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#![warn(missing_docs)]
//! `debug2` is a pretty printing crate based on [`std::fmt`]
//!
//! # Why not just use [`Debug`]
//!
//! The [`Debug`] trait is good, but the problem is it is not very good at nested stuctures.
//! Either you use `{:?}` and get a line that is too long, or too many lines with not enough
//! information on them.
//!
//! ```rust
//! let complex_structure = vec![
//! vec![Some(1), Some(2), Some(3), None],
//! vec![Some(2), None],
//! vec![Some(4), Some(7)],
//! vec![Some(1), Some(2), Some(3), None],
//! ];
//!
//! let one_line = format!("{:?}", complex_structure);
//!
//! assert_eq!(one_line, "[[Some(1), Some(2), Some(3), None], [Some(2), None], [Some(4), Some(7)], [Some(1), Some(2), Some(3), None]]");
//!
//! let many_lines = format!("{:#?}", complex_structure);
//!
//! assert_eq!(many_lines, "[
//! [
//! Some(
//! 1,
//! ),
//! Some(
//! 2,
//! ),
//! Some(
//! 3,
//! ),
//! None,
//! ],
//! [
//! Some(
//! 2,
//! ),
//! None,
//! ],
//! [
//! Some(
//! 4,
//! ),
//! Some(
//! 7,
//! ),
//! ],
//! [
//! Some(
//! 1,
//! ),
//! Some(
//! 2,
//! ),
//! Some(
//! 3,
//! ),
//! None,
//! ],
//! ]")
//! ```
//!
//! `pprint` aims to be a third alternative, that gets this correct.
//!
//! ```rust
//! use debug2::pprint;
//!
//! let complex_structure = vec![
//! vec![Some(1), Some(2), Some(3), None],
//! vec![Some(2), None],
//! vec![Some(4), Some(7)],
//! vec![Some(1), Some(2), Some(3), None],
//! vec![Some(2), None],
//! vec![Some(4), Some(7)],
//! vec![Some(1), Some(2), Some(3), None],
//! vec![Some(2), None],
//! vec![Some(4), Some(7)],
//! ];
//!
//! assert_eq!(
//! pprint(complex_structure),
//! "\
//! [
//! [Some(1), Some(2), Some(3), None],
//! [Some(2), None],
//! [Some(4), Some(7)],
//! [Some(1), Some(2), Some(3), None],
//! [Some(2), None],
//! [Some(4), Some(7)],
//! [Some(1), Some(2), Some(3), None],
//! [Some(2), None],
//! [Some(4), Some(7)],
//! ]"
//! );
//! ```
//!
//! To use, derive [`Debug`] for your types, and then use [`pprint`] to print them.
//!
//! You can also manually implement [`Debug`], using a subset of the API in [`std::fmt::Formatter`]
//!
//! # Limitations
//! - Speed: While doing this will always mean extra work, this crate is paticularly inefficient.
//! - Prevalence: Almost every type implements [`std::fmt::Debug`], but not this type
//! - The derive isn't great: The derive macro for [`std::fmt::Debug`] works everywhere. This one
//! is kind of basic, and will probably not work everywhere it should.
use std::fmt::{Debug as StdDebug, Error, Result, Write};
mod builders;
mod std_impls;
pub use builders::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
pub use debug2_derive::*;
const MAX_LEN: usize = 80;
/// Pretty Printed Formatting
///
/// This is much like [`std::fmt::Debug`], but it supports much better multiline output
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug};
///
/// #[derive(Debug)]
/// struct Numbers {
/// a: Vec<Vec<i32>>,
/// b: String,
/// }
///
/// let a = Numbers {
/// a: vec![vec![10; 10]; 2],
/// b: "FooBar".to_owned(),
/// };
///
/// assert_eq!(
/// pprint(&a),
/// "\
/// Numbers {
/// a: [
/// [10, 10, 10, 10, 10, 10, 10, 10, 10, 10],
/// [10, 10, 10, 10, 10, 10, 10, 10, 10, 10],
/// ],
/// b: \"FooBar\",
/// }"
/// );
/// ```
///
/// You can also implement `fmt` manually, using an API much like [`std::fmt::Formatter`]
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
///
/// struct Chunked10([u8; 100]);
///
/// impl Debug for Chunked10 {
/// fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
/// f.debug_list().entries(self.0.chunks(10)).finish()
/// }
/// }
///
/// assert_eq!(
/// pprint(Chunked10([0; 100])),
/// "\
/// [
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
/// ]"
/// );
/// ```
pub trait Debug {
/// Formats the value using the given formatter.
