SwiftLint/Tests/SwiftLintFrameworkTests/TrailingCommaRuleTests.swift

import SwiftLintFramework
import XCTest

class TrailingCommaRuleTests: XCTestCase {

    func testTrailingCommaRuleWithDefaultConfiguration() {
        // Verify TrailingCommaRule with test values for when mandatory_comma is false (default).
        if SwiftVersion.current >= .fourDotOne {
            let triggeringExamples = TrailingCommaRule.description.triggeringExamples +
                ["class C {\n #if true\n func f() {\n let foo = [1, 2, 3↓,]\n }\n #endif\n}"]
            verifyRule(TrailingCommaRule.description.with(triggeringExamples: triggeringExamples))
        } else {
            verifyRule(TrailingCommaRule.description)
        }

        // Ensure the rule produces the correct reason string.
        let failingCase = "let array = [\n\t1,\n\t2,\n]\n"
        XCTAssertEqual(trailingCommaViolations(failingCase), [
            StyleViolation(
                ruleDescription: TrailingCommaRule.description,
                location: Location(file: nil, line: 3, character: 3),
                reason: "Collection literals should not have trailing commas."
            )
        ])
    }

    private static let triggeringExamples = [
        "let foo = [1, 2,\n 3↓]\n",
        "let foo = [1: 2,\n 2: 3↓]\n",
        "let foo = [1: 2,\n 2: 3↓   ]\n",
        "struct Bar {\n let foo = [1: 2,\n 2: 3↓]\n}\n",
        "let foo = [1, 2,\n 3↓] + [4,\n 5, 6↓]\n",
        "let foo = [\"אבג\", \"αβγ\",\n\"🇺🇸\"↓]\n"
    ]

    private static let nonTriggeringExamples = [
        "let foo = []\n",
        "let foo = [:]\n",
        "let foo = [1, 2, 3,]\n",
        "let foo = [1, 2, 3, ]\n",
        "let foo = [1, 2, 3   ,]\n",
        "let foo = [1: 2, 2: 3, ]\n",
        "struct Bar {\n let foo = [1: 2, 2: 3,]\n}\n",
        "let foo = [Void]()\n",
        "let foo = [(Void, Void)]()\n",
        "let foo = [1, 2, 3]\n",
        "let foo = [1: 2, 2: 3]\n",
        "let foo = [1: 2, 2: 3   ]\n",
        "struct Bar {\n let foo = [1: 2, 2: 3]\n}\n",
        "let foo = [1, 2, 3] + [4, 5, 6]\n"
    ]

    private static let corrections: [String: String] = {
        let fixed = triggeringExamples.map { $0.replacingOccurrences(of: "↓", with: ",") }
        var result: [String: String] = [:]
        for (triggering, correction) in zip(triggeringExamples, fixed) {
            result[triggering] = correction
        }
        return result
    }()

    private let mandatoryCommaRuleDescription = TrailingCommaRule.description
        .with(nonTriggeringExamples: TrailingCommaRuleTests.nonTriggeringExamples)
        .with(triggeringExamples: TrailingCommaRuleTests.triggeringExamples)
        .with(corrections: TrailingCommaRuleTests.corrections)

    func testTrailingCommaRuleWithMandatoryComma() {
        // Verify TrailingCommaRule with test values for when mandatory_comma is true.
        let ruleDescription = mandatoryCommaRuleDescription
        let ruleConfiguration = ["mandatory_comma": true]

        verifyRule(ruleDescription, ruleConfiguration: ruleConfiguration)

        // Ensure the rule produces the correct reason string.
        let failingCase = "let array = [\n\t1,\n\t2\n]\n"
        XCTAssertEqual(trailingCommaViolations(failingCase, ruleConfiguration: ruleConfiguration), [
            StyleViolation(
                ruleDescription: TrailingCommaRule.description,
                location: Location(file: nil, line: 3, character: 3),
                reason: "Multi-line collection literals should have trailing commas."
            )
        ])
    }

    private func trailingCommaViolations(_ string: String, ruleConfiguration: Any? = nil) -> [StyleViolation] {
        let config = makeConfig(ruleConfiguration, TrailingCommaRule.description.identifier)!
        return SwiftLintFrameworkTests.violations(string, config: config)
    }
}