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//! `field()` and `message()` predicate factories.
use predicates::{
reflection::{Case, PredicateReflection, Product},
Predicate,
};
use std::{any::type_name, borrow::Borrow, fmt, marker::PhantomData};
use crate::{Captured, CapturedEvent};
use tracing_tunnel::{FromTracedValue, TracedValue};
/// Conversion into a predicate for a [`TracedValue`] used in the [`field()`] function.
pub trait IntoFieldPredicate {
/// Predicate output of the conversion. The exact type should be considered an implementation
/// detail and should not be relied upon.
type Predicate: Predicate<TracedValue>;
/// Performs the conversion.
fn into_predicate(self) -> Self::Predicate;
}
impl<P: Predicate<TracedValue>> IntoFieldPredicate for [P; 1] {
type Predicate = P;
fn into_predicate(self) -> Self::Predicate {
self.into_iter().next().unwrap()
}
}
macro_rules! impl_into_field_predicate {
($($ty:ty),+) => {
$(
impl IntoFieldPredicate for $ty {
type Predicate = EquivPredicate<Self>;
fn into_predicate(self) -> Self::Predicate {
EquivPredicate { value: self }
}
}
)+
};
}
impl_into_field_predicate!(bool, i64, i128, u64, u128, f64, &str);
/// Creates a predicate for a particular field of a [`CapturedSpan`] or [`CapturedEvent`].
///
/// # Arguments
///
/// The argument of this function is essentially a predicate for the [`TracedValue`] of the field.
/// It may be:
///
/// - `bool`, `i64`, `i128`, `u64`, `u128`, `f64`, `&str`: will be compared to the `TracedValue`
/// using the corresponding [`PartialEq`] implementation.
/// - A predicate produced by the [`value()`] function.
/// - Any `Predicate` for [`TracedValue`]. To bypass Rust orphaning rules, the predicate
/// must be enclosed in square brackets (i.e., a one-value array).
///
/// [`CapturedSpan`]: crate::CapturedSpan
///
/// # Examples
///
/// ```
/// # use predicates::{constant::always, ord::gt};
/// # use tracing_subscriber::{layer::SubscriberExt, Registry};
/// # use tracing_capture::{predicates::{field, value, ScanExt}, CaptureLayer, SharedStorage};
/// let storage = SharedStorage::default();
/// let subscriber = Registry::default().with(CaptureLayer::new(&storage));
/// tracing::subscriber::with_default(subscriber, || {
/// tracing::info_span!("compute", arg = 5_i32).in_scope(|| {
/// tracing::info!("done");
/// });
/// });
///
/// let storage = storage.lock();
/// // All of these access the single captured span.
/// let spans = storage.scan_spans();
/// let _ = spans.single(&field("arg", [always()]));
/// let _ = spans.single(&field("arg", 5_i64));
/// let _ = spans.single(&field("arg", value(gt(3_i64))));
/// ```
pub fn field<P: IntoFieldPredicate>(
name: &'static str,
matches: P,
) -> FieldPredicate<P::Predicate> {
FieldPredicate {
name,
matches: matches.into_predicate(),
}
}
/// Predicate for a particular field of a [`CapturedSpan`] or [`CapturedEvent`] returned by
/// the [`field()`] function.
///
/// [`CapturedSpan`]: crate::CapturedSpan
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct FieldPredicate<P> {
name: &'static str,
matches: P,
}
impl_bool_ops!(FieldPredicate<P>);
impl<P: Predicate<TracedValue>> fmt::Display for FieldPredicate<P> {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "fields.{}({})", self.name, self.matches)
}
}
impl<P: Predicate<TracedValue>> PredicateReflection for FieldPredicate<P> {}
impl<'a, P: Predicate<TracedValue>, T: Captured<'a>> Predicate<T> for FieldPredicate<P> {
fn eval(&self, variable: &T) -> bool {
variable
.value(self.name)
.map_or(false, |value| self.matches.eval(value))
}
fn find_case(&self, expected: bool, variable: &T) -> Option<Case<'_>> {
let Some(value) = variable.value(self.name) else {
return if expected {
None // was expecting a variable, but there is none
} else {
let product = Product::new(format!("fields.{}", self.name), "None");
Some(Case::new(Some(self), expected).add_product(product))
};
};
let child = self.matches.find_case(expected, value)?;
Some(Case::new(Some(self), expected).add_child(child))
}
}
#[doc(hidden)] // implementation detail (yet?)
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct EquivPredicate<V> {
value: V,
}
impl<V: fmt::Debug> fmt::Display for EquivPredicate<V> {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "var == {:?}", self.value)
}
}
impl<V: fmt::Debug> PredicateReflection for EquivPredicate<V> {}
impl<V: fmt::Debug + PartialEq<TracedValue>> Predicate<TracedValue> for EquivPredicate<V> {
fn eval(&self, variable: &TracedValue) -> bool {
self.value == *variable
}
fn find_case(&self, expected: bool, variable: &TracedValue) -> Option<Case<'_>> {
if self.eval(variable) == expected {
let product = Product::new("var", format!("{variable:?}"));
Some(Case::new(Some(self), expected).add_product(product))
} else {
None
}
}
}
/// Creates a predicate for a [`TracedValue`] that checks whether the value matches
/// the specified criteria for a particular subtype (e.g., an unsigned integer).
/// If the value has another subtype, the predicate is false.
///
/// Returned predicates can be supplied to the [`field()`] function.
