pretty_assertions/lib.rs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468
//! # Pretty Assertions
//!
//! When writing tests in Rust, you'll probably use `assert_eq!(a, b)` _a lot_.
//!
//! If such a test fails, it will present all the details of `a` and `b`.
//! But you have to spot the differences yourself, which is not always straightforward,
//! like here:
//!
//! 
//!
//! Wouldn't that task be _much_ easier with a colorful diff?
//!
//! 
//!
//! Yep — and you only need **one line of code** to make it happen:
//!
//! ```rust
//! use pretty_assertions::{assert_eq, assert_ne};
//! ```
//!
//! <details>
//! <summary>Show the example behind the screenshots above.</summary>
//!
//! ```rust,should_panic
//! // 1. add the `pretty_assertions` dependency to `Cargo.toml`.
//! // 2. insert this line at the top of each module, as needed
//! use pretty_assertions::{assert_eq, assert_ne};
//!
//! #[derive(Debug, PartialEq)]
//! struct Foo {
//! lorem: &'static str,
//! ipsum: u32,
//! dolor: Result<String, String>,
//! }
//!
//! let x = Some(Foo { lorem: "Hello World!", ipsum: 42, dolor: Ok("hey".to_string())});
//! let y = Some(Foo { lorem: "Hello Wrold!", ipsum: 42, dolor: Ok("hey ho!".to_string())});
//!
//! assert_eq!(x, y);
//! ```
//! </details>
//!
//! ## Tip
//!
//! Specify it as [`[dev-dependencies]`](http://doc.crates.io/specifying-dependencies.html#development-dependencies)
//! and it will only be used for compiling tests, examples, and benchmarks.
//! This way the compile time of `cargo build` won't be affected!
//!
//! Also add `#[cfg(test)]` to your `use` statements, like this:
//!
//! ```rust
//! #[cfg(test)]
//! use pretty_assertions::{assert_eq, assert_ne};
//! ```
//!
//! ## Note
//!
//! * Since `Rust 2018` edition, you need to declare
//! `use pretty_assertions::{assert_eq, assert_ne};` per module.
//! Before you would write `#[macro_use] extern crate pretty_assertions;`.
//! * The replacement is only effective in your own crate, not in other libraries
//! you include.
//! * `assert_ne` is also switched to multi-line presentation, but does _not_ show
//! a diff.
//!
//! ## Features
//!
//! Features provided by the crate are:
//!
//! - `std`: Use the Rust standard library. Enabled by default.
//! Exactly one of `std` and `alloc` is required.
//! - `alloc`: Use the `alloc` crate.
//! Exactly one of `std` and `alloc` is required.
//! - `unstable`: opt-in to unstable features that may not follow Semantic Versioning.
//! Implmenetion behind this feature is subject to change without warning between patch versions.
#![cfg_attr(not(feature = "std"), no_std)]
#![deny(clippy::all, missing_docs, unsafe_code)]
#[cfg(feature = "alloc")]
#[macro_use]
extern crate alloc;
pub use ansi_term::Style;
use core::fmt::{self, Debug, Display};
mod printer;
#[cfg(windows)]
use ctor::*;
#[cfg(windows)]
#[ctor]
fn init() {
output_vt100::try_init().ok(); // Do not panic on fail
}
/// A comparison of two values.
///
/// Where both values implement `Debug`, the comparison can be displayed as a pretty diff.
///
/// ```
/// use pretty_assertions::Comparison;
///
/// print!("{}", Comparison::new(&123, &134));
/// ```
///
/// The values may have different types, although in practice they are usually the same.
pub struct Comparison<'a, TLeft, TRight>
where
TLeft: ?Sized,
TRight: ?Sized,
{
left: &'a TLeft,
right: &'a TRight,
}
impl<'a, TLeft, TRight> Comparison<'a, TLeft, TRight>
where
TLeft: ?Sized,
TRight: ?Sized,
{
/// Store two values to be compared in future.
///
/// Expensive diffing is deferred until calling `Debug::fmt`.
pub fn new(left: &'a TLeft, right: &'a TRight) -> Comparison<'a, TLeft, TRight> {
Comparison { left, right }
}
}
impl<'a, TLeft, TRight> Display for Comparison<'a, TLeft, TRight>
where
TLeft: Debug + ?Sized,
TRight: Debug + ?Sized,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// To diff arbitary types, render them as debug strings
let left_debug = format!("{:#?}", self.left);
let right_debug = format!("{:#?}", self.right);
// And then diff the debug output
printer::write_header(f)?;
printer::write_lines(f, &left_debug, &right_debug)
}
}
/// A comparison of two strings.
