error_stack/hook/context.rs
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#[cfg_attr(feature = "std", allow(unused_imports))]
use alloc::boxed::Box;
use alloc::collections::BTreeMap;
use core::any::{Any, TypeId};
pub(crate) type Storage = BTreeMap<TypeId, BTreeMap<TypeId, Box<dyn Any>>>;
/// Private struct which is used to hold the information about the current count for every type.
/// This is used so that others cannot interfere with the counter and ensure that there's no
/// unexpected behavior.
pub(crate) struct Counter(isize);
impl Counter {
pub(crate) const fn new(value: isize) -> Self {
Self(value)
}
pub(crate) const fn as_inner(&self) -> isize {
self.0
}
pub(crate) fn increment(&mut self) {
self.0 += 1;
}
pub(crate) fn decrement(&mut self) {
self.0 -= 1;
}
}
pub(crate) struct Inner<T> {
storage: Storage,
extra: T,
}
impl<T> Inner<T> {
pub(crate) fn new(extra: T) -> Self {
Self {
storage: Storage::new(),
extra,
}
}
}
impl<T> Inner<T> {
pub(crate) const fn storage(&self) -> &Storage {
&self.storage
}
pub(crate) fn storage_mut(&mut self) -> &mut Storage {
&mut self.storage
}
pub(crate) const fn extra(&self) -> &T {
&self.extra
}
pub(crate) fn extra_mut(&mut self) -> &mut T {
&mut self.extra
}
}
macro_rules! impl_hook_context {
($(#[$meta:meta])* $vis:vis struct HookContext<$extra:ident> {..}) => {
// TODO: add link to serde hooks once implemented
// TODO: ideally we would want to make `HookContextInner` private, as it is an implementation
// detail, but "attribute privacy" as outlined in https://github.com/rust-lang/rust/pull/61969
// is currently not implemented for repr(transparent).
$(#[$meta])*
#[cfg_attr(not(doc), repr(transparent))]
$vis struct HookContext<T> {
inner: $crate::hook::context::Inner<$extra>,
_marker: core::marker::PhantomData<fn(&T)>,
}
impl HookContext<()> {
pub(crate) fn new(extra: $extra) -> Self {
Self {
inner: $crate::hook::context::Inner::new(extra),
_marker: core::marker::PhantomData,
}
}
}
impl<T> HookContext<T> {
pub(crate) const fn inner(&self) -> &$crate::hook::context::Inner<$extra> {
&self.inner
}
pub(crate) fn inner_mut(&mut self) -> &mut $crate::hook::context::Inner<$extra> {
&mut self.inner
}
fn storage(&self) -> &$crate::hook::context::Storage {
self.inner().storage()
}
fn storage_mut(&mut self) -> &mut $crate::hook::context::Storage {
self.inner_mut().storage_mut()
}
}
#[cfg(any(feature = "std", feature = "hooks"))]
impl<T> HookContext<T> {
/// Cast the [`HookContext`] to a new type `U`.
///
/// The storage of [`HookContext`] is partitioned, meaning that if `T` and `U` are different
/// types the values stored in [`HookContext<_, T>`] will be separated from values in
/// [`HookContext<_, U>`].
///
/// In most situations this functions isn't needed, as it transparently casts between different
/// partitions of the storage. Only hooks that share storage with hooks of different types
/// should need to use this function.
///
/// ### Example
///
/// ```rust
/// # // we only test with nightly, which means that `render()` is unused on earlier version
/// # #![cfg_attr(not(nightly), allow(dead_code, unused_variables, unused_imports))]
/// use std::io::ErrorKind;
///
/// use error_stack::Report;
///
/// struct Warning(&'static str);
/// struct Error(&'static str);
///
/// Report::install_debug_hook::<Error>(|Error(frame), context| {
/// let idx = context.increment_counter() + 1;
///
/// context.push_body(format!("[{idx}] [ERROR] {frame}"));
/// });
/// Report::install_debug_hook::<Warning>(|Warning(frame), context| {
/// // We want to share the same counter with `Error`, so that we're able to have
/// // a global counter to keep track of all errors and warnings in order, this means
/// // we need to access the storage of `Error` using `cast()`.
