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//! Rust types for working with Ruby Exceptions and other interrupts.
//!
//! See also [`Ruby`](Ruby#errors) for more error related methods.
use std::{any::Any, borrow::Cow, ffi::CString, fmt, mem::transmute, os::raw::c_int};
use rb_sys::{
rb_bug, rb_ensure, rb_errinfo, rb_exc_raise, rb_iter_break_value, rb_jump_tag, rb_protect,
rb_set_errinfo, rb_warning, ruby_special_consts, VALUE,
};
use crate::{
class::Class,
exception::Exception,
into_value::IntoValue,
module::Module,
value::{private::ReprValue as _, ReprValue, Value},
ExceptionClass, Ruby,
};
/// An error returned to indicate an attempt to interact with the Ruby API from
/// a non-Ruby thread or without aquiring the GVL.
#[derive(Debug)]
pub enum RubyUnavailableError {
/// GVL is not locked.
GvlUnlocked,
/// Current thread is not a Ruby thread.
NonRubyThread,
}
impl fmt::Display for RubyUnavailableError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::NonRubyThread => write!(f, "Current thread is not a Ruby thread."),
Self::GvlUnlocked => write!(f, "GVL is not locked."),
}
}
}
impl std::error::Error for RubyUnavailableError {}
/// # Errors
///
/// Functions for working with errors and flow control encoded as an [`Error`].
///
/// See also [`Error`] and the [`error`](self) module.
impl Ruby {
/// Create a new error that will break from a loop when returned to Ruby.
///
/// # Examples
///
/// ```
/// use magnus::{prelude::*, Error, Ruby};
///
/// fn example(ruby: &Ruby) -> Result<(), Error> {
/// let i: i64 = ruby
/// .range_new(1, 100, false)?
/// .block_call("each", (), |args, _block| {
/// let i = i64::try_convert(*args.get(0).unwrap())?;
/// if i % 3 == 0 && i % 5 == 0 {
/// // `block_call` takes a function pointer, not a
/// // closure, so can't capture `ruby`. As we know this
/// // will always be called from Ruby it's safe to get
/// // `Ruby` without the checks that we're on a Ruby
/// // thread.
/// let ruby = unsafe { Ruby::get_unchecked() };
/// Err(ruby.iter_break_value(i))
/// } else {
/// Ok(())
/// }
/// })?;
///
/// assert_eq!(i, 15);
/// Ok(())
/// }
/// # Ruby::init(example).unwrap()
/// ```
pub fn iter_break_value<T>(&self, val: T) -> Error
where
T: IntoValue,
{
let val = self.into_value(val);
protect(|| {
unsafe { rb_iter_break_value(val.as_rb_value()) };
// we never get here, but this is needed to satisfy the type system
#[allow(unreachable_code)]
self.qnil()
})
.unwrap_err()
}
/// Outputs `s` to Ruby's stderr if Ruby is configured to output warnings.
pub fn warning(&self, s: &str) {
let s = CString::new(s).unwrap();
unsafe { rb_warning(s.as_ptr()) };
}
}
/// Shorthand for `std::result::Result<T, magnus::Error>`.
pub type Result<T> = std::result::Result<T, Error>;
/// The possible types of [`Error`].
#[derive(Debug)]
pub enum ErrorType {
/// An interrupt, such as `break` or `throw`.
Jump(Tag),
/// An error generated in Rust code that will raise an exception when
/// returned to Ruby.
Error(ExceptionClass, Cow<'static, str>),
/// A Ruby `Exception` captured from Ruby as an Error.
Exception(Exception),
}
/// Wrapper type for Ruby `Exception`s or other interrupts.
#[derive(Debug)]
pub struct Error(ErrorType);
impl Error {
/// Create a new `Error` that can be raised as a Ruby `Exception` with
/// `msg`.
///
/// # Examples
///
/// ```
/// use magnus::{define_global_function, eval, exception, function, prelude::*, Error, Exception};
/// # let _cleanup = unsafe { magnus::embed::init() };
///
/// fn bang() -> Result<(), Error> {
/// Err(Error::new(exception::runtime_error(), "BANG"))
/// }
/// define_global_function("bang", function!(bang, 0));
///
/// let error: Exception = eval(
/// "
/// begin
/// bang
/// rescue => e
/// e
/// end
/// ",
/// )
/// .unwrap();
///
/// assert!(error.is_kind_of(exception::runtime_error()));
/// let msg: String = error.funcall("message", ()).unwrap();
/// assert_eq!(msg, "BANG")
/// ```
pub fn new<T>(class: ExceptionClass, msg: T) -> Self
where
T: Into<Cow<'static, str>>,
{
Self(ErrorType::Error(class, msg.into()))
}
pub(crate) fn from_tag(tag: Tag) -> Self {
Self(ErrorType::Jump(tag))
}
/// Create a new error that will break from a loop when returned to Ruby.
