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//! `Span` and `Event` key-value data.
//!
//! Spans and events may be annotated with key-value data, referred to as known
//! as _fields_. These fields consist of a mapping from a key (corresponding to
//! a `&str` but represented internally as an array index) to a [`Value`].
//!
//! # `Value`s and `Subscriber`s
//!
//! `Subscriber`s consume `Value`s as fields attached to [span]s or [`Event`]s.
//! The set of field keys on a given span or is defined on its [`Metadata`].
//! When a span is created, it provides [`Attributes`] to the `Subscriber`'s
//! [`new_span`] method, containing any fields whose values were provided when
//! the span was created; and may call the `Subscriber`'s [`record`] method
//! with additional [`Record`]s if values are added for more of its fields.
//! Similarly, the [`Event`] type passed to the subscriber's [`event`] method
//! will contain any fields attached to each event.
//!
//! `tracing` represents values as either one of a set of Rust primitives
//! (`i64`, `u64`, `f64`, `i128`, `u128`, `bool`, and `&str`) or using a
//! `fmt::Display` or `fmt::Debug` implementation. `Subscriber`s are provided
//! these primitive value types as `dyn Value` trait objects.
//!
//! These trait objects can be formatted using `fmt::Debug`, but may also be
//! recorded as typed data by calling the [`Value::record`] method on these
//! trait objects with a _visitor_ implementing the [`Visit`] trait. This trait
//! represents the behavior used to record values of various types. For example,
//! an implementation of `Visit` might record integers by incrementing counters
//! for their field names rather than printing them.
//!
//!
//! # Using `valuable`
//!
//! `tracing`'s [`Value`] trait is intentionally minimalist: it supports only a small
//! number of Rust primitives as typed values, and only permits recording
//! user-defined types with their [`fmt::Debug`] or [`fmt::Display`]
//! implementations. However, there are some cases where it may be useful to record
//! nested values (such as arrays, `Vec`s, or `HashMap`s containing values), or
//! user-defined `struct` and `enum` types without having to format them as
//! unstructured text.
//!
//! To address `Value`'s limitations, `tracing` offers experimental support for
//! the [`valuable`] crate, which provides object-safe inspection of structured
//! values. User-defined types can implement the [`valuable::Valuable`] trait,
//! and be recorded as a `tracing` field by calling their [`as_value`] method.
//! If the [`Subscriber`] also supports the `valuable` crate, it can
//! then visit those types fields as structured values using `valuable`.
//!
//! <pre class="ignore" style="white-space:normal;font:inherit;">
//! <strong>Note</strong>: <code>valuable</code> support is an
//! <a href = "../index.html#unstable-features">unstable feature</a>. See
//! the documentation on unstable features for details on how to enable it.
//! </pre>
//!
//! For example:
//! ```ignore
//! // Derive `Valuable` for our types:
//! use valuable::Valuable;
//!
//! #[derive(Clone, Debug, Valuable)]
//! struct User {
//! name: String,
//! age: u32,
//! address: Address,
//! }
//!
//! #[derive(Clone, Debug, Valuable)]
//! struct Address {
//! country: String,
//! city: String,
//! street: String,
//! }
//!
//! let user = User {
//! name: "Arwen Undomiel".to_string(),
//! age: 3000,
//! address: Address {
//! country: "Middle Earth".to_string(),
//! city: "Rivendell".to_string(),
//! street: "leafy lane".to_string(),
//! },
//! };
//!
//! // Recording `user` as a `valuable::Value` will allow the `tracing` subscriber
//! // to traverse its fields as a nested, typed structure:
//! tracing::info!(current_user = user.as_value());
//! ```
//!
//! Alternatively, the [`valuable()`] function may be used to convert a type
//! implementing [`Valuable`] into a `tracing` field value.
//!
//! When the `valuable` feature is enabled, the [`Visit`] trait will include an
//! optional [`record_value`] method. `Visit` implementations that wish to
//! record `valuable` values can implement this method with custom behavior.
//! If a visitor does not implement `record_value`, the [`valuable::Value`] will
//! be forwarded to the visitor's [`record_debug`] method.
//!
//! [`as_value`]: valuable::Valuable::as_value
//! [`Subscriber`]: crate::Subscriber
//! [`record_value`]: Visit::record_value
//! [`record_debug`]: Visit::record_debug
//!
