{"record":{"id":"a9ba90df7f9567d9","repo":"nautechsystems/nautilus_trader","slug":"error-no-ask-orders-for-best-ask-size","errorCode":null,"errorMessage":"Error: No ask orders for best ask size","messagePattern":"Error: No ask orders for best ask size","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"critical","filePath":"crates/model/src/ffi/orderbook/book.rs","lineNumber":297,"sourceCode":"/// Panics if there are no bid orders for best bid size.\n#[unsafe(no_mangle)]\n#[cfg_attr(feature = \"high-precision\", allow(improper_ctypes_definitions))]\npub extern \"C\" fn orderbook_best_bid_size(book: &mut OrderBook) -> Quantity {\n    abort_on_panic(|| {\n        book.best_bid_size()\n            .expect(\"Error: No bid orders for best bid size\")\n    })\n}\n\n/// # Panics\n///\n/// Panics if there are no ask orders for best ask size.\n#[unsafe(no_mangle)]\n#[cfg_attr(feature = \"high-precision\", allow(improper_ctypes_definitions))]\npub extern \"C\" fn orderbook_best_ask_size(book: &mut OrderBook) -> Quantity {\n    abort_on_panic(|| {\n        book.best_ask_size()\n            .expect(\"Error: No ask orders for best ask size\")\n    })\n}\n\n/// # Panics\n///\n/// Panics if unable to calculate spread (requires at least one bid and one ask).\n#[unsafe(no_mangle)]\npub extern \"C\" fn orderbook_spread(book: &mut OrderBook) -> f64 {\n    abort_on_panic(|| {\n        book.spread()\n            .expect(\"Error: Unable to calculate `spread` (no bid or ask)\")\n    })\n}\n\n/// # Panics\n///\n/// Panics if unable to calculate midpoint (requires at least one bid and one ask).\n#[unsafe(no_mangle)]","sourceCodeStart":279,"sourceCodeEnd":315,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/18893faf8b356be3320add8de2f861b0b647cf06/crates/model/src/ffi/orderbook/book.rs#L279-L315","documentation":"This panic fires in the FFI wrapper `orderbook_best_ask_size` when `OrderBook::best_ask_size()` returns None because no ask orders exist in the book. Under `abort_on_panic` the panic aborts the entire process rather than surfacing an error to the caller.","triggerScenarios":"Calling `orderbook_best_ask_size(book)` on a book with an empty ask side or with ask levels that carry no size data.","commonSituations":"Ask size missing from the market-data feed; querying a freshly created or cleared book; trade-only or bid-only data streams; illiquid symbols with no resting asks.","solutions":["Verify the ask side is non-empty before calling the FFI function.","Populate the book with quotes/depth containing ask sizes before querying.","Handle the empty case caller-side by returning None/skipping the computation.","Check feed connectivity and that ask-side volume updates are subscribed."],"exampleFix":"// before (Python FFI caller)\nask_size = orderbook_best_ask_size(book)\n// after\nif has_ask_orders(book):\n    ask_size = orderbook_best_ask_size(book)\nelse:\n    ask_size = None","handlingStrategy":"validation","validationCode":"def can_get_best_ask_size(book) -> bool:\n    return book.has_orders() and book.asks_len() > 0","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Confirm the data feed includes ask volume","Guard size queries on non-empty ask side","Treat empty books as an expected state and query optional accessors instead of FFI panicking ones","Remember FFI panics abort the process — they cannot be caught as exceptions"],"tags":["rust","ffi","orderbook","panic","process-abort"],"backgroundTag":"empty-result-set","analyzedSha":"18893faf8b356be3320add8de2f861b0b647cf06","analyzedAt":"2026-09-08T20:49:34.690Z","contentChangedAt":"2026-09-08T20:49:34.690Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}