Implement Data.init(contentsOf:ifNoFile:) for case when file does not…

… exist

Sources/SpellbookFoundation/Common/Extensions - StandardTypes.swift

@@ -97,6 +97,38 @@ extension Data {
     }
 }
 
+extension Data {
+    /// Initialize a `Data` with the contents of a `URL` or 
+    /// empty Data if URL is a file that does not exist.
+    ///
+    /// - parameter url: The `URL` to read.
+    /// - parameter options: Options for the read operation. Default value is `[]`.
+    /// - parameter ifNoFile: Optional `Data` replacement if a file does not exist.
+    /// - throws: An error in the Cocoa domain, if `url` cannot be read.
+    public init(contentsOf url: URL, options: Data.ReadingOptions = [], ifNoFile replacementContent: Data?) throws {
+        do {
+            try self.init(contentsOf: url, options: options)
+        } catch let error as CocoaError where [.fileNoSuchFile, .fileReadNoSuchFile].contains(error.code) {
+            if let replacementContent {
+                self = replacementContent
+            } else {
+                throw error
+            }
+        }
+    }
+
+    /// Initialize a `Data` with the contents of a file at path or
+    /// empty Data if URL is a file that does not exist.
+    ///
+    /// - parameter path: File path to read.
+    /// - parameter options: Options for the read operation. Default value is `[]`.
+    /// - parameter ifNoFile: Optional `Data` replacement if a file does not exist.
+    /// - throws: An error in the Cocoa domain, if `url` cannot be read.
+    public init(contentsOfFile path: String, options: Data.ReadingOptions = [], ifNoFile replacementContent: Data? = nil) throws {
+        try self.init(contentsOf: URL(fileURLWithPath: path), options: options, ifNoFile: replacementContent)
+    }
+}
+
 // MARK: - URL
 
 extension URL {

Sources/SpellbookFoundation/Filesystem & Bundle/FileStore.swift

@@ -49,10 +49,7 @@ extension FileStore where T == Data {
     public static var standard: FileStore {
         FileStore(
             read: { location, ifNotExists in
-                if let ifNotExists, !FileManager.default.fileExists(at: location) {
-                    return ifNotExists
-                }
-                return try Data(contentsOf: location)
+                try Data(contentsOf: location, ifNoFile: ifNotExists)
             },
             write: { data, location, createDirectories in
                 if createDirectories {

Tests/SpellbookTests/Extensions Tests/StandardTypesTests.swift

@@ -4,6 +4,18 @@ import SpellbookTestUtils
 import XCTest
 
 class StandardTypesExtensionsTests: XCTestCase {
+    private let tmp = TestTemporaryDirectory()
+
+    override func setUpWithError() throws {
+        try tmp.setUp()
+    }
+
+    override func tearDownWithError() throws {
+        try tmp.tearDown()
+    }
+}
+
+extension StandardTypesExtensionsTests {
     func test_Error_unwrapSafely() {
         let error: Error? = TestError()
         let unwrapped = error.safelyUnwrapped
@@ -34,7 +46,9 @@ class StandardTypesExtensionsTests: XCTestCase {
         let xpcCompatible = error.xpcCompatible()
         XCTAssertNoThrow(try NSKeyedArchiver.archivedData(withRootObject: xpcCompatible, requiringSecureCoding: true))
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_Result_success_failure() {
         let resultWithValue: Result<Bool, Error> = .success(true)
         XCTAssertEqual(resultWithValue.success, true)
@@ -57,7 +71,9 @@ class StandardTypesExtensionsTests: XCTestCase {
         XCTAssertEqual(Result<Int?, Error>(success: nil, failure: TestError()).success, nil)
         XCTAssertNotNil(Result<Int?, Error>(success: nil as Int??, failure: TestError()).failure)
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_Data_PODTypes_toData() {
         XCTAssertEqual(Data(pod: 0x10ff20), Data([0x20, 0xff, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00]))
         XCTAssertEqual(Data(pod: 0), Data([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]))
@@ -116,6 +132,22 @@ class StandardTypesExtensionsTests: XCTestCase {
         )
     }
 
