| //! A procedural macro attribute for instrumenting functions with [`tracing`]. |
| //! |
| //! [`tracing`] is a framework for instrumenting Rust programs to collect |
| //! structured, event-based diagnostic information. This crate provides the |
| //! [`#[instrument]`][instrument] procedural macro attribute. |
| //! |
| //! Note that this macro is also re-exported by the main `tracing` crate. |
| //! |
| //! ## Usage |
| //! |
| //! First, add this to your `Cargo.toml`: |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! tracing-attributes = "0.1.9" |
| //! ``` |
| //! |
| //! *Compiler support: requires rustc 1.39+* |
| //! |
| //! The [`#[instrument]`][instrument] attribute can now be added to a function |
| //! to automatically create and enter `tracing` [span] when that function is |
| //! called. For example: |
| //! |
| //! ``` |
| //! use tracing_attributes::instrument; |
| //! |
| //! #[instrument] |
| //! pub fn my_function(my_arg: usize) { |
| //! // ... |
| //! } |
| //! |
| //! # fn main() {} |
| //! ``` |
| //! |
| //! [`tracing`]: https://crates.io/crates/tracing |
| //! [span]: https://docs.rs/tracing/latest/tracing/span/index.html |
| //! [instrument]: attr.instrument.html |
| #![doc(html_root_url = "https://docs.rs/tracing-attributes/0.1.9")] |
| #![warn( |
| missing_debug_implementations, |
| missing_docs, |
| rust_2018_idioms, |
| unreachable_pub, |
| bad_style, |
| const_err, |
| dead_code, |
| improper_ctypes, |
| non_shorthand_field_patterns, |
| no_mangle_generic_items, |
| overflowing_literals, |
| path_statements, |
| patterns_in_fns_without_body, |
| private_in_public, |
| unconditional_recursion, |
| unused, |
| unused_allocation, |
| unused_comparisons, |
| unused_parens, |
| while_true |
| )] |
| // TODO: once `tracing` bumps its MSRV to 1.42, remove this allow. |
| #![allow(unused)] |
| extern crate proc_macro; |
| |
| use std::collections::{HashMap, HashSet}; |
| use std::iter; |
| |
| use proc_macro2::TokenStream; |
| use quote::{quote, quote_spanned, ToTokens, TokenStreamExt as _}; |
| use syn::ext::IdentExt as _; |
| use syn::parse::{Parse, ParseStream}; |
| use syn::{ |
| punctuated::Punctuated, spanned::Spanned, AttributeArgs, Block, Expr, ExprCall, FieldPat, |
| FnArg, Ident, Item, ItemFn, Lit, LitInt, LitStr, Meta, MetaList, MetaNameValue, NestedMeta, |
| Pat, PatIdent, PatReference, PatStruct, PatTuple, PatTupleStruct, PatType, Path, Signature, |
| Stmt, Token, |
| }; |
| /// Instruments a function to create and enter a `tracing` [span] every time |
| /// the function is called. |
| /// |
| /// The generated span's name will be the name of the function. Any arguments |
| /// to that function will be recorded as fields using [`fmt::Debug`]. To skip |
| /// recording a function's or method's argument, pass the argument's name |
| /// to the `skip` argument on the `#[instrument]` macro. For example, |
| /// `skip` can be used when an argument to an instrumented function does |
| /// not implement [`fmt::Debug`], or to exclude an argument with a verbose |
| /// or costly Debug implementation. Note that: |
| /// - multiple argument names can be passed to `skip`. |
| /// - arguments passed to `skip` do _not_ need to implement `fmt::Debug`. |
| /// |
| /// You can also pass additional fields (key-value pairs with arbitrary data) |
| /// to the generated span. This is achieved using the `fields` argument on the |
| /// `#[instrument]` macro. You can use a string, integer or boolean literal as |
| /// a value for each field. The name of the field must be a single valid Rust |
| /// identifier, nested (dotted) field names are not supported. |
| /// |
| /// Note that overlap between the names of fields and (non-skipped) arguments |
| /// will result in a compile error. |
| /// |
| /// # Examples |
| /// Instrumenting a function: |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument] |
