query_flow/
error.rs

1//! Error types for query execution.
2
3use std::fmt;
4
5/// System-level query errors.
6///
7/// These are distinct from user domain errors, which should be wrapped
8/// in `Query::Output` (e.g., `type Output = Result<T, MyError>`).
9#[derive(Debug, Clone)]
10pub enum QueryError {
11    /// Query is waiting for async loading to complete.
12    ///
13    /// This is returned when a dependency is still loading via a background task.
14    /// Use `runtime.query_async()` to wait for loading to complete, or handle
15    /// explicitly in your query logic.
16    Suspend,
17
18    /// Dependency cycle detected.
19    ///
20    /// The query graph contains a cycle, which would cause infinite recursion.
21    /// The `path` contains a debug representation of the cycle.
22    Cycle {
23        /// Debug representation of the queries forming the cycle.
24        path: Vec<String>,
25    },
26
27    /// Query execution was cancelled.
28    Cancelled,
29
30    /// A required dependency is missing.
31    MissingDependency {
32        /// Description of the missing dependency.
33        description: String,
34    },
35}
36
37impl fmt::Display for QueryError {
38    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
39        match self {
40            QueryError::Suspend => write!(f, "query suspended: waiting for async loading"),
41            QueryError::Cycle { path } => {
42                write!(f, "dependency cycle detected: {}", path.join(" -> "))
43            }
44            QueryError::Cancelled => write!(f, "query cancelled"),
45            QueryError::MissingDependency { description } => {
46                write!(f, "missing dependency: {}", description)
47            }
48        }
49    }
50}
51
52impl std::error::Error for QueryError {}
query_flow/error.rs

query_flow/
error.rs