//! [span]: super::span
//! [`Event`]: super::event::Event
//! [`Metadata`]: super::metadata::Metadata
//! [`Attributes`]: super::span::Attributes
//! [`Record`]: super::span::Record
//! [`new_span`]: super::subscriber::Subscriber::new_span
//! [`record`]: super::subscriber::Subscriber::record
//! [`event`]: super::subscriber::Subscriber::event
//! [`Value::record`]: Value::record
use crate::callsite;
use crate::stdlib::{
borrow::Borrow,
fmt,
hash::{Hash, Hasher},
num,
ops::Range,
string::String,
};
use self::private::ValidLen;
/// An opaque key allowing _O_(1) access to a field in a `Span`'s key-value
/// data.
///
/// As keys are defined by the _metadata_ of a span, rather than by an
/// individual instance of a span, a key may be used to access the same field
/// across all instances of a given span with the same metadata. Thus, when a
/// subscriber observes a new span, it need only access a field by name _once_,
/// and use the key for that name for all other accesses.
#[derive(Debug)]
pub struct Field {
i: usize,
fields: FieldSet,
}
/// An empty field.
///
/// This can be used to indicate that the value of a field is not currently
/// present but will be recorded later.
///
/// When a field's value is `Empty`. it will not be recorded.
#[derive(Debug, Eq, PartialEq)]
pub struct Empty;
/// Describes the fields present on a span.
///
/// ## Equality
///
/// In well-behaved applications, two `FieldSet`s [initialized] with equal
/// [callsite identifiers] will have identical fields. Consequently, in release
/// builds, [`FieldSet::eq`] *only* checks that its arguments have equal
/// callsites. However, the equality of field names is checked in debug builds.
///
/// [initialized]: Self::new
/// [callsite identifiers]: callsite::Identifier
pub struct FieldSet {
/// The names of each field on the described span.
names: &'static [&'static str],
/// The callsite where the described span originates.
callsite: callsite::Identifier,
}
/// A set of fields and values for a span.
pub struct ValueSet<'a> {
values: &'a [(&'a Field, Option<&'a (dyn Value + 'a)>)],
fields: &'a FieldSet,
}
/// An iterator over a set of fields.
#[derive(Debug)]
pub struct Iter {
idxs: Range<usize>,
fields: FieldSet,
}
/// Visits typed values.
///
/// An instance of `Visit` ("a visitor") represents the logic necessary to
/// record field values of various types. When an implementor of [`Value`] is
/// [recorded], it calls the appropriate method on the provided visitor to
/// indicate the type that value should be recorded as.
///
/// When a [`Subscriber`] implementation [records an `Event`] or a
/// [set of `Value`s added to a `Span`], it can pass an `&mut Visit` to the
/// `record` method on the provided [`ValueSet`] or [`Event`]. This visitor
/// will then be used to record all the field-value pairs present on that
/// `Event` or `ValueSet`.
///
/// # Examples
///
/// A simple visitor that writes to a string might be implemented like so:
/// ```
/// # extern crate tracing_core as tracing;
/// use std::fmt::{self, Write};
/// use tracing::field::{Value, Visit, Field};
/// pub struct StringVisitor<'a> {
/// string: &'a mut String,
/// }
///
/// impl<'a> Visit for StringVisitor<'a> {
/// fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
/// write!(self.string, "{} = {:?}; ", field.name(), value).unwrap();
/// }
/// }
/// ```
/// This visitor will format each recorded value using `fmt::Debug`, and
/// append the field name and formatted value to the provided string,
/// regardless of the type of the recorded value. When all the values have
/// been recorded, the `StringVisitor` may be dropped, allowing the string
/// to be printed or stored in some other data structure.
///
/// The `Visit` trait provides default implementations for `record_i64`,
/// `record_u64`, `record_bool`, `record_str`, and `record_error`, which simply
/// forward the recorded value to `record_debug`. Thus, `record_debug` is the
/// only method which a `Visit` implementation *must* implement. However,
/// visitors may override the default implementations of these functions in
/// order to implement type-specific behavior.
///
/// Additionally, when a visitor receives a value of a type it does not care
/// about, it is free to ignore those values completely. For example, a
/// visitor which only records numeric data might look like this:
///
/// ```
/// # extern crate tracing_core as tracing;
/// # use std::fmt::{self, Write};
/// # use tracing::field::{Value, Visit, Field};
/// pub struct SumVisitor {
/// sum: i64,
/// }
///
/// impl Visit for SumVisitor {
/// fn record_i64(&mut self, _field: &Field, value: i64) {
/// self.sum += value;
/// }
///
/// fn record_u64(&mut self, _field: &Field, value: u64) {
/// self.sum += value as i64;
/// }
///
/// fn record_debug(&mut self, _field: &Field, _value: &fmt::Debug) {
/// // Do nothing
/// }
/// }
/// ```
///
/// This visitor (which is probably not particularly useful) keeps a running
/// sum of all the numeric values it records, and ignores all other values. A
/// more practical example of recording typed values is presented in
/// `examples/counters.rs`, which demonstrates a very simple metrics system
/// implemented using `tracing`.