| /// pub fn my_function(my_arg: usize) { |
| /// // This event will be recorded inside a span named `my_function` with the |
| /// // field `my_arg`. |
| /// tracing::info!("inside my_function!"); |
| /// // ... |
| /// } |
| /// ``` |
| /// Setting the level for the generated span: |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument(level = "debug")] |
| /// pub fn my_function() { |
| /// // ... |
| /// } |
| /// ``` |
| /// Overriding the generated span's target: |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument(target = "my_target")] |
| /// pub fn my_function() { |
| /// // ... |
| /// } |
| /// ``` |
| /// |
| /// To skip recording an argument, pass the argument's name to the `skip`: |
| /// |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// struct NonDebug; |
| /// |
| /// #[instrument(skip(non_debug))] |
| /// fn my_function(arg: usize, non_debug: NonDebug) { |
| /// // ... |
| /// } |
| /// ``` |
| /// |
| /// To add an additional context to the span, you can pass key-value pairs to `fields`: |
| /// |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument(fields(foo="bar", id=1, show=true))] |
| /// fn my_function(arg: usize) { |
| /// // ... |
| /// } |
| /// ``` |
| /// |
| /// If the function returns a `Result<T, E>` and `E` implements `std::fmt::Display`, you can add |
| /// `err` to emit error events when the function returns `Err`: |
| /// |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument(err)] |
| /// fn my_function(arg: usize) -> Result<(), std::io::Error> { |
| /// Ok(()) |
| /// } |
| /// ``` |
| /// |
| /// If `tracing_futures` is specified as a dependency in `Cargo.toml`, |
| /// `async fn`s may also be instrumented: |
| /// |
| /// ``` |
| /// # use tracing_attributes::instrument; |
| /// #[instrument] |
| /// pub async fn my_function() -> Result<(), ()> { |
| /// // ... |
| /// # Ok(()) |
| /// } |
| /// ``` |
| /// |
| /// It also works with [async-trait](https://crates.io/crates/async-trait) |
| /// (a crate that allows async functions on traits, |
| /// something not currently possible with rustc alone), |
| /// and hopefully most libraries that exhibit similar behaviors: |
| /// |
| /// ``` |
| /// # use tracing::instrument; |
| /// use async_trait::async_trait; |
| /// |
| /// #[async_trait] |
| /// pub trait Foo { |
| /// async fn foo(&self, v: usize) -> (); |
| /// } |
| /// |
| /// #[derive(Debug)] |
| /// struct FooImpl; |
| /// |
| /// #[async_trait] |
| /// impl Foo for FooImpl { |
| /// #[instrument(skip(self))] |
| /// async fn foo(&self, v: usize) {} |
| /// } |
| /// ``` |
| |
| /// |
| /// [span]: https://docs.rs/tracing/latest/tracing/span/index.html |
| /// [`tracing`]: https://github.com/tokio-rs/tracing |
| /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html |
| #[proc_macro_attribute] |
| pub fn instrument( |
| args: proc_macro::TokenStream, |
| item: proc_macro::TokenStream, |
| ) -> proc_macro::TokenStream { |
| let input: ItemFn = syn::parse_macro_input!(item as ItemFn); |
| let args = syn::parse_macro_input!(args as InstrumentArgs); |
| |
| // check for async_trait-like patterns in the block and wrap the |
| // internal function with Instrument instead of wrapping the |
| // async_trait generated wrapper |
| if let Some(internal_fun_name) = |
| get_async_trait_name(&input.block, input.sig.asyncness.is_some()) |
| { |
| // let's rewrite some statements! |
| let mut stmts: Vec<Stmt> = input.block.stmts.to_vec(); |
| for stmt in &mut stmts { |
| if let Stmt::Item(Item::Fn(fun)) = stmt { |
| // instrument the function if we considered it as the one we truly want to trace |
| if fun.sig.ident == internal_fun_name { |
| *stmt = syn::parse2(gen_body(fun, args, Some(input.sig.ident.to_string()))) |
| .unwrap(); |
| break; |
| } |
| } |
| } |
| |
| let sig = &input.sig; |
| let attrs = &input.attrs; |
| quote!( |
