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superfluous_else
rule (#4696)
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152 changes: 152 additions & 0 deletions
152
Source/SwiftLintFramework/Rules/Style/SuperfluousElseRule.swift
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Original file line number | Diff line number | Diff line change |
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import SwiftSyntax | ||
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struct SuperfluousElseRule: SwiftSyntaxRule, ConfigurationProviderRule, OptInRule { | ||
var configuration = SeverityConfiguration(.warning) | ||
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init() {} | ||
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static var description = RuleDescription( | ||
identifier: "superfluous_else", | ||
name: "Superfluous Else", | ||
description: "Else branches should be avoided when the previous if-block exits the current scope", | ||
kind: .style, | ||
nonTriggeringExamples: [ | ||
Example(""" | ||
if i > 0 { | ||
// comment | ||
} else if i < 12 { | ||
return 2 | ||
} else { | ||
return 3 | ||
} | ||
"""), | ||
Example(""" | ||
if i > 0 { | ||
let a = 1 | ||
if a > 1 { | ||
// comment | ||
} else { | ||
return 1 | ||
} | ||
// comment | ||
} else { | ||
return 3 | ||
} | ||
"""), | ||
Example(""" | ||
if i > 0 { | ||
if a > 1 { | ||
return 1 | ||
} | ||
} else { | ||
return 3 | ||
} | ||
"""), | ||
Example(""" | ||
if i > 0 { | ||
if a > 1 { | ||
if a > 1 { | ||
// comment | ||
} else { | ||
return 1 | ||
} | ||
} | ||
} else { | ||
return 3 | ||
} | ||
""", excludeFromDocumentation: true) | ||
], | ||
triggeringExamples: [ | ||
Example(""" | ||
↓if i > 0 { | ||
return 1 | ||
// comment | ||
} else { | ||
return 2 | ||
} | ||
"""), | ||
Example(""" | ||
↓if i > 0 { | ||
return 1 | ||
} else ↓if i < 12 { | ||
return 2 | ||
} else if i > 18 { | ||
return 3 | ||
} | ||
"""), | ||
Example(""" | ||
↓if i > 0 { | ||
↓if i < 12 { | ||
return 5 | ||
} else { | ||
↓if i > 11 { | ||
return 6 | ||
} else { | ||
return 7 | ||
} | ||
} | ||
} else ↓if i < 12 { | ||
return 2 | ||
} else ↓if i < 24 { | ||
return 8 | ||
} else { | ||
return 3 | ||
} | ||
""") | ||
] | ||
) | ||
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func makeVisitor(file: SwiftLintFile) -> ViolationsSyntaxVisitor { | ||
Visitor(viewMode: .sourceAccurate) | ||
} | ||
} | ||
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private class Visitor: ViolationsSyntaxVisitor { | ||
override var skippableDeclarations: [DeclSyntaxProtocol.Type] { [ProtocolDeclSyntax.self] } | ||
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override func visitPost(_ node: IfExprSyntax) { | ||
if node.violatesRule { | ||
violations.append(node.ifKeyword.positionAfterSkippingLeadingTrivia) | ||
} | ||
} | ||
} | ||
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private extension IfExprSyntax { | ||
var violatesRule: Bool { | ||
if elseKeyword == nil { | ||
return false | ||
} | ||
let thenBodyReturns = lastStatementReturns(in: body) | ||
if thenBodyReturns, let parent = parent?.as(IfExprSyntax.self) { | ||
return parent.violatesRule | ||
} | ||
return thenBodyReturns | ||
} | ||
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private var returnsInAllBranches: Bool { | ||
guard lastStatementReturns(in: body) else { | ||
return false | ||
} | ||
if case let .ifExpr(nestedIfStmt) = elseBody { | ||
return nestedIfStmt.returnsInAllBranches | ||
} | ||
if case let .codeBlock(block) = elseBody { | ||
return lastStatementReturns(in: block) | ||
} | ||
return false | ||
} | ||
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private func lastStatementReturns(in block: CodeBlockSyntax) -> Bool { | ||
guard let lastItem = block.statements.last?.as(CodeBlockItemSyntax.self)?.item else { | ||
return false | ||
} | ||
if lastItem.is(ReturnStmtSyntax.self) { | ||
return true | ||
} | ||
if let exprStmt = lastItem.as(ExpressionStmtSyntax.self), | ||
let lastIfStmt = exprStmt.expression.as(IfExprSyntax.self) { | ||
return lastIfStmt.returnsInAllBranches | ||
} | ||
return false | ||
} | ||
} |
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