Crate miette[−][src]
Expand description
you run miette? You run her code like the software? Oh. Oh! Error code for coder! Error code for One Thousand Lines!
About
miette
is a diagnostic library for Rust. It includes a series of
traits/protocols that allow you to hook into its error reporting facilities,
and even write your own error reports! It lets you define error types that can
print out like this (or in any format you like!):
Table of Contents
Features
- Generic Diagnostic protocol, compatible (and dependent on)
std::error::Error
. - Unique error codes on every Diagnostic.
- Super handy derive macro for defining diagnostic metadata.
- Lightweight
anyhow
/eyre
-style error wrapper type, DiagnosticReport, which can be returned frommain
. - Generic support for arbitrary Sources for snippet data, with default support for
String
s included.
The miette
crate also comes bundles with a default DiagnosticReportPrinter with the following features:
- Fancy graphical diagnostic output, using ANSI/Unicode text
- single- and multi-line highlighting support
- Screen reader/braille support, gated on
NO_COLOR
, and other heuristics. - Fully customizable graphical theming (or overriding the printers entirely).
- Cause chain printing
Installing
Using cargo-edit
:
$ cargo add miette
Example
/*
You can derive a Diagnostic from any `std::error::Error` type.
`thiserror` is a great way to define them, and plays nicely with `miette`!
*/
use miette::{Diagnostic, SourceSpan};
use thiserror::Error;
#[derive(Error, Debug, Diagnostic)]
#[error("oops!")]
#[diagnostic(
code(oops::my::bad),
help("try doing it better next time?"),
)]
struct MyBad {
// The Source that we're gonna be printing snippets out of.
src: String,
// Snippets and highlights can be included in the diagnostic!
#[snippet(src, "This is the part that broke")]
snip: SourceSpan,
#[highlight(snip)]
bad_bit: SourceSpan,
}
/*
Now let's define a function!
Use this DiagnosticResult type (or its expanded version) as the return type
throughout your app (but NOT your libraries! Those should always return concrete
types!).
*/
use miette::DiagnosticResult;
fn this_fails() -> DiagnosticResult<()> {
// You can use plain strings as a `Source`, or anything that implements
// the one-method `Source` trait.
let src = "source\n text\n here".to_string();
let len = src.len();
Err(MyBad {
src,
snip: ("bad_file.rs", 0, len).into(),
bad_bit: ("this bit here", 9, 4).into(),
})?;
Ok(())
}
/*
Now to get everything printed nicely, just return a DiagnosticResult<()>
and you're all set!
Note: You can swap out the default reporter for a custom one using `miette::set_reporter()`
*/
fn pretend_this_is_main() -> DiagnosticResult<()> {
// kaboom~
this_fails()?;
Ok(())
}
And this is the output you’ll get if you run this program:
Usage
… in libraries
miette
is fully compatible with library usage. Consumers who don’t know
about, or don’t want, miette
features can safely use its error types as
regular std::error::Error.
We highly recommend using something like thiserror
to define unique error types and error wrappers for your library.
While miette
integrates smoothly with thiserror
, it is not required. If
you don’t want to use the Diagnostic derive macro, you can implement the
trait directly, just like with std::error::Error
.
// lib/error.rs
use thiserror::Error;
use miette::Diagnostic;
#[derive(Error, Diagnostic, Debug)]
pub enum MyLibError {
#[error(transparent)]
#[diagnostic(code(my_lib::io_error))]
IoError(#[from] std::io::Error),
#[error("Oops it blew up")]
#[diagnostic(code(my_lib::bad_code))]
BadThingHappened,
}
Then, return this error type from all your fallible public APIs. It’s a best
practice to wrap any “external” error types in your error enum
instead of
using something like eyre in a library.
… in application code
Application code tends to work a little differently than libraries. You don’t always need or care to define dedicated error wrappers for errors coming from external libraries and tools.
For this situation, miette
includes two tools: DiagnosticReport and
IntoDiagnostic. They work in tandem to make it easy to convert regular
std::error::Error
s into Diagnostics. Additionally, there’s a
DiagnosticResult type alias that you can use to be more terse:
// my_app/lib/my_internal_file.rs
use miette::{IntoDiagnostic, DiagnosticResult};
use semver::Version;
pub fn some_tool() -> DiagnosticResult<Version> {
Ok("1.2.x".parse().into_diagnostic("my_app::semver::parse_error")?)
