{
Debug.Assert(syntaxFacts.IsLeftSideOfAnyAssignment(node));
if (node.Parent is TStatementSyntax)
{
// For example, VB simple assignment statement "a = 0"
nodesToRemove.Add(node.Parent);
}
else if (node.Parent is TExpressionSyntax && node.Parent.Parent is TExpressionStatementSyntax)
{
// For example, C# simple assignment statement "a = 0;"
nodesToRemove.Add(node.Parent.Parent);
}
else
{
// For example, C# nested assignment statement "a = b = 0;", where assignment to 'b' is redundant.
// We replace the node with "a = 0;"
nodeReplacementMap.Add(node.Parent, syntaxFacts.GetRightHandSideOfAssignment(node.Parent));
}
}
}
}
else
{
// Value initialization/assignment where the right hand side may have side effects,
// and hence needs to be preserved in fixed code.
// For example, "x = MethodCall();" is replaced with "_ = MethodCall();" or "var unused = MethodCall();"
// Replace the flagged variable's indentifier token with new named, based on user's preference.
var newNameToken = preference == UnusedValuePreference.DiscardVariable
? editor.Generator.Identifier(AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.DiscardVariableName)
: nameGenerator.GenerateUniqueNameAtSpanStart(node);
newLocalNameOpt = newNameToken.ValueText;
var newNameNode = TryUpdateNameForFlaggedNode(node, newNameToken);
if (newNameNode == null)
{
continue;
}
// Is this is compound assignment?
if (syntaxFacts.IsLeftSideOfAnyAssignment(node) && !syntaxFacts.IsLeftSideOfAssignment(node))
{
// Compound assignment is changed to simple assignment.
// For example, "x += MethodCall();", where assignment to 'x' is redundant
// is replaced with "_ = MethodCall();" or "var unused = MethodCall();"
nodeReplacementMap.Add(node.Parent, GetReplacementNodeForCompoundAssignment(node.Parent, newNameNode, editor, syntaxFacts));
}
else
{
nodeReplacementMap.Add(node, newNameNode);
}
}
if (declaredLocal != null)
{
// We have a dead initialization for a local declaration.
// Introduce a new local declaration statement without an initializer for this local.
var declarationStatement = CreateLocalDeclarationStatement(declaredLocal.Type, declaredLocal.Name);
if (isUnusedLocalAssignment)
{
declarationStatement = declarationStatement.WithAdditionalAnnotations(s_unusedLocalDeclarationAnnotation);
}
nodesToAdd.Add((declarationStatement, node));
}
else
{
// We have a dead assignment to a local/parameter, which is not at the declaration site.
// Create a new local declaration for the unused local if both following conditions are met:
// 1. User prefers unused local variables for unused value assignment AND
// 2. Assignment value has side effects and hence cannot be removed.
if (preference == UnusedValuePreference.UnusedLocalVariable && !removeAssignments)
{
var type = semanticModel.GetTypeInfo(node, cancellationToken).Type;
Debug.Assert(type != null);
Debug.Assert(newLocalNameOpt != null);
var declarationStatement = CreateLocalDeclarationStatement(type, newLocalNameOpt);
nodesToAdd.Add((declarationStatement, node));
}
}
}
// Process candidate declaration statements for removal.
foreach (var localDeclarationStatement in candidateDeclarationStatementsForRemoval)
{
// If all the variable declarators for the local declaration statement are being removed,
// we can remove the entire local declaration statement.
if (ShouldRemoveStatement(localDeclarationStatement, out var variables))
{
nodesToRemove.Add(localDeclarationStatement);
nodesToRemove.RemoveRange(variables);
}
}
foreach (var nodeToAdd in nodesToAdd)
{
InsertLocalDeclarationStatement(nodeToAdd.declarationStatement, nodeToAdd.node);
}
if (hasAnyUnusedLocalAssignment)
{
// Local declaration statements with no initializer, but non-zero references are candidates for removal
// if the code fix removes all these references.
// We annotate such declaration statements with no initializer abd non-zero references here
// and remove them in post process document pass later, if the code fix did remove all these references.
foreach (var localDeclarationStatement in containingMemberDeclaration.DescendantNodes().OfType <TLocalDeclarationStatementSyntax>())
{
var variables = syntaxFacts.GetVariablesOfLocalDeclarationStatement(localDeclarationStatement);
if (variables.Count == 1 &&
syntaxFacts.GetInitializerOfVariableDeclarator(variables[0]) == null &&
!(await IsLocalDeclarationWithNoReferencesAsync(localDeclarationStatement, document, cancellationToken).ConfigureAwait(false)))
{
nodeReplacementMap.Add(localDeclarationStatement, localDeclarationStatement.WithAdditionalAnnotations(s_existingLocalDeclarationWithoutInitializerAnnotation));
}
}
}
foreach (var node in nodesToRemove)
{
var removeOptions = SyntaxGenerator.DefaultRemoveOptions;
// If the leading trivia was not added to a new node, process it now.
if (!processedNodes.Contains(node))
{
// Don't keep trivia if the node is part of a multiple declaration statement.