///
/// In contrast to [`Comparison`], which uses the [`core::fmt::Debug`] representation,
/// `StrComparison` uses the string values directly, resulting in multi-line output for multiline strings.
///
/// ```
/// use pretty_assertions::StrComparison;
///
/// print!("{}", StrComparison::new("foo\nbar", "foo\nbaz"));
/// ```
///
/// ## Value type bounds
///
/// Any value that can be referenced as a [`str`] via [`AsRef`] may be used:
///
/// ```
/// use pretty_assertions::StrComparison;
///
/// #[derive(PartialEq)]
/// struct MyString(String);
///
/// impl AsRef<str> for MyString {
/// fn as_ref(&self) -> &str {
/// &self.0
/// }
/// }
///
/// print!(
/// "{}",
/// StrComparison::new(
/// &MyString("foo\nbar".to_owned()),
/// &MyString("foo\nbaz".to_owned()),
/// ),
/// );
/// ```
///
/// The values may have different types, although in practice they are usually the same.
pub struct StrComparison<'a, TLeft, TRight>
where
TLeft: ?Sized,
TRight: ?Sized,
{
left: &'a TLeft,
right: &'a TRight,
}
impl<'a, TLeft, TRight> StrComparison<'a, TLeft, TRight>
where
TLeft: AsRef<str> + ?Sized,
TRight: AsRef<str> + ?Sized,
{
/// Store two values to be compared in future.
///
/// Expensive diffing is deferred until calling `Debug::fmt`.
pub fn new(left: &'a TLeft, right: &'a TRight) -> StrComparison<'a, TLeft, TRight> {
StrComparison { left, right }
}
}
impl<'a, TLeft, TRight> Display for StrComparison<'a, TLeft, TRight>
where
TLeft: AsRef<str> + ?Sized,
TRight: AsRef<str> + ?Sized,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
printer::write_header(f)?;
printer::write_lines(f, self.left.as_ref(), self.right.as_ref())
}
}
/// Asserts that two expressions are equal to each other (using [`PartialEq`]).
///
/// On panic, this macro will print a diff derived from [`Debug`] representation of
/// each value.
///
/// This is a drop in replacement for [`core::assert_eq!`].
/// You can provide a custom panic message if desired.
///
/// # Examples
///
/// ```
/// use pretty_assertions::assert_eq;
///
/// let a = 3;
/// let b = 1 + 2;
/// assert_eq!(a, b);
///
/// assert_eq!(a, b, "we are testing addition with {} and {}", a, b);
/// ```
#[macro_export]
macro_rules! assert_eq {
($left:expr, $right:expr$(,)?) => ({
$crate::assert_eq!(@ $left, $right, "", "");
});
($left:expr, $right:expr, $($arg:tt)*) => ({
$crate::assert_eq!(@ $left, $right, ": ", $($arg)+);
});
(@ $left:expr, $right:expr, $maybe_colon:expr, $($arg:tt)*) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
if !(*left_val == *right_val) {
use $crate::private::CreateComparison;
::core::panic!("assertion failed: `(left == right)`{}{}\
\n\
\n{}\
\n",
$maybe_colon,
format_args!($($arg)*),
(left_val, right_val).create_comparison()
)
}
}
}
});
}
/// Asserts that two expressions are equal to each other (using [`PartialEq`]).
///
/// On panic, this macro will print a diff derived from each value's [`str`] representation.
/// See [`StrComparison`] for further details.
///
/// This is a drop in replacement for [`core::assert_eq!`].
/// You can provide a custom panic message if desired.
///
/// # Examples
///
/// ```
/// use pretty_assertions::assert_str_eq;
///
/// let a = "foo\nbar";
/// let b = ["foo", "bar"].join("\n");
/// assert_str_eq!(a, b);
///
/// assert_str_eq!(a, b, "we are testing concatenation with {} and {}", a, b);
/// ```
#[macro_export]
macro_rules! assert_str_eq {
($left:expr, $right:expr$(,)?) => ({
$crate::assert_str_eq!(@ $left, $right, "", "");
});
($left:expr, $right:expr, $($arg:tt)*) => ({
$crate::assert_str_eq!(@ $left, $right, ": ", $($arg)+);
});
(@ $left:expr, $right:expr, $maybe_colon:expr, $($arg:tt)*) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
if !(*left_val == *right_val) {
::core::panic!("assertion failed: `(left == right)`{}{}\
\n\
\n{}\
\n",
$maybe_colon,
format_args!($($arg)*),
$crate::StrComparison::new(left_val, right_val)
)
}
}
}
});
}
/// Asserts that two expressions are not equal to each other (using [`PartialEq`]).