+    func test_Data_contentsOfIfExists() throws {
+        let nonexistentFile = "/\(UUID().uuidString)"
+        let emptyFile = try tmp.createFile("f1")
+        let nonemptyFile = try tmp.createFile("f2", content: Data(pod: 123))
+
+        let ifNoFile = Data(pod: 2)
+        XCTAssertEqual(try Data(contentsOfFile: nonexistentFile, ifNoFile: ifNoFile), ifNoFile)
+        XCTAssertEqual(try Data(contentsOf: emptyFile, ifNoFile: ifNoFile), Data())
+        XCTAssertEqual(try Data(contentsOf: nonemptyFile, ifNoFile: ifNoFile), Data(pod: 123))
+
+        XCTAssertThrowsError(try Data(contentsOfFile: "/etc/sudoers")) // No such file.
+        XCTAssertThrowsError(try Data(contentsOfFile: "/etc/sudoers", ifNoFile: Data())) // Permissions denied.
+    }
+}
+
+extension StandardTypesExtensionsTests {
     func test_Comparable_clamped() {
         XCTAssertEqual(5.clamped(to: 0 ... 10), 5)
         XCTAssertEqual(5.clamped(to: 5 ... 10), 5)
@@ -153,19 +185,25 @@ class StandardTypesExtensionsTests: XCTestCase {
         XCTAssertTrue(10.compare(to: 10, relation: .greaterThanOrEqual))
         XCTAssertFalse(10.compare(to: 11, relation: .greaterThanOrEqual))
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_URL_ensureFileURL() throws {
         XCTAssertNoThrow(try URL(fileURLWithPath: "relative").ensureFileURL())
         XCTAssertNoThrow(try URL(fileURLWithPath: "/absolute").ensureFileURL())
         XCTAssertNoThrow(try URL(fileURLWithPath: "/absolute/dir").ensureFileURL())
 
         XCTAssertThrowsError(try URL(staticString: "https://remote.com").ensureFileURL())
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_UUID_zero() {
         XCTAssertEqual(UUID.zero.uuidString, "00000000-0000-0000-0000-000000000000")
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_String_parseKeyValuePair() throws {
         XCTAssertThrowsError(try "".parseKeyValuePair(separator: ""))
         XCTAssertThrowsError(try "keyvalue".parseKeyValuePair(separator: "="))
@@ -189,7 +227,9 @@ class StandardTypesExtensionsTests: XCTestCase {
             [KeyValue("key1", "value1"), KeyValue("key1", "value2"), KeyValue("key3", "value3")]
         )
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_TimeInterval_fromTimespec() {
         let ts = timespec(tv_sec: 123, tv_nsec: 456)
         XCTAssertEqual(TimeInterval(ts: ts), 123.000000456, accuracy: 1 / Double(NSEC_PER_SEC))
@@ -200,7 +240,9 @@ class StandardTypesExtensionsTests: XCTestCase {
         let ts3 = timespec(tv_sec: 123, tv_nsec: 990_000_000)
         XCTAssertEqual(TimeInterval(ts: ts3), 123.990000000, accuracy: 1 / Double(NSEC_PER_SEC))
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_Date_fromTimespec() {
         let ts = timespec(tv_sec: 123, tv_nsec: 456)
         XCTAssertEqual(Date(ts: ts).timeIntervalSince1970, 123.000000456, accuracy: 100 / Double(NSEC_PER_SEC))
@@ -211,7 +253,9 @@ class StandardTypesExtensionsTests: XCTestCase {
         let ts3 = timespec(tv_sec: 123, tv_nsec: 990_000_000)
         XCTAssertEqual(Date(ts: ts3).timeIntervalSince1970, 123.990000000, accuracy: 100 / Double(NSEC_PER_SEC))
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_Calendar_endOfDay() {
         // GMT: Friday, 7 April 2023 y., 10:46:19
         let date = Date(timeIntervalSince1970: 1680864379)
@@ -227,7 +271,9 @@ class StandardTypesExtensionsTests: XCTestCase {
         // GMT: Saturday, 8 April 2023 y., 00:00:00
         XCTAssertLessThan(dayEnd, Date(timeIntervalSince1970: 1680912000))
     }
-
+}
+
+extension StandardTypesExtensionsTests {
     func test_Optional_default() {
         var value: Int? = nil
         XCTAssertEqual(value[default: 10], 10)