///
/// <div class="example-wrap" style="display:inline-block">
/// <pre class="ignore" style="white-space:normal;font:inherit;">
/// <strong>Note</strong>: The <code>record_error</code> trait method is only
/// available when the Rust standard library is present, as it requires the
/// <code>std::error::Error</code> trait.
/// </pre></div>
///
/// [recorded]: Value::record
/// [`Subscriber`]: super::subscriber::Subscriber
/// [records an `Event`]: super::subscriber::Subscriber::event
/// [set of `Value`s added to a `Span`]: super::subscriber::Subscriber::record
/// [`Event`]: super::event::Event
pub trait Visit {
/// Visits an arbitrary type implementing the [`valuable`] crate's `Valuable` trait.
///
#[cfg(all(tracing_unstable, feature = "valuable"))]
#[cfg_attr(docsrs, doc(cfg(all(tracing_unstable, feature = "valuable"))))]
fn record_value(&mut self, field: &Field, value: valuable::Value<'_>) {
self.record_debug(field, &value)
}
/// Visit a double-precision floating point value.
fn record_f64(&mut self, field: &Field, value: f64) {
self.record_debug(field, &value)
}
/// Visit a signed 64-bit integer value.
fn record_i64(&mut self, field: &Field, value: i64) {
self.record_debug(field, &value)
}
/// Visit an unsigned 64-bit integer value.
fn record_u64(&mut self, field: &Field, value: u64) {
self.record_debug(field, &value)
}
/// Visit a signed 128-bit integer value.
fn record_i128(&mut self, field: &Field, value: i128) {
self.record_debug(field, &value)
}
/// Visit an unsigned 128-bit integer value.
fn record_u128(&mut self, field: &Field, value: u128) {
self.record_debug(field, &value)
}
/// Visit a boolean value.
fn record_bool(&mut self, field: &Field, value: bool) {
self.record_debug(field, &value)
}
/// Visit a string value.
fn record_str(&mut self, field: &Field, value: &str) {
self.record_debug(field, &value)
}
/// Records a type implementing `Error`.
///
/// <div class="example-wrap" style="display:inline-block">
/// <pre class="ignore" style="white-space:normal;font:inherit;">
/// <strong>Note</strong>: This is only enabled when the Rust standard library is
/// present.
/// </pre>
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
fn record_error(&mut self, field: &Field, value: &(dyn std::error::Error + 'static)) {
self.record_debug(field, &DisplayValue(value))
}
/// Visit a value implementing `fmt::Debug`.
fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug);
}
/// A field value of an erased type.
///
/// Implementors of `Value` may call the appropriate typed recording methods on
/// the [visitor] passed to their `record` method in order to indicate how
/// their data should be recorded.
///
/// [visitor]: Visit
pub trait Value: crate::sealed::Sealed {
/// Visits this value with the given `Visitor`.
fn record(&self, key: &Field, visitor: &mut dyn Visit);
}
/// A `Value` which serializes using `fmt::Display`.
///
/// Uses `record_debug` in the `Value` implementation to
/// avoid an unnecessary evaluation.
#[derive(Clone)]
pub struct DisplayValue<T: fmt::Display>(T);
/// A `Value` which serializes as a string using `fmt::Debug`.
#[derive(Clone)]
pub struct DebugValue<T: fmt::Debug>(T);
/// Wraps a type implementing `fmt::Display` as a `Value` that can be
/// recorded using its `Display` implementation.
pub fn display<T>(t: T) -> DisplayValue<T>
where
T: fmt::Display,
{
DisplayValue(t)
}
/// Wraps a type implementing `fmt::Debug` as a `Value` that can be
/// recorded using its `Debug` implementation.
pub fn debug<T>(t: T) -> DebugValue<T>
where
T: fmt::Debug,
{
DebugValue(t)
}
/// Wraps a type implementing [`Valuable`] as a `Value` that
/// can be recorded using its `Valuable` implementation.
