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/*! # debug_iterator This is a simple iterator adapter thats is applicable to iterators where the Iterator::Item is std::fmt::Debug It prints to `stderr` by default, but using the feature 'logging' prints out to the `log` crate facade. ```rust use debug_iterator::DebugIterator as _; #[derive(Debug)] struct Person { name: String, age: i32 } let everyone_is_named_bob = "Bob".to_string(); let iter = (1..=3) .map(|k| k * 4) .map(|age| Person { name: everyone_is_named_bob.clone(), age, }) .clone(); // debug ("{:?}") iter.debug().for_each(|_| ()); // Person { name: "Bob", age: 4 } // Person { name: "Bob", age: 8 } // Person { name: "Bob", age: 12 } // debug_pretty ("{:#?}") iter.debug_pretty().for_each(|_| ()); // Person { // name: "Bob", // age: 4, // } // Person { // name: "Bob", // age: 8, // } // Person { // name: "Bob", // age: 12, // } // '{:?}' with a `&str` prefix: iter.debug_prefix("This person is").for_each(|_| ()); // This person is: Person { name: "Bob", age: 4 } // This person is: Person { name: "Bob", age: 8 } // This person is: Person { name: "Bob", age: 12 } // '{:#?}' with a `&str` prefix: iter.debug_prefix_pretty("This person is").for_each(|_| ()); // This person is: Person { // name: "Bob", // age: 4, // } // This person is: Person { // name: "Bob", // age: 8, // } // This person is: Person { // name: "Bob", // age: 12, // } ``` */ use std::borrow::Cow; /// [`DebugIterator`](./trait.DebugIterator.html) is an [`std::iter::Iterator`](https://doc.rust-lang.org/std/iter/trait.Iterator.html) adapter that simply prints out /// the debug representation of the [`Iterator::Item`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#associatedtype.Item) pub trait DebugIterator: Iterator { /// Create an adapter that prints out the [`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) representation of the Item fn debug<'a>(self) -> DebugPrinter<'a, Self> where Self: Sized, Self::Item: std::fmt::Debug, { DebugPrinter::new(self, false, None) } /// Create an adapter that prints out the [`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) alterntive representation of the Item fn debug_pretty<'a>(self) -> DebugPrinter<'a, Self> where Self: Sized, Self::Item: std::fmt::Debug, { DebugPrinter::new(self, true, None) } /// Create an adapter that prints out the [`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) representation of the Item, with a Prefix fn debug_prefix<'a, S>(self, prefix: S) -> DebugPrinter<'a, Self> where Self: Sized + 'a, Self::Item: std::fmt::Debug, S: Into<Cow<'a, str>>, { DebugPrinter::new(self, false, Some(prefix.into())) } /// Create an adapter that prints out the [`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) alterntive representation of the Item, with a Prefix fn debug_prefix_pretty<'a, S>(self, prefix: S) -> DebugPrinter<'a, Self> where Self: Sized + 'a, Self::Item: std::fmt::Debug, S: Into<Cow<'a, str>>, { DebugPrinter::new(self, true, Some(prefix.into())) } } /// [`DebugPrinter`](./struct.DebugPrinter.html) is the iterator for debug printing pub struct DebugPrinter<'a, T>(T, bool, Option<Cow<'a, str>>); impl<'a, T> DebugPrinter<'a, T> where T: Iterator, T::Item: std::fmt::Debug, { fn new(x: T, pretty: bool, msg: Option<Cow<'a, str>>) -> Self { Self(x, pretty, msg) } } impl<'a, T> Iterator for DebugPrinter<'a, T> where T: Iterator, T::Item: std::fmt::Debug, { type Item = T::Item; fn next(&mut self) -> Option<Self::Item> { let next = self.0.next()?; #[inline] macro_rules! _log_this { ($e:expr, $($xs:expr),* $(,)?) => {{ #[cfg(feature = "logging")] ::log::debug!("{}", format_args!($e, $($xs),*)); #[cfg(not(feature = "logging"))] eprintln!("{}", format_args!($e, $($xs),*)); }}; } match (self.1, &self.2) { (true, Some(prefix)) => _log_this!("{}: {:#?}", prefix, next), (false, Some(prefix)) => _log_this!("{}: {:?}", prefix, next), (true, None) => _log_this!("{:#?}", next), (false, None) => _log_this!("{:?}", next), } Some(next) } } impl<T: ?Sized> DebugIterator for T where T: Iterator {}