}
… in main()
main()
is just like any other part of your application-internal code. Use
DiagnosticResult
as your return value, and it will pretty-print your
diagnostics automatically.
use miette::{DiagnosticResult, IntoDiagnostic};
use semver::Version;
fn pretend_this_is_main() -> DiagnosticResult<()> {
let version: Version = "1.2.x".parse().into_diagnostic("my_app::semver::parse_error")?;
println!("{}", version);
Ok(())
}
… snippets
Along with its general error handling and reporting features, miette
also
includes facilities for adding error spans and annotations/highlights to your
output. This can be very useful when an error is syntax-related, but you can
even use it to print out sections of your own source code!
To achieve this, miette
defines its own lightweight SourceSpan type. This
is a basic byte-offset and length into an associated Source and, along with
the latter, gives miette
all the information it needs to pretty-print some
snippets!
The easiest way to define errors like this is to use the derive(Diagnostic)
macro:
use miette::{Diagnostic, SourceSpan};
use thiserror::Error;
#[derive(Diagnostic, Debug, Error)]
#[error("oops")]
#[diagnostic(code(my_lib::random_error))]
pub struct MyErrorType {
// The `Source` that miette will use.
src: String,
// A snippet that points to `src`, our `Source`. The filename can be
// provided at the callsite.
#[snippet(src, "This is the snippet")]
snip: SourceSpan,
// A highlight for the `snip` snippet we defined above. This will
// underline/mark the specific code inside the larger snippet context.
//
// The label is provided using `SourceSpan`'s label.
#[highlight(snip)]
err_span: SourceSpan,
}
Acknowledgements
miette
was not developed in a void. It owes enormous credit to various other projects and their authors:
anyhow
andcolor-eyre
: these two enormously influential error handling libraries have pushed forward the experience of application-level error handling and error reporting.miette
’sDiagnosticReport
type is an attempt at a very very rough version of theirReport
types.thiserror
for setting the standard for library-level error definitions, and for being the inspiration behindmiette
’s derive macro.rustc
and @estebank for their state-of-the-art work in compiler diagnostics.ariadne
for pushing forward how pretty these diagnostics can really look!
License
miette
is released to the Rust community under the Apache license 2.0.
It also includes some code taken from eyre
,
and some from thiserror
, also under
the Apache License. Some code is taken from
ariadne
, which is MIT licensed.
Structs
Convenience Diagnostic that can be used as an “anonymous” wrapper for Errors. This is intended to be paired with IntoDiagnostic.
When used with ?
/From
, this will wrap any Diagnostics and, when
formatted with Debug
, will fetch the current DiagnosticReportPrinter and
use it to format the inner Diagnostic.
A snippet from a Source to be displayed with a message and possibly some highlights.
A DiagnosticReportPrinter that displays a given crate::DiagnosticReport in a quasi-graphical way, using terminal colors, unicode drawing characters, and other such things.
Theme used by crate::GraphicalReportPrinter to render fancy crate::Diagnostic reports.
Literally what it says on the tin.
Basic implementation of the SpanContents trait, for convenience.
DiagnosticReportPrinter that renders plain text and avoids extraneous graphics. It’s optimized for screen readers and braille users, but is also used in any non-graphical environments, such as non-TTY output.
Newtype that represents the ByteOffset from the beginning of a Source
Span within a Source with an associated message.
Characters to be used when drawing when using crate::GraphicalReportPrinter.
Styles for various parts of graphical rendering for the crate::GraphicalReportPrinter.
Enums
Error enum for miette. Used by certain operations in the protocol.
Diagnostic severity. Intended to be used by DiagnosticReportPrinters to change the way different Diagnostics are displayed.
Traits
Adds rich metadata to your Error that can be used by DiagnosticReportPrinter to print really nice and human-friendly error messages.
Protocol for Diagnostic handlers, which are responsible for actually printing out Diagnostics.
Convenience trait that adds a .into_diagnostic()
method that converts a type to a Result<T, DiagnosticError>
.
Represents a readable source of some sort.
Contents of a Source covered by SourceSpan.
Functions
Set the global DiagnosticReportPrinter that will be used when you report using crate::DiagnosticReport.
Type Definitions
“Raw” type for the byte offset from the beginning of a Source.
Convenience alias. This is intended to be used as the return type for main()