/// let context = context.cast::<Error>();
/// let idx = context.increment_counter() + 1;
/// context.push_body(format!("[{idx}] [WARN] {frame}"))
/// });
///
/// let report = Report::new(std::io::Error::from(ErrorKind::InvalidInput))
/// .attach(Error("unable to reach remote host"))
/// .attach(Warning("disk nearly full"))
/// .attach(Error("cannot resolve example.com: unknown host"));
///
/// # Report::set_color_mode(error_stack::fmt::ColorMode::Emphasis);
/// # fn render(value: String) -> String {
/// # let backtrace = regex::Regex::new(r"backtrace no\. (\d+)\n(?: .*\n)* .*").unwrap();
/// # let backtrace_info = regex::Regex::new(r"backtrace( with (\d+) frames)? \((\d+)\)").unwrap();
/// #
/// # let value = backtrace.replace_all(&value, "backtrace no. $1\n [redacted]");
/// # let value = backtrace_info.replace_all(value.as_ref(), "backtrace ($3)");
/// #
/// # ansi_to_html::convert(value.as_ref()).unwrap()
/// # }
/// #
/// # #[cfg(nightly)]
/// # expect_test::expect_file![concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_cast.snap")].assert_eq(&render(format!("{report:?}")));
/// #
/// println!("{report:?}");
/// ```
///
/// <pre>
#[doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_cast.snap"))]
/// </pre>
#[must_use]
pub fn cast<U>(&mut self) -> &mut HookContext<U> {
// SAFETY: `HookContext` is marked as repr(transparent) and the changed generic is only used
// inside of the `PhantomData`
unsafe { &mut *(self as *mut Self).cast::<HookContext<U>>() }
}
}
#[cfg(any(feature = "std", feature = "hooks"))]
impl<T: 'static> HookContext<T> {
/// Return a reference to a value of type `U`, if a value of that type exists.
///
/// Values returned are isolated and "bound" to `T`, this means that [`HookContext<_, Warning>`]
/// and [`HookContext<_, Error>`] do not share the same values. Values are only valid during the
/// invocation of the corresponding call (e.g. [`Debug`]).
///
/// [`Debug`]: core::fmt::Debug
#[must_use]
pub fn get<U: 'static>(&self) -> Option<&U> {
self.storage()
.get(&TypeId::of::<T>())?
.get(&TypeId::of::<U>())?
.downcast_ref()
}
/// Return a mutable reference to a value of type `U`, if a value of that type exists.
///
/// Values returned are isolated and "bound" to `T`, this means that [`HookContext<_, Warning>`]
/// and [`HookContext<_, Error>`] do not share the same values. Values are only valid during the
/// invocation of the corresponding call (e.g. [`Debug`]).
///
/// [`Debug`]: core::fmt::Debug
pub fn get_mut<U: 'static>(&mut self) -> Option<&mut U> {
self.storage_mut()
.get_mut(&TypeId::of::<T>())?
.get_mut(&TypeId::of::<U>())?
.downcast_mut()
}
/// Insert a new value of type `U` into the storage of [`HookContext`].
///
/// The returned value will the previously stored value of the same type `U` scoped over type
/// `T`, if it existed, did no such value exist it will return [`None`].
pub fn insert<U: 'static>(&mut self, value: U) -> Option<U> {
self.storage_mut()
.entry(TypeId::of::<T>())
.or_default()
.insert(TypeId::of::<U>(), Box::new(value))?
.downcast()
.map(|boxed| *boxed)
.ok()
}
/// Remove the value of type `U` from the storage of [`HookContext`] if it existed.
///
/// The returned value will be the previously stored value of the same type `U` if it existed in
/// the scope of `T`, did no such value exist, it will return [`None`].
pub fn remove<U: 'static>(&mut self) -> Option<U> {
self.storage_mut()
.get_mut(&TypeId::of::<T>())?
.remove(&TypeId::of::<U>())?
.downcast()
.map(|boxed| *boxed)
.ok()
}
/// One of the most common interactions with [`HookContext`] is a counter to reference previous
/// frames in an entry to the appendix that was added using [`HookContext::push_appendix`].
///
/// This is a utility method, which uses the other primitive methods provided to automatically
/// increment a counter, if the counter wasn't initialized this method will return `0`.
