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/*! This crate introduces `Problem` type which can be used on high level APIs (e.g. in command line programs or prototypes) 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), * bubbling up errors (e.g. with `?`), * ignoring errors (e.g. using `Result::ok`). # Usage The core type of this crate is `Problem`. It is used to capture error, backtrace (if enabled) and any additional context information and present it in user friendly way via `Display` implementation. This library also provides many additional extension traits and some functions that make it easy to construct `Problem` type in different situations as well as report or abort programs on error. It is recommended to import all the types and traits via perlude module: `use problem::prelude::*`. `Problem` stores error cause information as `Box<dyn Error>` to dealy construction of error message to when it is actually needed. Additionally `Problem` can also store backtrace `String` (if enabled) and a chain of additional context messages as `Vec<String>`. In order to support conversion from arbitary types implementing `Error` trait, `Problem` does not implement this trait. # Creating `Problem` There are multiple ways to crate `Problem` value. ## Using constructor Using `Problem::from_error(error)` if `error` implements `Error` trait (via `Into<Box<dyn Error>>`). Note that `String` and `&str` implement `Into<Box<dyn Error>>` so `Problem` can be constructed directly from strings as well. ```rust use problem::prelude::*; use std::io; Problem::from_error(io::Error::new(io::ErrorKind::InvalidInput, "boom!")); Problem::from_error(Box::new(io::Error::new(io::ErrorKind::InvalidInput, "boom!"))); Problem::from_error("boom!"); ``` Use `Problem::from_error_message(error)` if you don't want to give up ownership of error or only want to keep final message string in memory. ```rust use problem::prelude::*; use std::io; let error = io::Error::new(io::ErrorKind::InvalidInput, "boom!"); let problem = Problem::from_error_message(&error); drop(error); drop(problem); ``` ## Implicitly Types implementing `Into<Box<dyn Error>>` trait can be converted to `Problem` via `From` trait. `?` will automatically convert types implementing `Error` to `Problem`. ```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 `Error::source` is available, the error message from cause chain will be displayed. ```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"); ``` ## By explicitly 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"); let problem: Result<(), Problem> = res.map_problem(); assert_eq!(problem.unwrap_err().to_string(), "oops"); ``` ## By conversion of `Option` into `Result` `Option<T>` can be converted into `Result<T, Problem>` with `.ok_or_problem(problem)` function where `problem` implements `Into<Problem>`. ```rust use problem::prelude::*; let opt: Option<()> = None; let problem: Result<(), Problem> = opt.ok_or_problem("oops"); assert_eq!(problem.unwrap_err().to_string(), "oops"); ``` ## From `Result` with `Err` containing `Option` `.map_problem_or(problem)` method is implemented for `Result<O, Option<E>>` and will map to `Result<O, Problem>` with provided problem for `Err(None)` variant. This may be usefult when working with FFI. ```rust use problem::prelude::*; let unknown: Result<(), Option<&'static str>> = Err(None); let known: Result<(), Option<&'static str>> = Err(Some("oops")); assert_eq!(unknown.map_problem_or("unknown error").unwrap_err().to_string(), "unknown error"); assert_eq!(known.map_problem_or("unknown error").unwrap_err().to_string(), "oops"); ``` There is also `.map_problem_or_else(problem_function)` variant provided that can be used to defer construction of error to error path. ```rust use problem::prelude::*; let unknown: Result<(), Option<&'static str>> = Err(None); let known: Result<(), Option<&'static str>> = Err(Some("oops")); assert_eq!(unknown.map_problem_or_else(|| "unknown error").unwrap_err().to_string(), "unknown error"); assert_eq!(known.map_problem_or_else(|| "unknown error").unwrap_err().to_string(), "oops"); ``` # Adding context to `Problem` A context information that provides clues on which good path has been taken that led to error can be added to `Problem` object. Adding context is a good way to convert other error types to `Problem` as well as providing extra information on where that happened. ## On `Result` error Method `.problem_while(message)` can be called on any `Result` value that error type can be converted to `Problem` to add context message (via `Dispaly` trait). ```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"); ``` There is also `.problem_while_with(message_function)` variant provided that can be used to defer construction of context message to error path. ```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"); ``` ## Using scope and `?