Update file_name rule to match fully-qualified names of nested types

This PR is aimed to address Issue #5840. It does the following:

1. Allows the `file_name` rule to match nested types when using fully-qualified names, meaning naming the following file `Nested.MyType.swift` is no longer a violation:

```
// Nested.MyType.swift

enum Nested {
    struct MyType {
    }
}
```

2. Introduces a new option `fully_qualified` to have the `file_name` rule enforce using fully-qualified names, meaning naming the above file `MyType.swift` instead of `Nested.MyType.swift` would become a violation where it wasn't before (naming the file `Nested.swift` would still not be a violation).

CHANGELOG.md

@@ -63,6 +63,12 @@
   [Martin Redington](https://github.com/mildm8nnered)
   [#5711](https://github.com/realm/SwiftLint/issues/5711)
 
+* Fixes `file_name` rule to match fully-qualified names of nested types.
+  Additionally adds a `fully_qualified` boolean option to enforce that
+  file names match nested types only using their fully-qualified name.
+  [fraioli](https://github.com/fraioli)
+  [#issue_number](https://github.com/realm/SwiftLint/issues/issue_number)
+
 ## 0.57.0: Squeaky Clean Cycle
 
 #### Breaking

Source/SwiftLintBuiltInRules/Rules/Idiomatic/FileNameRule.swift

@@ -35,7 +35,7 @@ struct FileNameRule: OptInRule, SourceKitFreeRule {
         }
 
         // Process nested type separator
-        let allDeclaredTypeNames = TypeNameCollectingVisitor(viewMode: .sourceAccurate)
+        let allDeclaredTypeNames = TypeNameCollectingVisitor(requireFullyQualifiedNames: configuration.fullyQualified)
             .walk(tree: file.syntaxTree, handler: \.names)
             .map {
                 $0.replacingOccurrences(of: ".", with: configuration.nestedTypeSeparator)
@@ -56,33 +56,98 @@ struct FileNameRule: OptInRule, SourceKitFreeRule {
 }
 
 private class TypeNameCollectingVisitor: SyntaxVisitor {
+    // All of a visited node's ancestor type names if that node is nested, starting with the furthest
+    // ancestor and ending with the direct parent
+    private var ancestorNames: [String] = []
+
+    // All of the type names found in the file
     private(set) var names: Set<String> = []
 
+    // If true, nested types are only allowed in the file name when used by their fully-qualified name
+    // (e.g. `My.Nested.Type` and not just `Type`)
+    private let requireFullyQualifiedNames: Bool
+
+    init(requireFullyQualifiedNames: Bool) {
+        self.requireFullyQualifiedNames = requireFullyQualifiedNames
+        super.init(viewMode: .sourceAccurate)
+    }
+
+    private func addVisitedNodeName(_ name: String) {
+        let fullyQualifiedName = (ancestorNames + [name]).joined(separator: ".")
+        names.insert(fullyQualifiedName)
+
+        if !requireFullyQualifiedNames {
+            names.insert(name)
+        }
+    }
+
+    override func visit(_ node: ClassDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
+    }
+
     override func visitPost(_ node: ClassDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: ActorDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
     }
 
     override func visitPost(_ node: ActorDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: StructDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
     }
 
     override func visitPost(_ node: StructDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: TypeAliasDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
     }
 
     override func visitPost(_ node: TypeAliasDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: EnumDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
     }
 
     override func visitPost(_ node: EnumDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: ProtocolDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.name.text)
+        return .visitChildren
     }
 
     override func visitPost(_ node: ProtocolDeclSyntax) {
-        names.insert(node.name.text)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.name.text)
+    }
+
+    override func visit(_ node: ExtensionDeclSyntax) -> SyntaxVisitorContinueKind {
+        ancestorNames.append(node.extendedType.trimmedDescription)
+        return .visitChildren
     }
 
     override func visitPost(_ node: ExtensionDeclSyntax) {
-        names.insert(node.extendedType.trimmedDescription)
+        ancestorNames.removeLast()
+        addVisitedNodeName(node.extendedType.trimmedDescription)
     }
 }

Source/SwiftLintBuiltInRules/Rules/RuleConfigurations/FileNameConfiguration.swift

@@ -14,4 +14,6 @@ struct FileNameConfiguration: SeverityBasedRuleConfiguration {
     private(set) var suffixPattern = "\\+.*"
     @ConfigurationElement(key: "nested_type_separator")
     private(set) var nestedTypeSeparator = "."
+    @ConfigurationElement(key: "fully_qualified")
+    private(set) var fullyQualified = false
 }

Tests/IntegrationTests/default_rule_configurations.yml

@@ -177,6 +177,7 @@ file_name:
   prefix_pattern: ""
   suffix_pattern: "\+.*"
   nested_type_separator: "."
+  fully_qualified: false
 file_name_no_space:
   severity: warning
   excluded: []

