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/*! This crate introduces `Problem` type which can be used on high level APIs (e.g. in command line program) for which error handling boils down to: * reporting error message (e.g. log with `error!` macro), * aborting program on error other than a bug (e.g. using `panic!` macro), * ignoring error. # Problem type `Problem` type is core of this library. It is basically a wrapper around `String`. In order to support conversion from types implementing `Error` trait it does not implement this trait. When converting other errors to `Problem` the `Display` message is produced of the original error and stored in `Problem` as cause message. Additionally `Problem` can also store message and another `Problem` which allows for nesting multiple contexts and problem causes. # Creating Problem There are multiple ways to crate `Problem` value. ## Directly Using `Problem::cause(msg)` function. ```rust use problem::prelude::*; Problem::cause("foo"); ``` ## Implicitly Types implementing `Error` trait can be converted to `Problem` via `From` trait so that `?` will work. ```rust use problem::prelude::*; fn foo() -> Result<String, Problem> { let str = String::from_utf8(vec![0, 123, 255])?; Ok(str) } assert_eq!(foo().unwrap_err().to_string(), "invalid utf-8 sequence of 1 bytes from index 2"); ``` If Error cause or source is available it will be shown as well. ```rust use problem::prelude::*; use std::fmt; use std::error::Error; #[derive(Debug)] struct ErrorWithCause(std::string::FromUtf8Error); impl fmt::Display for ErrorWithCause { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "bad things happened") } } impl Error for ErrorWithCause { fn cause(&self) -> Option<&dyn Error> { Some(&self.0) } } fn foo() -> Result<String, Problem> { let str = String::from_utf8(vec![0, 123, 255]).map_err(ErrorWithCause)?; Ok(str) } assert_eq!(foo().unwrap_err().to_string(), "bad things happened; caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` ## Explicitly Any type that implements `ToString` or `Display` can be converted to `Problem` with `.to_problem()`. ```rust use problem::prelude::*; assert_eq!("oops".to_problem().to_string(), "oops"); ``` ## From Option Often when working with C libraries actual errors may be unknown and function `Result` will have `Option<impl Error>` for their `Err` variant type. `.to_problem()` method is implemented for `Option<E>` and will contain "\<unknown error\>" message for `None` variant. ```rust use problem::prelude::*; let unknown: Option<&'static str> = None; let known: Option<&'static str> = Some("oops"); assert_eq!(unknown.to_problem().to_string(), "<unknown error>"); assert_eq!(known.to_problem().to_string(), "oops"); ``` ## By mapping Result `Result<T, E>` can be mapped into `Result<T, Problem>` with `.map_problem()` function. ```rust use problem::prelude::*; let res: Result<(), &'static str> = Err("oops"); assert_eq!(res.map_problem().unwrap_err().to_string(), "oops"); ``` ## By conversion of Option to Result `Option<T>` can be converted into `Result<T, Problem>` with `.ok_or_problem(message)` function. ```rust use problem::prelude::*; let opt: Option<()> = None; assert_eq!(opt.ok_or_problem("oops").unwrap_err().to_string(), "oops"); ``` # Adding context to Problem ## Inline Methods `.problem_while(message)` and `.problem_while_with(|| message)` can be called on any `Result` that error type can be implicitly converted to `Problem`. ```rust use problem::prelude::*; let res = String::from_utf8(vec![0, 123, 255]); assert_eq!(res.problem_while("creating string").unwrap_err().to_string(), "while creating string got error caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` The `_with` variant can be used to delay computation of error message to the moment when actual `Err` variant has occurred. ```rust use problem::prelude::*; let res = String::from_utf8(vec![0, 123, 255]); assert_eq!