Add more failure message context to XCT helpers (#109)

* Add more failure message context to XCT helpers

* wip

Sources/CasePaths/EnumReflection.swift

@@ -352,6 +352,10 @@ extension EnumMetadata {
 
  return type
  }
+
+ @_spi(Reflection) public func caseName(forTag tag: UInt32) -> String? {
+ self.typeDescriptor.fieldDescriptor?.field(atIndex: tag).name
+ }
 }
 
 @_silgen_name("swift_getTypeByMangledNameInContext")
@@ -541,6 +545,14 @@ private struct FieldRecord {
  .loadRelativePointer()
  .map { MangledTypeName(ptr: $0.assumingMemoryBound(to: UInt8.self)) }
  }
+
+ var name: String? {
+ self.ptr
+ .advanced(by: 4)
+ .advanced(by: 4)
+ .loadRelativePointer()
+ .map { String(cString: $0.assumingMemoryBound(to: CChar.self)) }
+ }
 }
 
 extension FieldRecord {

Sources/CasePaths/XCTUnwrap.swift

@@ -4,28 +4,33 @@ import Foundation
 /// Asserts that an enum value matches a particular case and returns the associated value.
 ///
 /// - Parameters:
-/// - expression: An enum value.
+/// - enum: An enum value.
 /// - extract: A closure that attempts to extract a particular case from the enum. You can supply
 /// a case path literal here, like '/Enum.case'.
 /// - message: An optional description of a failure.
 /// - Returns: The unwrapped associated value from the matched case of the enum.
-public func XCTUnwrap<Root, Case>(
- _ expression: @autoclosure () throws -> Root,
- case extract: (Root) -> Case?,
+public func XCTUnwrap<Enum, Case>(
+ _ enum: @autoclosure () throws -> Enum,
+ case extract: (Enum) -> Case?,
  _ message: @autoclosure () -> String = "",
  file: StaticString = #file,
  line: UInt = #line
 ) throws -> Case {
- guard let value = try extract(expression())
+ let `enum` = try `enum`()
+ guard let value = extract(`enum`)
  else {
  #if canImport(ObjectiveC)
  _ = XCTCurrentTestCase?.perform(Selector(("setContinueAfterFailure:")), with: false)
  #endif
  let message = message()
  XCTFail(
  """
- XCTUnwrap failed: expected non-nil value of type "\(typeName(Case.self))"\
- \(message.isEmpty ? "" : " - " + message)
+ XCTUnwrap failed: expected to extract value of type "\(typeName(Case.self))" from \
+ "\(typeName(Enum.self))"\
+ \(message.isEmpty ? "" : " - " + message) …
+
+ Actual:
+ \(String(describing: `enum`))
  """,
  file: file,
  line: line
@@ -38,19 +43,19 @@ public func XCTUnwrap<Root, Case>(
 /// Asserts that an enum value matches a particular case and modifies the associated value in place.
 ///
 /// - Parameters:
-/// - root: An enum value.
+/// - enum: An enum value.
 /// - casePath: A case path that can extract and embed the associated value of a particular case.
 /// - message: An optional description of a failure.
 /// - body: A closure that can modify the associated value of the given case.
-public func XCTModify<Root, Case>(
- _ root: inout Root,
- case casePath: CasePath<Root, Case>,
+public func XCTModify<Enum, Case>(
+ _ enum: inout Enum,
+ case casePath: CasePath<Enum, Case>,
  _ message: @autoclosure () -> String = "",
  _ body: (inout Case) throws -> Void,
  file: StaticString = #file,
  line: UInt = #line
 ) {
- guard var value = casePath.extract(from: root)
+ guard var value = casePath.extract(from: `enum`)
  else {
  #if canImport(ObjectiveC)
  _ = XCTCurrentTestCase?.perform(Selector(("setContinueAfterFailure:")), with: false)
@@ -59,8 +64,11 @@ public func XCTModify<Root, Case>(
  XCTFail(
  """
  XCTModify failed: expected to extract value of type "\(typeName(Case.self))" from \
- "\(typeName(Root.self))"\
- \(message.isEmpty ? "" : " - " + message)
+ "\(typeName(Enum.self))"\
+ \(message.isEmpty ? "" : " - " + message) …
+
+ Actual:
+ \(`enum`)
  """,
  file: file,
  line: line
@@ -85,7 +93,7 @@ public func XCTModify<Root, Case>(
  """)
  }
 
