fix: lead APIError's string form with the error message

packages/abstractions/kiota_abstractions/api_error.py

@@ -10,17 +10,14 @@ class APIError(Exception):
     response_status_code: Optional[int] = None
     response_headers: Optional[dict[str, str]] = None
 
+    @property
+    def primary_message(self) -> Optional[str]:
+        """The message shown for this error. Generated error models override it with the
+        message carried by the API's error payload."""
+        return self.message
+
     def __str__(self) -> str:
-        error = getattr(self, "error", None)
-        if error:
-            return f"""
-        APIError
-        Code: {self.response_status_code}
-        message: {self.message}
-        error: {error}
-        """
-        return f"""
-        APIError
-        Code: {self.response_status_code}
-        message: {self.message}
-        """
+        first_line = self.primary_message or type(self).__name__
+        if self.response_status_code is not None:
+            return f"{first_line} (status {self.response_status_code})"
+        return first_line

packages/abstractions/tests/test_api_error.py

@@ -0,0 +1,56 @@
+from dataclasses import dataclass
+from typing import Optional
+
+from kiota_abstractions.api_error import APIError
+
+
+@dataclass
+class MainError:
+    code: Optional[str] = None
+    message: Optional[str] = None
+
+
+@dataclass
+class GeneratedError(APIError):
+    """The shape kiota generates for an API's error model: an ``error`` payload and a
+    ``primary_message`` override, and no ``message`` set by the deserializer."""
+
+    error: Optional[MainError] = None
+
+    @property
+    def primary_message(self) -> Optional[str]:
+        if self.error is not None:
+            return self.error.message or ""
+        return ""
+
+
+def test_str_is_the_message():
+    assert str(APIError(message="boom")) == "boom"
+
+
+def test_str_appends_the_status_code():
+    assert str(APIError(message="boom", response_status_code=429)) == "boom (status 429)"
+
+
+def test_str_without_any_message_names_the_class():
+    assert str(APIError(response_status_code=502)) == "APIError (status 502)"
+
+
+def test_primary_message_defaults_to_the_message():
+    assert APIError(message="boom").primary_message == "boom"
+    assert APIError().primary_message is None
+
+
+def test_str_of_a_generated_error_uses_its_primary_message():
+    message = "Application is over its MailboxConcurrency limit."
+    error = GeneratedError(
+        response_status_code=429,
+        error=MainError(code="ApplicationThrottled", message=message),
+    )
+
+    assert str(error) == f"{message} (status 429)"
+
+
+def test_str_never_starts_with_a_blank_line():
+    for error in (APIError(), APIError(message="boom"), GeneratedError(error=MainError())):
+        assert str(error).splitlines()[0].strip()