` Function `in_context_of(message, closure)` can be used to wrap block of code in a closure that returns `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>` but `?` operator can convert to `Problem` automatically. ```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"); ``` There is also `in_context_of_with(message_function, closure)` variant provided that can be used to defer construction of context message to error path. ```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 layers 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!(message, 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. Alternatively 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. Panic hooks will produce backtrace of panic site if enabled via `RUST_BACKTRACE=1` environment variable along of the `Problem` object backtrace collected at object construction site. ```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!()` in case of `Err` variant with `Display` formatted message and error converted to `Problem` to format the error message with `Display` trait. ```rust,should_panic use problem::prelude::*; use problem::format_panic_to_stderr; format_panic_to_stderr(); // Prints message: let _s = String::from_utf8(vec![0, 123, 255]).or_failed_to("convert string"); // Failed to convert string due to: invalid utf-8 sequence of 1 bytes from index 2 ``` ## Panicking on `Option` Similarly to `.ok_or(error)`, method `.or_failed_to(message)` can be used to abort the program via `panic!()` with `Display` 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; let _s = nothing.or_failed_to("get something"); // 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. The error type will be converted to `Problem` just before panicing. ```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")]; let _ok: Vec<u32> = results.into_iter() .or_failed_to("collect numbers") .collect(); // Failed to collect numbers due to: oops ``` # Main function exit with error message and custom status `FatalProblem` and `result::FinalResult` types can be used on `main` function signature to allow programs to terminate with `Problem` formatted message and custom exit status. ```rust,should_panic use problem::prelude::*; fn main() -> FinalResult { // Prints "I'm sorry Dave, I'm afraid I can't do that" and exits with status 1 Err(Problem::from_error("I'm sorry Dave, I'm afraid I can't do that"))?; // Prints "I'm sorry Dave, I'm afraid I can't do that" and exits with status 42 Err(Problem::from_error("I'm sorry Dave, I'm afraid I can't do that")).fatal_with_status(42)?; Ok(()) } ``` # 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"), Ok(3), Err("oh"), 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: thread 'tests::test_panic_format_stderr_problem' panicked at src/lib.rs:657:35 with: Failed to complete processing task due to: while processing object, while processing input data, while parsing input got error caused by: boom! --- Cause 0: backtrace::backtrace::trace_unsynchronized::h936094cb968a67c2 at /Users/jpastuszek/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.13/src/backtrace/mod.rs:57 1: problem::Problem::from_error::hfdbc5afef77017de at /Users/jpastuszek/Documents/problem/src/lib.rs:435 2: <problem::Problem as core::convert::From<E>>::from::h3b5fdbec33645197 at /Users/jpastuszek/Documents/problem/src/lib.rs:500 3: <T as core::convert::Into<U>>::into::h37311b4bc5720d6d at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libcore/convert.rs:455 4: <core::result::Result<O, E> as problem::ProblemWhile>::problem_while::{{closure}}::h97ad232ce9ba14fb at /Users/jpastuszek/Documents/problem/src/lib.rs:617 5: <core::result::Result<T, E>>::map_err::he22546342a0a16ff at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libcore/result.rs:530 6: <core::result::Result<O, E> as problem::ProblemWhile>::problem_while::he5e05f693d81f439 at /Users/jpastuszek/Documents/problem/src/lib.rs:617 7: problem::tests::test_panic_format_stderr_problem::he7f271034488edfe at /Users/jpastuszek/Documents/problem/src/lib.rs:1053 8: problem::tests::test_panic_format_stderr_problem::{{closure}}::hd06e112465364a39 at /Users/jpastuszek/Documents/problem/src/lib.rs:1051 