Reject duplicate headers after key normalization

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

hyperbrowser/header_utils.py

@@ -30,6 +30,10 @@ def normalize_headers(
             or "\r" in value
         ):
             raise HyperbrowserError("headers must not contain newline characters")
+        if normalized_key in normalized_headers:
+            raise HyperbrowserError(
+                "duplicate header names are not allowed after normalization"
+            )
         normalized_headers[normalized_key] = value
     return normalized_headers
 

tests/test_config.py

@@ -200,6 +200,17 @@ def test_client_config_normalizes_header_name_whitespace():
     assert config.headers == {"X-Correlation-Id": "value"}
 
 
+def test_client_config_rejects_duplicate_header_names_after_normalization():
+    with pytest.raises(
+        HyperbrowserError,
+        match="duplicate header names are not allowed after normalization",
+    ):
+        ClientConfig(
+            api_key="test-key",
+            headers={"X-Correlation-Id": "one", "  X-Correlation-Id  ": "two"},
+        )
+
+
 def test_client_config_accepts_mapping_header_inputs():
     headers = MappingProxyType({"X-Correlation-Id": "abc123"})
     config = ClientConfig(api_key="test-key", headers=headers)

tests/test_header_utils.py

@@ -21,6 +21,17 @@ def test_normalize_headers_rejects_empty_header_name():
         )
 
 
+def test_normalize_headers_rejects_duplicate_names_after_normalization():
+    with pytest.raises(
+        HyperbrowserError,
+        match="duplicate header names are not allowed after normalization",
+    ):
+        normalize_headers(
+            {"X-Trace-Id": "one", "  X-Trace-Id  ": "two"},
+            mapping_error_message="headers must be a mapping of string pairs",
+        )
+
+
 def test_parse_headers_env_json_ignores_blank_values():
     assert parse_headers_env_json("   ") is None