Remove swift-tools-support-core dependency.

TSC was mostly used for its argument parser. Now that
we've migrated to swift-argument-parser, the remaining
file system and path APIs in TSC are only used by the
Format command and can be fairly easily replaced by
Foundation APIs instead.

Author: allevato

Package.resolved

@@ -22,7 +22,6 @@ let package = Package(
   ],
   dependencies: [
     .package(url: "https://github.com/apple/swift-syntax", from: "0.50200.0"),
-    .package(url: "https://github.com/apple/swift-tools-support-core.git", from: "0.0.1"),
     .package(url: "https://github.com/apple/swift-argument-parser.git", .upToNextMinor(from: "0.0.4")),
   ],
   targets: [
@@ -62,12 +61,11 @@ let package = Package(
     .target(
       name: "swift-format",
       dependencies: [
+        "ArgumentParser",
         "SwiftFormat",
         "SwiftFormatConfiguration",
         "SwiftFormatCore",
         "SwiftSyntax",
-        "SwiftToolsSupport-auto",
-        "ArgumentParser",
       ]
     ),
     .testTarget(

Package.swift

@@ -13,8 +13,6 @@
 import ArgumentParser
 import Foundation
 import SwiftFormatConfiguration
-import TSCBasic
-import TSCUtility
 
 extension SwiftFormatCommand {
   /// Dumps the tool's default configuration in JSON format to standard output.

Sources/swift-format/Subcommands/DumpConfiguration.swift

@@ -15,7 +15,6 @@ import Foundation
 import SwiftFormat
 import SwiftFormatConfiguration
 import SwiftSyntax
-import TSCBasic
 
 extension SwiftFormatCommand {
   /// Formats one or more files containing Swift code.
@@ -89,31 +88,29 @@ private func formatMain(
   // fixed anyway.
   let formatter = SwiftFormatter(configuration: configuration, diagnosticEngine: nil)
   formatter.debugOptions = debugOptions
-  let assumingFileURL = URL(fileURLWithPath: assumingFilename ?? "<stdin>")
+
+  let path = assumingFilename ?? "<stdin>"
+  let assumingFileURL = URL(fileURLWithPath: path)
 
   guard let source = readSource(from: sourceFile) else {
     diagnosticEngine.diagnose(
-      Diagnostic.Message(
-        .error, "Unable to read source for formatting from \(assumingFileURL.path)."))
+      Diagnostic.Message(.error, "Unable to read source for formatting from \(path)."))
     return
   }
 
+  var stdoutStream = FileHandle.standardOutput
   do {
     if inPlace {
-      let cwd = FileManager.default.currentDirectoryPath
-      var buffer = BufferedOutputByteStream()
+      var buffer = ""
       try formatter.format(source: source, assumingFileURL: assumingFileURL, to: &buffer)
-      buffer.flush()
-      try localFileSystem.writeFileContents(
-        AbsolutePath(assumingFileURL.path, relativeTo: AbsolutePath(cwd)),
-        bytes: buffer.bytes
-      )
+
+      let bufferData = buffer.data(using: .utf8)!  // Conversion to UTF-8 cannot fail
+      try bufferData.write(to: assumingFileURL, options: .atomic)
     } else {
       try formatter.format(source: source, assumingFileURL: assumingFileURL, to: &stdoutStream)
-      stdoutStream.flush()
+      stdoutStream.synchronizeFile()
     }
   } catch SwiftFormatError.fileNotReadable {
-    let path = assumingFileURL.path
     diagnosticEngine.diagnose(
       Diagnostic.Message(
         .error, "Unable to format \(path): file is not readable or does not exist."))
@@ -125,17 +122,15 @@ private func formatMain(
         return
       }
       stdoutStream.write(source)
-      stdoutStream.flush()
+      stdoutStream.synchronizeFile()
       return
     }
-    let path = assumingFileURL.path
     let location = SourceLocationConverter(file: path, source: source).location(for: position)
     diagnosticEngine.diagnose(
       Diagnostic.Message(.error, "file contains invalid or unrecognized Swift syntax."),
       location: location)
     return
   } catch {
-    let path = assumingFileURL.path
     diagnosticEngine.diagnose(Diagnostic.Message(.error, "Unable to format \(path): \(error)"))
     return
   }

Sources/swift-format/Subcommands/Format.swift

@@ -16,7 +16,6 @@ import SwiftFormat
 import SwiftFormatConfiguration
 import SwiftFormatCore
 import SwiftSyntax
-import TSCBasic
 
 extension SwiftFormatCommand {
   /// Keep the legacy `-m/--mode` flag working temporarily when no other subcommand is specified.

Sources/swift-format/Subcommands/LegacyMain.swift

@@ -15,7 +15,6 @@ import Foundation
 import SwiftFormat
 import SwiftFormatConfiguration
 import SwiftSyntax
-import TSCBasic
 
 extension SwiftFormatCommand {
   /// Emits style diagnostics for one or more files containing Swift code.

Sources/swift-format/Subcommands/Lint.swift

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+extension FileHandle: TextOutputStream {
+  public func write(_ string: String) {
+    self.write(string.data(using: .utf8)!)  // Conversion to UTF-8 cannot fail
+  }
+}

Sources/swift-format/Utilities/FileHandle+TextOutputStream.swift

@@ -16,7 +16,6 @@ import SwiftFormat
 import SwiftFormatConfiguration
 import SwiftFormatCore
 import SwiftSyntax
-import TSCBasic
 
 /// Throws an error that causes the current command to exit the process with a failure exit code if
 /// any of the preceding operations emitted diagnostics.