9: core::ops::function::FnOnce::call_once::hb512c264f284bc3f at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libcore/ops/function.rs:238 10: <F as alloc::boxed::FnBox<A>>::call_box::h0b961cc85c049bee at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/liballoc/boxed.rs:673 11: ___rust_maybe_catch_panic at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libpanic_unwind/lib.rs:102 12: std::sys_common::backtrace::__rust_begin_short_backtrace::h07f538384f587585 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libtest/lib.rs:1426 13: std::panicking::try::do_call::h4953be8a0738d6ec at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:310 14: ___rust_maybe_catch_panic at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libpanic_unwind/lib.rs:102 15: <F as alloc::boxed::FnBox<A>>::call_box::h5a5d3b35dc8857f3 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/thread/mod.rs:476 16: std::sys::unix::thread::Thread::new::thread_start::hb66fd5e16b37cfd7 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/sys_common/thread.rs:24 17: __pthread_body 18: __pthread_start --- Panicked 0: backtrace::backtrace::trace_unsynchronized::h936094cb968a67c2 at /Users/jpastuszek/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.13/src/backtrace/mod.rs:57 1: problem::format_panic_to_stderr::{{closure}}::h24ae835f59658f26 at /Users/jpastuszek/Documents/problem/src/lib.rs:868 2: std::panicking::rust_panic_with_hook::h3fe6a67edb032589 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:495 3: std::panicking::continue_panic_fmt::hf7169aba6b1afe9c at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:398 4: std::panicking::begin_panic_fmt::hb5f6d46d54559b8a at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:353 5: <core::result::Result<O, E> as problem::FailedTo<O>>::or_failed_to::{{closure}}::h8e0b5d62111b80f4 at /Users/jpastuszek/Documents/problem/src/lib.rs:657 6: <core::result::Result<T, E>>::unwrap_or_else::h8bcc063ecb00981e at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libcore/result.rs:774 7: <core::result::Result<O, E> as problem::FailedTo<O>>::or_failed_to::h2e59dbec5efe6366 at /Users/jpastuszek/Documents/problem/src/lib.rs:657 8: problem::tests::test_panic_format_stderr_problem::he7f271034488edfe at /Users/jpastuszek/Documents/problem/src/lib.rs:1058 9: problem::tests::test_panic_format_stderr_problem::{{closure}}::hd06e112465364a39 at /Users/jpastuszek/Documents/problem/src/lib.rs:1051 10: core::ops::function::FnOnce::call_once::hb512c264f284bc3f at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libcore/ops/function.rs:238 11: <F as alloc::boxed::FnBox<A>>::call_box::h0b961cc85c049bee at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/liballoc/boxed.rs:673 12: ___rust_maybe_catch_panic at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libpanic_unwind/lib.rs:102 13: std::sys_common::backtrace::__rust_begin_short_backtrace::h07f538384f587585 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libtest/lib.rs:1426 14: std::panicking::try::do_call::h4953be8a0738d6ec at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:310 15: ___rust_maybe_catch_panic at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libpanic_unwind/lib.rs:102 16: <F as alloc::boxed::FnBox<A>>::call_box::h5a5d3b35dc8857f3 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/thread/mod.rs:476 17: std::sys::unix::thread::Thread::new::thread_start::hb66fd5e16b37cfd7 at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/sys_common/thread.rs:24 18: __pthread_body 19: __pthread_start ``` ## Access Formatted backtrace `&str` can be accessed via `Problem::backtrace` function that will return `Some` if `backtrace` feature is enabled and `RUST_BACKTRACE=1` environment variable is set. ```rust use problem::prelude::*; Problem::from_error("foo").backtrace(); // Some(" 0: backtrace...") ``` */ #[cfg(feature = "log")] #[macro_use] extern crate log; use std::error::Error; use std::fmt::{self, Display, Write}; use std::panic; const DEFAULT_FATAL_STATUS: i32 = 1; /// 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, Fatal, FatalProblem, MapProblem, MapProblemOr, OkOrProblem, Problem, ProblemWhile, }; pub use super::result::FinalResult; // Note that `result::Result` is not part of prelude as it may conflict with standard library or // custom library result types. #[cfg(feature = "log")] pub use super::logged::{OkOrLog, OkOrLogIter}; } /// Wraps error, context and backtrace information and formats it for display. /// Data