///
/// # Panics
///
/// Panics if called from a non-Ruby thread. See [`Ruby::iter_break_value`]
/// for the non-panicking version.
///
/// # Examples
///
/// ```
/// use magnus::{prelude::*, Error};
/// # let _cleanup = unsafe { magnus::embed::init() };
///
/// let i: i64 = magnus::Range::new(1, 100, false)
/// .unwrap()
/// .block_call("each", (), |args, _block| {
/// let i = i64::try_convert(*args.get(0).unwrap())?;
/// if i % 3 == 0 && i % 5 == 0 {
/// Err(Error::iter_break(i))
/// } else {
/// Ok(())
/// }
/// })
/// .unwrap();
///
/// assert_eq!(i, 15);
/// ```
#[cfg_attr(
not(feature = "friendly-api"),
deprecated(note = "please use `Ruby::iter_break_value` instead")
)]
#[inline]
pub fn iter_break<T>(val: T) -> Self
where
T: IntoValue,
{
get_ruby!().iter_break_value(val)
}
/// Matches the internal `Exception` against `class` with same semantics as
/// Ruby's `rescue`.
///
/// # Examples
///
/// ```
/// use magnus::{
/// class, eval, exception::ExceptionClass, prelude::*, Error, RModule, TryConvert, Value,
/// };
/// # let _cleanup = unsafe { magnus::embed::init() };
///
/// let err: Error = eval::<Value>(
/// "
/// class ExampleError < StandardError
/// end
/// module Tag
/// end
/// class SpecificError < ExampleError
/// include Tag
/// end
/// raise SpecificError
/// ",
/// )
/// .unwrap_err();
///
/// fn get<T: TryConvert>(name: &str) -> T {
/// class::object().const_get::<_, T>(name).unwrap()
/// }
/// assert!(err.is_kind_of(get::<ExceptionClass>("SpecificError")));
/// assert!(err.is_kind_of(get::<ExceptionClass>("ExampleError")));
/// assert!(err.is_kind_of(get::<ExceptionClass>("StandardError")));
/// assert!(err.is_kind_of(get::<ExceptionClass>("Exception")));
/// assert!(err.is_kind_of(get::<RModule>("Tag")));
///
/// assert!(!err.is_kind_of(get::<ExceptionClass>("NoMethodError")));
/// assert!(!err.is_kind_of(get::<RModule>("Math")));
/// ```
pub fn is_kind_of<T>(&self, class: T) -> bool
where
T: ReprValue + Module,
{
match self.0 {
ErrorType::Jump(_) => false,
ErrorType::Error(c, _) => c.is_inherited(class),
ErrorType::Exception(e) => e.is_kind_of(class),
}
}
/// Consumes `self`, returning an `Exception`.
///
/// # Panics
///
/// Panics if called on an `Error::Jump`.
fn exception(self) -> Exception {
let handle = unsafe { Ruby::get_unchecked() };
match self.0 {
ErrorType::Jump(_) => panic!("Error::exception() called on {}", self),
ErrorType::Error(class, msg) => {
match class.new_instance((handle.str_new(msg.as_ref()),)) {
Ok(e) | Err(Error(ErrorType::Exception(e))) => e,
Err(err) => unreachable!("*very* unexpected error: {}", err),
}
}
ErrorType::Exception(e) => e,
}
}
/// Returns the [`ErrorType`] for self.
pub fn error_type(&self) -> &ErrorType {
&self.0
}
/// Returns the inner [`Value`] of `self`, if there is one.
///
/// The returned `Value` may be a subclass or an instance of `Exception`.
///
/// This function is provided for rare cases where the `Error` needs to be
/// stored on the heap and the inner value needs to be
/// [marked](`crate::gc::mark`) to avoid being garbage collected.
pub fn value(&self) -> Option<Value> {
match self.0 {
ErrorType::Jump(_) => None,
ErrorType::Error(c, _) => Some(c.as_value()),
ErrorType::Exception(e) => Some(e.as_value()),
}
}
/// Create an `Error` from the error value of [`std::panic::catch_unwind`].
