Merge pull request #894 from Quick/benil-for-nested-optional

Support nested optionals in `beNil` matcher

Author: ikesyo

Sources/Nimble/Matchers/BeNil.swift

@@ -1,7 +1,19 @@
+/// A protocol which represents whether the value is nil or not.
+private protocol _OptionalProtocol {
+    var isNil: Bool { get }
+}
+
+extension Optional: _OptionalProtocol {
+    var isNil: Bool { self == nil }
+}
+
 /// A Nimble matcher that succeeds when the actual value is nil.
 public func beNil<T>() -> Predicate<T> {
     return Predicate.simpleNilable("be nil") { actualExpression in
         let actualValue = try actualExpression.evaluate()
+        if let actual = actualValue, let nestedOptionl = actual as? _OptionalProtocol {
+            return PredicateStatus(bool: nestedOptionl.isNil)
+        }
         return PredicateStatus(bool: actualValue == nil)
     }
 }

Tests/NimbleTests/Matchers/AllPassTest.swift

@@ -76,10 +76,9 @@ final class AllPassTest: XCTestCase {
         }
     }
 
-    func testAllPassCollectionsWithOptionalsDontWork() {
-        failsWithErrorMessage("expected to all be nil, but failed first at element <nil> in <[nil, nil, nil]>") {
-            expect([nil, nil, nil] as [Int?]).to(allPass(beNil()))
-        }
+    func testAllPassCollectionsWithOptionals() {
+        expect([nil, nil, nil] as [Int?]).to(allPass(beNil()))
+
         failsWithErrorMessage("expected to all pass a condition, but failed first at element <nil> in <[nil, nil, nil]>") {
             expect([nil, nil, nil] as [Int?]).to(allPass({$0 == nil}))
         }