///
#[cfg(all(tracing_unstable, feature = "valuable"))]
#[cfg_attr(docsrs, doc(cfg(all(tracing_unstable, feature = "valuable"))))]
pub fn valuable<T>(t: &T) -> valuable::Value<'_>
where
T: valuable::Valuable,
{
t.as_value()
}
// ===== impl Visit =====
impl<'a, 'b> Visit for fmt::DebugStruct<'a, 'b> {
fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
self.field(field.name(), value);
}
}
impl<'a, 'b> Visit for fmt::DebugMap<'a, 'b> {
fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
self.entry(&format_args!("{}", field), value);
}
}
impl<F> Visit for F
where
F: FnMut(&Field, &dyn fmt::Debug),
{
fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
(self)(field, value)
}
}
// ===== impl Value =====
macro_rules! impl_values {
( $( $record:ident( $( $whatever:tt)+ ) ),+ ) => {
$(
impl_value!{ $record( $( $whatever )+ ) }
)+
}
}
macro_rules! ty_to_nonzero {
(u8) => {
NonZeroU8
};
(u16) => {
NonZeroU16
};
(u32) => {
NonZeroU32
};
(u64) => {
NonZeroU64
};
(u128) => {
NonZeroU128
};
(usize) => {
NonZeroUsize
};
(i8) => {
NonZeroI8
};
(i16) => {
NonZeroI16
};
(i32) => {
NonZeroI32
};
(i64) => {
NonZeroI64
};
(i128) => {
NonZeroI128
};
(isize) => {
NonZeroIsize
};
}
macro_rules! impl_one_value {
(f32, $op:expr, $record:ident) => {
impl_one_value!(normal, f32, $op, $record);
};
(f64, $op:expr, $record:ident) => {
impl_one_value!(normal, f64, $op, $record);
};
(bool, $op:expr, $record:ident) => {
impl_one_value!(normal, bool, $op, $record);
};
($value_ty:tt, $op:expr, $record:ident) => {
impl_one_value!(normal, $value_ty, $op, $record);
impl_one_value!(nonzero, $value_ty, $op, $record);
};
(normal, $value_ty:tt, $op:expr, $record:ident) => {
impl $crate::sealed::Sealed for $value_ty {}
impl $crate::field::Value for $value_ty {
fn record(&self, key: &$crate::field::Field, visitor: &mut dyn $crate::field::Visit) {
visitor.$record(key, $op(*self))
}
}
};
(nonzero, $value_ty:tt, $op:expr, $record:ident) => {
// This `use num::*;` is reported as unused because it gets emitted
// for every single invocation of this macro, so there are multiple `use`s.
// All but the first are useless indeed.
// We need this import because we can't write a path where one part is
// the `ty_to_nonzero!($value_ty)` invocation.
#[allow(clippy::useless_attribute, unused)]
use num::*;
impl $crate::sealed::Sealed for ty_to_nonzero!($value_ty) {}
impl $crate::field::Value for ty_to_nonzero!($value_ty) {
fn record(&self, key: &$crate::field::Field, visitor: &mut dyn $crate::field::Visit) {
visitor.$record(key, $op(self.get()))
}
}
};
}
macro_rules! impl_value {
( $record:ident( $( $value_ty:tt ),+ ) ) => {
$(
impl_one_value!($value_ty, |this: $value_ty| this, $record);
)+
};
( $record:ident( $( $value_ty:tt ),+ as $as_ty:ty) ) => {
$(
impl_one_value!($value_ty, |this: $value_ty| this as $as_ty, $record);
)+
};
}
// ===== impl Value =====
impl_values! {
record_u64(u64),
record_u64(usize, u32, u16, u8 as u64),
record_i64(i64),
record_i64(isize, i32, i16, i8 as i64),
record_u128(u128),
record_i128(i128),
record_bool(bool),
record_f64(f64, f32 as f64)
}
impl<T: crate::sealed::Sealed> crate::sealed::Sealed for Wrapping<T> {}
impl<T: crate::field::Value> crate::field::Value for Wrapping<T> {
fn record(&self, key: &crate::field::Field, visitor: &mut dyn crate::field::Visit) {
self.0.record(key, visitor)
}
}
impl crate::sealed::Sealed for str {}
impl Value for str {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_str(key, self)
}
}
#[cfg(feature = "std")]
impl crate::sealed::Sealed for dyn std::error::Error + 'static {}
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl Value for dyn std::error::Error + 'static {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_error(key, self)
}
}
#[cfg(feature = "std")]
impl crate::sealed::Sealed for dyn std::error::Error + Send + 'static {}
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl Value for dyn std::error::Error + Send + 'static {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
(self as &dyn std::error::Error).record(key, visitor)
}
}
#[cfg(feature = "std")]
impl crate::sealed::Sealed for dyn std::error::Error + Sync + 'static {}
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl Value for dyn std::error::Error + Sync + 'static {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
(self as &dyn std::error::Error).record(key, visitor)
}
}
#[cfg(feature = "std")]
impl crate::sealed::Sealed for dyn std::error::Error + Send + Sync + 'static {}
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl Value for dyn std::error::Error + Send + Sync + 'static {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
(self as &dyn std::error::Error).record(key, visitor)
}
}
impl<'a, T: ?Sized> crate::sealed::Sealed for &'a T where T: Value + crate::sealed::Sealed + 'a {}
impl<'a, T: ?Sized> Value for &'a T
where
T: Value + 'a,
{
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
(*self).record(key, visitor)
}
}
impl<'a, T: ?Sized> crate::sealed::Sealed for &'a mut T where T: Value + crate::sealed::Sealed + 'a {}
impl<'a, T: ?Sized> Value for &'a mut T
where
T: Value + 'a,
{
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
// Don't use `(*self).record(key, visitor)`, otherwise would
// cause stack overflow due to `unconditional_recursion`.
