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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import SwiftSyntax
/// Enforces rules around parentheses in conditions or matched expressions.
///
/// Parentheses are not used around any condition of an `if`, `guard`, or `while` statement, or
/// around the matched expression in a `switch` statement.
///
/// Lint: If a top-most expression in a `switch`, `if`, `guard`, or `while` statement is surrounded
/// by parentheses, and it does not include a function call with a trailing closure, a lint
/// error is raised.
///
/// Format: Parentheses around such expressions are removed, if they do not cause a parse ambiguity.
/// Specifically, parentheses are allowed if and only if the expression contains a function
/// call with a trailing closure.
@_spi(Rules)
public final class NoParensAroundConditions: SyntaxFormatRule {
public override func visit(_ node: IfExprSyntax) -> ExprSyntax {
var result = node
fixKeywordTrailingTrivia(&result.ifKeyword.trailingTrivia)
result.conditions = visit(node.conditions)
result.body = visit(node.body)
if let elseBody = node.elseBody {
result.elseBody = visit(elseBody)
}
return ExprSyntax(result)
}
public override func visit(_ node: ConditionElementSyntax) -> ConditionElementSyntax {
guard
case .expression(let condition) = node.condition,
let newExpr = minimalSingleExpression(condition)
else {
return super.visit(node)
}
var result = node
result.condition = .expression(newExpr)
return result
}
public override func visit(_ node: GuardStmtSyntax) -> StmtSyntax {
var result = node
fixKeywordTrailingTrivia(&result.guardKeyword.trailingTrivia)
result.conditions = visit(node.conditions)
result.body = visit(node.body)
return StmtSyntax(result)
}
public override func visit(_ node: SwitchExprSyntax) -> ExprSyntax {
guard let newSubject = minimalSingleExpression(node.subject) else {
return super.visit(node)
}
var result = node
fixKeywordTrailingTrivia(&result.switchKeyword.trailingTrivia)
result.subject = newSubject
result.cases = visit(node.cases)
return ExprSyntax(result)
}
public override func visit(_ node: RepeatStmtSyntax) -> StmtSyntax {
guard let newCondition = minimalSingleExpression(node.condition) else {
return super.visit(node)
}
var result = node
fixKeywordTrailingTrivia(&result.whileKeyword.trailingTrivia)
result.condition = newCondition
result.body = visit(node.body)
return StmtSyntax(result)
}
public override func visit(_ node: WhileStmtSyntax) -> StmtSyntax {
var result = node
fixKeywordTrailingTrivia(&result.whileKeyword.trailingTrivia)
result.conditions = visit(node.conditions)
result.body = visit(node.body)
return StmtSyntax(result)
}
private func fixKeywordTrailingTrivia(_ trivia: inout Trivia) {
guard trivia.isEmpty else { return }
trivia = [.spaces(1)]
}
private func minimalSingleExpression(_ original: ExprSyntax) -> ExprSyntax? {
guard
let tuple = original.as(TupleExprSyntax.self),
tuple.elements.count == 1,
let expr = tuple.elements.first?.expression
else {
return nil
}
// If the condition is a function with a trailing closure or if it's an immediately called
// closure, removing the outer set of parentheses introduces a parse ambiguity.
if let fnCall = expr.as(FunctionCallExprSyntax.self) {
if fnCall.trailingClosure != nil {
// Leave parentheses around call with trailing closure.
return ExprSyntax(tuple)
} else if fnCall.calledExpression.as(ClosureExprSyntax.self) != nil {
// Leave parentheses around immediately called closure.
return ExprSyntax(tuple)
}
}
diagnose(.removeParensAroundExpression, on: tuple.leftParen)
var visitedExpr = visit(expr)
visitedExpr.leadingTrivia = tuple.leftParen.leadingTrivia
visitedExpr.trailingTrivia = tuple.rightParen.trailingTrivia
return visitedExpr
}
}
extension Finding.Message {
fileprivate static let removeParensAroundExpression: Finding.Message =
"remove the parentheses around this expression"
}
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