tinyflows 0.2.0

A Rust-based workflow management solution.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

//! Error types shared across validation, compilation, and execution.

use thiserror::Error;

/// Errors produced while validating a [`crate::model::WorkflowGraph`].
#[derive(Debug, Error, Clone, PartialEq, Eq)]
pub enum ValidationError {
    /// The graph has no trigger node (exactly one is required).
    #[error("workflow has no trigger node")]
    MissingTrigger,

    /// The graph has more than one trigger node.
    #[error("workflow has multiple trigger nodes: {0:?}")]
    MultipleTriggers(Vec<String>),

    /// An edge references a node id that does not exist.
    #[error("edge references unknown node id: {0}")]
    UnknownNode(String),

    /// Two nodes share the same id.
    #[error("duplicate node id: {0}")]
    DuplicateNodeId(String),

    /// The graph contains a cycle through nodes that may not participate in loops.
    #[error("illegal cycle detected involving node: {0}")]
    IllegalCycle(String),

    /// A node's configuration is invalid for its kind.
    #[error("invalid config for node {node}: {reason}")]
    InvalidNodeConfig {
        /// The offending node id.
        node: String,
        /// Why the configuration is invalid.
        reason: String,
    },
}

/// Errors produced while compiling or running a workflow.
#[derive(Debug, Error)]
pub enum EngineError {
    /// The workflow graph failed validation before compilation.
    #[error("validation failed: {0}")]
    Validation(#[from] ValidationError),

    /// A feature required by the graph is not yet implemented in this stage.
    #[error("not yet implemented: {0}")]
    Unimplemented(&'static str),

    /// A host capability call failed at runtime.
    #[error("capability error: {0}")]
    Capability(String),
}

/// Convenience result alias for compile/run operations.
pub type Result<T> = std::result::Result<T, EngineError>;

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn validation_error_display() {
        assert_eq!(
            ValidationError::MissingTrigger.to_string(),
            "workflow has no trigger node"
        );
        assert_eq!(
            ValidationError::MultipleTriggers(vec!["t1".to_string(), "t2".to_string()]).to_string(),
            "workflow has multiple trigger nodes: [\"t1\", \"t2\"]"
        );
        assert_eq!(
            ValidationError::UnknownNode("ghost".to_string()).to_string(),
            "edge references unknown node id: ghost"
        );
        assert_eq!(
            ValidationError::DuplicateNodeId("dup".to_string()).to_string(),
            "duplicate node id: dup"
        );
        assert_eq!(
            ValidationError::IllegalCycle("loop".to_string()).to_string(),
            "illegal cycle detected involving node: loop"
        );
        assert_eq!(
            ValidationError::InvalidNodeConfig {
                node: "n1".to_string(),
                reason: "missing url".to_string(),
            }
            .to_string(),
            "invalid config for node n1: missing url"
        );
    }

    #[test]
    fn engine_error_display() {
        assert_eq!(
            EngineError::Unimplemented("checkpoint replay").to_string(),
            "not yet implemented: checkpoint replay"
        );
        assert_eq!(
            EngineError::Capability("http timed out".to_string()).to_string(),
            "capability error: http timed out"
        );
        assert_eq!(
            EngineError::Validation(ValidationError::MissingTrigger).to_string(),
            "validation failed: workflow has no trigger node"
        );
    }

    #[test]
    fn validation_error_converts_into_engine_error() {
        let engine: EngineError = ValidationError::MissingTrigger.into();
        assert!(matches!(
            engine,
            EngineError::Validation(ValidationError::MissingTrigger)
        ));
    }

    #[test]
    fn question_mark_operator_lifts_validation_error() {
        fn inner() -> Result<()> {
            Err(ValidationError::DuplicateNodeId("dup".to_string()))?;
            Ok(())
        }
        match inner() {
            Err(EngineError::Validation(ValidationError::DuplicateNodeId(id))) => {
                assert_eq!(id, "dup");
            }
            other => panic!("expected lifted validation error, got {other:?}"),
        }
    }

    #[test]
    fn validation_error_is_comparable_and_cloneable() {
        let err = ValidationError::UnknownNode("x".to_string());
        assert_eq!(err.clone(), err);
        assert_ne!(err, ValidationError::MissingTrigger);
    }
}