Tests/SwiftLintFrameworkTests/FileNameRuleTests.swift

@@ -5,26 +5,33 @@ private let fixturesDirectory = "\(TestResources.path)/FileNameRuleFixtures"
 
 final class FileNameRuleTests: SwiftLintTestCase {
     private func validate(fileName: String,
-                          excludedOverride: [String]? = nil,
+                          excluded: [String]? = nil,
                           prefixPattern: String? = nil,
                           suffixPattern: String? = nil,
-                          nestedTypeSeparator: String? = nil) throws -> [StyleViolation] {
+                          nestedTypeSeparator: String? = nil,
+                          fullyQualified: Bool = false) throws -> [StyleViolation] {
         let file = SwiftLintFile(path: fixturesDirectory.stringByAppendingPathComponent(fileName))!
-        let rule: FileNameRule
-        if let excluded = excludedOverride {
-            rule = try FileNameRule(configuration: ["excluded": excluded])
-        } else if let prefixPattern, let suffixPattern {
-            rule = try FileNameRule(configuration: ["prefix_pattern": prefixPattern, "suffix_pattern": suffixPattern])
-        } else if let prefixPattern {
-            rule = try FileNameRule(configuration: ["prefix_pattern": prefixPattern])
-        } else if let suffixPattern {
-            rule = try FileNameRule(configuration: ["suffix_pattern": suffixPattern])
-        } else if let nestedTypeSeparator {
-            rule = try FileNameRule(configuration: ["nested_type_separator": nestedTypeSeparator])
-        } else {
-            rule = FileNameRule()
+
+        var configuration = [String: Any]()
+
+        if let excluded {
+            configuration["excluded"] = excluded
+        }
+        if let prefixPattern {
+            configuration["prefix_pattern"] = prefixPattern
+        }
+        if let suffixPattern {
+            configuration["suffix_pattern"] = suffixPattern
+        }
+        if let nestedTypeSeparator {
+            configuration["nested_type_separator"] = nestedTypeSeparator
+        }
+        if fullyQualified {
+            configuration["fully_qualified"] = fullyQualified
         }
 
+        let rule = try FileNameRule(configuration: configuration)
+
         return rule.validate(file: file)
     }
 
@@ -52,6 +59,22 @@ final class FileNameRuleTests: SwiftLintTestCase {
         XCTAssert(try validate(fileName: "Notification.Name+Extension.swift").isEmpty)
     }
 
+    func testNestedTypeDoesntTrigger() {
+        XCTAssert(try validate(fileName: "Nested.MyType.swift").isEmpty)
+    }
+
+    func testMultipleLevelsDeeplyNestedTypeDoesntTrigger() {
+        XCTAssert(try validate(fileName: "Multiple.Levels.Deeply.Nested.MyType.swift").isEmpty)
+    }
+
+    func testNestedTypeNotFullyQualifiedDoesntTrigger() {
+        XCTAssert(try validate(fileName: "MyType.swift").isEmpty)
+    }
+
+    func testNestedTypeNotFullyQualifiedDoesTriggerWithOverride() {
+        XCTAssert(try !validate(fileName: "MyType.swift", fullyQualified: true).isEmpty)
+    }
+
     func testNestedTypeSeparatorDoesntTrigger() {
         XCTAssert(try validate(fileName: "NotificationName+Extension.swift", nestedTypeSeparator: "").isEmpty)
         XCTAssert(try validate(fileName: "Notification__Name+Extension.swift", nestedTypeSeparator: "__").isEmpty)
@@ -67,11 +90,11 @@ final class FileNameRuleTests: SwiftLintTestCase {
     }
 
     func testMisspelledNameDoesntTriggerWithOverride() {
-        XCTAssert(try validate(fileName: "MyStructf.swift", excludedOverride: ["MyStructf.swift"]).isEmpty)
+        XCTAssert(try validate(fileName: "MyStructf.swift", excluded: ["MyStructf.swift"]).isEmpty)
     }
 
     func testMainDoesTriggerWithoutOverride() {
-        XCTAssertEqual(try validate(fileName: "main.swift", excludedOverride: []).count, 1)
+        XCTAssertEqual(try validate(fileName: "main.swift", excluded: []).count, 1)
     }
 
     func testCustomSuffixPattern() {

Tests/SwiftLintFrameworkTests/Resources/FileNameRuleFixtures/Multiple.Levels.Deeply.Nested.MyType.swift

@@ -0,0 +1,9 @@
+extension Multiple {
+    enum Levels {
+        class Deeply {
+            struct Nested {
+                actor MyType {}
+            }
+        }
+    }
+}

Tests/SwiftLintFrameworkTests/Resources/FileNameRuleFixtures/MyType.swift

@@ -0,0 +1,3 @@
+enum Nested {
+    struct MyType {}
+}

Tests/SwiftLintFrameworkTests/Resources/FileNameRuleFixtures/Nested.MyType.swift

@@ -0,0 +1,4 @@
+enum Nested {
+    struct MyType {
+    }
+}