Update identity chain validation to use case-insensitive comparisons

packages/smithy-aws-core/.changes/next-release/smithy-aws-core-enhancement-14481b3143ee48f28828876920f5ff2f.json

@@ -0,0 +1,4 @@
+{
+  "type": "enhancement",
+  "description": "Update identity chain validation to use case-insensitive comparisons for provider names."
+}

packages/smithy-aws-core/src/smithy_aws_core/identity/chain/__init__.py

@@ -99,12 +99,13 @@ def _validate_providers(providers: Sequence[ChainIdentityProvider]) -> None:
     discovered_standard_slots: dict[StandardProvider, ChainIdentityProvider] = {}
 
     for provider in providers:
-        if (previous := discovered_names.get(provider.name)) is not None:
+        normalized_name = provider.name.casefold()
+        if (previous := discovered_names.get(normalized_name)) is not None:
             raise IdentityChainConfigurationError(
                 f"Credential providers {type(previous).__name__} and "
                 f"{type(provider).__name__} use the same name: {provider.name}."
             )
-        discovered_names[provider.name] = provider
+        discovered_names[normalized_name] = provider
 
         ordering = provider.ordering
         if isinstance(ordering, Standard):

packages/smithy-aws-core/tests/unit/identity/chain/test_chain.py

@@ -198,6 +198,18 @@ def test_validate_rejects_duplicate_names() -> None:
         chain_module._validate_providers((first, second))
 
 
+def test_validate_rejects_case_insensitive_duplicate_names() -> None:
+    first = _StubProvider("Duplicate", Standard(slot=StandardProvider.ENVIRONMENT))
+    second = _StubProvider("duplicate", Standard(slot=StandardProvider.SHARED_CONFIG))
+
+    with pytest.raises(
+        IdentityChainConfigurationError,
+        match="Credential providers _StubProvider and _StubProvider use the "
+        "same name: duplicate",
+    ):
+        chain_module._validate_providers((first, second))
+
+
 def test_validate_rejects_duplicate_standard_slots() -> None:
     first = _StubProvider("a", Standard(slot=StandardProvider.ENVIRONMENT))
     second = _StubProvider("b", Standard(slot=StandardProvider.ENVIRONMENT))