Add --output option to lint and analyze commands

CHANGELOG.md

@@ -20,6 +20,11 @@ accordingly._
   [JP Simard](https://github.com/jpsim)
   [#2495](https://github.com/realm/SwiftLint/issues/2495)
 
+* Add `--output` option to lint and analyze commands to write to a file instead
+  of to stdout.  
+  [JP Simard](https://github.com/jpsim)
+  [#4048](https://github.com/realm/SwiftLint/issues/4048)
+
 #### Bug Fixes
 
 * Migrate `empty_xctest_method` rule to SwiftSyntax fixing some false positives.  
@@ -36,6 +41,10 @@ accordingly._
   [Martin Hosna](https://github.com/mhosna)
   [#4142](https://github.com/realm/SwiftLint/issues/4142)
 
+* Consistently print error/info messages to stderr instead of stdout,
+  which wasn't being done for errors regarding remote configurations.  
+  [JP Simard](https://github.com/jpsim)
+
 ## 0.49.0: Asynchronous Defuzzer
 
 _Note: The default branch for the SwiftLint git repository will be renamed from

Source/SwiftLintFramework/Extensions/Configuration+Remote.swift

@@ -119,7 +119,7 @@ internal extension Configuration.FileGraph.FilePath {
 
     private mutating func handleMissingNetwork(urlString: String, cachedFilePath: String?) throws -> String {
         if let cachedFilePath = cachedFilePath {
-            queuedPrint(
+            queuedPrintError(
                 "warning: No internet connectivity: Unable to load remote config from \"\(urlString)\". "
                     + "Using cached version as a fallback."
             )
@@ -141,11 +141,11 @@ internal extension Configuration.FileGraph.FilePath {
     ) throws -> String {
         if let cachedFilePath = cachedFilePath {
             if taskDone {
-                queuedPrint(
+                queuedPrintError(
                     "warning: Unable to load remote config from \"\(urlString)\". Using cached version as a fallback."
                 )
             } else {
-                queuedPrint(
+                queuedPrintError(
                     "warning: Timeout (\(timeout) sec): Unable to load remote config from \"\(urlString)\". "
                         + "Using cached version as a fallback."
                 )
@@ -170,7 +170,7 @@ internal extension Configuration.FileGraph.FilePath {
 
     private mutating func handleFileWriteFailure(urlString: String, cachedFilePath: String?) throws -> String {
         if let cachedFilePath = cachedFilePath {
-            queuedPrint("Unable to cache remote config from \"\(urlString)\". Using cached version as a fallback.")
+            queuedPrintError("Unable to cache remote config from \"\(urlString)\". Using cached version as a fallback.")
             self = .existing(path: cachedFilePath)
             return cachedFilePath
         } else {

Source/swiftlint/Commands/Analyze.swift

@@ -43,6 +43,7 @@ extension SwiftLint {
                 benchmark: common.benchmark,
                 reporter: common.reporter,
                 quiet: quiet,
+                output: common.output,
                 cachePath: nil,
                 ignoreCache: true,
                 enableAllRules: false,

Source/swiftlint/Commands/Lint.swift

@@ -47,6 +47,7 @@ extension SwiftLint {
                 benchmark: common.benchmark,
                 reporter: common.reporter,
                 quiet: quiet,
+                output: common.output,
                 cachePath: cachePath,
                 ignoreCache: noCache,
                 enableAllRules: enableAllRules,

Source/swiftlint/Helpers/LintOrAnalyzeArguments.swift

@@ -39,6 +39,8 @@ struct LintOrAnalyzeArguments: ParsableArguments {
     var reporter: String?
     @Flag(help: "Use the in-process version of SourceKit.")
     var inProcessSourcekit = false
+    @Option(help: "The file where violations should be saved. Prints to stdout by default.")
+    var output: String?
 }
 
 // MARK: - Common Argument Help

Source/swiftlint/Helpers/LintOrAnalyzeCommand.swift

@@ -77,7 +77,7 @@ struct LintOrAnalyzeCommand {
                 }
             }
             linter.file.invalidateCache()
-            builder.reporter.report(violations: currentViolations, realtimeCondition: true)
+            builder.report(violations: currentViolations, realtimeCondition: true)
         }
     }
 
@@ -89,9 +89,9 @@ struct LintOrAnalyzeCommand {
             builder.violations.append(
                 createThresholdViolation(threshold: configuration.warningThreshold!)
             )
-            builder.reporter.report(violations: [builder.violations.last!], realtimeCondition: true)
+            builder.report(violations: [builder.violations.last!], realtimeCondition: true)
         }
-        builder.reporter.report(violations: builder.violations, realtimeCondition: false)
+        builder.report(violations: builder.violations, realtimeCondition: false)
         let numberOfSeriousViolations = builder.violations.filter({ $0.severity == .error }).count
         if !options.quiet {
             printStatus(violations: builder.violations, files: files, serious: numberOfSeriousViolations,
@@ -183,8 +183,8 @@ struct LintOrAnalyzeCommand {
 
                 let corrections = linter.correct(using: storage)
                 if !corrections.isEmpty && !options.quiet && !options.useSTDIN {
-                    let correctionLogs = corrections.map({ $0.consoleDescription })
-                    queuedPrint(correctionLogs.joined(separator: "\n"))
+                    let correctionLogs = corrections.map(\.consoleDescription)
+                    options.writeToOutput(correctionLogs.joined(separator: "\n"))
                 }
             }
 
@@ -210,6 +210,7 @@ struct LintOrAnalyzeOptions {
     let benchmark: Bool
     let reporter: String?
     let quiet: Bool
+    let output: String?
     let cachePath: String?
     let ignoreCache: Bool
     let enableAllRules: Bool
@@ -243,8 +244,44 @@ private class LintOrAnalyzeResultBuilder {
             Configuration(options: options)
         }
         configuration = config
-        reporter = reporterFrom(optionsReporter: options.reporter, configuration: config)
+        reporter = reporterFrom(identifier: options.reporter ?? config.reporter)
         cache = options.ignoreCache ? nil : LinterCache(configuration: config)
         self.options = options
+
+        if let outFile = options.output {
+            do {
+                try Data().write(to: URL(fileURLWithPath: outFile))
+            } catch {
+                queuedPrintError("Could not write to file at path \(outFile)")
+            }
+        }
+    }
+
+    func report(violations: [StyleViolation], realtimeCondition: Bool) {
+        if reporter.isRealtime == realtimeCondition {
+            let report = reporter.generateReport(violations)
+            if !report.isEmpty {
+                options.writeToOutput(report)
+            }
+        }
+    }
+}
+
+private extension LintOrAnalyzeOptions {
+    func writeToOutput(_ string: String) {
+        guard let outFile = output else {
+            queuedPrint(string)
+            return
+        }
+
+        do {
+            let outFileURL = URL(fileURLWithPath: outFile)
+            let fileUpdater = try FileHandle(forUpdating: outFileURL)
+            fileUpdater.seekToEndOfFile()
+            fileUpdater.write(Data((string + "\n").utf8))
+            fileUpdater.closeFile()
+        } catch {
+            queuedPrintError("Could not write to file at path \(outFile)")
+        }
     }
 }