{"record":{"id":"441c76d281fc1c97","repo":"DioxusLabs/dioxus","slug":"tried-to-unwrap-a-result-that-was-an-error","errorCode":null,"errorMessage":"Tried to unwrap a Result that was an error","messagePattern":"Tried to unwrap a Result that was an error","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"packages/signals/src/write.rs","lineNumber":460,"sourceCode":"        T: 'static,\n    {\n        WriteLock::filter_map(self.write(), |v: &mut Option<T>| v.as_mut())\n    }\n}\n\nimpl<T, W> WritableOptionExt<T> for W where W: Writable<Target = Option<T>> {}\n\n/// An extension trait for [`Writable<Result<T, E>>`] that provides some convenience methods.\npub trait WritableResultExt<T, E>: Writable<Target = Result<T, E>> {\n    /// Unwraps the inner value mutably, panicking if the Result is an error.\n    #[track_caller]\n    fn unwrap_mut(&mut self) -> WritableRef<'_, Self, T>\n    where\n        T: 'static,\n        E: 'static,\n    {\n        WriteLock::filter_map(self.write(), |v| v.as_mut().ok())\n            .expect(\"Tried to unwrap a Result that was an error\")\n    }\n\n    /// Attempts to mutably access the inner value of the Result.\n    #[track_caller]\n    fn as_mut(&mut self) -> Result<WritableRef<'_, Self, T>, WritableRef<'_, Self, E>>\n    where\n        T: 'static,\n        E: 'static,\n    {\n        let write = self.write();\n        match write.as_ref() {\n            Ok(_) => Ok(WriteLock::map(write, |v| {\n                v.as_mut()\n                    .ok()\n                    .expect(\"Result variant changed between read and write\")\n            })),\n            Err(_) => Err(WriteLock::map(write, |v| {\n                v.as_mut()","sourceCodeStart":442,"sourceCodeEnd":478,"githubUrl":"https://github.com/DioxusLabs/dioxus/blob/393d190a801ccb441d41923e232289b4f8a5c669/packages/signals/src/write.rs#L442-L478","documentation":"WritableResultExt::unwrap_mut locks a signal holding a Result and filters the write lock to the Ok variant via WriteLock::filter_map. If the current value is Err, the filter returns None and this expect panics — the reactive equivalent of Result::unwrap, with the same failure mode.","triggerScenarios":"Calling signal_of_result.unwrap_mut() while the signal currently holds Err(e): a query/async signal storing its last outcome that has failed, or an optimistic update that left an error behind.","commonSituations":"Modeling async state as Signal<Result<T, E>> and unwrapping during render after a failed request; error state never cleared before code that assumes success.","solutions":["Handle both variants with .as_mut(), which returns Result<WritableRef<T>, WritableRef<E>>","Check state first: if signal.read().is_err(), render or propagate the error instead of unwrapping","Reset the signal to an Ok/default value before code that requires unwrap_mut","If unwrap semantics are required, store T and the error in separate signals"],"exampleFix":"// before\nlet value = result_signal.unwrap_mut(); // panics when Err\n// after\nmatch result_signal.as_mut() {\n    Ok(mut ok) => { *ok += 1; }\n    Err(mut err) => { tracing::error!(\"query failed: {err:?}\"); }\n}","handlingStrategy":"validation","validationCode":"if result_signal.read().is_ok() {\n    let mut value = result_signal.unwrap_mut(); // safe now\n    *value += 1;\n} else {\n    // surface the error state instead\n}","typeGuard":"fn signal_is_ok<R: Writable<Target = Result<T, E>>, T, E>(sig: &R) -> bool {\n    sig.read().is_ok()\n}","tryCatchPattern":null,"preventionTips":["Prefer as_mut() over unwrap_mut() whenever the error case is representable","Clear or reset Result signals after surfacing their error to the user","Treat unwrap_mut on Result like Result::unwrap: only after proving Ok","Consider separate signals for value and error in success-required flows"],"tags":["signals","state","result","unwrap","panic"],"backgroundTag":null,"analyzedSha":"393d190a801ccb441d41923e232289b4f8a5c669","analyzedAt":"2026-08-16T11:27:45.815Z","schemaVersion":2},"datasetVersion":"2026-08-16T13:17:31.715Z"}