Use CallException for unknown errors

Author: JordonPhillips

codegen/core/src/main/java/software/amazon/smithy/python/codegen/CodegenUtils.java

@@ -89,10 +89,7 @@ public static Symbol getPluginSymbol(PythonSettings settings) {
     /**
      * Gets the service error symbol.
      *
-     * <p>This error is the top-level error for the client. Errors surfaced by the client
-     * MUST be a subclass of this or SmithyException so that customers can reliably catch
-     * all the exceptions a client throws. The request pipeline will wrap exceptions of
-     * other types.
+     * <p>This error is the top-level error for modeled client errors.
      *
      * @param settings The client settings, used to account for module configuration.
      * @return Returns the symbol for the client's error class.

codegen/core/src/main/java/software/amazon/smithy/python/codegen/integrations/HttpProtocolGeneratorUtils.java

@@ -136,24 +136,26 @@ public static void generateErrorDispatcher(
         var transportResponse = context.applicationProtocol().responseType();
         var delegator = context.writerDelegator();
         var errorDispatcher = context.protocolGenerator().getErrorDeserializationFunction(context, operation);
-        var apiError = CodegenUtils.getServiceError(context.settings());
         var canReadResponseBody = canReadResponseBody(operation, context.model());
         delegator.useFileWriter(errorDispatcher.getDefinitionFile(), errorDispatcher.getNamespace(), writer -> {
             writer.pushState(new ErrorDispatcherSection(operation, errorShapeToCode, errorMessageCodeGenerator));
+            writer.addImport("smithy_core.exceptions", "CallException");
             writer.write("""
-                    async def $1L(http_response: $2T, config: $3T) -> $4T:
-                        ${5C|}
+                    async def $1L(http_response: $2T, config: $3T) -> CallException:
+                        ${4C|}
 
                         match code.lower():
-                            ${6C|}
+                            ${5C|}
 
                             case _:
-                                return $4T(f"{code}: {message}")
+                                return CallException(
+                                    message=f"{code}: {message}",
+                                    fault="client" if http_response.status < 500 else "server"
+                                )
                     """,
                     errorDispatcher.getName(),
                     transportResponse,
                     configSymbol,
-                    apiError,
                     writer.consumer(w -> errorMessageCodeGenerator.accept(context, w, canReadResponseBody)),
                     writer.consumer(w -> errorCases(context, w, operation, errorShapeToCode)));
             writer.popState();

packages/smithy-core/src/smithy_core/exceptions.py

@@ -35,7 +35,10 @@ class CallException(SmithyException, RetryInfo):
     """Base exceptio to be used in application-level errors."""
 
     fault: Literal["client", "server"] | None = None
-    """Whether the client or server is at fault."""
+    """Whether the client or server is at fault.
+
+    If None, then there was not enough information to determine fault.
+    """
 
     message: str = field(default="", kw_only=False)
     """The message of the error."""
@@ -46,10 +49,13 @@ def __post_init__(self):
 
 @dataclass(kw_only=True)
 class ModeledException(CallException):
-    """Base excetpion to be used for modeled errors."""
+    """Base exception to be used for modeled errors."""
 
     fault: Literal["client", "server"] | None = "client"
-    """Whether the client or server is at fault."""
+    """Whether the client or server is at fault.
+
+    If None, then there was not enough information to determine fault.
+    """
 
 
 class SerializationException(Exception):