mcp-exec 0.4.8

Greentic executor for running wasix:mcp-compatible WebAssembly components with policy-driven verification and sandboxing.
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//! Structured error types produced across the resolution, verification, and runtime pipeline.

use std::io;
use std::time::Duration;

use anyhow::Error as AnyError;
use serde_json::Value;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum ExecError {
    #[error("failed to resolve component `{component}`: {source}")]
    Resolve {
        component: String,
        #[source]
        source: ResolveError,
    },
    #[error("artifact verification failed for `{component}`: {source}")]
    Verification {
        component: String,
        #[source]
        source: VerificationError,
    },
    #[error("runtime error while executing `{component}`: {source}")]
    Runner {
        component: String,
        #[source]
        source: RunnerError,
    },
    #[error("action `{action}` not found on component `{component}`")]
    NotFound { component: String, action: String },
    #[error("tool `{component}` returned error `{code}` for action `{action}`")]
    Tool {
        component: String,
        action: String,
        code: String,
        payload: Value,
    },
}

impl ExecError {
    pub fn resolve(component: impl Into<String>, source: ResolveError) -> Self {
        Self::Resolve {
            component: component.into(),
            source,
        }
    }

    pub fn verification(component: impl Into<String>, source: VerificationError) -> Self {
        Self::Verification {
            component: component.into(),
            source,
        }
    }

    pub fn runner(component: impl Into<String>, source: RunnerError) -> Self {
        Self::Runner {
            component: component.into(),
            source,
        }
    }

    pub fn not_found(component: impl Into<String>, action: impl Into<String>) -> Self {
        Self::NotFound {
            component: component.into(),
            action: action.into(),
        }
    }

    pub fn tool_error(
        component: impl Into<String>,
        action: impl Into<String>,
        code: impl Into<String>,
        payload: Value,
    ) -> Self {
        Self::Tool {
            component: component.into(),
            action: action.into(),
            code: code.into(),
            payload,
        }
    }
}

#[derive(Debug, Error)]
pub enum ResolveError {
    #[error("component was not found in the configured store(s)")]
    NotFound,
    #[error("I/O error while reading artifact")]
    Io(#[from] io::Error),
    #[error("tool store error: {0}")]
    Store(AnyError),
}

#[derive(Debug, Error)]
pub enum VerificationError {
    #[error("digest mismatch: expected {expected}, got {actual}")]
    DigestMismatch { expected: String, actual: String },
    #[error("artifact is unsigned and policy does not allow it")]
    UnsignedRejected,
}

#[derive(Debug, Error)]
pub enum RunnerError {
    #[error("wasm execution timed out after {elapsed:?}")]
    Timeout { elapsed: Duration },
    #[error("wasmtime error: {0}")]
    Wasmtime(#[from] wasmtime::Error),
    #[error("serde error: {0}")]
    Serde(#[from] serde_json::Error),
    #[error("action `{action}` not implemented by the tool")]
    ActionNotFound { action: String },
    #[error("tool `{component}` transient failure: {message}")]
    ToolTransient { component: String, message: String },
    #[error("internal runner error: {0}")]
    Internal(String),
    #[error("runner is not implemented for this configuration")]
    NotImplemented,
}