Rename test projects for consistency

Rename all the classes that write files to disk to create a test project that we can open in sourcekit-lsp to end with `TestProject`. This is better than the old `Workspace` suffix because it avoids ambiguities with the `Workspace` type inside sourcekit-lsp.

- IndexedSingleSwiftFileWorkspace -> IndexedSingleSwiftFileTestProject
- MultiFileTestWorkspace -> MultiFileTestProject
- SwiftPMTestWorkspace -> SwiftPMTestProject

Sources/SKTestSupport/MultiFileTestProject.swift

@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 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
+import LanguageServerProtocol
+import SKCore
+
+/// The location of a test file within test workspace.
+public struct RelativeFileLocation: Hashable, ExpressibleByStringLiteral {
+  /// The subdirectories in which the file is located.
+  public let directories: [String]
+
+  /// The file's name.
+  public let fileName: String
+
+  public init(directories: [String] = [], _ fileName: String) {
+    self.directories = directories
+    self.fileName = fileName
+  }
+
+  public init(stringLiteral value: String) {
+    let components = value.components(separatedBy: "/")
+    self.init(directories: components.dropLast(), components.last!)
+  }
+}
+
+/// A test project that writes multiple files to disk and opens a `TestSourceKitLSPClient` client with a workspace
+/// pointing to a temporary directory containing those files.
+///
+/// The temporary files will be deleted when the `TestSourceKitLSPClient` is destructed.
+public class MultiFileTestProject {
+  /// Information necessary to open a file in the LSP server by its filename.
+  private struct FileData {
+    /// The URI at which the file is stored on disk.
+    let uri: DocumentURI
+
+    /// The contents of the file including location markers.
+    let markedText: String
+  }
+
+  public let testClient: TestSourceKitLSPClient
+
+  /// Information necessary to open a file in the LSP server by its filename.
+  private let fileData: [String: FileData]
+
+  enum Error: Swift.Error {
+    /// No file with the given filename is known to the `MultiFileTestProject`.
+    case fileNotFound
+  }
+
+  /// The directory in which the temporary files are being placed.
+  public let scratchDirectory: URL
+
+  /// Writes the specified files to a temporary directory on disk and creates a `TestSourceKitLSPClient` for that
+  /// temporary directory.
+  ///
+  /// The file contents can contain location markers, which are returned when opening a document using
+  /// ``openDocument(_:)``.
+  ///
+  /// File contents can also contain `$TEST_DIR`, which gets replaced by the temporary directory.
+  public init(
+    files: [RelativeFileLocation: String],
+    workspaces: (URL) -> [WorkspaceFolder] = { [WorkspaceFolder(uri: DocumentURI($0))] },
+    usePullDiagnostics: Bool = true,
+    testName: String = #function
+  ) async throws {
+    scratchDirectory = try testScratchDir(testName: testName)
+    try FileManager.default.createDirectory(at: scratchDirectory, withIntermediateDirectories: true)
+
+    var fileData: [String: FileData] = [:]
+    for (fileLocation, markedText) in files {
+      let markedText = markedText.replacingOccurrences(of: "$TEST_DIR", with: scratchDirectory.path)
+      var fileURL = scratchDirectory
+      for directory in fileLocation.directories {
+        fileURL = fileURL.appendingPathComponent(directory)
+      }
+      fileURL = fileURL.appendingPathComponent(fileLocation.fileName)
+      try FileManager.default.createDirectory(
+        at: fileURL.deletingLastPathComponent(),
+        withIntermediateDirectories: true
+      )
+      try extractMarkers(markedText).textWithoutMarkers.write(to: fileURL, atomically: false, encoding: .utf8)
+
+      if fileData[fileLocation.fileName] != nil {
+        // If we already have a file with this name, remove its data. That way we can't reference any of the two
+        // conflicting documents and will throw when trying to open them, instead of non-deterministically picking one.
+        fileData[fileLocation.fileName] = nil
+      } else {
+        fileData[fileLocation.fileName] = FileData(
+          uri: DocumentURI(fileURL),
+          markedText: markedText
+        )
+      }
+    }
+    self.fileData = fileData
+
+    self.testClient = try await TestSourceKitLSPClient(
+      usePullDiagnostics: usePullDiagnostics,
+      workspaceFolders: workspaces(scratchDirectory),
+      cleanUp: { [scratchDirectory] in
+        if cleanScratchDirectories {
+          try? FileManager.default.removeItem(at: scratchDirectory)
+        }
+      }
+    )
+  }
+
+  /// Opens the document with the given file name in the SourceKit-LSP server.
+  ///
+  /// - Returns: The URI for the opened document and the positions of the location markers.
+  public func openDocument(_ fileName: String, language: Language? = nil) throws -> (
+    uri: DocumentURI, positions: DocumentPositions
+  ) {
+    guard let fileData = self.fileData[fileName] else {
+      throw Error.fileNotFound
+    }
+    let positions = testClient.openDocument(fileData.markedText, uri: fileData.uri, language: language)
+    return (fileData.uri, positions)
+  }
+
+  /// Returns the URI of the file with the given name.
+  public func uri(for fileName: String) throws -> DocumentURI {
+    guard let fileData = self.fileData[fileName] else {
+      throw Error.fileNotFound
+    }
+    return fileData.uri
+  }
+
+  /// Returns the position of the given marker in the given file.
+  public func position(of marker: String, in fileName: String) throws -> Position {
+    guard let fileData = self.fileData[fileName] else {
+      throw Error.fileNotFound
+    }
+    return DocumentPositions(markedText: fileData.markedText)[marker]
+  }
+}