sourcekit-lsp/Sources/SwiftLanguageService/DocumentFormatting.swift

//===----------------------------------------------------------------------===//
//
// 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
@_spi(SourceKitLSP) package import LanguageServerProtocol
@_spi(SourceKitLSP) import LanguageServerProtocolExtensions
@_spi(SourceKitLSP) import LanguageServerProtocolTransport
@_spi(SourceKitLSP) import SKLogging
import SKUtilities
import SourceKitLSP
import SwiftExtensions
import SwiftParser
import SwiftSyntax
import TSCExtensions
import ToolchainRegistry
@_spi(SourceKitLSP) import ToolsProtocolsSwiftExtensions

import struct TSCBasic.AbsolutePath
import class TSCBasic.LocalFileOutputByteStream
import class TSCBasic.Process
import protocol TSCBasic.WritableByteStream

fileprivate extension String {
  init?(bytes: [UInt8], encoding: Encoding) {
    let data = bytes.withUnsafeBytes { buffer in
      guard let baseAddress = buffer.baseAddress else {
        return Data()
      }
      return Data(bytes: baseAddress, count: buffer.count)
    }
    self.init(data: data, encoding: encoding)
  }
}

/// If a parent directory of `fileURI` contains a `.swift-format` file, return the path to that file.
/// Otherwise, return `nil`.
private func swiftFormatFile(for fileURI: DocumentURI) -> AbsolutePath? {
  guard var path = try? AbsolutePath(validating: fileURI.pseudoPath) else {
    return nil
  }
  repeat {
    path = path.parentDirectory
    let configFile = path.appending(component: ".swift-format")
    if FileManager.default.isReadableFile(atPath: configFile.pathString) {
      return configFile
    }
  } while !path.isRoot
  return nil
}

/// If a `.swift-format` file is discovered that applies to `fileURI`, return the path to that file.
/// Otherwise, return a JSON object containing the configuration parameters from `options`.
///
/// The result of this function can be passed to the `--configuration` parameter of swift-format.
private func swiftFormatConfiguration(
  for fileURI: DocumentURI,
  options: FormattingOptions
) throws -> String {
  if let configFile = swiftFormatFile(for: fileURI) {
    // If we find a .swift-format file, we ignore the options passed to us by the editor.
    // Most likely, the editor inferred them from the current document and thus the options
    // passed by the editor are most likely less correct than those in .swift-format.
    return configFile.pathString
  }

  // The following options are not supported by swift-format and ignored:
  // - trimTrailingWhitespace: swift-format always trims trailing whitespace
  // - insertFinalNewline: swift-format always inserts a final newline to the file
  // - trimFinalNewlines: swift-format always trims final newlines

  if options.insertSpaces {
    return """
      {
        "version": 1,
        "tabWidth": \(options.tabSize),
        "indentation": { "spaces": \(options.tabSize) }
      }
      """
  } else {
    return """
      {
        "version": 1,
        "tabWidth": \(options.tabSize),
        "indentation": { "tabs": 1 }
      }
      """
  }
}

extension CollectionDifference.Change {
  var offset: Int {
    switch self {
    case .insert(let offset, element: _, associatedWith: _):
      return offset
    case .remove(let offset, element: _, associatedWith: _):
      return offset
    }
  }
}

/// Compute the text edits that need to be made to transform `original` into `edited`.
private func edits(from original: DocumentSnapshot, to edited: String) -> [TextEdit] {
  let difference = edited.utf8.difference(from: original.text.utf8)

  let sequentialEdits = difference.map { change in
    switch change {
    case .insert(let offset, let element, associatedWith: _):
      let absolutePosition = AbsolutePosition(utf8Offset: offset)
      return SourceEdit(range: absolutePosition..<absolutePosition, replacement: [element])
    case .remove(let offset, element: _, associatedWith: _):
      let absolutePosition = AbsolutePosition(utf8Offset: offset)
      return SourceEdit(range: absolutePosition..<absolutePosition.advanced(by: 1), replacement: [])
    }
  }

  let concurrentEdits = ConcurrentEdits(fromSequential: sequentialEdits)

