Do not use dummy frontend for effective config printing

Author: andre-richter

Sources/SwiftFormat/API/Configuration+Dump.swift

@@ -19,11 +19,7 @@ extension Configuration {
 
     do {
       let encoder = JSONEncoder()
-      encoder.outputFormatting = [.prettyPrinted]
-      if #available(macOS 10.13, *) {
-        encoder.outputFormatting.insert(.sortedKeys)
-      }
-
+      encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
       data = try encoder.encode(self)
     } catch {
       throw SwiftFormatError.configurationDumpFailed("\(error)")

Sources/swift-format/CMakeLists.txt

@@ -12,7 +12,6 @@ add_executable(swift-format
   SwiftFormatCommand.swift
   VersionOptions.swift
   Frontend/ConfigurationLoader.swift
-  Frontend/DumpConfigurationFrontend.swift
   Frontend/FormatFrontend.swift
   Frontend/Frontend.swift
   Frontend/LintFrontend.swift

Sources/swift-format/Frontend/DumpConfigurationFrontend.swift

@@ -16,6 +16,118 @@ import SwiftParser
 import SwiftSyntax
 
 class Frontend {
+  /// Provides formatter configurations for given `.swift` source files, configuration files or configuration strings.
+  struct ConfigurationProvider {
+    /// Loads formatter configuration files and chaches them in memory.
+    private var configurationLoader: ConfigurationLoader = ConfigurationLoader()
+
+    /// The diagnostic engine to which warnings and errors will be emitted.
+    private let diagnosticsEngine: DiagnosticsEngine
+
+    /// Creates a new instance with the given options.
+    ///
+    /// - Parameter diagnosticsEngine: The diagnostic engine to which warnings and errors will be emitted.
+    init(diagnosticsEngine: DiagnosticsEngine) {
+      self.diagnosticsEngine = diagnosticsEngine
+    }
+
+    /// Checks if all the rules in the given configuration are supported by the registry.
+    ///
+    /// If there are any rules that are not supported, they are emitted as a warning.
+    private func checkForUnrecognizedRules(in configuration: Configuration) {
+      // If any rules in the decoded configuration are not supported by the registry,
+      // emit them into the diagnosticsEngine as warnings.
+      // That way they will be printed out, but we'll continue execution on the valid rules.
+      let invalidRules = configuration.rules.filter { !RuleRegistry.rules.keys.contains($0.key) }
+      for rule in invalidRules {
+        diagnosticsEngine.emitWarning("Configuration contains an unrecognized rule: \(rule.key)", location: nil)
+      }
+    }
+
+    /// Returns the configuration that applies to the given `.swift` source file, when an explicit
+    /// configuration path is also perhaps provided.
+    ///
+    /// This method also checks for unrecognized rules within the configuration.
+    ///
+    /// - Parameters:
+    ///   - pathOrString: A string containing either the path to a configuration file that will be
+    ///     loaded, JSON configuration data directly, or `nil` to try to infer it from
+    ///     `swiftFileURL`.
+    ///   - swiftFileURL: The path to a `.swift` file, which will be used to infer the path to the
+    ///     configuration file if `configurationFilePath` is nil.
+    ///
+    /// - Returns: If successful, the returned configuration is the one loaded from `pathOrString` if
+    ///   it was provided, or by searching in paths inferred by `swiftFileURL` if one exists, or the
+    ///   default configuration otherwise. If an error occurred when reading the configuration, a
+    ///   diagnostic is emitted and `nil` is returned. If neither `pathOrString` nor `swiftFileURL`
+    ///   were provided, a default `Configuration()` will be returned.
+    mutating func provide(
+      forConfigPathOrString pathOrString: String?,
+      orForSwiftFileAt swiftFileURL: URL?
+    ) -> Configuration? {
+      if let pathOrString = pathOrString {
+        // If an explicit configuration file path was given, try to load it and fail if it cannot be
+        // loaded. (Do not try to fall back to a path inferred from the source file path.)
+        let configurationFileURL = URL(fileURLWithPath: pathOrString)
+        do {
+          let configuration = try configurationLoader.configuration(at: configurationFileURL)
+          self.checkForUnrecognizedRules(in: configuration)
+          return configuration
+        } catch {
+          // If we failed to load this from the path, try interpreting the string as configuration
+          // data itself because the user might have written something like `--configuration '{...}'`,
+          let data = pathOrString.data(using: .utf8)!
+          if let configuration = try? Configuration(data: data) {
+            return configuration
+          }
+
+          // Fail if the configuration flag was neither a valid file path nor valid configuration
+          // data.
+          diagnosticsEngine.emitError("Unable to read configuration: \(error.localizedDescription)")
+          return nil
+        }
+      }
+
+      // If no explicit configuration file path was given but a `.swift` source file path was given,
+      // then try to load the configuration by inferring it based on the source file path.
+      if let swiftFileURL = swiftFileURL {
+        do {
+          if let configuration = try configurationLoader.configuration(forPath: swiftFileURL) {
+            self.checkForUnrecognizedRules(in: configuration)
+            return configuration
+          }
+          // Fall through to the default return at the end of the function.
+        } catch {
+          diagnosticsEngine.emitError(
+            "Unable to read configuration for \(swiftFileURL.path): \(error.localizedDescription)"
+          )
+          return nil
+        }
+      } else {
+        // If reading from stdin and no explicit configuration file was given,
+        // walk up the file tree from the cwd to find a config.
+
+        let cwd = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
+        // Definitely a Swift file. Definitely not a directory. Shhhhhh.
+        do {
+          if let configuration = try configurationLoader.configuration(forPath: cwd) {
+            self.checkForUnrecognizedRules(in: configuration)
+            return configuration
+          }
+        } catch {
+          diagnosticsEngine.emitError(
+            "Unable to read configuration for \(cwd): \(error.localizedDescription)"
+          )
+          return nil
+        }
+      }
+
+      // An explicit configuration has not been given, and one cannot be found.
+      // Return the default configuration.
+      return Configuration()
+    }
+  }
+
   /// Represents a file to be processed by the frontend and any file-specific options associated
   /// with it.
   final class FileToProcess {
@@ -73,8 +185,8 @@ class Frontend {
   /// Options that apply during formatting or linting.
   final let lintFormatOptions: LintFormatOptions
 