| #(#attrs) * |
| #sig { |
| #(#stmts) * |
| } |
| ) |
| .into() |
| } else { |
| gen_body(&input, args, None).into() |
| } |
| } |
| |
| fn gen_body( |
| input: &ItemFn, |
| args: InstrumentArgs, |
| fun_name: Option<String>, |
| ) -> proc_macro2::TokenStream { |
| // these are needed ahead of time, as ItemFn contains the function body _and_ |
| // isn't representable inside a quote!/quote_spanned! macro |
| // (Syn's ToTokens isn't implemented for ItemFn) |
| let ItemFn { |
| attrs, |
| vis, |
| block, |
| sig, |
| .. |
| } = input; |
| |
| let Signature { |
| output: return_type, |
| inputs: params, |
| unsafety, |
| asyncness, |
| constness, |
| abi, |
| ident, |
| generics: |
| syn::Generics { |
| params: gen_params, |
| where_clause, |
| .. |
| }, |
| .. |
| } = sig; |
| |
| let err = args.err; |
| let warnings = args.warnings(); |
| |
| // generate the span's name |
| let span_name = args |
| // did the user override the span's name? |
| .name |
| .as_ref() |
| .map(|name| quote!(#name)) |
| // are we overriding the name because the span is inside a function |
| // generated by `async-trait`? |
| .or_else(|| fun_name.as_ref().map(|name| quote!(#name))) |
| // if neither override is present, use the parsed function's name. |
| .unwrap_or_else(|| { |
| let name = ident.to_string(); |
| quote!(#name) |
| }); |
| |
| // generate this inside a closure, so we can return early on errors. |
| let span = (|| { |
| // Pull out the arguments-to-be-skipped first, so we can filter results |
| // below. |
| let param_names: Vec<(Ident, Ident)> = params |
| .clone() |
| .into_iter() |
| .flat_map(|param| match param { |
| FnArg::Typed(PatType { pat, .. }) => param_names(*pat), |
| FnArg::Receiver(_) => Box::new(iter::once(Ident::new("self", param.span()))), |
| }) |
| // if we are inside a function generated by async-trait, we |
| // should take care to rewrite "_self" as "self" for |
| // 'user convenience' |
| .map(|x| { |
| if fun_name.is_some() && x == "_self" { |
| (Ident::new("self", x.span()), x) |
| } else { |
| (x.clone(), x) |
| } |
| }) |
| .collect(); |
| |
| // TODO: allow the user to rename fields at will (all the |
| // machinery should be here) |
| |
| // Little dance with new (user-exposed) names and old (internal) |
| // names of identifiers. That way, you can do the following |
| // even though async_trait rewrite "self" as "_self": |
| // ``` |
| // #[async_trait] |
| // impl Foo for FooImpl { |
| // #[instrument(skip(self))] |
| // async fn foo(&self, v: usize) {} |
| // } |
| // ``` |
| |
| for skip in &args.skips { |
| if !param_names.iter().map(|(user, _)| user).any(|y| y == skip) { |
| return quote_spanned! {skip.span()=> |
| compile_error!("attempting to skip non-existent parameter") |
| }; |
| } |
| } |
| |
| let level = args.level(); |
| let target = args.target(); |
| |
| // filter out skipped fields |
| let mut quoted_fields: Vec<_> = param_names |
| .into_iter() |
| .filter(|(param, _)| { |
| if args.skips.contains(param) { |
| return false; |
| } |
| |
| // If any parameters have the same name as a custom field, skip |
| // and allow them to be formatted by the custom field. |
| if let Some(ref fields) = args.fields { |
| fields.0.iter().all(|Field { ref name, .. }| { |
| let first = name.first(); |
| first != name.last() || !first.iter().any(|name| name == ¶m) |
| }) |
| } else { |
| true |
| } |
| }) |
| .map(|(user_name, real_name)| quote!(#user_name = tracing::field::debug(&#real_name))) |
| .collect(); |
| let custom_fields = &args.fields; |
| let custom_fields = if quoted_fields.is_empty() { |
| quote! { #custom_fields } |
| } else { |
| quote! {, #custom_fields } |
| }; |
| |
| quote!(tracing::span!( |
| target: #target, |
| #level, |
| #span_name, |
| #(#quoted_fields),* |
| #custom_fields |
| |
| )) |
| })(); |
| |
| // Generate the instrumented function body. |
