Improve invalid header encoding errors

src/httpx2/httpx2/_models.py

@@ -152,15 +152,14 @@ def __init__(
 
         if isinstance(headers, Headers):
             self._list = list(headers._list)
-        elif isinstance(headers, Mapping):
-            for k, v in headers.items():
-                bytes_key = _normalize_header_key(k, encoding)
-                bytes_value = _normalize_header_value(v, encoding)
-                self._list.append((bytes_key, bytes_key.lower(), bytes_value))
         elif headers is not None:
-            for k, v in headers:
+            header_items = headers.items() if isinstance(headers, Mapping) else headers
+            for k, v in header_items:
                 bytes_key = _normalize_header_key(k, encoding)
-                bytes_value = _normalize_header_value(v, encoding)
+                try:
+                    bytes_value = _normalize_header_value(v, encoding)
+                except UnicodeEncodeError as exc:
+                    raise ValueError(f"Unable to encode header value for {k!r}") from exc
                 self._list.append((bytes_key, bytes_key.lower(), bytes_value))
 
         self._encoding = encoding

tests/httpx2/models/test_headers.py

@@ -36,6 +36,22 @@ def test_headers() -> None:
     assert repr(h) == "Headers({'a': '123', 'b': '789'})"
 
 
+@pytest.mark.parametrize(
+    "headers",
+    [
+        {"auth": "שלום"},
+        [("auth", "שלום")],
+    ],
+)
+def test_header_value_encoding_error_includes_header_name(
+    headers: dict[str, str] | list[tuple[str, str]],
+) -> None:
+    with pytest.raises(ValueError, match="auth") as exc_info:
+        httpx2.Headers(headers)
+
+    assert isinstance(exc_info.value.__cause__, UnicodeEncodeError)
+
+
 def test_header_mutations() -> None:
     h = httpx2.Headers()
     assert dict(h) == {}