(res.problem_while_with(|| "creating string").unwrap_err().to_string(), "while creating string got error caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` ## Wrapped Functions `in_context_of(message, closure)` and `in_context_of_with(|| message, closure)` can be used to wrap block of code in closure that return `Result`. This is useful when you want to add context to any error that can happen in the block of code and use `?` operator. The return type of the closure needs to be `Result<T, Problem>`. ```rust use problem::prelude::*; let res = in_context_of("processing string", || { let _s = String::from_utf8(vec![0, 123, 255])?; // do some processing of _s Ok(()) }); assert_eq!(res.unwrap_err().to_string(), "while processing string got error caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` The `_with` variant can be used to delay computation of error message to the moment when actual `Err` variant has occurred. ```rust use problem::prelude::*; let res = in_context_of_with(|| "processing string", || { let _s = String::from_utf8(vec![0, 123, 255])?; // do some processing of _s Ok(()) }); assert_eq!(res.unwrap_err().to_string(), "while processing string got error caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` ## Nested context Context methods can be used multiple times to add another layer of context. ```rust use problem::prelude::*; fn foo() -> Result<String, Problem> { let str = String::from_utf8(vec![0, 123, 255])?; Ok(str) } let res = in_context_of("doing stuff", || { let _s = foo().problem_while("running foo")?; // do some processing of _s Ok(()) }); assert_eq!(res.unwrap_err().to_string(), "while doing stuff, while running foo got error caused by: invalid utf-8 sequence of 1 bytes from index 2"); ``` # Aborting program on Problem `panic!(msg, problem)` macro can be used directly to abort program execution but error message printed on the screen will be formatted with `Debug` implementation. This library provides function `format_panic_to_stderr()` to set up hook that will use `eprintln!("{}", message)` to report panics. If `log` feature is enabled (default) function `format_panic_to_error_log()` will set up hook that will log with `error!("{}", message)` to report panics. ```noformat ERROR: Panicked in libcore/slice/mod.rs:2334:5: index 18492 out of range for slice of length 512 ``` ## Panicking on Result with Problem Similarly to `.expect(message)`, method `.or_failed_to(message)` can be used to abort the program via `panic!()` with `Display` formatted message when called on `Err` variant of `Result` with error type implementing `Display` trait. ```rust,should_panic use problem::prelude::*; use problem::format_panic_to_stderr; format_panic_to_stderr(); // Prints message: Failed to convert string due to: invalid utf-8 sequence of 1 bytes from index 2 let _s = String::from_utf8(vec![0, 123, 255]).or_failed_to("convert string"); ``` ## Panicking on Option Similarly to `.ok_or(error)`, method `.or_failed_to(message)` can be used to abort the program via `panic!()` with formatted message on `None` variant of `Option` type. ```rust,should_panic use problem::prelude::*; use problem::format_panic_to_stderr; format_panic_to_stderr(); let nothing: Option<&'static str> = None; // Prints message: Failed to get something let _s = nothing.or_failed_to("get something"); ``` ## Panicking on iterators of Result Method `.or_failed_to(message)` can be used to abort the program via `panic!()` with formatted message on iterators with `Result` item when first `Err` is encountered otherwise unwrapping the `Ok` value. ```rust,should_panic use problem::prelude::*; use problem::format_panic_to_stderr; format_panic_to_stderr(); let results = vec![Ok(1u32), Ok(2u32), Err("oops".to_problem())]; // Prints message: Failed to collect numbers due to: oops let _ok: Vec<u32> = results.into_iter() .or_failed_to("collect numbers") .collect(); ``` # Logging errors If `log` feature is enabled (default) function `ok_or_log_warn()` or `ok_or_log_error()` can be used on `Result` and iterator of `Result` items to convert `Result` into `Option` while logging `Err` wariants as warnings or errors. When used on iterators `flatten()` addaptor can be used to filter out all `Err` variant items after they were logged and converted to `None`. ```rust use problem::prelude::*; # #[cfg(feature = "log")] # fn test_with_log_feature() { let results = vec![Ok(1u32), Ok(2), Err("oops".to_problem()), Ok(3), Err("oh".to_problem()), Ok(4)]; // Logs warning message: Continuing with error oops // Logs warning message: Continuing with error oh let ok: Vec<u32> = results.into_iter() .ok_or_log_warn() .flatten() .collect(); assert_eq!