542 lines
14 KiB
Rust
542 lines
14 KiB
Rust
//! A few wrappers for the `fmt::Write` objects that efficiently appends and remove
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//! common indentation after every newline
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//!
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//! # Setup
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//!
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//! Add this to your `Cargo.toml`:
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//!
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//! ```toml
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//! [dependencies]
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//! indenter = "0.2"
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//! ```
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//!
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//! # Examples
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//!
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//! ## Indentation only
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//!
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//! This type is intended primarily for writing error reporters that gracefully
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//! format error messages that span multiple lines.
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//!
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//! ```rust
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//! use std::error::Error;
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//! use core::fmt::{self, Write};
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//! use indenter::indented;
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//!
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//! struct ErrorReporter<'a>(&'a dyn Error);
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//!
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//! impl fmt::Debug for ErrorReporter<'_> {
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//! fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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//! let mut source = Some(self.0);
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//! let mut i = 0;
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//!
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//! while let Some(error) = source {
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//! writeln!(f)?;
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//! write!(indented(f).ind(i), "{}", error)?;
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//!
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//! source = error.source();
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//! i += 1;
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//! }
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//!
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//! Ok(())
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//! }
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//! }
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//! ```
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//!
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//! ## "Dedenting" (removing common leading indendation)
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//!
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//! This type is intended primarily for formatting source code. For example, when
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//! generating code.
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//!
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//! This type requires the feature `std`.
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//!
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//! ```rust
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//! # #[cfg(feature = "std")]
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//! # fn main() {
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//! use std::error::Error;
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//! use core::fmt::{self, Write};
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//! use indenter::CodeFormatter;
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//!
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//! let mut output = String::new();
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//! let mut f = CodeFormatter::new(&mut output, " ");
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//!
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//! write!(
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//! f,
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//! r#"
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//! Hello
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//! World
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//! "#,
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//! );
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//!
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//! assert_eq!(output, "Hello\n World\n");
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//!
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//! let mut output = String::new();
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//! let mut f = CodeFormatter::new(&mut output, " ");
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//!
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//! // it can also indent...
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//! f.indent(2);
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//!
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//! write!(
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//! f,
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//! r#"
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//! Hello
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//! World
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//! "#,
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//! );
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//!
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//! assert_eq!(output, " Hello\n World\n");
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//! # }
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//! # #[cfg(not(feature = "std"))]
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//! # fn main() {
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//! # }
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//! ```
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#![cfg_attr(not(feature = "std"), no_std)]
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#![doc(html_root_url = "https://docs.rs/indenter/0.3.3")]
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#![warn(
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missing_debug_implementations,
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missing_docs,
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missing_doc_code_examples,
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rust_2018_idioms,
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unreachable_pub,
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bad_style,
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const_err,
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dead_code,
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improper_ctypes,
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non_shorthand_field_patterns,
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no_mangle_generic_items,
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overflowing_literals,
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path_statements,
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patterns_in_fns_without_body,
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private_in_public,
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unconditional_recursion,
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unused,
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unused_allocation,
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unused_comparisons,
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unused_parens,
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while_true
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)]
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use core::fmt;
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/// The set of supported formats for indentation
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#[allow(missing_debug_implementations)]
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pub enum Format<'a> {
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/// Insert uniform indentation before every line
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///
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/// This format takes a static string as input and inserts it after every newline
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Uniform {
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/// The string to insert as indentation
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indentation: &'static str,
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},
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/// Inserts a number before the first line
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///
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/// This format hard codes the indentation level to match the indentation from
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/// `core::backtrace::Backtrace`
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Numbered {
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/// The index to insert before the first line of output
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ind: usize,
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},
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/// A custom indenter which is executed after every newline
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///
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/// Custom indenters are passed the current line number and the buffer to be written to as args
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Custom {
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/// The custom indenter
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inserter: &'a mut Inserter,
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},
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}
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/// Helper struct for efficiently indenting multi line display implementations
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///
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/// # Explanation
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///
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/// This type will never allocate a string to handle inserting indentation. It instead leverages
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/// the `write_str` function that serves as the foundation of the `core::fmt::Write` trait. This
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/// lets it intercept each piece of output as its being written to the output buffer. It then
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/// splits on newlines giving slices into the original string. Finally we alternate writing these
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/// lines and the specified indentation to the output buffer.