-  /// Loads formatter configuration files.
-  final var configurationLoader = ConfigurationLoader()
+  /// The provider for formatter configurations.
+  final var configurationProvider: ConfigurationProvider
 
   /// Advanced options that are useful for developing/debugging but otherwise not meant for general
   /// use.
@@ -95,8 +207,8 @@ class Frontend {
     self.diagnosticPrinter = StderrDiagnosticPrinter(
       colorMode: lintFormatOptions.colorDiagnostics.map { $0 ? .on : .off } ?? .auto
     )
-    self.diagnosticsEngine =
-      DiagnosticsEngine(diagnosticsHandlers: [diagnosticPrinter.printDiagnostic])
+    self.diagnosticsEngine = DiagnosticsEngine(diagnosticsHandlers: [diagnosticPrinter.printDiagnostic])
+    self.configurationProvider = ConfigurationProvider(diagnosticsEngine: self.diagnosticsEngine)
   }
 
   /// Runs the linter or formatter over the inputs.
@@ -142,9 +254,9 @@ class Frontend {
     let assumedUrl = lintFormatOptions.assumeFilename.map(URL.init(fileURLWithPath:))
 
     guard
-      let configuration = configuration(
-        fromPathOrString: configurationOptions.configuration,
-        orInferredFromSwiftFileAt: assumedUrl
+      let configuration = configurationProvider.provide(
+        forConfigPathOrString: configurationOptions.configuration,
+        orForSwiftFileAt: assumedUrl
       )
     else {
       // Already diagnosed in the called method.
@@ -193,9 +305,9 @@ class Frontend {
     }
 
     guard
-      let configuration = configuration(
-        fromPathOrString: configurationOptions.configuration,
-        orInferredFromSwiftFileAt: url
+      let configuration = configurationProvider.provide(
+        forConfigPathOrString: configurationOptions.configuration,
+        orForSwiftFileAt: url
       )
     else {
       // Already diagnosed in the called method.
@@ -210,98 +322,4 @@ class Frontend {
     )
   }
 