  // Map the offset-based edits to line-column based edits to be consumed by LSP

  return concurrentEdits.edits.compactMap {
    TextEdit(range: original.absolutePositionRange(of: $0.range), newText: $0.replacement)
  }
}

extension SwiftLanguageService {
  package func documentFormatting(_ req: DocumentFormattingRequest) async throws -> [TextEdit]? {
    return try await format(
      snapshot: documentManager.latestSnapshot(req.textDocument.uri),
      textDocument: req.textDocument,
      options: req.options
    )
  }

  package func documentRangeFormatting(_ req: DocumentRangeFormattingRequest) async throws -> [TextEdit]? {
    return try await format(
      snapshot: documentManager.latestSnapshot(req.textDocument.uri),
      textDocument: req.textDocument,
      options: req.options,
      range: req.range
    )
  }

  package func documentOnTypeFormatting(_ req: DocumentOnTypeFormattingRequest) async throws -> [TextEdit]? {
    let snapshot = try documentManager.latestSnapshot(req.textDocument.uri)
    guard let line = snapshot.lineTable.line(at: req.position.line) else {
      return nil
    }

    let lineStartPosition = snapshot.position(of: line.startIndex, fromLine: req.position.line)
    let lineEndPosition = snapshot.position(of: line.endIndex, fromLine: req.position.line)

    return try await format(
      snapshot: snapshot,
      textDocument: req.textDocument,
      options: req.options,
      range: lineStartPosition..<lineEndPosition
    )
  }

  private func format(
    snapshot: DocumentSnapshot,
    textDocument: TextDocumentIdentifier,
    options: FormattingOptions,
    range: Range<Position>? = nil
  ) async throws -> [TextEdit]? {
    guard let swiftFormat = toolchain.swiftFormat else {
      throw ResponseError.unknown(
        "Formatting not supported because the toolchain is missing the swift-format executable"
      )
    }

    var args = try [
      swiftFormat.filePath,
      "format",
      "-",  // Read file contents from stdin
      "--configuration",
      swiftFormatConfiguration(for: textDocument.uri, options: options),
    ]
    if let range {
      let utf8Range = snapshot.utf8OffsetRange(of: range)
      // swift-format takes an inclusive range, but Swift's `Range.upperBound` is exclusive.
      // Also make sure `upperBound` does not go less than `lowerBound`.
      let utf8UpperBound = max(utf8Range.lowerBound, utf8Range.upperBound - 1)
      args += [
        "--offsets",
        "\(utf8Range.lowerBound):\(utf8UpperBound)",
      ]
    }
    let process = TSCBasic.Process(arguments: args)
    let writeStream: any WritableByteStream
    do {
      writeStream = try process.launch()
    } catch {
      throw ResponseError.unknown("Launching swift-format failed: \(error)")
    }
    #if canImport(Darwin)
    // On Darwin, we can disable SIGPIPE for a single pipe. This is not available on all platforms, in which case we
    // resort to disabling SIGPIPE globally to avoid crashing SourceKit-LSP with SIGPIPE if swift-format crashes before
    // we could send all data to its stdin.
    if let byteStream = writeStream as? LocalFileOutputByteStream {
      orLog("Disable SIGPIPE for swift-format stdin") {
        try byteStream.disableSigpipe()
      }
    } else {
      logger.fault("Expected write stream to process to be a LocalFileOutputByteStream")
    }
    #else
    globallyDisableSigpipeIfNeeded()
    #endif

    do {
      // Send the file to format to swift-format's stdin. That way we don't have to write it to a file.
      //
      // If we are on Windows, `writeStream` is not a swift-tools-support-core type but a `FileHandle`. In that case,
      // call the throwing `write(contentsOf:)` method on it so that we can catch a `ERROR_BROKEN_PIPE` error. The
      // `send` method that we use on all other platforms ends up calling the non-throwing `FileHandle.write(_:)`, which
      // calls `write(contentsOf:)` using `try!` and thus crashes SourceKit-LSP if the pipe to swift-format is closed,
      // eg. because swift-format has crashed.
      if let fileHandle = writeStream as? FileHandle {
        try fileHandle.write(contentsOf: Data(snapshot.text.utf8))
      } else {
        writeStream.send(snapshot.text.utf8)
      }
      try writeStream.close()
    } catch {
      throw ResponseError.unknown("Writing to swift-format stdin failed: \(error)")
    }

    let result = try await withTimeout(.seconds(60)) {
      try await process.waitUntilExitStoppingProcessOnTaskCancellation()
    }
    guard result.exitStatus == .terminated(code: 0) else {
      let swiftFormatErrorMessage: String
      switch result.stderrOutput {
      case .success(let stderrBytes):
        swiftFormatErrorMessage = String(bytes: stderrBytes, encoding: .utf8) ?? "unknown error"
      case .failure(let error):
        swiftFormatErrorMessage = String(describing: error)
      }
      throw ResponseError.unknown(
        """
        Running swift-format failed
        \(swiftFormatErrorMessage)
        """
      )
    }
    let formattedBytes: [UInt8]
    switch result.output {
    case .success(let bytes):
      formattedBytes = bytes
    case .failure(let error):
      throw error
    }

    guard let formattedString = String(bytes: formattedBytes, encoding: .utf8) else {
      throw ResponseError.unknown("Failed to decode response from swift-format as UTF-8")
    }

    return edits(from: snapshot, to: formattedString)
  }
}