ContainerRegistry: Reject capital letters in repository names

Author: euanh

Sources/ContainerRegistry/ImageReference.swift

@@ -16,6 +16,7 @@ import RegexBuilder
 
 public enum ReferenceError: Error, Equatable {
     case emptyString
+    case containsUppercaseLetters(String)
     case unexpected(String)
 }
 
@@ -61,6 +62,10 @@ public struct Repository: Sendable, Equatable, CustomStringConvertible, CustomDe
             throw ReferenceError.emptyString
         }
 
+        if (rawValue.contains { $0.isUppercase }) {
+            throw ReferenceError.containsUppercaseLetters(rawValue)
+        }
+
         value = rawValue
     }
 

Tests/ContainerRegistryTests/ImageReferenceTests.swift

@@ -134,6 +134,18 @@ struct ReferenceTests {
         #expect(throws: ReferenceError.emptyString) {
             try ImageReference(fromString: "", defaultRegistry: "default")
         }
+
+        #expect(throws: ReferenceError.emptyString) {
+            try ImageReference(fromString: "example.com/")
+        }
+
+        #expect(throws: ReferenceError.containsUppercaseLetters("helloWorld")) {
+            try ImageReference(fromString: "helloWorld", defaultRegistry: "default")
+        }
+
+        #expect(throws: ReferenceError.containsUppercaseLetters("helloWorld")) {
+            try ImageReference(fromString: "localhost:5555/helloWorld")
+        }
     }
 
     @Test