///
/// On panic, this macro will print the values of the expressions with their
/// [`Debug`] representations.
///
/// This is a drop in replacement for [`core::assert_ne!`].
/// You can provide a custom panic message if desired.
///
/// # Examples
///
/// ```
/// use pretty_assertions::assert_ne;
///
/// let a = 3;
/// let b = 2;
/// assert_ne!(a, b);
///
/// assert_ne!(a, b, "we are testing that the values are not equal");
/// ```
#[macro_export]
macro_rules! assert_ne {
($left:expr, $right:expr$(,)?) => ({
$crate::assert_ne!(@ $left, $right, "", "");
});
($left:expr, $right:expr, $($arg:tt)+) => ({
$crate::assert_ne!(@ $left, $right, ": ", $($arg)+);
});
(@ $left:expr, $right:expr, $maybe_colon:expr, $($arg:tt)+) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
if *left_val == *right_val {
::core::panic!("assertion failed: `(left != right)`{}{}\
\n\
\n{}:\
\n{:#?}\
\n\
\n",
$maybe_colon,
format_args!($($arg)+),
$crate::Style::new().bold().paint("Both sides"),
left_val
)
}
}
}
});
}
/// Asserts that a value matches a pattern.
///
/// On panic, this macro will print a diff derived from [`Debug`] representation of
/// the value, and a string representation of the pattern.
///
/// This is a drop in replacement for [`core::assert_matches::assert_matches!`].
/// You can provide a custom panic message if desired.
///
/// # Examples
///
/// ```
/// use pretty_assertions::assert_matches;
///
/// let a = Some(3);
/// assert_matches!(a, Some(_));
///
/// assert_matches!(a, Some(value) if value > 2, "we are testing {:?} with a pattern", a);
/// ```
///
/// # Features
///
/// Requires the `unstable` feature to be enabled.
///
/// **Please note:** implementation under the `unstable` feature may be changed between
/// patch versions without warning.
#[cfg(feature = "unstable")]
#[macro_export]
macro_rules! assert_matches {
($left:expr, $( $pattern:pat )|+ $( if $guard: expr )? $(,)?) => ({
match $left {
$( $pattern )|+ $( if $guard )? => {}
ref left_val => {
$crate::assert_matches!(
@
left_val,
::core::stringify!($($pattern)|+ $(if $guard)?),
"",
""
);
}
}
});
($left:expr, $( $pattern:pat )|+ $( if $guard: expr )?, $($arg:tt)+) => ({
match $left {
$( $pattern )|+ $( if $guard )? => {}
ref left_val => {
$crate::assert_matches!(
@
left_val,
::core::stringify!($($pattern)|+ $(if $guard)?),
": ",
$($arg)+
);
}
}
});
(@ $left:expr, $right:expr, $maybe_colon:expr, $($arg:tt)*) => ({
match (&($left), &($right)) {
(left_val, right_val) => {
// Use the Display implementation to display the pattern,
// as using Debug would add another layer of quotes to the output.
struct Pattern<'a>(&'a str);
impl ::core::fmt::Debug for Pattern<'_> {
fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
::core::fmt::Display::fmt(self.0, f)
}
}
::core::panic!("assertion failed: `(left matches right)`{}{}\
\n\
\n{}\
\n",
$maybe_colon,
format_args!($($arg)*),
$crate::Comparison::new(left_val, &Pattern(right_val))
)
}
}
});
}
// Not public API. Used by the expansion of this crate's assert macros.
#[doc(hidden)]
pub mod private {
#[cfg(feature = "alloc")]
use alloc::string::String;
pub trait CompareAsStrByDefault: AsRef<str> {}
impl CompareAsStrByDefault for str {}
impl CompareAsStrByDefault for String {}
impl<T: CompareAsStrByDefault + ?Sized> CompareAsStrByDefault for &T {}
pub trait CreateComparison {
type Comparison;
fn create_comparison(self) -> Self::Comparison;
}
impl<'a, T, U> CreateComparison for &'a (T, U) {
type Comparison = crate::Comparison<'a, T, U>;
fn create_comparison(self) -> Self::Comparison {
crate::Comparison::new(&self.0, &self.1)
}
}
impl<'a, T, U> CreateComparison for (&'a T, &'a U)
where
T: CompareAsStrByDefault + ?Sized,
U: CompareAsStrByDefault + ?Sized,
{
type Comparison = crate::StrComparison<'a, T, U>;
fn create_comparison(self) -> Self::Comparison {
crate::StrComparison::new(self.0, self.1)
}
}
}