///
/// The Ruby Exception will be `fatal`, terminating the Ruby process, but
/// allowing cleanup code to run.
pub(crate) fn from_panic(e: Box<dyn Any + Send + 'static>) -> Self {
let msg = if let Some(&m) = e.downcast_ref::<&'static str>() {
m.into()
} else if let Some(m) = e.downcast_ref::<String>() {
m.clone().into()
} else {
"panic".into()
};
Self(ErrorType::Error(
unsafe { Ruby::get_unchecked().exception_fatal() },
msg,
))
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match &self.0 {
ErrorType::Jump(s) => s.fmt(f),
ErrorType::Error(e, m) => write!(f, "{}: {}", e, m),
ErrorType::Exception(e) => e.fmt(f),
}
}
}
impl From<Exception> for Error {
fn from(val: Exception) -> Self {
Self(ErrorType::Exception(val))
}
}
/// A wrapper to make a [`Error`] [`Send`] + [`Sync`].
///
/// [`Error`] is not [`Send`] or [`Sync`] as it provides a way to call some of
/// Ruby's APIs, which are not safe to call from a non-Ruby thread.
///
/// [`Error`] is safe to send between Ruby threads, but Rust's trait system
/// currently can not model this detail.
///
/// To resolve this, the `OpaqueError` type makes an [`Error`] [`Send`] +
/// [`Sync`] by removing the ability use it with any Ruby APIs.
///
/// [`OpaqueError::into_error_with`] provides a way to safely get an [`Error`]
/// from a `OpaqueError`].
///
/// Note that `OpaqueError` contains a Ruby value, so must be kept on the stack
/// of a Ruby thread to prevent it from being Garbage Collected (or otherwise
/// protected from premature GC).
pub struct OpaqueError(ErrorType);
unsafe impl Send for OpaqueError {}
unsafe impl Sync for OpaqueError {}
impl OpaqueError {
/// Convert an `OpaqueError` into an [`Error`].
///
/// # Examples
///
/// ```
/// use magnus::{error::OpaqueError, Error, Ruby};
/// # let _cleanup = unsafe { magnus::embed::init() };
///
/// let ruby = Ruby::get().unwrap(); // errors on non-Ruby thread
/// let opaque_err = OpaqueError::from(Error::new(ruby.exception_runtime_error(), "test"));
///
/// // send to another Ruby thread
///
/// let ruby = Ruby::get().unwrap(); // errors on non-Ruby thread
/// let err = OpaqueError::into_error_with(opaque_err, &ruby);
/// assert!(err.is_kind_of(ruby.exception_runtime_error()));
/// ```
#[allow(unused_variables)]
pub fn into_error_with(this: Self, handle: &Ruby) -> Error {
Error(this.0)
}
}
impl From<Error> for OpaqueError {
fn from(err: Error) -> Self {
Self(err.0)
}
}
/// The state of a call to Ruby exiting early, interrupting the normal flow
/// of code.
#[derive(Debug)]
#[repr(i32)]
pub enum Tag {
// None = 0,
/// Early return from a block.
Return = 1,
/// Break from a block.
Break = 2,
/// Early return from a block, continuing to next block call.
Next = 3,
/// Break from a block after an error, block will be subsequently re-run.
Retry = 4,
/// Break from a block that will be subsequently re-run.
Redo = 5,
/// Ruby stack unwound with an error.
Raise = 6,
/// Ruby stack unwound as flow control.
Throw = 7,
/// Block or method exiting early due to unrecoverable error.
Fatal = 8,
}
impl Tag {
fn resume(self) -> ! {
unsafe { rb_jump_tag(self as c_int) };
}
}
impl fmt::Display for Tag {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
// Self::None => write!(f, "None"),
Self::Return => write!(f, "Return"),
Self::Break => write!(f, "Break"),
Self::Next => write!(f, "Next"),
Self::Retry => write!(f, "Retry"),
Self::Redo => write!(f, "Redo"),
Self::Raise => write!(f, "Raise"),
Self::Throw => write!(f, "Throw"),
Self::Fatal => write!(f, "Fatal"),
}
}
}
/// Calls the given closure, rescuing Ruby Exceptions and returning them as
/// an [`Error`].
///
/// All functions exposed by magnus that call Ruby in a way that may raise
/// already use this internally, but this is provided for anyone calling
/// the Ruby C API directly.
pub(crate) fn protect<F, T>(func: F) -> Result<T>
where
F: FnOnce() -> T,
T: ReprValue,
{
// nested function as this is totally unsafe to call out of this context
// arg should not be a VALUE, but a mutable pointer to F, cast to VALUE
unsafe extern "C" fn call<F, T>(arg: VALUE) -> VALUE
where
F: FnOnce() -> T,
T: ReprValue,
{
let closure = (*(arg as *mut Option<F>)).take().unwrap();
(closure)().as_rb_value()
}
// Tag::None
let mut state = 0;
// rb_protect takes:
// arg1: function pointer that returns a VALUE
// arg2: a VALUE
// arg3: a pointer to an int.
