Add --parent-config option to lint command

CHANGELOG.md

@@ -18,6 +18,11 @@
 
 ### Enhancements
 
+* Add a `--parent-config` option to the `lint` command, allowing a parent
+  configuration to be supplied without modifying the child configuration file.  
+  [LizunovSergey](https://github.com/LizunovSergey)
+  [#5421](https://github.com/realm/SwiftLint/issues/5421)
+
 * Speed up the `collection_alignment` rule, which read the whole file's
   source lines once per element of a dictionary literal.  
   [Brett-Best](https://github.com/Brett-Best)

Source/SwiftLintFramework/Configuration+CommandLine.swift

@@ -288,11 +288,12 @@ extension Configuration {
 
     init(options: LintOrAnalyzeOptions) {
         self.init(
-            configurationFiles: options.configurationFiles,
+            configurationFiles: options.effectiveConfigurationFiles,
             enableAllRules: options.enableAllRules,
             onlyRule: options.onlyRule,
             cachePath: options.cachePath
         )
+        basedOnCustomConfigurationFiles = options.configurationFiles.isNotEmpty
     }
 }
 

Source/SwiftLintFramework/Configuration/Configuration.swift

@@ -53,7 +53,7 @@ public struct Configuration {
     /// This value is `true` iff the `--config` parameter was used to specify (a) configuration file(s)
     /// In particular, this means that the value is also `true` if the `--config` parameter
     /// was used to explicitly specify the default `.swiftlint.yml` as the configuration file
-    public private(set) var basedOnCustomConfigurationFiles = false
+    public internal(set) var basedOnCustomConfigurationFiles = false
 
     // MARK: Public Computed
     /// All rules enabled in this configuration

Source/SwiftLintFramework/LintOrAnalyzeCommand.swift

@@ -34,6 +34,7 @@ package struct LintOrAnalyzeOptions {
     let paths: [URL]
     let useSTDIN: Bool
     let configurationFiles: [URL]
+    let parentConfigurationFile: URL?
     let strict: Bool
     let lenient: Bool
     let forceExclude: Bool
@@ -63,6 +64,7 @@ package struct LintOrAnalyzeOptions {
                  paths: [URL],
                  useSTDIN: Bool,
                  configurationFiles: [URL],
+                 parentConfigurationFile: URL?,
                  strict: Bool,
                  lenient: Bool,
                  forceExclude: Bool,
@@ -91,6 +93,7 @@ package struct LintOrAnalyzeOptions {
         self.paths = paths
         self.useSTDIN = useSTDIN
         self.configurationFiles = configurationFiles
+        self.parentConfigurationFile = parentConfigurationFile
         self.strict = strict
         self.lenient = lenient
         self.forceExclude = forceExclude
@@ -124,6 +127,22 @@ package struct LintOrAnalyzeOptions {
     var capitalizedVerb: String {
         verb.capitalized
     }
+
+    var effectiveConfigurationFiles: [URL] {
+        guard let parentConfigurationFile else {
+            return configurationFiles
+        }
+
+        let defaultConfigurationFile = Configuration.defaultFileName.url()
+        let childConfigurationFiles: [URL] = if configurationFiles.isNotEmpty {
+            configurationFiles
+        } else if defaultConfigurationFile.exists {
+            [defaultConfigurationFile]
+        } else {
+            []
+        }
+        return [parentConfigurationFile] + childConfigurationFiles
+    }
 }
 
 package struct LintOrAnalyzeCommand {

Source/swiftlint/Commands/Analyze.swift

@@ -25,6 +25,7 @@ extension SwiftLint {
                 paths: allPaths,
                 useSTDIN: false,
                 configurationFiles: common.config,
+                parentConfigurationFile: nil,
                 strict: common.leniency == .strict,
                 lenient: common.leniency == .lenient,
                 forceExclude: common.forceExclude,

Source/swiftlint/Commands/Lint.swift

@@ -8,6 +8,8 @@ extension SwiftLint {
 
         @OptionGroup
         var common: LintOrAnalyzeArguments
+        @Option(help: "The path to a parent SwiftLint configuration file.")
+        var parentConfig: URL?
         @Flag(help: "Lint standard input.")
         var useSTDIN = false
         @Flag(help: quietOptionDescription(for: .lint))
@@ -42,6 +44,7 @@ extension SwiftLint {
                 paths: allPaths,
                 useSTDIN: useSTDIN,
                 configurationFiles: common.config,
+                parentConfigurationFile: parentConfig,
                 strict: common.leniency == .strict,
                 lenient: common.leniency == .lenient,
                 forceExclude: common.forceExclude,

