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Add type-erased AnyError for generic contexts #198

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merged 6 commits into from
Nov 29, 2016
Merged

Add type-erased AnyError for generic contexts #198

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7b1d6ab
Add type-erased `AnyError` for generic contexts
ikesyo Nov 14, 2016
a7d0cdc
[AnyError] Add CustomStringConvertible conformance
ikesyo Nov 14, 2016
fd89d0e
Fix typo
ikesyo Nov 15, 2016
3cafe3e
[AnyError] Remove Equatable conformance
ikesyo Nov 15, 2016
1a12328
[AnyError] initializer: Check if the given error is AnyError
ikesyo Nov 15, 2016
aac425d
[AnyError] Separate protocol conformances from the type
ikesyo Nov 28, 2016
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45 changes: 44 additions & 1 deletion Result/Result.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -108,10 +108,26 @@ public enum Result<T, Error: Swift.Error>: ResultProtocol, CustomStringConvertib

// MARK: - Derive result from failable closure

public func materialize<T>(_ f: () throws -> T) -> Result<T, AnyError> {
return materialize(try f())
}

public func materialize<T>(_ f: @autoclosure () throws -> T) -> Result<T, AnyError> {
do {
return .success(try f())
} catch let error as AnyError {
return .failure(error)
} catch {
return .failure(AnyError(error))
}
}

@available(*, deprecated, message: "Use the overload which returns `Result<T, AnyError>` instead")
public func materialize<T>(_ f: () throws -> T) -> Result<T, NSError> {
return materialize(try f())
}

@available(*, deprecated, message: "Use the overload which returns `Result<T, AnyError>` instead")
public func materialize<T>(_ f: @autoclosure () throws -> T) -> Result<T, NSError> {
do {
return .success(try f())
Expand Down Expand Up @@ -160,7 +176,7 @@ extension NSError: ErrorProtocolConvertible {
}
}

// MARK: -
// MARK: - Errors

/// An “error” that is impossible to construct.
///
Expand All @@ -169,6 +185,33 @@ extension NSError: ErrorProtocolConvertible {
/// contains an `Int`eger and is guaranteed never to be a `failure`.
public enum NoError: Swift.Error { }

/// A type-erased error which wraps an arbitrary error instance. This should be
/// useful for generic contexts.
public struct AnyError: Swift.Error, ErrorProtocolConvertible, Equatable, CustomStringConvertible {
/// The underlying error.
public let error: Swift.Error

public init(_ error: Swift.Error) {
self.error = error
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Don't we need to check if error is AnyError?

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Addressed in 1a12328.

}

public static func error(from error: Error) -> AnyError {
if let anyError = error as? AnyError {
return anyError
}
return AnyError(error)
}

public static func ==(lhs: AnyError, rhs: AnyError) -> Bool {
return lhs.error._code == rhs.error._code
&& lhs.error._domain == rhs.error._domain
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@norio-nomura norio-nomura Nov 15, 2016 •
edited
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_domain should be compared before _code.

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Sorry, I withdraw my comment.

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Quick question: Are _domain and _code allowed to use?

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Are _domain and _code allowed to use?

I'm not confident. It should be okay to remove Equatable conformance (in that case use them for testing purpose only).

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I'm not confident. It should be okay to remove Equatable conformance (in that case use them for testing purpose only).

+1. I also think removing Equatable is safer to ship :shipit:

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Addressed in 3cafe3e.

}

public var description: String {
return String(describing: error)
}
}

// MARK: - migration support
extension Result {
@available(*, unavailable, renamed: "success")
Expand Down
74 changes: 28 additions & 46 deletions Tests/ResultTests/ResultTests.swift
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Expand Up @@ -38,71 +38,54 @@ final class ResultTests: XCTestCase {
// MARK: Try - Catch

func testTryCatchProducesSuccesses() {
let result: Result<String, NSError> = Result(try tryIsSuccess("success"))
let result: Result<String, AnyError> = Result(try tryIsSuccess("success"))
XCTAssert(result == success)
}

