saola-user-facing-errors 0.1.0

#![deny(unsafe_code, warnings, rust_2018_idioms)]
#![allow(clippy::derive_partial_eq_without_eq)]

mod panic_hook;

pub mod common;
#[cfg(feature = "sql")]
pub mod quaint;
pub mod query_engine;
pub mod schema_engine;

use serde::{Deserialize, Serialize};
use std::{backtrace::Backtrace, borrow::Cow};

pub use panic_hook::set_panic_hook;

pub trait UserFacingError: serde::Serialize {
    const ERROR_CODE: &'static str;

    fn message(&self) -> String;
}

/// A less dynamic type of user-facing errors. This is used in the introspection and migration
/// engines for simpler, more robust and helpful error handling — extra details are attached
/// opportunistically.
pub trait SimpleUserFacingError {
    const ERROR_CODE: &'static str;
    const MESSAGE: &'static str;
}

impl<T> UserFacingError for T
where
    T: SimpleUserFacingError + Serialize,
{
    const ERROR_CODE: &'static str = <Self as SimpleUserFacingError>::ERROR_CODE;

    fn message(&self) -> String {
        <Self as SimpleUserFacingError>::MESSAGE.to_owned()
    }
}

#[derive(Serialize, Deserialize, Clone, PartialEq, Debug)]
pub struct KnownError {
    pub message: String,
    pub meta: serde_json::Value,
    pub error_code: Cow<'static, str>,
}

impl KnownError {
    pub fn new<T: UserFacingError>(inner: T) -> KnownError {
        KnownError {
            message: inner.message(),
            meta: serde_json::to_value(&inner).expect("Failed to render user facing error metadata to JSON"),
            error_code: Cow::from(T::ERROR_CODE),
        }
    }
}

#[derive(Serialize, Deserialize, PartialEq, Debug, Clone)]
pub struct UnknownError {
    pub message: String,
    pub backtrace: Option<String>,
}

impl UnknownError {
    pub fn new(err: &dyn std::error::Error) -> Self {
        UnknownError {
            message: err.to_string(),
            backtrace: None,
        }
    }
}

#[derive(Serialize, Deserialize, PartialEq, Debug, Clone)]
pub struct Error {
    is_panic: bool,
    #[serde(flatten)]
    inner: ErrorType,

    #[serde(skip_serializing_if = "Option::is_none")]
    batch_request_idx: Option<usize>,
}

#[derive(Serialize, Deserialize, PartialEq, Debug, Clone)]
#[serde(untagged)]
enum ErrorType {
    Known(KnownError),
    Unknown(UnknownError),
}

impl Error {
    /// Try to interpret the error as a known error.
    pub fn as_known(&self) -> Option<&KnownError> {
        match &self.inner {
            ErrorType::Known(err) => Some(err),
            ErrorType::Unknown(_) => None,
        }
    }

    pub fn message(&self) -> &str {
        match &self.inner {
            ErrorType::Known(err) => &err.message,
            ErrorType::Unknown(err) => &err.message,
        }
    }

    pub fn batch_request_idx(&self) -> Option<usize> {
        self.batch_request_idx
    }

    pub fn new_non_panic_with_current_backtrace(message: String) -> Self {
        Error {
            inner: ErrorType::Unknown(UnknownError {
                message,
                backtrace: Some(format!("{:?}", Backtrace::force_capture())),
            }),
            is_panic: false,
            batch_request_idx: None,
        }
    }

    /// Construct a new UnknownError from a [`std::panic::PanicHookInfo`] in a
    /// panic hook. [`UnknownError`]s created with this constructor will have a
    /// proper, useful backtrace.
    pub fn new_in_panic_hook(panic_info: &std::panic::PanicHookInfo<'_>) -> Self {
        let message = panic_utils::downcast_ref_to_string(panic_info.payload()).unwrap_or("<unknown panic>");

        let backtrace = Some(format!("{:?}", Backtrace::force_capture()));
        let location = panic_info
            .location()
            .map(|loc| format!("{loc}"))
            .unwrap_or_else(|| "<unknown location>".to_owned());

        Error {
            inner: ErrorType::Unknown(UnknownError {
                message: format!("[{location}] {message}"),
                backtrace,
            }),
            is_panic: true,
            batch_request_idx: None,
        }
    }

    /// Build from a KnownError
    pub fn new_known(err: KnownError) -> Self {
        Error {
            inner: ErrorType::Known(err),
            is_panic: false,
            batch_request_idx: None,
        }
    }

    pub fn from_panic_payload(panic_payload: Box<dyn std::any::Any + Send + 'static>) -> Self {
        let message = Self::extract_panic_message(panic_payload).unwrap_or_else(|| "<unknown panic>".to_owned());

        Error {
            inner: ErrorType::Unknown(UnknownError {
                message,
                backtrace: None,
            }),
            is_panic: true,
            batch_request_idx: None,
        }
    }

    pub fn extract_panic_message(panic_payload: Box<dyn std::any::Any + Send + 'static>) -> Option<String> {
        panic_payload
            .downcast_ref::<&str>()
            .map(|s| -> String { (*s).to_owned() })
            .or_else(|| panic_payload.downcast_ref::<String>().map(|s| s.to_owned()))
    }

    /// Extract the inner known error, or panic.
    pub fn unwrap_known(self) -> KnownError {
        match self.inner {
            ErrorType::Known(err) => err,
            err @ ErrorType::Unknown(_) => panic!("Expected known error, got {err:?}"),
        }
    }

    pub fn set_batch_request_idx(&mut self, batch_request_idx: usize) {
        self.batch_request_idx = Some(batch_request_idx)
    }
}

pub fn new_backtrace() -> Backtrace {
    Backtrace::force_capture()
}

impl<T: UserFacingError> From<T> for Error {
    fn from(err: T) -> Self {
        Self::from(KnownError::new(err))
    }
}

impl From<UnknownError> for Error {
    fn from(unknown_error: UnknownError) -> Self {
        Error {
            inner: ErrorType::Unknown(unknown_error),
            is_panic: false,
            batch_request_idx: None,
        }
    }
}

impl From<KnownError> for Error {
    fn from(known_error: KnownError) -> Self {
        Error {
            is_panic: false,
            inner: ErrorType::Known(known_error),
            batch_request_idx: None,
        }
    }
}