///
/// # Arguments
///
/// The argument must be a predicate for one of types that can be obtained from a [`TracedValue`]
/// reference: `bool`, `i64`, `i128`, `u64`, `u128`, `f64`, or `str`. The type can be specified
/// explicitly, but usually you can make Rust properly infer it.
///
/// # Examples
///
/// ```
/// # use predicates::{ord::{gt, ne}, iter::in_hash, str::contains};
/// # use tracing_capture::predicates::{field, value};
/// let _ = field("return", value(gt(5.0)));
/// let _ = field("name", value(contains("test")));
/// let _ = field("float", value(in_hash([3_u64, 5])));
/// // ^ Note the specified integer type.
/// ```
pub fn value<T, P>(matches: P) -> ValuePredicate<T, P>
where
T: for<'a> FromTracedValue<'a> + ?Sized,
P: Predicate<T>,
{
ValuePredicate {
matches,
_ty: PhantomData,
}
}
/// Predicate for [`TracedValue`]s returned by the [`value()`] function.
#[derive(Debug)]
pub struct ValuePredicate<T: ?Sized, P> {
matches: P,
_ty: PhantomData<fn(T)>,
}
impl<T: ?Sized, P: Clone> Clone for ValuePredicate<T, P> {
fn clone(&self) -> Self {
Self {
matches: self.matches.clone(),
_ty: PhantomData,
}
}
}
impl<T: ?Sized, P: Copy> Copy for ValuePredicate<T, P> {}
impl<T: ?Sized, P: PartialEq> PartialEq for ValuePredicate<T, P> {
fn eq(&self, other: &Self) -> bool {
self.matches == other.matches
}
}
impl<T, P> fmt::Display for ValuePredicate<T, P>
where
T: for<'a> FromTracedValue<'a> + ?Sized,
P: Predicate<T>,
{
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "is<{}>({})", type_name::<T>(), self.matches)
}
}
impl<T, P> PredicateReflection for ValuePredicate<T, P>
where
T: for<'a> FromTracedValue<'a> + ?Sized,
P: Predicate<T>,
{
}
impl<T, P> Predicate<TracedValue> for ValuePredicate<T, P>
where
T: for<'a> FromTracedValue<'a> + ?Sized,
P: Predicate<T>,
{
fn eval(&self, variable: &TracedValue) -> bool {
T::from_value(variable).map_or(false, |value| self.matches.eval(value.borrow()))
}
fn find_case(&self, expected: bool, variable: &TracedValue) -> Option<Case<'_>> {
let value = T::from_value(variable);
let value = if let Some(value) = &value {
value.borrow()
} else {
return if expected {
None // was expecting another var type
} else {
let product = Product::new(format!("var.as<{}>", type_name::<T>()), "None");
Some(Case::new(Some(self), expected).add_product(product))
};
};
let child = self.matches.find_case(expected, value)?;
Some(Case::new(Some(self), expected).add_child(child))
}
}
impl<T, P> IntoFieldPredicate for ValuePredicate<T, P>
where
T: for<'a> FromTracedValue<'a> + ?Sized,
P: Predicate<T>,
{
type Predicate = Self;
fn into_predicate(self) -> Self::Predicate {
self
}
}
/// Creates a predicate for the message of a [`CapturedEvent`].
///
/// # Arguments
///
/// The argument of this function is a `str` predicate for the event message.
///
/// # Examples
///
/// ```
/// # use predicates::{ord::eq, str::contains};
/// # use tracing_subscriber::{layer::SubscriberExt, Registry};
/// # use tracing_capture::{predicates::{message, ScanExt}, CaptureLayer, SharedStorage};
/// let storage = SharedStorage::default();
/// let subscriber = Registry::default().with(CaptureLayer::new(&storage));
/// tracing::subscriber::with_default(subscriber, || {
/// tracing::info_span!("compute").in_scope(|| {
/// tracing::info!(result = 42, "computations completed");
/// });
/// });
///
/// let storage = storage.lock();
/// // All of these access the single captured event.
/// let events = storage.scan_events();
/// let _ = events.single(&message(eq("computations completed")));
/// let _ = events.single(&message(contains("completed")));
/// ```
pub fn message<P: Predicate<str>>(matches: P) -> MessagePredicate<P> {
MessagePredicate { matches }
}
/// Predicate for the message of a [`CapturedEvent`] returned by the [`message()`] function.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct MessagePredicate<P> {
matches: P,
}
impl_bool_ops!(MessagePredicate<P>);
impl<P: Predicate<str>> fmt::Display for MessagePredicate<P> {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(formatter, "message({})", self.matches)
}
}
impl<P: Predicate<str>> PredicateReflection for MessagePredicate<P> {}
impl<P: Predicate<str>> Predicate<CapturedEvent<'_>> for MessagePredicate<P> {
fn eval(&self, variable: &CapturedEvent<'_>) -> bool {
variable
.message()
.map_or(false, |value| self.matches.eval(value))
}
fn find_case(&self, expected: bool, variable: &CapturedEvent<'_>) -> Option<Case<'_>> {
let Some(message) = variable.message() else {
return if expected {
None // was expecting a variable, but there is none
} else {
let product = Product::new("message", "None");
Some(Case::new(Some(self), expected).add_product(product))
};
};
let child = self.matches.find_case(expected, message)?;
Some(Case::new(Some(self), expected).add_child(child))
}
}