func testTryCatchProducesFailures() {
#if os(Linux)
/// FIXME: skipped on Linux because of crash with swift-3.0-PREVIEW-4.
print("Test Case `\(#function)` skipped on Linux because of crash with swift-3.0-PREVIEW-4.")
#else
let result: Result<String, NSError> = Result(try tryIsSuccess(nil))
XCTAssert(result.error == error)
#endif
let result: Result<String, AnyError> = Result(try tryIsSuccess(nil))
XCTAssert(result.error == error)
}

func testTryCatchWithFunctionProducesSuccesses() {
let function = { try tryIsSuccess("success") }

let result: Result<String, NSError> = Result(attempt: function)
let result: Result<String, AnyError> = Result(attempt: function)
XCTAssert(result == success)
}

func testTryCatchWithFunctionCatchProducesFailures() {
#if os(Linux)
/// FIXME: skipped on Linux because of crash with swift-3.0-PREVIEW-4.
print("Test Case `\(#function)` skipped on Linux because of crash with swift-3.0-PREVIEW-4.")
#else
let function = { try tryIsSuccess(nil) }

let result: Result<String, NSError> = Result(attempt: function)
XCTAssert(result.error == error)
#endif
let function = { try tryIsSuccess(nil) }

let result: Result<String, AnyError> = Result(attempt: function)
XCTAssert(result.error == error)
}

func testMaterializeProducesSuccesses() {
let result1 = materialize(try tryIsSuccess("success"))
let result1: Result<String, AnyError> = materialize(try tryIsSuccess("success"))
XCTAssert(result1 == success)

let result2: Result<String, NSError> = materialize { try tryIsSuccess("success") }
let result2: Result<String, AnyError> = materialize { try tryIsSuccess("success") }
XCTAssert(result2 == success)
}

func testMaterializeProducesFailures() {
#if os(Linux)
/// FIXME: skipped on Linux because of crash with swift-3.0-PREVIEW-4.
print("Test Case `\(#function)` skipped on Linux because of crash with swift-3.0-PREVIEW-4.")
#else
let result1 = materialize(try tryIsSuccess(nil))
XCTAssert(result1.error == error)

let result2: Result<String, NSError> = materialize { try tryIsSuccess(nil) }
XCTAssert(result2.error == error)
#endif
let result1: Result<String, AnyError> = materialize(try tryIsSuccess(nil))
XCTAssert(result1.error == error)

let result2: Result<String, AnyError> = materialize { try tryIsSuccess(nil) }
XCTAssert(result2.error == error)
}

// MARK: Recover

func testRecoverProducesLeftForLeftSuccess() {
let left = Result<String, NSError>.success("left")
let left = Result<String, Error>.success("left")
XCTAssertEqual(left.recover("right"), "left")
}

func testRecoverProducesRightForLeftFailure() {
struct Error: Swift.Error {}

let left = Result<String, Error>.failure(Error())
let left = Result<String, Error>.failure(Error.a)
XCTAssertEqual(left.recover("right"), "right")
}

Expand Down Expand Up @@ -169,13 +152,8 @@ final class ResultTests: XCTestCase {
}

func testTryMapProducesFailure() {
#if os(Linux)
/// FIXME: skipped on Linux because of crash with swift-3.0-PREVIEW-4.
print("Test Case `\(#function)` skipped on Linux because of crash with swift-3.0-PREVIEW-4.")
#else
let result = Result<String, NSError>.success("fail").tryMap(tryIsSuccess)
XCTAssert(result == failure)
#endif
let result = Result<String, AnyError>.success("fail").tryMap(tryIsSuccess)
XCTAssert(result == failure)
}

// MARK: Operators
Expand All @@ -202,11 +180,15 @@ final class ResultTests: XCTestCase {

// MARK: - Fixtures

let success = Result<String, NSError>.success("success")
let error = NSError(domain: "com.antitypical.Result", code: 1, userInfo: nil)
let error2 = NSError(domain: "com.antitypical.Result", code: 2, userInfo: nil)
let failure = Result<String, NSError>.failure(error)
let failure2 = Result<String, NSError>.failure(error2)
private enum Error: Swift.Error {
case a, b
}

let success = Result<String, AnyError>.success("success")
let error = AnyError(Error.a)
let error2 = AnyError(Error.b)
let failure = Result<String, AnyError>.failure(error)
let failure2 = Result<String, AnyError>.failure(error2)


// MARK: - Helpers
Expand Down