T::record(self, key, visitor)
}
}
impl<'a> crate::sealed::Sealed for fmt::Arguments<'a> {}
impl<'a> Value for fmt::Arguments<'a> {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_debug(key, self)
}
}
impl<T: ?Sized> crate::sealed::Sealed for crate::stdlib::boxed::Box<T> where T: Value {}
impl<T: ?Sized> Value for crate::stdlib::boxed::Box<T>
where
T: Value,
{
#[inline]
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
self.as_ref().record(key, visitor)
}
}
impl crate::sealed::Sealed for String {}
impl Value for String {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_str(key, self.as_str())
}
}
impl fmt::Debug for dyn Value {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// We are only going to be recording the field value, so we don't
// actually care about the field name here.
struct NullCallsite;
static NULL_CALLSITE: NullCallsite = NullCallsite;
impl crate::callsite::Callsite for NullCallsite {
fn set_interest(&self, _: crate::subscriber::Interest) {
unreachable!("you somehow managed to register the null callsite?")
}
fn metadata(&self) -> &crate::Metadata<'_> {
unreachable!("you somehow managed to access the null callsite?")
}
}
static FIELD: Field = Field {
i: 0,
fields: FieldSet::new(&[], crate::identify_callsite!(&NULL_CALLSITE)),
};
let mut res = Ok(());
self.record(&FIELD, &mut |_: &Field, val: &dyn fmt::Debug| {
res = write!(f, "{:?}", val);
});
res
}
}
impl fmt::Display for dyn Value {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(self, f)
}
}
// ===== impl DisplayValue =====
impl<T: fmt::Display> crate::sealed::Sealed for DisplayValue<T> {}
impl<T> Value for DisplayValue<T>
where
T: fmt::Display,
{
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_debug(key, self)
}
}
impl<T: fmt::Display> fmt::Debug for DisplayValue<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(self, f)
}
}
impl<T: fmt::Display> fmt::Display for DisplayValue<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.0.fmt(f)
}
}
// ===== impl DebugValue =====
impl<T: fmt::Debug> crate::sealed::Sealed for DebugValue<T> {}
impl<T> Value for DebugValue<T>
where
T: fmt::Debug,
{
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_debug(key, &self.0)
}
}
impl<T: fmt::Debug> fmt::Debug for DebugValue<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.0.fmt(f)
}
}
// ===== impl ValuableValue =====
#[cfg(all(tracing_unstable, feature = "valuable"))]
impl crate::sealed::Sealed for valuable::Value<'_> {}
#[cfg(all(tracing_unstable, feature = "valuable"))]
#[cfg_attr(docsrs, doc(cfg(all(tracing_unstable, feature = "valuable"))))]
impl Value for valuable::Value<'_> {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_value(key, *self)
}
}
#[cfg(all(tracing_unstable, feature = "valuable"))]
impl crate::sealed::Sealed for &'_ dyn valuable::Valuable {}
#[cfg(all(tracing_unstable, feature = "valuable"))]
#[cfg_attr(docsrs, doc(cfg(all(tracing_unstable, feature = "valuable"))))]
impl Value for &'_ dyn valuable::Valuable {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
visitor.record_value(key, self.as_value())
}
}
impl crate::sealed::Sealed for Empty {}
impl Value for Empty {
#[inline]
fn record(&self, _: &Field, _: &mut dyn Visit) {}
}
impl<T: Value> crate::sealed::Sealed for Option<T> {}
impl<T: Value> Value for Option<T> {
fn record(&self, key: &Field, visitor: &mut dyn Visit) {
if let Some(v) = &self {
v.record(key, visitor)
}
}
}
// ===== impl Field =====
impl Field {
/// Returns an [`Identifier`] that uniquely identifies the [`Callsite`]
/// which defines this field.