// rb_protect then calls arg1 with arg2 and returns the VALUE that arg1
// returns. If a Ruby exception is raised (or other interrupt) the VALUE
// returned is instead Qnil, and arg3 is set to non-zero.
// As arg2 is only ever passed to arg1 and otherwise not touched we can
// pack in whatever data we want that will fit into a VALUE. This is part
// of the api and safe to do.
// In this case we use arg2 to pass a pointer the Rust closure we actually
// want to call, and arg1 is just a simple adapter to call arg2.
let result = unsafe {
let mut some_func = Some(func);
let closure = &mut some_func as *mut Option<F> as VALUE;
rb_protect(Some(call::<F, T>), closure, &mut state as *mut c_int)
};
match state {
// Tag::None
0 => unsafe { Ok(T::from_value_unchecked(Value::new(result))) },
// Tag::Raise
6 => unsafe {
let ex = Exception::from_rb_value_unchecked(rb_errinfo());
rb_set_errinfo(Ruby::get_unchecked().qnil().as_rb_value());
Err(ex.into())
},
other => Err(Error::from_tag(unsafe { transmute(other) })),
}
}
pub(crate) fn ensure<F1, F2, T>(func: F1, ensure: F2) -> T
where
F1: FnOnce() -> T,
F2: FnOnce(),
T: ReprValue,
{
unsafe extern "C" fn call_func<F1, T>(arg: VALUE) -> VALUE
where
F1: FnOnce() -> T,
T: ReprValue,
{
let closure = (*(arg as *mut Option<F1>)).take().unwrap();
(closure)().as_rb_value()
}
unsafe extern "C" fn call_ensure<F2>(arg: VALUE) -> VALUE
where
F2: FnOnce(),
{
let closure = (*(arg as *mut Option<F2>)).take().unwrap();
(closure)();
ruby_special_consts::RUBY_Qnil as VALUE
}
let result = unsafe {
let call_func_ptr = call_func::<F1, T> as unsafe extern "C" fn(VALUE) -> VALUE;
#[cfg(ruby_lt_2_7)]
let call_func_ptr: unsafe extern "C" fn() -> VALUE = std::mem::transmute(call_func_ptr);
let mut some_func = Some(func);
let func_closure = &mut some_func as *mut Option<F1> as VALUE;
let call_ensure_ptr = call_ensure::<F2> as unsafe extern "C" fn(VALUE) -> VALUE;
#[cfg(ruby_lt_2_7)]
let call_ensure_ptr: unsafe extern "C" fn() -> VALUE = std::mem::transmute(call_ensure_ptr);
let mut some_ensure = Some(ensure);
let ensure_closure = &mut some_ensure as *mut Option<F2> as VALUE;
rb_ensure(
Some(call_func_ptr),
func_closure,
Some(call_ensure_ptr),
ensure_closure,
)
};
unsafe { T::from_value_unchecked(Value::new(result)) }
}
pub(crate) fn raise(e: Error) -> ! {
match e.0 {
ErrorType::Jump(tag) => tag.resume(),
_ => {
unsafe { rb_exc_raise(e.exception().as_rb_value()) }
// friendly reminder: we really never get here, and as such won't
// drop any values still in scope, make sure everything has been
// consumed/dropped
}
};
}
pub(crate) fn bug_from_panic(e: Box<dyn Any + Send + 'static>, or: &str) -> ! {
let msg: Cow<'_, str> = if let Some(&m) = e.downcast_ref::<&'static str>() {
m.into()
} else if let Some(m) = e.downcast_ref::<String>() {
m.clone().into()
} else {
or.into()
};
bug(&msg)
}
/// Immediately terminate the process, printing Ruby internal state for
/// debugging.
pub fn bug(s: &str) -> ! {
let s = CString::new(s).unwrap_or_else(|_| CString::new("panic").unwrap());
unsafe { rb_bug(s.as_ptr()) };
// as we never get here `s` isn't dropped, technically this is a memory
// leak, in practice we don't care because we just hard crashed
}
/// Outputs `s` to Ruby's stderr if Ruby is configured to output warnings.
///
/// Otherwise does nothing.
///
/// # Panics
///
/// Panics if called from a non-Ruby thread. See [`Ruby::warning`] for the
/// non-panicking version.
#[cfg_attr(
not(feature = "friendly-api"),
deprecated(note = "please use `Ruby::warning` instead")
)]
#[inline]
pub fn warning(s: &str) {
get_ruby!().warning(s)
}