-  /// Returns the configuration that applies to the given `.swift` source file, when an explicit
-  /// configuration path is also perhaps provided.
-  ///
-  /// This method also checks for unrecognized rules within the configuration.
-  ///
-  /// - Parameters:
-  ///   - pathOrString: A string containing either the path to a configuration file that will be
-  ///     loaded, JSON configuration data directly, or `nil` to try to infer it from
-  ///     `swiftFilePath`.
-  ///   - swiftFilePath: The path to a `.swift` file, which will be used to infer the path to the
-  ///     configuration file if `configurationFilePath` is nil.
-  ///
-  /// - Returns: If successful, the returned configuration is the one loaded from `pathOrString` if
-  ///   it was provided, or by searching in paths inferred by `swiftFilePath` if one exists, or the
-  ///   default configuration otherwise. If an error occurred when reading the configuration, a
-  ///   diagnostic is emitted and `nil` is returned. If neither `pathOrString` nor `swiftFilePath`
-  ///   were provided, a default `Configuration()` will be returned.
-  private func configuration(
-    fromPathOrString pathOrString: String?,
-    orInferredFromSwiftFileAt swiftFileURL: URL?
-  ) -> Configuration? {
-    if let pathOrString = pathOrString {
-      // If an explicit configuration file path was given, try to load it and fail if it cannot be
-      // loaded. (Do not try to fall back to a path inferred from the source file path.)
-      let configurationFileURL = URL(fileURLWithPath: pathOrString)
-      do {
-        let configuration = try configurationLoader.configuration(at: configurationFileURL)
-        self.checkForUnrecognizedRules(in: configuration)
-        return configuration
-      } catch {
-        // If we failed to load this from the path, try interpreting the string as configuration
-        // data itself because the user might have written something like `--configuration '{...}'`,
-        let data = pathOrString.data(using: .utf8)!
-        if let configuration = try? Configuration(data: data) {
-          return configuration
-        }
-
-        // Fail if the configuration flag was neither a valid file path nor valid configuration
-        // data.
-        diagnosticsEngine.emitError("Unable to read configuration: \(error.localizedDescription)")
-        return nil
-      }
-    }
-
-    // If no explicit configuration file path was given but a `.swift` source file path was given,
-    // then try to load the configuration by inferring it based on the source file path.
-    if let swiftFileURL = swiftFileURL {
-      do {
-        if let configuration = try configurationLoader.configuration(forPath: swiftFileURL) {
-          self.checkForUnrecognizedRules(in: configuration)
-          return configuration
-        }
-        // Fall through to the default return at the end of the function.
-      } catch {
-        diagnosticsEngine.emitError(
-          "Unable to read configuration for \(swiftFileURL.path): \(error.localizedDescription)"
-        )
-        return nil
-      }
-    } else {
-      // If reading from stdin and no explicit configuration file was given,
-      // walk up the file tree from the cwd to find a config.
-
-      let cwd = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
-      // Definitely a Swift file. Definitely not a directory. Shhhhhh.
-      do {
-        if let configuration = try configurationLoader.configuration(forPath: cwd) {
-          self.checkForUnrecognizedRules(in: configuration)
-          return configuration
-        }
-      } catch {
-        diagnosticsEngine.emitError(
-          "Unable to read configuration for \(cwd): \(error.localizedDescription)"
-        )
-        return nil
-      }
-    }
-
-    // An explicit configuration has not been given, and one cannot be found.
-    // Return the default configuration.
-    return Configuration()
-  }
-
-  /// Checks if all the rules in the given configuration are supported by the registry.
-  /// If there are any rules that are not supported, they are emitted as a warning.
-  private func checkForUnrecognizedRules(in configuration: Configuration) {
-    // If any rules in the decoded configuration are not supported by the registry,
-    // emit them into the diagnosticsEngine as warnings.
-    // That way they will be printed out, but we'll continue execution on the valid rules.
-    let invalidRules = configuration.rules.filter { !RuleRegistry.rules.keys.contains($0.key) }
-    for rule in invalidRules {
-      diagnosticsEngine.emitWarning("Configuration contains an unrecognized rule: \(rule.key)", location: nil)
-    }
-  }
 }

Sources/swift-format/Frontend/Frontend.swift

@@ -40,30 +40,34 @@ extension SwiftFormatCommand {
     }
 
     func run() throws {
-      if !effective {
-        let configuration = try Configuration().asJsonString()
-        print(configuration)
-        return
-      }
+      let diagnosticPrinter = StderrDiagnosticPrinter(colorMode: .auto)
+      let diagnosticsEngine = DiagnosticsEngine(diagnosticsHandlers: [diagnosticPrinter.printDiagnostic])
 
-      // Pretend to use stdin, so that the configuration loading machinery in the Frontend base class can be used in the
-      // next step. This produces the same results as if "format" or "lint" subcommands were called.
-      let lintFormatOptions = try LintFormatOptions.parse(["-"])
+      let configuration: Configuration
+      if effective {
+        var configurationProvider = Frontend.ConfigurationProvider(diagnosticsEngine: diagnosticsEngine)
 
-      let frontend = DumpConfigurationFrontend(
-        configurationOptions: configurationOptions,
-        lintFormatOptions: lintFormatOptions
-      )
-      frontend.run()
-      if frontend.diagnosticsEngine.hasErrors {
-        throw ExitCode.failure
+        guard
+          let effectiveConfiguration = configurationProvider.provide(
+            forConfigPathOrString: configurationOptions.configuration,
+            orForSwiftFileAt: nil
+          )
+        else {
+          // Already diagnosed in the called method through the diagnosticsEngine.
+          throw ExitCode.failure
+        }
+
+        configuration = effectiveConfiguration
+      } else {
+        configuration = Configuration()
       }
 
-      switch frontend.dumpedConfiguration {
-      case .success(let configuration):
-        print(configuration)
-      case .failure(let error):
-        throw error
+      do {
+        let configurationAsJson = try configuration.asJsonString()
+        print(configurationAsJson)
+      } catch {
+        diagnosticsEngine.emitError("\(error.localizedDescription)")
+        throw ExitCode.failure
       }
     }
   }