| // If the function is an `async fn`, this will wrap it in an async block, |
| // which is `instrument`ed using `tracing-futures`. Otherwise, this will |
| // enter the span and then perform the rest of the body. |
| // If `err` is in args, instrument any resulting `Err`s. |
| let body = if asyncness.is_some() { |
| if err { |
| quote_spanned! {block.span()=> |
| let __tracing_attr_span = #span; |
| tracing_futures::Instrument::instrument(async move { |
| match async move { #block }.await { |
| Ok(x) => Ok(x), |
| Err(e) => { |
| tracing::error!(error = %e); |
| Err(e) |
| } |
| } |
| }, __tracing_attr_span).await |
| } |
| } else { |
| quote_spanned!(block.span()=> |
| let __tracing_attr_span = #span; |
| tracing_futures::Instrument::instrument( |
| async move { #block }, |
| __tracing_attr_span |
| ) |
| .await |
| ) |
| } |
| } else if err { |
| quote_spanned!(block.span()=> |
| let __tracing_attr_span = #span; |
| let __tracing_attr_guard = __tracing_attr_span.enter(); |
| match { #block } { |
| Ok(x) => Ok(x), |
| Err(e) => { |
| tracing::error!(error = %e); |
| Err(e) |
| } |
| } |
| ) |
| } else { |
| quote_spanned!(block.span()=> |
| let __tracing_attr_span = #span; |
| let __tracing_attr_guard = __tracing_attr_span.enter(); |
| #block |
| ) |
| }; |
| |
| quote!( |
| #(#attrs) * |
| #vis #constness #unsafety #asyncness #abi fn #ident<#gen_params>(#params) #return_type |
| #where_clause |
| { |
| #warnings |
| #body |
| } |
| ) |
| } |
| |
| #[derive(Default, Debug)] |
| struct InstrumentArgs { |
| level: Option<Level>, |
| name: Option<LitStr>, |
| target: Option<LitStr>, |
| skips: HashSet<Ident>, |
| fields: Option<Fields>, |
| err: bool, |
| /// Errors describing any unrecognized parse inputs that we skipped. |
| parse_warnings: Vec<syn::Error>, |
| } |
| |
| impl InstrumentArgs { |
| fn level(&self) -> impl ToTokens { |
| fn is_level(lit: &LitInt, expected: u64) -> bool { |
| match lit.base10_parse::<u64>() { |
| Ok(value) => value == expected, |
| Err(_) => false, |
| } |
| } |
| |
| match &self.level { |
| Some(Level::Str(ref lit)) if lit.value().eq_ignore_ascii_case("trace") => { |
| quote!(tracing::Level::TRACE) |
| } |
| Some(Level::Str(ref lit)) if lit.value().eq_ignore_ascii_case("debug") => { |
| quote!(tracing::Level::DEBUG) |
| } |
| Some(Level::Str(ref lit)) if lit.value().eq_ignore_ascii_case("info") => { |
| quote!(tracing::Level::INFO) |
| } |
| Some(Level::Str(ref lit)) if lit.value().eq_ignore_ascii_case("warn") => { |
| quote!(tracing::Level::WARN) |
| } |
| Some(Level::Str(ref lit)) if lit.value().eq_ignore_ascii_case("error") => { |
| quote!(tracing::Level::ERROR) |
| } |
| Some(Level::Int(ref lit)) if is_level(lit, 1) => quote!(tracing::Level::TRACE), |
| Some(Level::Int(ref lit)) if is_level(lit, 2) => quote!(tracing::Level::DEBUG), |
| Some(Level::Int(ref lit)) if is_level(lit, 3) => quote!(tracing::Level::INFO), |
| Some(Level::Int(ref lit)) if is_level(lit, 4) => quote!(tracing::Level::WARN), |
| Some(Level::Int(ref lit)) if is_level(lit, 5) => quote!(tracing::Level::ERROR), |
| Some(Level::Path(ref pat)) => quote!(#pat), |
| Some(lit) => quote! { |
| compile_error!( |
| "unknown verbosity level, expected one of \"trace\", \ |
| \"debug\", \"info\", \"warn\", or \"error\", or a number 1-5" |
| ) |
| }, |
| None => quote!(tracing::Level::INFO), |
| } |
| } |
| |
| fn target(&self) -> impl ToTokens { |
| if let Some(ref target) = self.target { |
| quote!(#target) |
| } else { |
| quote!(module_path!()) |
| } |
| } |
| |
| /// Generate "deprecation" warnings for any unrecognized attribute inputs |
| /// that we skipped. |
| /// |
| /// For backwards compatibility, we need to emit compiler warnings rather |
| /// than errors for unrecognized inputs. Generating a fake deprecation is |
| /// the only way to do this on stable Rust right now. |
| fn warnings(&self) -> impl ToTokens { |