Tests/FrameworkTests/LintOrAnalyzeOptionsTests.swift

@@ -1,4 +1,6 @@
+import Foundation
 @testable import SwiftLintFramework
+import TestHelpers
 import Testing
 
 @Suite
@@ -38,14 +40,96 @@ struct LintOrAnalyzeOptionsTests {
             }
         }
     }
+
+    @Test
+    func parentConfigurationFilePrecedesExplicitConfigurationFiles() {
+        let options = LintOrAnalyzeOptions(
+            configurationFiles: ["child-1.yml".url(), "child-2.yml".url()],
+            parentConfigurationFile: "parent.yml".url()
+        )
+
+        #expect(options.effectiveConfigurationFiles == [
+            "parent.yml".url(),
+            "child-1.yml".url(),
+            "child-2.yml".url(),
+        ])
+    }
+
+    @Test(.temporaryDirectory)
+    func parentConfigurationFilePrecedesDefaultConfigurationFile() throws {
+        try "reporter: csv".write(
+            to: Configuration.defaultFileName.url(),
+            atomically: true,
+            encoding: .utf8
+        )
+        let options = LintOrAnalyzeOptions(
+            configurationFiles: [],
+            parentConfigurationFile: "parent.yml".url()
+        )
+
+        #expect(options.effectiveConfigurationFiles == [
+            "parent.yml".url(),
+            Configuration.defaultFileName.url(),
+        ])
+    }
+
+    @Test(.temporaryDirectory)
+    func parentConfigurationFileWorksWithoutDefaultConfigurationFile() {
+        let options = LintOrAnalyzeOptions(
+            configurationFiles: [],
+            parentConfigurationFile: "parent.yml".url()
+        )
+
+        #expect(options.effectiveConfigurationFiles == ["parent.yml".url()])
+    }
+
+    @Test(.rulesRegistered, .temporaryDirectory)
+    func parentConfigurationFilePreservesNestedConfigurations() throws {
+        let parentConfigurationFile = "parent.yml".url()
+        try "disabled_rules: []".write(to: parentConfigurationFile, atomically: true, encoding: .utf8)
+        try "disabled_rules: []".write(
+            to: Configuration.defaultFileName.url(),
+            atomically: true,
+            encoding: .utf8
+        )
+
+        let nestedDirectory = URL.cwd.appending(path: "Nested", directoryHint: .isDirectory)
+        try FileManager.default.createDirectory(at: nestedDirectory, withIntermediateDirectories: true)
+        try "disabled_rules: [line_length]".write(
+            to: nestedDirectory.appending(path: Configuration.defaultFileName),
+            atomically: true,
+            encoding: .utf8
+        )
+
+        let options = LintOrAnalyzeOptions(
+            configurationFiles: [],
+            parentConfigurationFile: parentConfigurationFile
+        )
+        let configuration = Configuration(options: options)
+        let nestedFile = SwiftLintFile(
+            pathDeferringReading: nestedDirectory.appending(path: "Example.swift")
+        )
+
+        #expect(!configuration.basedOnCustomConfigurationFiles)
+        #expect(!configuration.rulesWrapper.disabledRuleIdentifiers.contains("line_length"))
+        #expect(
+            configuration.configuration(for: nestedFile)
+                .rulesWrapper.disabledRuleIdentifiers.contains("line_length")
+        )
+    }
 }
 
 private extension LintOrAnalyzeOptions {
-    init(leniency: Leniency) {
+    init(
+        leniency: Leniency = (strict: false, lenient: false),
+        configurationFiles: [URL] = [],
+        parentConfigurationFile: URL? = nil
+    ) {
         self.init(mode: .lint,
                   paths: [],
                   useSTDIN: true,
-                  configurationFiles: [],
+                  configurationFiles: configurationFiles,
+                  parentConfigurationFile: parentConfigurationFile,
                   strict: leniency.strict,
                   lenient: leniency.lenient,
                   forceExclude: false,