is heap allocated to avoid type parameters or lifetimes. #[derive(Debug)] pub struct Problem { error: Box<dyn Error>, context: Vec<String>, backtrace: Option<String>, } impl Problem { /// Create `Problem` from types implementing `Into<Box<dyn Error>>` (including `String` and `&str`) so that `Error::cause` /// chain is followed through in the `Display` message pub fn from_error(error: impl Into<Box<dyn Error>>) -> Problem { Problem { error: error.into(), context: Vec::new(), backtrace: format_backtrace(), } } /// Same as `Problem::from_error` but stores only final message as `String` and does not take ownership of the error pub fn from_error_message(error: &impl Error) -> Problem { let mut message = String::new(); write_error_message(error, &mut message).unwrap(); Problem { error: message.into(), context: Vec::new(), backtrace: format_backtrace(), } } /// Get backtrace associated with this `Problem` instance if available pub fn backtrace(&self) -> Option<&str> { self.backtrace.as_ref().map(String::as_str) } } #[allow(deprecated)] fn write_error_message(error: &dyn Error, w: &mut impl Write) -> fmt::Result { write!(w, "{}", error)?; let mut error_cause = error; loop { // Note: using Error::cause() here to be backward compatible with older errors if let Some(cause) = error_cause.cause() { write!(w, "; caused by: {}", cause)?; error_cause = cause; } else { break; } } Ok(()) } impl Display for Problem { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { if let Some(context) = self.context.last() { write!(f, "while {}", context)?; } for context in self.context.iter().rev().skip(1) { write!(f, ", while {}", context)?; } if !self.context.is_empty() { write!(f, " got error caused by: ")?; } write_error_message(self.error.as_ref(), f)?; if let Some(backtrace) = self.backtrace.as_ref() { write!(f, "\n--- Cause\n{}", backtrace)?; } Ok(()) } } /// Every type implementing `Into<Box<dyn Error>>` trait (including `String` and `&str` types) can be converted to `Problem` via `?` operator impl<E> From<E> for Problem where E: Into<Box<dyn Error>>, { fn from(error: E) -> Problem { Problem::from_error(error) } } /// This error type is meant to be used as `main()` result error. It implements `Debug` display so /// that the program can terminate with nice message formatted with `Problem` and custom exit /// status. pub struct FatalProblem { status: i32, problem: Problem, } impl From<Problem> for FatalProblem { fn from(problem: Problem) -> FatalProblem { FatalProblem { status: DEFAULT_FATAL_STATUS, problem, } } } impl<E> From<E> for FatalProblem where E: Into<Box<dyn std::error::Error>>, { fn from(error: E) -> FatalProblem { FatalProblem { status: DEFAULT_FATAL_STATUS, problem: Problem::from_error(error), } } } impl fmt::Debug for FatalProblem { fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result { eprintln!("{}", self.problem); std::process::exit(self.status) } } /// Extension trait to map `Option` to `Result` with `Problem` pub trait Fatal<O> { fn fatal(self) -> Result<O, FatalProblem>; fn fatal_with_status(self, status: i32) -> Result<O, FatalProblem>; } /// Extension trait that allow to convert to `Result` with `FatalProblem` impl<O> Fatal<O> for Result<O, Problem> { /// Converts to `Result` with `FatalProblem` and default exit status fn fatal(self) -> Result<O, FatalProblem> { self.fatal_with_status(DEFAULT_FATAL_STATUS) } /// Converts to `Result` with `FatalProblem` and given exit status fn fatal_with_status(self, status: i32) -> Result<O, FatalProblem> { self.map_err(|problem| FatalProblem { status, problem }) } } pub mod result { //! Handy Result types using `Problem` as error. use super::{FatalProblem, Problem}; /// `Result` with `Problem` pub type Result<T> = std::result::Result<T, Problem>; /// `Result` with `FatalProblem` to be used as `main()` return value pub type FinalResult = std::result::Result<(), FatalProblem>; } /// Map type containing error to type containing `Problem` pub trait MapProblem { type ProblemCarrier; fn map_problem(self) -> Self::ProblemCarrier; } /// Mapping `Result` with error to `Result` with `Problem` impl<O, E> MapProblem for Result<O, E> where E: Into<Problem>, { type ProblemCarrier = Result<O, Problem>; fn map_problem(self) -> Result<O, Problem> { self.map_err(|e| e.into()) } } /// Map type not containing any error to type containing given `Problem` pub trait MapProblemOr { type ProblemCarrier; fn map_problem_or(self, problem: impl Into<Problem>) -> Self::ProblemCarrier; fn map_problem_or_else<F, P>(self, problem: F) -> Self::ProblemCarrier where F: FnOnce() -> P, P: Into<Problem>; } /// Mapping `Result` with `Option<E>` to `Result` with `Problem` where `E` implements `Into<Problem>` impl<O, E> MapProblemOr for Result<O, Option<E>> where E: Into<Problem>, { type ProblemCarrier = Result<O, Problem>; fn map_problem_or(self, problem: impl Into<Problem>) -> Result<O, Problem> { self.map_err(|e| e.map(Into::into).unwrap_or_else(|| problem.into())) } fn map_problem_or_else<F, P>(self, problem: F) -> Self::ProblemCarrier where F: FnOnce() -> P, P: Into<Problem>, { self.map_err(|e| e.map(Into::into).unwrap_or_else(|| problem().into())) } } /// Extension trait to map `Option` to `Result` with `Problem` pub trait OkOrProblem<O> { fn ok_or_problem<P>(self, problem: P) -> Result<O, Problem> where P: Into<Problem>; fn ok_or_problem_with<F, P>(self, problem: F) -> Result<O, Problem> where F: FnOnce() -> P, P: Into<Problem>; } impl<O> OkOrProblem<O> for Option<O> { fn ok_or_problem<P>(self, problem: P) -> Result<O, Problem> where P: Into<Problem>, { self.ok_or_else(|| problem.into()) } fn ok_or_problem_with<F, P>(self, problem: F) -> Result<O, Problem> where F: FnOnce() -> P, P: Into<Problem>, { self.ok_or_else(|| problem().into()) } } /// Convert to `Problem` if needed and add context to it pub trait ProblemWhile { type WithContext; /// Add context information fn problem_while(self, message: impl ToString) -> Self::WithContext; /// Add context information from function call fn problem_while_with<F, M>(self, message: F) -> Self::WithContext where F: FnOnce() -> M, M: ToString; } impl ProblemWhile for Problem { type WithContext = Problem; fn problem_while(mut self, message: impl ToString) -> Problem { self.context.push(message.to_string()); self } fn problem_while_with<F, M>(self, message: F) -> Problem where F: FnOnce() -> M, M: ToString, { self.problem_while(message()) } } impl<O, E> ProblemWhile for Result<O, E> where E: Into<Problem>, { type WithContext = Result<O, Problem>; fn problem_while(self, message: impl ToString) -> Result<O, Problem> { self.map_err(|err| err.into().problem_while(message)) } fn problem_while_with<F, M>(self, message: F) -> Result<O, Problem> where F: FnOnce() -> M, M: ToString, { self.map_err(|err| err.into().problem_while_with(message)) } } /// Executes closure with `problem_while` context pub fn in_context_of<O, B>(message: &str, body: B) -> Result<O, Problem> where B: FnOnce() -> Result<O, Problem>, { body().problem_while(message) } /// Executes closure with `problem_while_with` context pub fn in_context_of_with<O, F, M, B>(message: F, body: B) -> Result<O, Problem> where F: FnOnce() -> M, M: ToString, B: FnOnce() -> Result<O, Problem>, { body().problem_while_with(message) } /// 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, message: impl Display) -> O; } impl<O, E> FailedTo<O> for Result<O, E> where E: Into<Problem>, { fn or_failed_to(self, message: impl Display) -> O { self.unwrap_or_else(|err| panic!("Failed to {} due to: {}", message, err.into())) } } impl<O> FailedTo<O> for Option<O> { fn or_failed_to(self, message: impl Display) -> O { self.unwrap_or_else(|| panic!("Failed to {}", message)) } } /// Iterator that will panic on first error with message displaying `Display` formatted message pub struct ProblemIter<I, M> { inner: I, message: M, } impl<I, O, E, M> Iterator for ProblemIter<I, M> where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, M: Display, { type Item = O; fn next(&mut self) -> Option<Self::Item> { self.inner.next().map(|res| res.or_failed_to(&self.message)) } } /// Convert `Iterator` of `Result<O, E>` to iterator of `O` and panic on first `E` with problem message pub trait FailedToIter<O, E, M>: Sized { fn or_failed_to(self, message: M) -> ProblemIter<Self, M>; } impl<I, O, E, M> FailedToIter<O, E, M> for I where I: Iterator<Item = Result<O, E>>, E: Into<Problem>, M: Display, { fn or_failed_to(self, message: M) -> ProblemIter<Self, M> { ProblemIter { inner: self, message: message, } } } #[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> { self.map_err(|err| warn!("Continuing with error: {}", err.into())) .ok() } fn ok_or_log_error(self) -> Option<O> { self.map_err(|err| error!("Continuing with error: {}", err.into())) .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 } /* Use default Rust format like: 0: std::sys_common::backtrace::_print at C:\projects\rust\src\libstd\sys_common\backtrace.rs:94 1: std::sys_common::backtrace::_print at C:\projects\rust\src\libstd\sys_common\backtrace.rs:71 */ #[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(); let mut frame_no: u32 = 0; backtrace::trace(|frame| { let ip = frame.ip(); if frame_no > 0 { backtrace.push_str("\n"); } backtrace::resolve(ip, |symbol| { if let Some(name) = symbol.name() { write!