| let warnings = self.parse_warnings.iter().map(|err| { |
| let msg = format!("found unrecognized input, {}", err); |
| let msg = LitStr::new(&msg, err.span()); |
| // TODO(eliza): This is a bit of a hack, but it's just about the |
| // only way to emit warnings from a proc macro on stable Rust. |
| // Eventually, when the `proc_macro::Diagnostic` API stabilizes, we |
| // should definitely use that instead. |
| quote_spanned! {err.span()=> |
| #[warn(deprecated)] |
| { |
| #[deprecated(since = "not actually deprecated", note = #msg)] |
| const TRACING_INSTRUMENT_WARNING: () = (); |
| let _ = TRACING_INSTRUMENT_WARNING; |
| } |
| } |
| }); |
| quote! { |
| { #(#warnings)* } |
| } |
| } |
| } |
| |
| impl Parse for InstrumentArgs { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let mut args = Self::default(); |
| while !input.is_empty() { |
| let lookahead = input.lookahead1(); |
| if lookahead.peek(kw::name) { |
| if args.name.is_some() { |
| return Err(input.error("expected only a single `name` argument")); |
| } |
| let name = input.parse::<StrArg<kw::name>>()?.value; |
| args.name = Some(name); |
| } else if lookahead.peek(LitStr) { |
| // XXX: apparently we support names as either named args with an |
| // sign, _or_ as unnamed string literals. That's weird, but |
| // changing it is apparently breaking. |
| if args.name.is_some() { |
| return Err(input.error("expected only a single `name` argument")); |
| } |
| args.name = Some(input.parse()?); |
| } else if lookahead.peek(kw::target) { |
| if args.target.is_some() { |
| return Err(input.error("expected only a single `target` argument")); |
| } |
| let target = input.parse::<StrArg<kw::target>>()?.value; |
| args.target = Some(target); |
| } else if lookahead.peek(kw::level) { |
| if args.level.is_some() { |
| return Err(input.error("expected only a single `level` argument")); |
| } |
| args.level = Some(input.parse()?); |
| } else if lookahead.peek(kw::skip) { |
| if !args.skips.is_empty() { |
| return Err(input.error("expected only a single `skip` argument")); |
| } |
| let Skips(skips) = input.parse()?; |
| args.skips = skips; |
| } else if lookahead.peek(kw::fields) { |
| if args.fields.is_some() { |
| return Err(input.error("expected only a single `fields` argument")); |
| } |
| args.fields = Some(input.parse()?); |
| } else if lookahead.peek(kw::err) { |
| let _ = input.parse::<kw::err>()?; |
| args.err = true; |
| } else if lookahead.peek(Token![,]) { |
| let _ = input.parse::<Token![,]>()?; |
| } else { |
| // We found a token that we didn't expect! |
| // We want to emit warnings for these, rather than errors, so |
| // we'll add it to the list of unrecognized inputs we've seen so |
| // far and keep going. |
| args.parse_warnings.push(lookahead.error()); |
| // Parse the unrecognized token tree to advance the parse |
| // stream, and throw it away so we can keep parsing. |
| let _ = input.parse::<proc_macro2::TokenTree>(); |
| } |
| } |
| Ok(args) |
| } |
| } |
| |
| struct StrArg<T> { |
| value: LitStr, |
| _p: std::marker::PhantomData<T>, |
| } |
| |
| impl<T: Parse> Parse for StrArg<T> { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let _ = input.parse::<T>()?; |
| let _ = input.parse::<Token![=]>()?; |
| let value = input.parse()?; |
| Ok(Self { |
| value, |
| _p: std::marker::PhantomData, |
| }) |
| } |
| } |
| |
| struct Skips(HashSet<Ident>); |
| |
| impl Parse for Skips { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let _ = input.parse::<kw::skip>(); |
| let content; |
| let _ = syn::parenthesized!(content in input); |
| let names: Punctuated<Ident, Token![,]> = content.parse_terminated(Ident::parse_any)?; |
| let mut skips = HashSet::new(); |
| for name in names { |
| if skips.contains(&name) { |
| return Err(syn::Error::new( |
| name.span(), |
| "tried to skip the same field twice", |
| )); |
| } else { |
| skips.insert(name); |
| } |
| } |
