From 0d6a6a1cea1dd30e92057fcc1f310a9d11415ae9 Mon Sep 17 00:00:00 2001
From: William Laverty <wlaverty13@gmail.com>
Date: Mon, 2 Feb 2026 01:02:23 -0800
Subject: [PATCH] Handle non-JSON error payloads gracefully

Fixes #136

When a registry returns an error response with a non-JSON body (e.g.,
plain text like 'page not found'), ContainerRegistry now catches the
DecodingError and throws a more informative RegistryClientError with
the HTTP status code and raw response body, instead of propagating
the confusing JSONDecoder error.

Added new error case:
- RegistryClientError.unexpectedRegistryResponse(status:body:)

This provides clearer error messages when registries don't follow
the OCI distribution spec for error responses.
---
 .../ContainerRegistry/RegistryClient.swift    | 23 +++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/Sources/ContainerRegistry/RegistryClient.swift b/Sources/ContainerRegistry/RegistryClient.swift
index 41fcfda..474ab40 100644
--- a/Sources/ContainerRegistry/RegistryClient.swift
+++ b/Sources/ContainerRegistry/RegistryClient.swift
@@ -26,6 +26,7 @@ public enum RegistryClientError: Error {
     case invalidUploadLocation(String)
     case invalidDigestAlgorithm(String)
     case digestMismatch(expected: String, registry: String)
+    case unexpectedRegistryResponse(status: Int, body: String)
 }
 
 extension RegistryClientError: CustomStringConvertible {
@@ -38,6 +39,8 @@ extension RegistryClientError: CustomStringConvertible {
         case let .invalidDigestAlgorithm(digest): return "Invalid or unsupported digest algorithm: \(digest)"
         case let .digestMismatch(expected, registry):
             return "Digest mismatch: expected \(expected), registry sent \(registry)"
+        case let .unexpectedRegistryResponse(status, body):
+            return "Registry returned HTTP \(status): \(body)"
         }
     }
 }
@@ -369,8 +372,14 @@ extension RegistryClient {
         } catch HTTPClientError.unexpectedStatusCode(let status, _, let .some(responseData))
             where errors.contains(status)
         {
-            let decoded = try decoder.decode(DistributionErrors.self, from: responseData)
-            throw decoded
+            // Try to decode as JSON; if that fails, throw a generic error with the raw response body
+            do {
+                let decoded = try decoder.decode(DistributionErrors.self, from: responseData)
+                throw decoded
+            } catch is DecodingError {
+                let bodyText = String(data: responseData, encoding: .utf8) ?? "<non-UTF8 response>"
+                throw RegistryClientError.unexpectedRegistryResponse(status: status.code, body: bodyText)
+            }
         }
     }
 
@@ -410,8 +419,14 @@ extension RegistryClient {
         } catch HTTPClientError.unexpectedStatusCode(let status, _, let .some(responseData))
             where errors.contains(status)
         {
-            let decoded = try decoder.decode(DistributionErrors.self, from: responseData)
-            throw decoded
+            // Try to decode as JSON; if that fails, throw a generic error with the raw response body
+            do {
+                let decoded = try decoder.decode(DistributionErrors.self, from: responseData)
+                throw decoded
+            } catch is DecodingError {
+                let bodyText = String(data: responseData, encoding: .utf8) ?? "<non-UTF8 response>"
+                throw RegistryClientError.unexpectedRegistryResponse(status: status.code, body: bodyText)
+            }
         }
     }