(ok.as_slice(), [1, 2, 3, 4]); # } # # #[cfg(feature = "log")] # test_with_log_feature(); ``` # Backtraces When compiled with `backtrace` feature (default) formatting of backtraces for `Problem` cause and `panic!` locations can be enabled via `RUST_BACKTRACE=1` environment variable. ```noformat Fatal error: Panicked in src/lib.rs:189:25: Failed to complete processing task due to: while processing object, while processing input data, while parsing input got error caused by: boom! --- Cause at backtrace::backtrace::trace_unsynchronized::h7e40b70e3b5d7257(/Users/wcc/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.13/src/backtrace/mod.rs:57) at problem::Problem::cause::h8e82f78cae379944(/Users/wcc/Documents/problem/src/lib.rs:17) at <problem::Problem as core::convert::From<E>>::from::h68fcd01f7485d6fd(/Users/wcc/Documents/problem/src/lib.rs:55) at <T as core::convert::Into<U>>::into::hf86686e788a07f6b(/Users/wcc/Documents/problem/libcore/convert.rs:456) at <core::result::Result<O, E> as problem::ProblemWhile<O>>::problem_while::{{closure}}::h712c2996b4c3f676(/Users/wcc/Documents/problem/src/lib.rs:147) at <core::result::Result<T, E>>::map_err::h6da0ba4797049470(/Users/wcc/Documents/problem/libcore/result.rs:530) at <core::result::Result<O, E> as problem::ProblemWhile<O>>::problem_while::h108bd26e9cdec72e(/Users/wcc/Documents/problem/src/lib.rs:147) at problem::tests::test_panic_format_stderr_problem::h519245df9f30ee8f(/Users/wcc/Documents/problem/src/lib.rs:412) at problem::tests::test_panic_format_stderr_problem::{{closure}}::haaae053a88c4688a(/Users/wcc/Documents/problem/src/lib.rs:410) at core::ops::function::FnOnce::call_once::h805a1d08e5489f20(/Users/wcc/Documents/problem/libcore/ops/function.rs:238) at <F as alloc::boxed::FnBox<A>>::call_box::h7cd9458e96c61134(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/liballoc/boxed.rs:672) at ___rust_maybe_catch_panic(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libpanic_unwind/lib.rs:102) at std::sys_common::backtrace::__rust_begin_short_backtrace::h907b48cdce2bf28d(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libtest/lib.rs:1423) at std::panicking::try::do_call::hffc427c76ef62020(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/panicking.rs:310) at ___rust_maybe_catch_panic(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libpanic_unwind/lib.rs:102) at <F as alloc::boxed::FnBox<A>>::call_box::h44749feefaa83f3d(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/thread/mod.rs:408) at std::sys_common::thread::start_thread::h24d08beb3985b9d2(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/sys_common/thread.rs:24) at std::sys::unix::thread::Thread::new::thread_start::h9ca5dbae56c6730a(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/sys/unix/thread.rs:90) at __pthread_body() at __pthread_start() --- Panicked at backtrace::backtrace::trace_unsynchronized::h7e40b70e3b5d7257(/Users/wcc/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.13/src/backtrace/mod.rs:57) at problem::format_panic_to_stderr::{{closure}}::h5e5215e229ccf82b(/Users/wcc/Documents/problem/src/lib.rs:319) at std::panicking::rust_panic_with_hook::h11860e91fb60d90b(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/panicking.rs:480) at std::panicking::continue_panic_fmt::h28d8e12e50184e99(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/panicking.rs:390) at std::panicking::begin_panic_fmt::h2bdefd173f570a0b(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/panicking.rs:345) at <core::result::Result<O, E> as problem::FailedTo<O>>::or_failed_to::h23df6bc9680c971b(/Users/wcc/Documents/problem/src/lib.rs:189) at problem::tests::test_panic_format_stderr_problem::h519245df9f30ee8f(/Users/wcc/Documents/problem/src/lib.rs:417) at problem::tests::test_panic_format_stderr_problem::{{closure}}::haaae053a88c4688a(/Users/wcc/Documents/problem/src/lib.rs:410) at core::ops::function::FnOnce::call_once::h805a1d08e5489f20(/Users/wcc/Documents/problem/libcore/ops/function.rs:238) at <F as alloc::boxed::FnBox<A>>::call_box::h7cd9458e96c61134(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/liballoc/boxed.rs:672) at ___rust_maybe_catch_panic(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libpanic_unwind/lib.rs:102) at std::sys_common::backtrace::__rust_begin_short_backtrace::h907b48cdce2bf28d(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libtest/lib.rs:1423) at std::panicking::try::do_call::hffc427c76ef62020(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/panicking.rs:310) at ___rust_maybe_catch_panic(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libpanic_unwind/lib.rs:102) at <F as alloc::boxed::FnBox<A>>::call_box::h44749feefaa83f3d(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/thread/mod.rs:408) at std::sys_common::thread::start_thread::h24d08beb3985b9d2(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/sys_common/thread.rs:24) at std::sys::unix::thread::Thread::new::thread_start::h9ca5dbae56c6730a(/rustc/abe02cefd6cd1916df62ad7dc80161bea50b72e8/src/libstd/sys/unix/thread.rs:90) at __pthread_body() at __pthread_start() ``` ## Access Formatted backtrace `&str` can be accessed via `Problem::backtrace` function that will return `Some` if `backtrace` feature is available and `RUST_BACKTRACE=1` environment variable is set. ```rust use problem::prelude::*; Problem::cause("foo").backtrace(); // Some(<&str>) ``` */ #[cfg(feature = "log")] #[macro_use] extern crate log; use std::error::Error; use std::fmt::{self, Display}; use std::panic; /// Includes `Problem` type and related conversion traits and `in_context_of*` functions pub mod prelude { pub use super::{ in_context_of, in_context_of_with, FailedTo, FailedToIter, OptionErrorToProblem, OptionToProblem, Problem, ProblemWhile, ResultOptionToProblem, ResultToProblem, ToProblem, }; #[cfg(feature = "log")] pub use super::logged::{OkOrLog, OkOrLogIter}; } /// Error type that is not supposed to be handled but reported, panicked on or ignored #[derive(Debug)] pub enum Problem { Cause(String, Option<String>), Context(String, Box<Problem>), } impl Problem { /// Create `Problem` from any type implementing `ToString` or `Display` pub fn cause(msg: impl ToString) -> Problem { Problem::Cause(msg.to_string(), format_backtrace()) } /// Create `Problem` from type implement `Error` so that `Error::cause` is followed through pub fn from_error(error: &dyn Error) -> Problem { let message = if let Some(cause) = error.cause() { // make sure we follow through the cause chain let cause_problem: Problem = Problem::from_error(cause); format!("{}; caused by: {}", error.to_string(), cause_problem) } else { error.to_string() }; Problem::Cause(message, format_backtrace()) } /// Add context information to this `Problem` instance pub fn while_context(self, msg: impl ToString) -> Problem { Problem::Context(msg.to_string(), Box::new(self)) } /// Get backtrace associated with this `Problem` instance if available pub fn backtrace(&self) -> Option<&str> { match self { &Problem::Cause(_, ref backtrace) => backtrace.as_ref().map(String::as_str), &Problem::Context(_, ref problem) => problem.backtrace(), } } } impl Display for Problem { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match self { &Problem::Cause(ref msg, None) => write!(f, "{}", msg), &Problem::Cause(ref msg, Some(ref backtrace)) => { write!(f, "{}\n\t--- Cause\n{}", msg, backtrace) } &Problem::Context(ref msg, ref inner) => match inner.as_ref() { cause @ &Problem::Cause(..) => { write!(f, "while {} got error caused by: {}", msg, cause) } inner => write!