// e.g. int x = 0, y = 0, z = 0; any white space left behind can cause problems if the declaration gets split apart.
var containingDeclaration = node.GetAncestor <TLocalDeclarationStatementSyntax>();
if (containingDeclaration != null && candidateDeclarationStatementsForRemoval.Contains(containingDeclaration))
{
removeOptions = SyntaxRemoveOptions.KeepNoTrivia;
}
else
{
removeOptions |= SyntaxRemoveOptions.KeepLeadingTrivia;
}
}
editor.RemoveNode(node, removeOptions);
}
foreach (var kvp in nodeReplacementMap)
{
editor.ReplaceNode(kvp.Key, kvp.Value.WithAdditionalAnnotations(Formatter.Annotation));
}
}
finally
{
nodeReplacementMap.Free();
nodesToRemove.Free();
nodesToAdd.Free();
processedNodes.Free();
}
return;
// Local functions.
IEnumerable <(SyntaxNode node, bool isUnusedLocalAssignment)> GetNodesToFix()
{
foreach (var diagnostic in diagnostics)
{
var node = root.FindNode(diagnostic.Location.SourceSpan, getInnermostNodeForTie: true);
var isUnusedLocalAssignment = AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.GetIsUnusedLocalDiagnostic(diagnostic);
yield return(node, isUnusedLocalAssignment);
}
}
// Mark generated local declaration statement with:
// 1. "s_newLocalDeclarationAnnotation" for post processing in "MoveNewLocalDeclarationsNearReference" below.
// 2. Simplifier annotation so that 'var'/explicit type is correctly added based on user options.
TLocalDeclarationStatementSyntax CreateLocalDeclarationStatement(ITypeSymbol type, string name)
=> (TLocalDeclarationStatementSyntax)editor.Generator.LocalDeclarationStatement(type, name)
.WithLeadingTrivia(editor.Generator.ElasticCarriageReturnLineFeed)
.WithAdditionalAnnotations(s_newLocalDeclarationStatementAnnotation, Simplifier.Annotation);
void InsertLocalDeclarationStatement(TLocalDeclarationStatementSyntax declarationStatement, SyntaxNode node)
{
// Find the correct place to insert the given declaration statement based on the node's ancestors.
var insertionNode = node.FirstAncestorOrSelf <SyntaxNode>(n => n.Parent is TSwitchCaseBlockSyntax ||
syntaxFacts.IsExecutableBlock(n.Parent) &&
!(n is TCatchStatementSyntax) &&
!(n is TCatchBlockSyntax));
if (insertionNode is TSwitchCaseLabelOrClauseSyntax)
{
InsertAtStartOfSwitchCaseBlockForDeclarationInCaseLabelOrClause(insertionNode.GetAncestor <TSwitchCaseBlockSyntax>(), editor, declarationStatement);
}
else if (insertionNode is TStatementSyntax)
{
// If the insertion node is being removed, keep the leading trivia with the new declaration.
if (nodesToRemove.Contains(insertionNode) && !processedNodes.Contains(insertionNode))
{
declarationStatement = declarationStatement.WithLeadingTrivia(insertionNode.GetLeadingTrivia());
// Mark the node as processed so that the trivia only gets added once.
processedNodes.Add(insertionNode);
}
editor.InsertBefore(insertionNode, declarationStatement);
}
}
bool ShouldRemoveStatement(TLocalDeclarationStatementSyntax localDeclarationStatement, out SeparatedSyntaxList <SyntaxNode> variables)
{
Debug.Assert(removeAssignments);
// We should remove the entire local declaration statement if all its variables are marked for removal.
variables = syntaxFacts.GetVariablesOfLocalDeclarationStatement(localDeclarationStatement);
foreach (var variable in variables)
{
if (!nodesToRemove.Contains(variable))
{
return(false);
}
}
return(true);
}
}
private static string GetEquivalenceKey(UnusedValuePreference preference, bool isRemovableAssignment) => preference.ToString() + isRemovableAssignment;
private static string GetUnusedExpressionAssignmentPreferenceEditorConfigString(CodeStyleOption <UnusedValuePreference> option, UnusedValuePreference defaultPreference)
{
Debug.Assert(s_unusedExpressionAssignmentPreferenceMap.ContainsValue(option.Value));
var value = s_unusedExpressionAssignmentPreferenceMap.GetKeyOrDefault(option.Value) ?? s_unusedExpressionAssignmentPreferenceMap.GetKeyOrDefault(defaultPreference);
return(option.Notification == null ? value : $"{value}:{option.Notification.ToEditorConfigString()}");
}