| Ok(Self(skips)) |
| } |
| } |
| |
| #[derive(Debug)] |
| struct Fields(Punctuated<Field, Token![,]>); |
| |
| #[derive(Debug)] |
| struct Field { |
| name: Punctuated<Ident, Token![.]>, |
| value: Option<Expr>, |
| kind: FieldKind, |
| } |
| |
| #[derive(Debug, Eq, PartialEq)] |
| enum FieldKind { |
| Debug, |
| Display, |
| Value, |
| } |
| |
| impl Parse for Fields { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let _ = input.parse::<kw::fields>(); |
| let content; |
| let _ = syn::parenthesized!(content in input); |
| let fields: Punctuated<_, Token![,]> = content.parse_terminated(Field::parse)?; |
| Ok(Self(fields)) |
| } |
| } |
| |
| impl ToTokens for Fields { |
| fn to_tokens(&self, tokens: &mut TokenStream) { |
| self.0.to_tokens(tokens) |
| } |
| } |
| |
| impl Parse for Field { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let mut kind = FieldKind::Value; |
| if input.peek(Token![%]) { |
| input.parse::<Token![%]>()?; |
| kind = FieldKind::Display; |
| } else if input.peek(Token![?]) { |
| input.parse::<Token![?]>()?; |
| kind = FieldKind::Debug; |
| }; |
| let name = Punctuated::parse_separated_nonempty_with(input, Ident::parse_any)?; |
| let value = if input.peek(Token![=]) { |
| input.parse::<Token![=]>()?; |
| if input.peek(Token![%]) { |
| input.parse::<Token![%]>()?; |
| kind = FieldKind::Display; |
| } else if input.peek(Token![?]) { |
| input.parse::<Token![?]>()?; |
| kind = FieldKind::Debug; |
| }; |
| Some(input.parse()?) |
| } else { |
| None |
| }; |
| Ok(Self { name, kind, value }) |
| } |
| } |
| |
| impl ToTokens for Field { |
| fn to_tokens(&self, tokens: &mut TokenStream) { |
| if let Some(ref value) = self.value { |
| let name = &self.name; |
| let kind = &self.kind; |
| tokens.extend(quote! { |
| #name = #kind#value |
| }) |
| } else if self.kind == FieldKind::Value { |
| // XXX(eliza): I don't like that fields without values produce |
| // empty fields rather than local variable shorthand...but, |
| // we've released a version where field names without values in |
| // `instrument` produce empty field values, so changing it now |
| // is a breaking change. agh. |
| let name = &self.name; |
| tokens.extend(quote!(#name = tracing::field::Empty)) |
| } else { |
| self.kind.to_tokens(tokens); |
| self.name.to_tokens(tokens); |
| } |
| } |
| } |
| |
| impl ToTokens for FieldKind { |
| fn to_tokens(&self, tokens: &mut TokenStream) { |
| match self { |
| FieldKind::Debug => tokens.extend(quote! { ? }), |
| FieldKind::Display => tokens.extend(quote! { % }), |
| _ => {} |
| } |
| } |
| } |
| |
| #[derive(Debug)] |
| enum Level { |
| Str(LitStr), |
| Int(LitInt), |
| Path(Path), |
| } |
| |
| impl Parse for Level { |
| fn parse(input: ParseStream<'_>) -> syn::Result<Self> { |
| let _ = input.parse::<kw::level>()?; |
| let _ = input.parse::<Token![=]>()?; |
| let lookahead = input.lookahead1(); |
| if lookahead.peek(LitStr) { |
| Ok(Self::Str(input.parse()?)) |
| } else if lookahead.peek(LitInt) { |
| Ok(Self::Int(input.parse()?)) |
| } else if lookahead.peek(Ident) { |
| Ok(Self::Path(input.parse()?)) |
| } else { |
| Err(lookahead.error()) |
| } |
| } |
| } |
| |
| fn param_names(pat: Pat) -> Box<dyn Iterator<Item = Ident>> { |
| match pat { |
| Pat::Ident(PatIdent { ident, .. }) => Box::new(iter::once(ident)), |
| Pat::Reference(PatReference { pat, .. }) => param_names(*pat), |
| Pat::Struct(PatStruct { fields, .. }) => Box::new( |
| fields |
| .into_iter() |
| .flat_map(|FieldPat { pat, .. }| param_names(*pat)), |
| ), |
| Pat::Tuple(PatTuple { elems, .. }) => Box::new(elems.into_iter().flat_map(param_names)), |
| Pat::TupleStruct(PatTupleStruct { |
| pat: PatTuple { elems, .. }, |
| .. |
| }) => Box::new(elems.into_iter().flat_map(param_names)), |
| |
| // The above *should* cover all cases of irrefutable patterns, |
| // but we purposefully don't do any funny business here |