///
/// Note that this may be called more than once for any invocation of `pprint`, if you do
/// side effects in this, make sure they are idempotent. In general, don't relly on how often
/// this function is called, as it may change in a future release.
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
}
/// Configuration for formatting.
///
/// A `Formatter` represents various options related to formatting. Users do not
/// construct `Formatter`s directly; a mutable reference to one is passed to
/// the `fmt` method of [`Debug`].
///
/// To interact with a `Formatter`, you'll call various methods to change the
/// various options related to formatting. For examples, please see the
/// documentation of the methods defined on `Formatter` below.
pub struct Formatter<'a> {
buf: &'a mut (dyn Write + 'a),
mode: Mode,
}
#[derive(Clone, Copy, PartialEq, Eq)]
enum Mode {
Pretty,
Flat,
}
fn flatprint_checked<T: Debug>(x: T) -> std::result::Result<String, Error> {
pprint_mode(x, Mode::Flat)
}
fn pprint_mode<T: Debug>(x: T, mode: Mode) -> std::result::Result<String, Error> {
let mut out = String::new();
let mut f = Formatter {
buf: &mut out,
mode,
};
x.fmt(&mut f)?;
Ok(out)
}
/// Pretty Print an item to a string, or return an error
///
/// ```rust
/// use debug2::{pprint_checked, Debug, Formatter};
/// use std::fmt;
///
/// struct Good;
/// struct Bad;
///
/// impl Debug for Good {
/// fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
/// f.debug_struct("Good").finish()
/// }
/// }
///
/// impl Debug for Bad {
/// fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
/// Err(fmt::Error)
/// }
/// }
///
/// assert!(pprint_checked(Good).is_ok());
/// assert!(pprint_checked(Bad).is_err());
/// ```
pub fn pprint_checked<T: Debug>(x: T) -> std::result::Result<String, Error> {
let flat = flatprint_checked(&x)?;
if flat.len() <= MAX_LEN {
Ok(flat)
} else {
pprint_mode(x, Mode::Pretty)
}
}
/// Pretty Print an item to a string
///
/// ```rust
/// use debug2::pprint;
///
/// let x: Vec<Option<&[i32]>> = vec![Some(&[1; 20]), None, None, Some(&[1, 2, 3])];
///
/// assert_eq!(
/// pprint(x),
/// "\
/// [
/// Some([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]),
/// None,
/// None,
/// Some([1, 2, 3]),
/// ]"
/// );
/// ```
///
/// Note that while this takes a `T`, you can also pass a reference due to the
/// `impl<T: Debug> Debug for `&T`
///
/// # Panics
///
/// This will panic if `<T as Debug>::fmt` returns an error
///
pub fn pprint<T: Debug>(x: T) -> String {
pprint_checked(x).unwrap()
}
impl<'a> Formatter<'a> {
fn write_debug<T: StdDebug>(&mut self, val: &T) -> Result {
write!(self.buf, "{:?}", val)
}
fn write_str(&mut self, data: &str) -> Result {
self.buf.write_str(data)
}
/// Creates a [`DebugStruct`] builder designed to assist with creation of
/// [`Debug`] implementations for structs.