///
/// [`Identifier`]: super::callsite::Identifier
/// [`Callsite`]: super::callsite::Callsite
#[inline]
pub fn callsite(&self) -> callsite::Identifier {
self.fields.callsite()
}
/// Returns a string representing the name of the field.
pub fn name(&self) -> &'static str {
self.fields.names[self.i]
}
}
impl fmt::Display for Field {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(self.name())
}
}
impl AsRef<str> for Field {
fn as_ref(&self) -> &str {
self.name()
}
}
impl PartialEq for Field {
fn eq(&self, other: &Self) -> bool {
self.callsite() == other.callsite() && self.i == other.i
}
}
impl Eq for Field {}
impl Hash for Field {
fn hash<H>(&self, state: &mut H)
where
H: Hasher,
{
self.callsite().hash(state);
self.i.hash(state);
}
}
impl Clone for Field {
fn clone(&self) -> Self {
Field {
i: self.i,
fields: FieldSet {
names: self.fields.names,
callsite: self.fields.callsite(),
},
}
}
}
// ===== impl FieldSet =====
impl FieldSet {
/// Constructs a new `FieldSet` with the given array of field names and callsite.
pub const fn new(names: &'static [&'static str], callsite: callsite::Identifier) -> Self {
Self { names, callsite }
}
/// Returns an [`Identifier`] that uniquely identifies the [`Callsite`]
/// which defines this set of fields..
///
/// [`Identifier`]: super::callsite::Identifier
/// [`Callsite`]: super::callsite::Callsite
pub(crate) fn callsite(&self) -> callsite::Identifier {
callsite::Identifier(self.callsite.0)
}
/// Returns the [`Field`] named `name`, or `None` if no such field exists.
///
/// [`Field`]: super::Field
pub fn field<Q: ?Sized>(&self, name: &Q) -> Option<Field>
where
Q: Borrow<str>,
{
let name = &name.borrow();
self.names.iter().position(|f| f == name).map(|i| Field {
i,
fields: FieldSet {
names: self.names,
callsite: self.callsite(),
},
})
}
/// Returns `true` if `self` contains the given `field`.
///
/// <div class="example-wrap" style="display:inline-block">
/// <pre class="ignore" style="white-space:normal;font:inherit;">
/// <strong>Note</strong>: If <code>field</code> shares a name with a field
/// in this <code>FieldSet</code>, but was created by a <code>FieldSet</code>
/// with a different callsite, this <code>FieldSet</code> does <em>not</em>
/// contain it. This is so that if two separate span callsites define a field
/// named "foo", the <code>Field</code> corresponding to "foo" for each
/// of those callsites are not equivalent.
/// </pre></div>
pub fn contains(&self, field: &Field) -> bool {
field.callsite() == self.callsite() && field.i <= self.len()
}
/// Returns an iterator over the `Field`s in this `FieldSet`.
pub fn iter(&self) -> Iter {
let idxs = 0..self.len();
Iter {
idxs,
fields: FieldSet {
names: self.names,
callsite: self.callsite(),
},
}
}
/// Returns a new `ValueSet` with entries for this `FieldSet`'s values.
///
/// Note that a `ValueSet` may not be constructed with arrays of over 32
/// elements.
#[doc(hidden)]
pub fn value_set<'v, V>(&'v self, values: &'v V) -> ValueSet<'v>
where
V: ValidLen<'v>,
{
ValueSet {
fields: self,
values: values.borrow(),
}
}
/// Returns the number of fields in this `FieldSet`.
#[inline]
pub fn len(&self) -> usize {
self.names.len()
}
/// Returns whether or not this `FieldSet` has fields.
#[inline]
pub fn is_empty(&self) -> bool {
self.names.is_empty()
}
}
impl<'a> IntoIterator for &'a FieldSet {
type IntoIter = Iter;
type Item = Field;
#[inline]
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
impl fmt::Debug for FieldSet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FieldSet")
.field("names", &self.names)
.field("callsite", &self.callsite)
.finish()
}
}
impl fmt::Display for FieldSet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_set()
.entries(self.names.iter().map(display))
.finish()
}
}
impl Eq for FieldSet {}
impl PartialEq for FieldSet {
fn eq(&self, other: &Self) -> bool {
if core::ptr::eq(&self, &other) {
true
} else if cfg!(not(debug_assertions)) {
// In a well-behaving application, two `FieldSet`s can be assumed to
// be totally equal so long as they share the same callsite.
self.callsite == other.callsite
} else {
// However, when debug-assertions are enabled, do NOT assume that
// the application is well-behaving; check every the field names of
// each `FieldSet` for equality.