(f, "while {}, {}", msg, inner), }, } } } /// Every type implementing Error trait can implicitly be converted to Problem via ? operator impl<E> From<E> for Problem where E: Error, { fn from(error: E) -> Problem { Problem::from_error(&error) } } /// Explicit conversion to Problem pub trait ToProblem { fn to_problem(self) -> Problem; } /// T that has Display or ToString implemented can be converted to Problem impl<T> ToProblem for T where T: ToString, { fn to_problem(self) -> Problem { Problem::cause(self) } } /// Option of T that has Display or ToString implemented can be converted to Problem that displays <unknown error> for None variant pub trait OptionErrorToProblem { fn to_problem(self) -> Problem; } impl<E> OptionErrorToProblem for Option<E> where E: ToProblem, { fn to_problem(self) -> Problem { self.map(ToProblem::to_problem) .unwrap_or(Problem::cause("<unknown error>")) } } /// Mapping Result with error to Result with Problem pub trait ResultToProblem<O> { fn map_problem(self) -> Result<O, Problem>; } impl<O, E> ResultToProblem<O> for Result<O, E> where E: ToProblem, { fn map_problem(self) -> Result<O, Problem> { self.map_err(|e| e.to_problem()) } } /// Mapping Result with Option<Error> to Result with Problem pub trait ResultOptionToProblem<O> { fn map_problem(self) -> Result<O, Problem>; } impl<O, E> ResultOptionToProblem<O> for Result<O, Option<E>> where E: ToProblem, { fn map_problem(self) -> Result<O, Problem> { self.map_err(OptionErrorToProblem::to_problem) } } /// Map Option to Result with Problem pub trait OptionToProblem<O> { fn ok_or_problem<M>(self, msg: M) -> Result<O, Problem> where M: ToString; } impl<O> OptionToProblem<O> for Option<O> { fn ok_or_problem<M>(self, msg: M) -> Result<O, Problem> where M: ToString, { self.ok_or_else(|| Problem::cause(msg)) } } /// Add context to Result with Problem or that can be implicitly mapped to one pub trait ProblemWhile<O> { fn problem_while(self, msg: impl Display) -> Result<O, Problem>; fn problem_while_with<F, M>(self, msg: F) -> Result<O, Problem> where F: FnOnce() -> M, M: Display; } impl<O, E> ProblemWhile<O> for Result<O, E> where E: Into<Problem>, { fn problem_while(self, msg: impl Display) -> Result<O, Problem> { self.map_err(|err| err.into().while_context(msg)) } fn problem_while_with<F, M>(self, msg: F) -> Result<O, Problem> where F: FnOnce() -> M, M: Display, { self.map_err(|err| err.into().while_context(msg())) } } /// Executes closure with problem_while context pub fn in_context_of<O, M, B>(msg: M, body: B) -> Result<O, Problem> where M: Display, B: FnOnce() -> Result<O, Problem>, { body().problem_while(msg) } /// Executes closure with problem_while_with context pub fn in_context_of_with<O, F, M, B>(msg: F, body: B) -> Result<O, Problem> where F: FnOnce() -> M, M: Display, B: FnOnce() -> Result<O, Problem>, { body().problem_while_with(msg) } /// Extension of Result that allows program to panic with Display message on Err for fatal application errors that are not bugs pub trait FailedTo<O> { fn or_failed_to(self, msg: impl Display) -> O; } impl<O, E> FailedTo<O> for Result<O, E> where E: Into<Problem>, { fn or_failed_to(self, msg: impl Display) -> O { match self { Err(err) => panic!("Failed to {} due to: {}", msg, err.into()), Ok(ok) => ok, } } } impl<O> FailedTo<O> for Option<O> { fn or_failed_to(self, msg: impl Display) -> O { match self { None => panic!("Failed to {}", msg), Some(ok) => ok, } } } /// Iterator that will panic on first error with message displaying Display formatted message pub struct ProblemIter<I> { inner: I, message: String, } impl<I, O, E> Iterator for ProblemIter<I> where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, { type Item = O; fn next(&mut self) -> Option<Self::Item> { self.inner .next() .map(|res| res.or_failed_to(self.message.as_str())) } } /// Convert Iterator of Result<O, E> to iterator of O and panic on first E with problem message pub trait FailedToIter<O, E>: Sized { fn or_failed_to(self, msg: impl ToString) -> ProblemIter<Self>; } impl<I, O, E> FailedToIter<O, E> for