///
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
/// use std::net::Ipv4Addr;
///
/// struct Foo {
/// bar: i32,
/// baz: String,
/// addr: Ipv4Addr,
/// }
///
/// impl Debug for Foo {
/// fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
/// fmt.debug_struct("Foo")
/// .field("bar", &self.bar)
/// .field("baz", &self.baz)
/// # // TODO: The viersion in `std` uses `format_args`, which gives
/// # // a different result, because it doesn't have "" around the content
/// # // I should have a macro that delegated to `format!`, but returns a
/// # // newtype that doesnt add quotes
/// .field("addr", &format!("{}", self.addr))
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// "Foo { bar: 10, baz: \"Hello World\", addr: \"127.0.0.1\" }",
/// pprint(Foo {
/// bar: 10,
/// baz: "Hello World".to_string(),
/// addr: Ipv4Addr::new(127, 0, 0, 1),
/// })
/// );
/// ```
pub fn debug_struct<'b>(&'b mut self, name: &str) -> DebugStruct<'b, 'a> {
builders::debug_struct_new(self, name)
}
/// Creates a [`DebugTuple`] builder designed to assist with creation of
/// [`Debug`] implementations for tuple structs.
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
/// use std::marker::PhantomData;
///
/// struct Foo<T>(i32, String, PhantomData<T>);
///
/// impl<T> Debug for Foo<T> {
/// fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
/// fmt.debug_tuple("Foo")
/// .field(&self.0)
/// .field(&self.1)
/// .field(&format!("_"))
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// "Foo(10, \"Hello\", \"_\")",
/// pprint(Foo(10, "Hello".to_string(), PhantomData::<u8>))
/// );
/// ```
pub fn debug_tuple<'b>(&'b mut self, name: &str) -> DebugTuple<'b, 'a> {
builders::debug_tuple_new(self, name)
}
/// Creates a [`DebugList`] builder designed to assist with creation of
/// [`Debug`] implementations for list-like structures.
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl Debug for Foo {
/// fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
/// fmt.debug_list().entries(self.0.iter()).finish()
/// }
/// }
///
/// assert_eq!(pprint(Foo(vec![10, 11])), "[10, 11]");
/// ```
pub fn debug_list<'b>(&'b mut self) -> DebugList<'b, 'a> {
builders::debug_list_new(self)
}
/// Creates a [`DebugSet`] builder designed to assist with creation of
/// [`Debug`] implementations for set-like structures.
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl Debug for Foo {
/// fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
/// fmt.debug_set().entries(self.0.iter()).finish()
/// }
/// }
///
/// assert_eq!(pprint(Foo(vec![10, 11])), "{10, 11}");
/// ```
pub fn debug_set<'b>(&'b mut self) -> DebugSet<'b, 'a> {
builders::debug_set_new(self)
}
/// Creates a [`DebugMap`] builder designed to assist with creation of
/// [`Debug`] implementations for map-like structures.
///
/// # Examples
///
/// ```rust
/// use debug2::{pprint, Debug, Formatter};
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl Debug for Foo {
/// fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
/// fmt.debug_map()
/// .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// pprint(Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"A": 10, "B": 11}"#
/// );
/// ```
pub fn debug_map<'b>(&'b mut self) -> DebugMap<'b, 'a> {
builders::debug_map_new(self)
}
}
impl<'a> Formatter<'a> {
fn wrap_buf<'b, 'c, F>(&'b mut self, wrap: F) -> Formatter<'c>
where
'b: 'c,
F: FnOnce(&'b mut (dyn Write + 'b)) -> &'c mut (dyn Write + 'c),
{
Formatter {
// We want to change this
buf: wrap(self.buf),
// And preserve these
mode: self.mode
// flags: self.flags,
// fill: self.fill,
// align: self.align,
// width: self.width,
// precision: self.precision,
}
}
fn is_pretty(&self) -> bool {
self.mode == Mode::Pretty
}
}
/// Prints and returns the value of a given expression for quick and dirty debugging.
///
/// Like [`std::dbg`], but used [`crate::Debug`] instead of [`std::fmt::Debug`]
///
/// # Stability
///
/// The exact output printed by this macro should not be relied upon and is subject to future changes.
///
/// # Panics
///
/// Panics if writing to [`std::io::stderr`] fails.
#[macro_export]
macro_rules! dbg {
() => {
eprintln!("[{}:{}]", file!(), line!())
};
($val:expr $(,)?) => {
match $val {
tmp => {
eprintln!(
"[{}:{}] {} = {}",
file!(),
line!(),
stringify!($val),
$crate::pprint(&tmp)
);
tmp
}
}
};
($($val:expr),+ $(,)?) => {
$crate::dbg!($($val:expr),+)
};
}