// `FieldSet` is destructured here to ensure a compile-error if the
// fields of `FieldSet` change.
let Self {
names: lhs_names,
callsite: lhs_callsite,
} = self;
let Self {
names: rhs_names,
callsite: rhs_callsite,
} = &other;
// Check callsite equality first, as it is probably cheaper to do
// than str equality.
lhs_callsite == rhs_callsite && lhs_names == rhs_names
}
}
}
// ===== impl Iter =====
impl Iterator for Iter {
type Item = Field;
fn next(&mut self) -> Option<Field> {
let i = self.idxs.next()?;
Some(Field {
i,
fields: FieldSet {
names: self.fields.names,
callsite: self.fields.callsite(),
},
})
}
}
// ===== impl ValueSet =====
impl<'a> ValueSet<'a> {
/// Returns an [`Identifier`] that uniquely identifies the [`Callsite`]
/// defining the fields this `ValueSet` refers to.
///
/// [`Identifier`]: super::callsite::Identifier
/// [`Callsite`]: super::callsite::Callsite
#[inline]
pub fn callsite(&self) -> callsite::Identifier {
self.fields.callsite()
}
/// Visits all the fields in this `ValueSet` with the provided [visitor].
///
/// [visitor]: Visit
pub fn record(&self, visitor: &mut dyn Visit) {
let my_callsite = self.callsite();
for (field, value) in self.values {
if field.callsite() != my_callsite {
continue;
}
if let Some(value) = value {
value.record(field, visitor);
}
}
}
/// Returns the number of fields in this `ValueSet` that would be visited
/// by a given [visitor] to the [`ValueSet::record()`] method.
///
/// [visitor]: Visit
/// [`ValueSet::record()`]: ValueSet::record()
pub fn len(&self) -> usize {
let my_callsite = self.callsite();
self.values
.iter()
.filter(|(field, _)| field.callsite() == my_callsite)
.count()
}
/// Returns `true` if this `ValueSet` contains a value for the given `Field`.
pub(crate) fn contains(&self, field: &Field) -> bool {
field.callsite() == self.callsite()
&& self
.values
.iter()
.any(|(key, val)| *key == field && val.is_some())
}
/// Returns true if this `ValueSet` contains _no_ values.
pub fn is_empty(&self) -> bool {
let my_callsite = self.callsite();
self.values
.iter()
.all(|(key, val)| val.is_none() || key.callsite() != my_callsite)
}
pub(crate) fn field_set(&self) -> &FieldSet {
self.fields
}
}
impl<'a> fmt::Debug for ValueSet<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.values
.iter()
.fold(&mut f.debug_struct("ValueSet"), |dbg, (key, v)| {
if let Some(val) = v {
val.record(key, dbg);
}
dbg
})
.field("callsite", &self.callsite())
.finish()
}
}
impl<'a> fmt::Display for ValueSet<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.values
.iter()
.fold(&mut f.debug_map(), |dbg, (key, v)| {
if let Some(val) = v {
val.record(key, dbg);
}
dbg
})
.finish()
}
}
// ===== impl ValidLen =====
mod private {
use super::*;
/// Marker trait implemented by arrays which are of valid length to
/// construct a `ValueSet`.
///
/// `ValueSet`s may only be constructed from arrays containing 32 or fewer
/// elements, to ensure the array is small enough to always be allocated on the
/// stack. This trait is only implemented by arrays of an appropriate length,
/// ensuring that the correct size arrays are used at compile-time.