I where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, { fn or_failed_to(self, msg: impl ToString) -> ProblemIter<Self> { ProblemIter { inner: self, message: msg.to_string(), } } } #[cfg(feature = "log")] pub mod logged { use super::*; use log::{error, warn}; /// Extension of Result that allows program to log on Err with Display message for application errors that are not critical pub trait OkOrLog<O> { fn ok_or_log_warn(self) -> Option<O>; fn ok_or_log_error(self) -> Option<O>; } impl<O, E> OkOrLog<O> for Result<O, E> where E: Into<Problem>, { fn ok_or_log_warn(self) -> Option<O> { match self { Err(err) => { warn!("Continuing with error {}", err.into()); None } Ok(ok) => Some(ok), } } fn ok_or_log_error(self) -> Option<O> { match self { Err(err) => { error!("Continuing with error {}", err.into()); None } Ok(ok) => Some(ok), } } } /// Iterator that will log as warn Display formatted message on Err and skip to next item; it can be flattened to skip failed items pub struct ProblemWarnLoggingIter<I> { inner: I, } impl<I, O, E> Iterator for ProblemWarnLoggingIter<I> where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, { type Item = Option<O>; fn next(&mut self) -> Option<Self::Item> { self.inner.next().map(|res| res.ok_or_log_warn()) } } /// Iterator that will log as error Display formatted message on Err and skip to next item; it can be flattened to skip failed items pub struct ProblemErrorLoggingIter<I> { inner: I, } impl<I, O, E> Iterator for ProblemErrorLoggingIter<I> where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, { type Item = Option<O>; fn next(&mut self) -> Option<Self::Item> { self.inner.next().map(|res| res.ok_or_log_error()) } } /// Convert Iterator of Result<O, E> to iterator of Option<O> and log any Err variants pub trait OkOrLogIter<O, E>: Sized { fn ok_or_log_warn(self) -> ProblemWarnLoggingIter<Self>; fn ok_or_log_error(self) -> ProblemErrorLoggingIter<Self>; } impl<I, O, E> OkOrLogIter<O, E> for I where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, { fn ok_or_log_warn(self) -> ProblemWarnLoggingIter<Self> { ProblemWarnLoggingIter { inner: self } } fn ok_or_log_error(self) -> ProblemErrorLoggingIter<Self> { ProblemErrorLoggingIter { inner: self } } } } #[cfg(not(feature = "backtrace"))] fn format_backtrace() -> Option<String> { None } #[cfg(feature = "backtrace")] #[inline(always)] fn format_backtrace() -> Option<String> { if let Ok("1") = std::env::var("RUST_BACKTRACE").as_ref().map(String::as_str) { let mut backtrace = String::new(); backtrace::trace(|frame| { let ip = frame.ip(); //let symbol_address = frame.symbol_address(); backtrace.push_str("\tat "); backtrace::resolve(ip, |symbol| { if let Some(name) = symbol.name() { backtrace.push_str(&name.to_string()); } backtrace.push_str("("); if let Some(filename) = symbol.filename() { backtrace.push_str(&filename.display().to_string()); } if let Some(lineno) = symbol.lineno() { backtrace.push_str(":"); backtrace.push_str(&lineno.to_string()); } backtrace.push_str(")"); }); backtrace.push_str("\n"); true // keep going to the next frame }); backtrace.pop(); // last \n Some(backtrace) } else { None } } fn format_panic(panic: &std::panic::PanicInfo, backtrace: Option<String>) -> String { let mut message = String::new(); if let Some(location) = panic.location() { message.push_str(&format!( "Panicked in {}:{}:{}: ", location.file(), location.line(), location.column() )); }; if let Some(value) = panic.payload().downcast_ref::<String>() { message.push_str(&value); } else if let Some(value) = panic.payload().downcast_ref::<&str>() { message.push_str(value); } else if let Some(value) = panic.payload().downcast_ref::<&Error>() { message.push_str(&format!("{} ({:?})", value, value)); } else { message.push_str(&format!("{:?}", panic)); }; if let Some(backtrace) = backtrace { message.push_str("\n\t--- Panicked\n"); message.push_str(&backtrace); }; message } /// Set panic hook so that when program panics it will print the Display version of error massage to stderr pub fn format_panic_to_stderr() { panic::set_hook(Box::new(|panic_info| { let backtrace = format_backtrace(); eprintln!