(backtrace, "{:4}: {}", frame_no, name).unwrap(); } if let (Some(filename), Some(lineno)) = (symbol.filename(), symbol.lineno()) { write!( backtrace, "\n at {}:{}", filename.display(), lineno ) .unwrap(); } }); frame_no += 1; true // keep going to the next frame }); Some(backtrace) } else { None } } fn format_panic(panic: &std::panic::PanicInfo, backtrace: Option<String>) -> String { let mut message = String::new(); let thread = std::thread::current(); let name = thread.name().unwrap_or("<unnamed>"); // taken from libstd let msg = match panic.payload().downcast_ref::<&'static str>() { Some(s) => *s, None => match panic.payload().downcast_ref::<String>() { Some(s) => &s[..], None => "Box<Any>", }, }; match (backtrace.is_some(), panic.location()) { (true, Some(location)) => write!( message, "thread '{}' panicked at {} with: {}", name, location, msg ) .ok(), (true, None) => write!(message, "thread '{}' panicked with: {}", name, msg).ok(), (false, _) => write!(message, "{}", msg).ok(), }; if let Some(backtrace) = backtrace { message.push_str("\n--- Panicked\n"); message.push_str(&backtrace); } message } /// Set panic hook so that formats error message to `stderr` with more `Problem` friendly way 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 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::prelude::*; use super::{format_panic_to_stderr, in_context_of}; use std::error::Error; use std::fmt::{self, Display}; 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) } } #[derive(Debug)] struct Baz(Bar); impl Display for Baz { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "Baz error") } } impl Error for Baz { fn source(&self) -> Option<&(dyn Error + 'static)> { Some(&self.0) } } #[test] fn test_convertion() { let _: Problem = io::Error::new(io::ErrorKind::InvalidInput, "boom!").into(); let _: Problem = "boom!".into(); // via impl<'a> From<&'a str> for Box<dyn Error> } #[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: boom!" )] fn test_integration_message() { Err("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: Baz error; caused by: Bar error; caused by: Foo error" )] fn test_integration_cause_chain() { Err(Baz(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: Baz error; caused by: Bar error; caused by: Foo error" )] fn test_result_cause_chain() { Err(Baz(Bar(Foo))).or_failed_to("quix") } #[test] #[should_panic( expected = "Failed to quix due to: Baz error; caused by: Bar error; caused by: Foo error" )] fn test_result_cause_chain_message() { let error = Baz(Bar(Foo)); Err(Problem::from_error_message(&error)).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("<unknown error>") .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("<unknown error>").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!")]; 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] #[should_panic] fn test_panic_format_stderr_unwrap() { format_panic_to_stderr(); let result: Result<(), io::Error> = Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!")); result.unwrap(); } #[test] #[should_panic] fn test_panic_format_stderr_expect() { format_panic_to_stderr(); let result: Result<(), io::Error> = Err(io::Error::new(io::ErrorKind::InvalidInput, "boom!")); result.expect("foo"); } #[test] #[cfg(feature = "backtrace")] fn test_problem_backtrace() { let p = Problem::from_error("foo") .problem_while("bar") .problem_while("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()); } } #[test] #[cfg(feature = "log")] fn test_problem_log_error() { loggerv::init_quiet().ok(); let error: Result<(), _> = Err(Baz(Bar(Foo))); error.ok_or_log_error(); } #[test] #[cfg(feature = "log")] fn test_problem_log_warn() { loggerv::init_quiet().ok(); let error: Result<(), _> = Err(Baz(Bar(Foo))); error.ok_or_log_warn(); } #[test] #[cfg(feature = "log")] fn test_problem_log_iter_error() { loggerv::init_quiet().ok(); assert_eq!( vec![Ok(1), Err(Foo), Err(Foo), Ok(2), Err(Foo), Ok(3)] .into_iter() .ok_or_log_error() .flatten() .collect::<Vec<_>>(), vec![1, 2, 3] ); } #[test] #[cfg(feature = "log")] fn test_problem_log_iter_warn() { loggerv::init_quiet().ok(); assert_eq!( vec![Ok(1), Err(Foo), Err(Foo), Ok(2), Err(Foo), Ok(3)] .into_iter() .ok_or_log_warn() .flatten() .collect::<Vec<_>>(), vec![1, 2, 3] ); } }