Preserve inner error type

Author: finestructure

Sources/Retry/Retry.swift

@@ -16,8 +16,8 @@ import Foundation
 
 
 public enum Retry {
-    public enum Error: Swift.Error, Equatable {
-        case retryLimitExceeded(lastError: String?)
+    public enum Error: Swift.Error {
+        case retryLimitExceeded(lastError: Swift.Error?)
     }
 
     public static func backedOffDelay(baseDelay: Double, attempt: Int) -> UInt32 {
@@ -32,7 +32,7 @@ public enum Retry {
                                   _ block: () throws -> T) throws -> T {
         var retriesLeft = retries
         var currentTry = 1
-        var lastError: String?
+        var lastError: Swift.Error?
         while true {
             if currentTry > 1 {
                 logger.onStartOfRetry(label: label, attempt: currentTry)
@@ -41,7 +41,7 @@ public enum Retry {
                 return try block()
             } catch {
                 logger.onError(label: label, error: error)
-                lastError = "\(error)"
+                lastError = error
                 guard retriesLeft > 0 else { break }
                 let delay = backedOffDelay(baseDelay: delay, attempt: currentTry)
                 logger.onStartOfDelay(label: label, delay: Double(delay))
@@ -61,7 +61,7 @@ public enum Retry {
                                   _ block: () async throws -> T) async throws -> T {
         var retriesLeft = retries
         var currentTry = 1
-        var lastError: String?
+        var lastError: Swift.Error?
         while true {
             if currentTry > 1 {
                 logger.onStartOfRetry(label: label, attempt: currentTry)
@@ -70,7 +70,7 @@ public enum Retry {
                 return try await block()
             } catch {
                 logger.onError(label: label, error: error)
-                lastError = "\(error)"
+                lastError = error
                 guard retriesLeft > 0 else { break }
                 let delay = backedOffDelay(baseDelay: delay, attempt: currentTry)
                 logger.onStartOfDelay(label: label, delay: Double(delay))

Tests/RetryTests/RetryTests.swift

@@ -60,14 +60,16 @@ final class RetryTests: XCTestCase {
         }
 
         // MUT
-        XCTAssertThrowsError(
+        do {
             try Retry.attempt("", delay: 0, retries: 3) {
                 called += 1
                 throw Error()
             }
-
-        ) { error in
-            XCTAssertEqual(error as? Retry.Error, .retryLimitExceeded(lastError: "test error"))
+            XCTFail("expected an error to be thrown")
+        } catch let Retry.Error.retryLimitExceeded(lastError: .some(error)) {
+            XCTAssertEqual("\(error)", "test error")
+        } catch {
+            XCTFail("unexpected error: \(error)")
         }
 
         // validation