| // (such as panicking) because that would obscure rustc's |
| // much more informative error message. |
| _ => Box::new(iter::empty()), |
| } |
| } |
| |
| mod kw { |
| syn::custom_keyword!(fields); |
| syn::custom_keyword!(skip); |
| syn::custom_keyword!(level); |
| syn::custom_keyword!(target); |
| syn::custom_keyword!(name); |
| syn::custom_keyword!(err); |
| } |
| |
| // Get the name of the inner function we need to hook, if the function |
| // was generated by async-trait. |
| // When we are given a function generated by async-trait, that function |
| // is only a "temporary" one that returns a pinned future, and it is |
| // that pinned future that needs to be instrumented, otherwise we will |
| // only collect information on the moment the future was "built", |
| // and not its true span of execution. |
| // So we inspect the block of the function to find if we can find the |
| // pattern `async fn foo<...>(...) {...}; Box::pin(foo<...>(...))` and |
| // return the name `foo` if that is the case. Our caller will then be |
| // able to use that information to instrument the proper function. |
| // (this follows the approach suggested in |
| // https://github.com/dtolnay/async-trait/issues/45#issuecomment-571245673) |
| fn get_async_trait_name(block: &Block, block_is_async: bool) -> Option<String> { |
| // are we in an async context? If yes, this isn't a async_trait-like pattern |
| if block_is_async { |
| return None; |
| } |
| |
| // list of async functions declared inside the block |
| let mut inside_funs = Vec::new(); |
| // last expression declared in the block (it determines the return |
| // value of the block, so that if we are working on a function |
| // whose `trait` or `impl` declaration is annotated by async_trait, |
| // this is quite likely the point where the future is pinned) |
| let mut last_expr = None; |
| |
| // obtain the list of direct internal functions and the last |
| // expression of the block |
| for stmt in &block.stmts { |
| if let Stmt::Item(Item::Fn(fun)) = &stmt { |
| // is the function declared as async? If so, this is a good |
| // candidate, let's keep it in hand |
| if fun.sig.asyncness.is_some() { |
| inside_funs.push(fun.sig.ident.to_string()); |
| } |
| } else if let Stmt::Expr(e) = &stmt { |
| last_expr = Some(e); |
| } |
| } |
| |
| // let's play with (too much) pattern matching |
| // is the last expression a function call? |
| if let Some(Expr::Call(ExprCall { |
| func: outside_func, |
| args: outside_args, |
| .. |
| })) = last_expr |
| { |
| if let Expr::Path(path) = outside_func.as_ref() { |
| // is it a call to `Box::pin()`? |
| if "Box::pin" == path_to_string(&path.path) { |
| // does it takes at least an argument? (if it doesn't, |
| // it's not gonna compile anyway, but that's no reason |
| // to (try to) perform an out of bounds access) |
| if outside_args.is_empty() { |
| return None; |
| } |
| // is the argument to Box::pin a function call itself? |
| if let Expr::Call(ExprCall { func, args, .. }) = &outside_args[0] { |
| if let Expr::Path(inside_path) = func.as_ref() { |
| // "stringify" the path of the function called |
| let func_name = path_to_string(&inside_path.path); |
| // is this function directly defined insided the current block? |
| if inside_funs.contains(&func_name) { |
| // we must hook this function now |
| return Some(func_name); |
| } |
| } |
| } |
| } |
| } |
| } |
| None |
| } |
| |
| // Return a path as a String |
| fn path_to_string(path: &Path) -> String { |
| use std::fmt::Write; |
| // some heuristic to prevent too many allocations |
| let mut res = String::with_capacity(path.segments.len() * 5); |
| for i in 0..path.segments.len() { |
| write!(&mut res, "{}", path.segments[i].ident) |
| .expect("writing to a String should never fail"); |
| if i < path.segments.len() - 1 { |
| res.push_str("::"); |
| } |
| } |
| res |
| } |