- root = casePath.embed(value)
+ `enum` = casePath.embed(value)
 }
 
 @_spi(Internals) public enum XCTModifyLocals {

Tests/CasePathsTests/XCTModifyTests.swift

@@ -3,12 +3,15 @@
  import XCTest
 
  final class XCTModifyTests: XCTestCase {
- func testXCTModiftyFailure() throws {
+ func testXCTModifyFailure() throws {
  try XCTSkipIf(ProcessInfo.processInfo.environment["CI"] != nil)
 
  XCTExpectFailure {
  $0.compactDescription == """
- XCTModify failed: expected to extract value of type "Int" from "Result<Int, Error>"
+ XCTModify failed: expected to extract value of type "Int" from "Result<Int, Error>" …
+
+ Actual:
+ failure(CasePathsTests.SomeError())
  """
  }
 
@@ -18,13 +21,16 @@
  }
  }
 
- func testXCTModiftyFailure_OptionalPromotion() throws {
+ func testXCTModifyFailure_OptionalPromotion() throws {
  try XCTSkipIf(ProcessInfo.processInfo.environment["CI"] != nil)
 
  XCTExpectFailure {
  $0.compactDescription == """
  XCTModify failed: expected to extract value of type "Sheet.State" from \
- "Destination.State?"
+ "Destination.State?" …
+
+ Actual:
+ Optional(CasePathsTests.Destination.State.alert)
  """
  }
 
@@ -34,13 +40,16 @@
  }
  }
 
- func testXCTModiftyFailure_Nil_OptionalPromotion() throws {
+ func testXCTModifyFailure_Nil_OptionalPromotion() throws {
  try XCTSkipIf(ProcessInfo.processInfo.environment["CI"] != nil)
 
  XCTExpectFailure {
  $0.compactDescription == """
  XCTModify failed: expected to extract value of type "Int" from \
- "Optional<Result<Int, Error>>"
+ "Optional<Result<Int, Error>>" …
+
+ Actual:
+ nil
  """
  }
 
@@ -56,7 +65,10 @@
  XCTExpectFailure {
  $0.compactDescription == """
  XCTModify failed: expected to extract value of type "Int" from "Result<Int, Error>" - \
- Should be success
+ Should be success …
+
+ Actual:
+ failure(CasePathsTests.SomeError())
  """
  }
 
@@ -131,7 +143,7 @@
  }
  }
 
- private struct SomeError: Error, Equatable {}
+ struct SomeError: Error, Equatable {}
 
  struct Sheet {
  struct State {

Tests/CasePathsTests/XCTUnwrapTests.swift

@@ -8,7 +8,10 @@
 
  XCTExpectFailure {
  $0.compactDescription == """
- XCTUnwrap failed: expected non-nil value of type "Error"
+ XCTUnwrap failed: expected to extract value of type "Error" from "Result<Int, Error>" …
+
+ Actual:
+ success(2)
  """
  }
  _ = try XCTUnwrap(Result<Int, Error>.success(2), case: /Result.failure)
@@ -19,10 +22,14 @@
 
  XCTExpectFailure {
  $0.compactDescription == """
- XCTUnwrap failed: expected non-nil value of type "Error" - Should be success
+ XCTUnwrap failed: expected to extract value of type "Error" from "Result<Int, Error>" - \
+ Should be 'failure' …
+
+ Actual:
+ success(2)
  """
  }
- _ = try XCTUnwrap(Result<Int, Error>.success(2), case: /Result.failure, "Should be success")
+ _ = try XCTUnwrap(Result<Int, Error>.success(2), case: /Result.failure, "Should be 'failure'")
  }
 
  func testXCTUnwrapPass() throws {