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use std::fmt;
use std::sync::Arc;
use std::error::Error as StdError;
use std::result::Result as StdResult;
/// Error type returned by `rlua` methods.
#[derive(Debug, Clone)]
pub enum Error {
/// Syntax error while parsing Lua source code.
SyntaxError {
/// The error message as returned by Lua.
message: String,
/// `true` if the error can likely be fixed by appending more input to the source code.
///
/// This is useful for implementing REPLs as they can query the user for more input if this
/// is set.
incomplete_input: bool,
},
/// Lua runtime error, aka `LUA_ERRRUN`.
///
/// The Lua VM returns this error when a builtin operation is performed on incompatible types.
/// Among other things, this includes invoking operators on wrong types (such as calling or
/// indexing a `nil` value).
RuntimeError(String),
/// Lua garbage collector error, aka `LUA_ERRGCMM`.
///
/// The Lua VM returns this error when there is an error running a `__gc` metamethod.
GarbageCollectorError(String),
/// A callback has triggered Lua code that has called the same callback again.
///
/// This is an error because `rlua` callbacks are FnMut and thus can only be mutably borrowed
/// once.
RecursiveCallbackError,
/// Lua code has accessed a [`UserData`] value that was already garbage collected
///
/// This can happen when a [`UserData`] has a custom `__gc` metamethod, this method resurrects
/// the [`UserData`], and then the [`UserData`] is subsequently accessed.
/// [`UserData`]: trait.UserData.html
ExpiredUserData,
/// A Rust value could not be converted to a Lua value.
ToLuaConversionError {
/// Name of the Rust type that could not be converted.
from: &'static str,
/// Name of the Lua type that could not be created.
to: &'static str,
/// A message indicating why the conversion failed in more detail.
message: Option<String>,
},
/// A Lua value could not be converted to the expected Rust type.
FromLuaConversionError {
/// Name of the Lua type that could not be converted.
from: &'static str,
/// Name of the Rust type that could not be created.
to: &'static str,
/// A string containing more detailed error information.
message: Option<String>,
},
/// [`Thread::resume`] was called on an inactive coroutine.
///
/// A coroutine is inactive if its main function has returned or if an error has occured inside
/// the coroutine.
///
/// [`Thread::status`] can be used to check if the coroutine can be resumed without causing this
/// error.
///
/// [`Thread::resume`]: struct.Thread.html#method.resume
/// [`Thread::status`]: struct.Thread.html#method.status
CoroutineInactive,
/// An [`AnyUserData`] is not the expected type in a borrow.
///
/// This error can only happen when manually using [`AnyUserData`], or when implementing
/// metamethods for binary operators. Refer to the documentation of [`UserDataMethods`] for
/// details.
///
/// [`AnyUserData`]: struct.AnyUserData.html
/// [`UserDataMethods`]: struct.UserDataMethods.html
UserDataTypeMismatch,
/// An [`AnyUserData`] immutable borrow failed because it is already borrowed mutably.
///
/// This error can occur when a method on a [`UserData`] type calls back into Lua, which then
/// tries to call a method on the same [`UserData`] type. Consider restructuring your API to
/// prevent these errors.
///
/// [`AnyUserData`]: struct.AnyUserData.html
/// [`UserData`]: trait.UserData.html
UserDataBorrowError,
/// An [`AnyUserData`] mutable borrow failed because it is already borrowed.
///
/// This error can occur when a method on a [`UserData`] type calls back into Lua, which then
/// tries to call a method on the same [`UserData`] type. Consider restructuring your API to
/// prevent these errors.
///
/// [`AnyUserData`]: struct.AnyUserData.html
/// [`UserData`]: trait.UserData.html
UserDataBorrowMutError,
/// A Rust callback returned `Err`, raising the contained `Error` as a Lua error.
CallbackError {
/// Lua call stack backtrace.
traceback: String,
/// Original error returned by the Rust code.
cause: Arc<Error>,
},
/// A custom error.
///
/// This can be used for returning user-defined errors from callbacks.