///
/// ```rust
/// # // we only test with nightly, which means that `render()` is unused on earlier version
/// # #![cfg_attr(not(nightly), allow(dead_code, unused_variables, unused_imports))]
/// use std::io::ErrorKind;
///
/// use error_stack::Report;
///
/// struct Suggestion(&'static str);
///
/// Report::install_debug_hook::<Suggestion>(|Suggestion(value), context| {
/// let idx = context.increment_counter();
/// context.push_body(format!("suggestion {idx}: {value}"));
/// });
///
/// let report = Report::new(std::io::Error::from(ErrorKind::InvalidInput))
/// .attach(Suggestion("use a file you can read next time!"))
/// .attach(Suggestion("don't press any random keys!"));
///
/// # Report::set_color_mode(error_stack::fmt::ColorMode::Emphasis);
/// # fn render(value: String) -> String {
/// # let backtrace = regex::Regex::new(r"backtrace no\. (\d+)\n(?: .*\n)* .*").unwrap();
/// # let backtrace_info = regex::Regex::new(r"backtrace( with (\d+) frames)? \((\d+)\)").unwrap();
/// #
/// # let value = backtrace.replace_all(&value, "backtrace no. $1\n [redacted]");
/// # let value = backtrace_info.replace_all(value.as_ref(), "backtrace ($3)");
/// #
/// # ansi_to_html::convert(value.as_ref()).unwrap()
/// # }
/// #
/// # #[cfg(nightly)]
/// # expect_test::expect_file![concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_increment.snap")].assert_eq(&render(format!("{report:?}")));
/// #
/// println!("{report:?}");
/// ```
///
/// <pre>
#[doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_increment.snap"))]
/// </pre>
///
/// [`Debug`]: core::fmt::Debug
pub fn increment_counter(&mut self) -> isize {
let counter = self.get_mut::<$crate::hook::context::Counter>();
match counter {
None => {
// if the counter hasn't been set yet, default to `0`
self.insert($crate::hook::context::Counter::new(0));
0
}
Some(ctr) => {
ctr.increment();
ctr.as_inner()
}
}
}
/// One of the most common interactions with [`HookContext`] is a counter to reference previous
/// frames in an entry to the appendix that was added using [`HookContext::push_appendix`].
///
/// This is a utility method, which uses the other primitive method provided to automatically
/// decrement a counter, if the counter wasn't initialized this method will return `-1` to stay
/// consistent with [`HookContext::increment_counter`].
///
/// ```rust
/// # // we only test with nightly, which means that `render()` is unused on earlier version
/// # #![cfg_attr(not(nightly), allow(dead_code, unused_variables, unused_imports))]
/// use std::io::ErrorKind;
///
/// use error_stack::Report;
///
/// struct Suggestion(&'static str);
///
/// Report::install_debug_hook::<Suggestion>(|Suggestion(value), context| {
/// let idx = context.decrement_counter();
/// context.push_body(format!("suggestion {idx}: {value}"));
/// });
///
/// let report = Report::new(std::io::Error::from(ErrorKind::InvalidInput))
/// .attach(Suggestion("use a file you can read next time!"))
/// .attach(Suggestion("don't press any random keys!"));
///
/// # Report::set_color_mode(error_stack::fmt::ColorMode::Emphasis);
/// # fn render(value: String) -> String {
/// # let backtrace = regex::Regex::new(r"backtrace no\. (\d+)\n(?: .*\n)* .*").unwrap();
/// # let backtrace_info = regex::Regex::new(r"backtrace( with (\d+) frames)? \((\d+)\)").unwrap();
/// #
/// # let value = backtrace.replace_all(&value, "backtrace no. $1\n [redacted]");
/// # let value = backtrace_info.replace_all(value.as_ref(), "backtrace ($3)");
/// #
/// # ansi_to_html::convert(value.as_ref()).unwrap()
/// # }
/// #
/// # #[cfg(nightly)]
/// # expect_test::expect_file![concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_decrement.snap")].assert_eq(&render(format!("{report:?}")));
/// #
/// println!("{report:?}");
/// ```
///
/// <pre>
#[doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/tests/snapshots/doc/fmt__hookcontext_decrement.snap"))]
/// </pre>
pub fn decrement_counter(&mut self) -> isize {
let counter = self.get_mut::<$crate::hook::context::Counter>();
match counter {
None => {
// given that increment starts with `0` (which is therefore the implicit default
// value) decrementing the default value results in `-1`,
// which is why we output that value.
self.insert($crate::hook::context::Counter::new(-1));
-1
}
Some(ctr) => {
ctr.decrement();
ctr.as_inner()
}
}
}
}
};
}
pub(crate) use impl_hook_context;