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/* Copyright 2018 Christopher Bacher * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ //! This crate is intended to ease the use of multi-line strings in Rust. //! When embedding strings with multiple lines in Rust all whitespaces, tabs, etc. are preserved even if they are just used for layouting one's code nicely. //! //! ``` //! fn main() { //! println!("-----------------------"); //! let misrepresented_multiline_string = " //! This is string //! spans over multiple lines, //! but its rendering preserves all whitespaces. //! //! Which is not what we usually intend in this case. //! "; //! println!("{}", misrepresented_multiline_string); //! println!("-----------------------"); //! //! println!("-----------------------"); //! let correctly_layouted_string = "For displaying //! the a multiline strin properly //! it would need to be layouted //! like this. //! //! Which is not very nice."; //! println!("{}", correctly_layouted_string); //! println!("-----------------------"); //! } //! ``` //! //! The `trim-margin` crate supports you with the proper layouting. //! By introducing a margin in the multi-line string the `trim_margin` method can filter out unwanted whitespaces and blank lines. //! //! ``` //! extern crate trim_margin; //! use trim_margin::MarginTrimmable; //! //! fn main() { //! let multiline_string_with_margin = " //! |This string has a margin //! |indicated by the '|' character. //! | //! |The following method call will remove ... //! | * a blank first/last line //! | * blanks before the margin prefix //! | * the margin prefix itself //! ".trim_margin().unwrap(); //! println!("{}", multiline_string_with_margin); //! } //! ``` #[cfg(test)] #[macro_use] extern crate galvanic_assert; /// An interface for removing the margin of multi-line string-like objects. pub trait MarginTrimmable { /// Removes blanks and the `margin_prefix` from multiline strings. /// /// If the first or last line is blank (contains only whitespace, tabs, etc.) they are removed. /// From each remaining line leading blank characters and the subsequent are removed /// /// # Returns /// * The trimmed string or `None` if not every line starts with a `margin_prefix`. /// * Strings without line break unmodified fn trim_margin_with<M: AsRef<str>>(&self, margin_prefix: M) -> Option<String>; /// Short-hand for `trin_margin_with("|")`. fn trim_margin(&self) -> Option<String> { self.trim_margin_with("|") } } impl<S: AsRef<str>> MarginTrimmable for S { fn trim_margin_with<M: AsRef<str>>(&self, margin_prefix: M) -> Option<String> { let lines: Vec<_> = self.as_ref().split('\n').map(|line| line.trim_left()).collect(); if lines.len() <= 1 { return Some(self.as_ref().into()); } let mut with_margin: Vec<&str> = Vec::with_capacity(lines.len()); let mut line_iter = lines.into_iter().peekable(); if line_iter.peek().map_or(false, |l| l.is_empty()) { line_iter.next(); } let prefix = margin_prefix.as_ref(); while let Some(line) = line_iter.next() { let is_last_line = line_iter.peek().is_none(); if is_last_line && line.is_empty() { continue; } if !line.starts_with(prefix) { return None; } with_margin.push(&line[prefix.len()..]); }; Some(with_margin.join("\n")) } } #[cfg(test)] mod tests { use galvanic_assert::matchers::*; use galvanic_assert::matchers::variant::*; use super::*; #[test] fn should_not_modify_empty_string() { assert_that!(&"".trim_margin(), maybe_some(eq(String::new()))); } #[test] fn should_not_modify_single_line_string() { assert_that!(&"hello, world".trim_margin(), maybe_some(eq("hello, world".into()))); } #[test] fn should_trim_margin_of_multiline_string() { let txt = "|this | is a | multiline string |with margin"; assert_that!(&txt.trim_margin(), maybe_some(eq(vec!["this", " is a", " multiline string", "with margin"].join("\n")))); } #[test] fn should_remove_first_and_last_line_if_blank() { let txt = " |ignore blank |surrounding lines "; assert_that!(&txt.trim_margin(), maybe_some(eq(vec!["ignore blank", "surrounding lines"].join("\n")))); } #[test] fn should_allow_arbitrary_margin_character() { let txt = " #ignore blank #surrounding lines "; assert_that!(&txt.trim_margin_with("#"), maybe_some(eq(vec!["ignore blank", "surrounding lines"].join("\n")))); } }