///
/// Returning `Err(ExternalError(...))` from a Rust callback will raise the error as a Lua
/// error. The Rust code that originally invoked the Lua code then receives a `CallbackError`,
/// from which the original error (and a stack traceback) can be recovered.
ExternalError(Arc<StdError + Send + Sync>),
}
/// A specialized `Result` type used by `rlua`'s API.
pub type Result<T> = StdResult<T, Error>;
impl fmt::Display for Error {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
match *self {
Error::SyntaxError { ref message, .. } => write!(fmt, "syntax error: {}", message),
Error::RuntimeError(ref msg) => write!(fmt, "runtime error: {}", msg),
Error::GarbageCollectorError(ref msg) => {
write!(fmt, "garbage collector error: {}", msg)
}
Error::RecursiveCallbackError => write!(fmt, "callback called recursively"),
Error::ExpiredUserData => write!(
fmt,
"access of userdata which has already been garbage collected"
),
Error::ToLuaConversionError {
from,
to,
ref message,
} => {
write!(fmt, "error converting {} to Lua {}", from, to)?;
match *message {
None => Ok(()),
Some(ref message) => write!(fmt, " ({})", message),
}
}
Error::FromLuaConversionError {
from,
to,
ref message,
} => {
write!(fmt, "error converting Lua {} to {}", from, to)?;
match *message {
None => Ok(()),
Some(ref message) => write!(fmt, " ({})", message),
}
}
Error::CoroutineInactive => write!(fmt, "cannot resume inactive coroutine"),
Error::UserDataTypeMismatch => write!(fmt, "userdata is not expected type"),
Error::UserDataBorrowError => write!(fmt, "userdata already mutably borrowed"),
Error::UserDataBorrowMutError => write!(fmt, "userdata already borrowed"),
Error::CallbackError { ref traceback, .. } => {
write!(fmt, "callback error: {}", traceback)
}
Error::ExternalError(ref err) => err.fmt(fmt),
}
}
}
impl StdError for Error {
fn description(&self) -> &str {
match *self {
Error::SyntaxError { .. } => "syntax error",
Error::RuntimeError(_) => "runtime error",
Error::GarbageCollectorError(_) => "garbage collector error",
Error::RecursiveCallbackError => "callback called recursively",
Error::ExpiredUserData => "access of userdata which has already been garbage collected",
Error::ToLuaConversionError { .. } => "conversion error to lua",
Error::FromLuaConversionError { .. } => "conversion error from lua",
Error::CoroutineInactive => "attempt to resume inactive coroutine",
Error::UserDataTypeMismatch => "userdata type mismatch",
Error::UserDataBorrowError => "userdata already mutably borrowed",
Error::UserDataBorrowMutError => "userdata already borrowed",
Error::CallbackError { .. } => "callback error",
Error::ExternalError(ref err) => err.description(),
}
}
fn cause(&self) -> Option<&StdError> {
match *self {
Error::CallbackError { ref cause, .. } => Some(cause.as_ref()),
Error::ExternalError(ref err) => err.cause(),
_ => None,
}
}
}
impl Error {
pub fn external<T: 'static + StdError + Send + Sync>(err: T) -> Error {
Error::ExternalError(Arc::new(err))
}
}
pub trait ExternalError {
fn to_lua_err(self) -> Error;
}
impl<E> ExternalError for E
where
E: Into<Box<StdError + Send + Sync>>,
{
fn to_lua_err(self) -> Error {
struct WrapError(Box<StdError + Send + Sync>);
impl fmt::Debug for WrapError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Debug::fmt(&self.0, f)
}
}
impl fmt::Display for WrapError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(&self.0, f)
}
}
impl StdError for WrapError {
fn description(&self) -> &str {
self.0.description()
}
fn cause(&self) -> Option<&StdError> {
self.0.cause()
}
}
Error::external(WrapError(self.into()))
}
}
pub trait ExternalResult<T> {
fn to_lua_err(self) -> Result<T>;
}
impl<T, E> ExternalResult<T> for StdResult<T, E>
where
E: ExternalError,
{
fn to_lua_err(self) -> Result<T> {
self.map_err(|e| e.to_lua_err())
}
}