Fix crash when using --config and --path with a Swift file

Fixes #1694

CHANGELOG.md

@@ -71,6 +71,11 @@
   [Jamie Edge](https://github.com/JamieEdge)
   [#1586](https://github.com/realm/SwiftLint/issues/1586)
 
+* Fix crash when using `--config` with a relative path and 
+  `--path` with a file.  
+  [Marcelo Fabri](https://github.com/marcelofabri)
+  [#1694](https://github.com/realm/SwiftLint/issues/1694)
+
 ## 0.20.1: More Liquid Fabric Softener
 
 ##### Breaking

Source/SwiftLintFramework/Models/Configuration.swift

@@ -112,7 +112,7 @@ public struct Configuration: Equatable {
     public init(path: String = Configuration.fileName, rootPath: String? = nil,
                 optional: Bool = true, quiet: Bool = false, enableAllRules: Bool = false, cachePath: String? = nil) {
         let fullPath: String
-        if let rootPath = rootPath {
+        if let rootPath = rootPath, rootPath.isDirectory() {
             fullPath = path.bridge().absolutePathRepresentation(rootDirectory: rootPath)
         } else {
             fullPath = path.bridge().absolutePathRepresentation()
@@ -201,3 +201,14 @@ private func containsDuplicateIdentifiers(_ identifiers: [String]) -> Bool {
     }.joined(separator: "\n"))
     return true
 }
+
+private extension String {
+    func isDirectory() -> Bool {
+        var isDir: ObjCBool = false
+        if FileManager.default.fileExists(atPath: self, isDirectory:&isDir) {
+            return isDir.boolValue
+        }
+
+        return false
+    }
+}

Tests/LinuxMain.swift

@@ -53,6 +53,7 @@ extension ConfigurationTests {
     static var allTests: [(String, (ConfigurationTests) -> () throws -> Void)] = [
         ("testInit", testInit),
         ("testEmptyConfiguration", testEmptyConfiguration),
+        ("testInitWithRelativePathAndRootPath", testInitWithRelativePathAndRootPath),
         ("testWhitelistRules", testWhitelistRules),
         ("testWarningThreshold_value", testWarningThreshold_value),
         ("testWarningThreshold_nil", testWarningThreshold_nil),

Tests/SwiftLintFrameworkTests/ConfigurationTests.swift

@@ -44,6 +44,23 @@ class ConfigurationTests: XCTestCase {
         XCTAssertEqual(reporterFrom(identifier: config.reporter).identifier, "xcode")
     }
 
+    func testInitWithRelativePathAndRootPath() {
+        let previousWorkingDir = FileManager.default.currentDirectoryPath
+        let rootPath = projectMockSwift0
+        let expectedConfig = projectMockConfig0
+        FileManager.default.changeCurrentDirectoryPath(projectMockPathLevel0)
+
+        let config = Configuration(path: ".swiftlint.yml", rootPath: rootPath,
+                                   optional: false, quiet: true)
+
+        XCTAssertEqual(config.disabledRules, expectedConfig.disabledRules)
+        XCTAssertEqual(config.included, expectedConfig.included)
+        XCTAssertEqual(config.excluded, expectedConfig.excluded)
+        XCTAssertEqual(config.reporter, expectedConfig.reporter)
+
+        FileManager.default.changeCurrentDirectoryPath(previousWorkingDir)
+    }
+
     func testWhitelistRules() {
         let whitelist = ["nesting", "todo"]
         let config = Configuration(dict: ["whitelist_rules": whitelist])!