Process: .currentDirectoryURL and .executableURL fixes

- currentDirectoryURL should be of type URL?

- Disallow setting either property to nil or a non-File URL,
  to match Darwin.

- PWD environment variable should be set to the current directory of
  the parent, to match Darwin.

Author: spevans

Foundation/Process.swift

@@ -232,8 +232,28 @@ open class Process: NSObject {
     }
 
     // These properties can only be set before a launch.
-    open var executableURL: URL?
-    open var currentDirectoryURL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath, isDirectory: true)
+    private var _executable: URL?
+    open var executableURL: URL? {
+        get { _executable }
+        set {
+            guard let url = newValue, url.isFileURL else {
+                fatalError("must provide a launch path")
+            }
+            _executable = url
+        }
+    }
+
+    private var _currentDirectoryURL: URL? = URL(fileURLWithPath: FileManager.default.currentDirectoryPath, isDirectory: true)
+    open var currentDirectoryURL: URL? {
+        get { _currentDirectoryURL }
+        set {
+            guard let url = newValue, url.isFileURL else {
+                fatalError("non-file URL argument")
+            }
+            _currentDirectoryURL = url
+        }
+    }
+
     open var arguments: [String]?
     open var environment: [String : String]? // if not set, use current
 
@@ -245,7 +265,7 @@ open class Process: NSObject {
 
     @available(*, deprecated, renamed: "currentDirectoryURL")
     open var currentDirectoryPath: String {
-        get { return currentDirectoryURL.path }
+        get { return currentDirectoryURL!.path }
         set { currentDirectoryURL = URL(fileURLWithPath: newValue) }
     }
 
@@ -478,8 +498,8 @@ open class Process: NSObject {
         if let env = self.environment {
           environment = env
         } else {
-          environment = ProcessInfo.processInfo.environment
-          environment["PWD"] = currentDirectoryURL.path
+            environment = ProcessInfo.processInfo.environment
+            environment["PWD"] = FileManager.default.currentDirectoryPath
         }
 
         // On Windows, the PATH is required in order to locate dlls needed by
@@ -658,7 +678,7 @@ open class Process: NSObject {
             env = e
         } else {
             env = ProcessInfo.processInfo.environment
-            env["PWD"] = currentDirectoryURL.path
+            env["PWD"] = FileManager.default.currentDirectoryPath
         }
 
         let nenv = env.count
@@ -839,7 +859,7 @@ open class Process: NSObject {
 
         let fileManager = FileManager()
         let previousDirectoryPath = fileManager.currentDirectoryPath
-        if !fileManager.changeCurrentDirectoryPath(currentDirectoryURL.path) {
+        if let dir = currentDirectoryURL?.path, !fileManager.changeCurrentDirectoryPath(dir) {
             throw _NSErrorWithErrno(errno, reading: true, url: currentDirectoryURL)
         }
 

TestFoundation/TestProcess.swift

@@ -265,7 +265,7 @@ class TestProcess : XCTestCase {
         do {
             let (pwd, _) = try runTask([xdgTestHelperURL().path, "--getcwd"], currentDirectoryPath: tmpDir)
             // Check the sub-process used the correct directory
-            XCTAssertEqual(pwd.trimmingCharacters(in: .newlines), tmpDir)
+            XCTAssertEqual(pwd.trimmingCharacters(in: .newlines).standardizePath(), tmpDir.standardizePath())
         } catch {
             XCTFail("Test failed: \(error)")
         }
@@ -274,7 +274,9 @@ class TestProcess : XCTestCase {
         do {
             let (pwd, _) = try runTask([xdgTestHelperURL().path, "--echo-PWD"], currentDirectoryPath: tmpDir)
             // Check the sub-process used the correct directory
-            XCTAssertEqual(pwd.trimmingCharacters(in: .newlines), tmpDir)
+            let cwd = FileManager.default.currentDirectoryPath
+            XCTAssertNotEqual(tmpDir, cwd)
+            XCTAssertEqual(pwd.trimmingCharacters(in: .newlines), cwd)
         } catch {
             XCTFail("Test failed: \(error)")
         }
@@ -566,6 +568,42 @@ class TestProcess : XCTestCase {
     }
 
 
+    func test_currentDirectory() throws {
+
+        let process = Process()
+        XCTAssertNil(process.executableURL)
+        XCTAssertNotNil(process.currentDirectoryURL)
+        process.executableURL = URL(fileURLWithPath: "/some_file_that_doesnt_exist", isDirectory: false)
+        XCTAssertThrowsError(try process.run()) {
+            let code = CocoaError.Code(rawValue: ($0 as? NSError)!.code)
+            XCTAssertEqual(code, .fileReadNoSuchFile)
+        }
+
+        do {
+            let (stdout, _) = try runTask([xdgTestHelperURL().path, "--getcwd"], currentDirectoryPath: "/")
+            XCTAssertEqual(stdout.trimmingCharacters(in: CharacterSet(["\n", "\r"])), "/")
+        }
+
+        do {
+            XCTAssertNotEqual("/", FileManager.default.currentDirectoryPath)
+            XCTAssertNotEqual(FileManager.default.currentDirectoryPath, "/")
+            let (stdout, _) = try runTask([xdgTestHelperURL().path, "--echo-PWD"], currentDirectoryPath: "/")
+            let directory = stdout.trimmingCharacters(in: CharacterSet(["\n", "\r"]))
+            XCTAssertEqual(directory, FileManager.default.currentDirectoryPath)
+            XCTAssertNotEqual(directory, "/")
+        }
+
+        do {
+            try runTask([xdgTestHelperURL().path, "--getcwd"], currentDirectoryPath: "/some_directory_that_doesnt_exsit")
+        } catch {
+            let code = CocoaError.Code(rawValue: (error as? NSError)!.code)
+            XCTAssertEqual(code, .fileReadNoSuchFile)
+            return
+        }
+        XCTFail("Failed to catch error")
+    }
+
+
     static var allTests: [(String, (TestProcess) -> () throws -> Void)] {
         var tests = [
             ("test_exit0" , test_exit0),
@@ -592,6 +630,7 @@ class TestProcess : XCTestCase {
             ("test_redirect_all_using_null", test_redirect_all_using_null),
             ("test_redirect_all_using_nil", test_redirect_all_using_nil),
             ("test_plutil", test_plutil),
+            ("test_currentDirectory", test_currentDirectory),
         ]
 
 #if !os(Windows)
@@ -690,6 +729,7 @@ class _SignalHelperRunner {
     }
 }
 
+@discardableResult
 internal func runTask(_ arguments: [String], environment: [String: String]? = nil, currentDirectoryPath: String? = nil) throws -> (String, String) {
     let process = Process()
 

TestFoundation/Utilities.swift

@@ -621,6 +621,12 @@ extension XCTest {
     }
 }
 
+extension String {
+    public func standardizePath() -> String {
+        URL(fileURLWithPath: self).resolvingSymlinksInPath().path
+    }
+}
+
 extension FileHandle: TextOutputStream {
     public func write(_ string: String) {
         write(Data(string.utf8))