("Fatal error: {}", format_panic(panic_info, backtrace)); })); } /// Set panic hook so that when program panics it will log the Display version of error massage with error! macro #[cfg(feature = "log")] pub fn format_panic_to_error_log() { panic::set_hook(Box::new(|panic_info| { let backtrace = format_backtrace(); error!("{}", format_panic(panic_info, backtrace)); })); } #[cfg(test)] mod tests { use super::*; use std::io; #[derive(Debug)] struct Foo; impl Display for Foo { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "Foo error") } } impl Error for Foo {} #[derive(Debug)] struct Bar(Foo); impl Display for Bar { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "Bar error") } } impl Error for Bar { fn source(&self) -> Option<&(dyn Error + 'static)> { Some(&self.0) } } #[test] #[should_panic( expected = "Failed to complete processing task due to: while processing object, while processing input data, while parsing input got error caused by: boom!" )] fn test_integration() { Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!")) .problem_while("parsing input") .problem_while("processing input data") .problem_while("processing object") .or_failed_to("complete processing task") } #[test] #[should_panic( expected = "Failed to complete processing task due to: while processing object, while processing input data, while parsing input got error caused by: Bar error; caused by: Foo error" )] fn test_integration_cause_chain() { Err(Bar(Foo)) .problem_while("parsing input") .problem_while("processing input data") .problem_while("processing object") .or_failed_to("complete processing task") } #[test] #[should_panic( expected = "Failed to complete processing task due to: while doing stuff got error caused by: boom!" )] fn test_in_context_of() { in_context_of("doing stuff", || { Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!"))? }) .or_failed_to("complete processing task") } #[test] #[should_panic(expected = "Failed to foo due to: boom!")] fn test_result() { Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!")).or_failed_to("foo") } #[test] #[should_panic(expected = "Failed to quix due to: Bar error; caused by: Foo error")] fn test_result_cause_chain() { Err(Bar(Foo)).or_failed_to("quix") } #[test] #[should_panic(expected = "Failed to foo")] fn test_option() { None.or_failed_to("foo") } #[test] #[should_panic(expected = "Failed to foo due to: boom!")] fn test_option_errors() { Err(Some(io::Error::new(io::ErrorKind::InvalidInput, "boom!"))) .map_problem() .or_failed_to("foo") } #[test] #[should_panic(expected = "Failed to foo due to: <unknown error>")] fn test_result_option_errors_unknown() { let err: Result<(), Option<io::Error>> = Err(None); err.map_problem().or_failed_to("foo") } #[test] #[should_panic(expected = "Failed to foo due to: nothing here")] fn test_result_ok_or_problem() { None.ok_or_problem("nothing here").or_failed_to("foo") } #[test] #[should_panic(expected = "Failed to foo due to: omg!")] fn test_result_iter_or_failed_to() { let results = vec![Ok(1u32), Ok(2u32), Err("omg!".to_problem())]; let _ok = results.into_iter().or_failed_to("foo").collect::<Vec<_>>(); } #[test] #[should_panic] fn test_panic_format_stderr() { format_panic_to_stderr(); panic!("foo bar!"); } #[test] #[should_panic] fn test_panic_format_stderr_problem() { format_panic_to_stderr(); let result: Result<(), Problem> = Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!")) .problem_while("parsing input") .problem_while("processing input data") .problem_while("processing object"); result.or_failed_to("complete processing task"); } #[test] #[cfg(feature = "backtrace")] fn test_problem_backtrace() { let p = Problem::cause("foo") .while_context("bar") .while_context("baz"); if let Ok("1") = std::env::var("RUST_BACKTRACE").as_ref().map(String::as_str) { assert!(p.backtrace().is_some()); println!("{}", p.backtrace().unwrap()); } else { assert!(p.backtrace().is_none()); } } }