pub trait ValidLen<'a>: Borrow<[(&'a Field, Option<&'a (dyn Value + 'a)>)]> {}
}
macro_rules! impl_valid_len {
( $( $len:tt ),+ ) => {
$(
impl<'a> private::ValidLen<'a> for
[(&'a Field, Option<&'a (dyn Value + 'a)>); $len] {}
)+
}
}
impl_valid_len! {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32
}
#[cfg(test)]
mod test {
use super::*;
use crate::metadata::{Kind, Level, Metadata};
use crate::stdlib::{borrow::ToOwned, string::String};
struct TestCallsite1;
static TEST_CALLSITE_1: TestCallsite1 = TestCallsite1;
static TEST_META_1: Metadata<'static> = metadata! {
name: "field_test1",
target: module_path!(),
level: Level::INFO,
fields: &["foo", "bar", "baz"],
callsite: &TEST_CALLSITE_1,
kind: Kind::SPAN,
};
impl crate::callsite::Callsite for TestCallsite1 {
fn set_interest(&self, _: crate::subscriber::Interest) {
unimplemented!()
}
fn metadata(&self) -> &Metadata<'_> {
&TEST_META_1
}
}
struct TestCallsite2;
static TEST_CALLSITE_2: TestCallsite2 = TestCallsite2;
static TEST_META_2: Metadata<'static> = metadata! {
name: "field_test2",
target: module_path!(),
level: Level::INFO,
fields: &["foo", "bar", "baz"],
callsite: &TEST_CALLSITE_2,
kind: Kind::SPAN,
};
impl crate::callsite::Callsite for TestCallsite2 {
fn set_interest(&self, _: crate::subscriber::Interest) {
unimplemented!()
}
fn metadata(&self) -> &Metadata<'_> {
&TEST_META_2
}
}
#[test]
fn value_set_with_no_values_is_empty() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), None),
(&fields.field("bar").unwrap(), None),
(&fields.field("baz").unwrap(), None),
];
let valueset = fields.value_set(values);
assert!(valueset.is_empty());
}
#[test]
fn empty_value_set_is_empty() {
let fields = TEST_META_1.fields();
let valueset = fields.value_set(&[]);
assert!(valueset.is_empty());
}
#[test]
fn value_sets_with_fields_from_other_callsites_are_empty() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), Some(&1 as &dyn Value)),
(&fields.field("bar").unwrap(), Some(&2 as &dyn Value)),
(&fields.field("baz").unwrap(), Some(&3 as &dyn Value)),
];
let valueset = TEST_META_2.fields().value_set(values);
assert!(valueset.is_empty())
}
#[test]
fn sparse_value_sets_are_not_empty() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), None),
(&fields.field("bar").unwrap(), Some(&57 as &dyn Value)),
(&fields.field("baz").unwrap(), None),
];
let valueset = fields.value_set(values);
assert!(!valueset.is_empty());
}
#[test]
fn fields_from_other_callsets_are_skipped() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), None),
(
&TEST_META_2.fields().field("bar").unwrap(),
Some(&57 as &dyn Value),
),
(&fields.field("baz").unwrap(), None),
];
struct MyVisitor;
impl Visit for MyVisitor {
fn record_debug(&mut self, field: &Field, _: &dyn (crate::stdlib::fmt::Debug)) {
assert_eq!(field.callsite(), TEST_META_1.callsite())
}
}
let valueset = fields.value_set(values);
valueset.record(&mut MyVisitor);
}
#[test]
fn empty_fields_are_skipped() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), Some(&Empty as &dyn Value)),
(&fields.field("bar").unwrap(), Some(&57 as &dyn Value)),
(&fields.field("baz").unwrap(), Some(&Empty as &dyn Value)),
];
struct MyVisitor;
impl Visit for MyVisitor {
fn record_debug(&mut self, field: &Field, _: &dyn (crate::stdlib::fmt::Debug)) {
assert_eq!(field.name(), "bar")
}
}
let valueset = fields.value_set(values);
valueset.record(&mut MyVisitor);
}
#[test]
fn record_debug_fn() {
let fields = TEST_META_1.fields();
let values = &[
(&fields.field("foo").unwrap(), Some(&1 as &dyn Value)),
(&fields.field("bar").unwrap(), Some(&2 as &dyn Value)),
(&fields.field("baz").unwrap(), Some(&3 as &dyn Value)),
];
let valueset = fields.value_set(values);
let mut result = String::new();
valueset.record(&mut |_: &Field, value: &dyn fmt::Debug| {
use crate::stdlib::fmt::Write;
write!(&mut result, "{:?}", value).unwrap();
});
assert_eq!(result, "123".to_owned());
}
#[test]
#[cfg(feature = "std")]
fn record_error() {
let fields = TEST_META_1.fields();
let err: Box<dyn std::error::Error + Send + Sync + 'static> =
std::io::Error::new(std::io::ErrorKind::Other, "lol").into();
let values = &[
(&fields.field("foo").unwrap(), Some(&err as &dyn Value)),
(&fields.field("bar").unwrap(), Some(&Empty as &dyn Value)),
(&fields.field("baz").unwrap(), Some(&Empty as &dyn Value)),
];
let valueset = fields.value_set(values);
let mut result = String::new();
valueset.record(&mut |_: &Field, value: &dyn fmt::Debug| {
use core::fmt::Write;
write!(&mut result, "{:?}", value).unwrap();
});
assert_eq!(result, format!("{}", err));
}
}