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#[allow(missing_debug_implementations)]
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pub struct Indented<'a, D: ?Sized> {
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inner: &'a mut D,
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needs_indent: bool,
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format: Format<'a>,
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}
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/// A callback for `Format::Custom` used to insert indenation after a new line
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///
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/// The first argument is the line number within the output, starting from 0
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pub type Inserter = dyn FnMut(usize, &mut dyn fmt::Write) -> fmt::Result;
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impl Format<'_> {
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fn insert_indentation(&mut self, line: usize, f: &mut dyn fmt::Write) -> fmt::Result {
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match self {
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Format::Uniform { indentation } => write!(f, "{}", indentation),
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Format::Numbered { ind } => {
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if line == 0 {
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write!(f, "{: >4}: ", ind)
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} else {
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write!(f, " ")
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}
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}
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Format::Custom { inserter } => inserter(line, f),
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}
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}
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}
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impl<'a, D> Indented<'a, D> {
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/// Sets the format to `Format::Numbered` with the provided index
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pub fn ind(self, ind: usize) -> Self {
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self.with_format(Format::Numbered { ind })
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}
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/// Sets the format to `Format::Uniform` with the provided static string
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pub fn with_str(self, indentation: &'static str) -> Self {
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self.with_format(Format::Uniform { indentation })
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}
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/// Construct an indenter with a user defined format
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pub fn with_format(mut self, format: Format<'a>) -> Self {
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self.format = format;
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self
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}
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}
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impl<T> fmt::Write for Indented<'_, T>
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where
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T: fmt::Write + ?Sized,
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{
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fn write_str(&mut self, s: &str) -> fmt::Result {
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for (ind, line) in s.split('\n').enumerate() {
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if ind > 0 {
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self.inner.write_char('\n')?;
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self.needs_indent = true;
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}
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if self.needs_indent {
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// Don't render the line unless its actually got text on it
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if line.is_empty() {
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continue;
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}
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self.format.insert_indentation(ind, &mut self.inner)?;
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self.needs_indent = false;
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}
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self.inner.write_fmt(format_args!("{}", line))?;
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}
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Ok(())
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}
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}
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/// Helper function for creating a default indenter
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pub fn indented<D: ?Sized>(f: &mut D) -> Indented<'_, D> {
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Indented {
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inner: f,
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needs_indent: true,
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format: Format::Uniform {
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indentation: " ",
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},
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}
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}
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/// Helper struct for efficiently dedent and indent multi line display implementations
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///
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/// # Explanation
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///
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/// This type allocates a string once to get the formatted result and then uses the internal
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/// formatter efficiently to: first dedent the output, then re-indent to the desired level.
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#[cfg(feature = "std")]
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#[allow(missing_debug_implementations)]
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pub struct CodeFormatter<'a, T> {
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f: &'a mut T,
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level: u32,
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indentation: String,
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}
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#[cfg(feature = "std")]
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impl<'a, T: fmt::Write> fmt::Write for CodeFormatter<'a, T> {
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fn write_str(&mut self, input: &str) -> fmt::Result {
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let input = match input.chars().next() {
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Some('\n') => &input[1..],
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_ => return self.f.write_str(input),
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};
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let min = input
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.split('\n')
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.map(|line| line.chars().take_while(char::is_ascii_whitespace).count())
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.filter(|count| *count > 0)
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.min()
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.unwrap_or_default();
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let input = input.trim_end_matches(|c| char::is_ascii_whitespace(&c));
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for line in input.split('\n') {
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if line.len().saturating_sub(min) > 0 {
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for _ in 0..self.level {
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self.f.write_str(&self.indentation)?;
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}
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}
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if line.len() >= min {
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self.f.write_str(&line[min..])?;
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} else {
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self.f.write_str(&line)?;
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}
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self.f.write_char('\n')?;
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}
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Ok(())
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}
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fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> fmt::Result {
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self.write_str(&args.to_string())
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}
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}
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#[cfg(feature = "std")]
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impl<'a, T: fmt::Write> CodeFormatter<'a, T> {
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/// Wrap the formatter `f`, use `indentation` as base string indentation and return a new
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/// formatter that implements `std::fmt::Write` that can be used with the macro `write!()`
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pub fn new<S: Into<String>>(f: &'a mut T, indentation: S) -> Self {
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Self {
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f,
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level: 0,
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indentation: indentation.into(),
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}
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}
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/// Set the indentation level to a specific value
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pub fn set_level(&mut self, level: u32) {
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self.level = level;
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}
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/// Increase the indentation level by `inc`
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pub fn indent(&mut self, inc: u32) {
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self.level = self.level.saturating_add(inc);
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}
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/// Decrease the indentation level by `inc`
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pub fn dedent(&mut self, inc: u32) {
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self.level = self.level.saturating_sub(inc);
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}
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}
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#[cfg(test)]
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mod tests {
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extern crate alloc;
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use super::*;
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use alloc::string::String;
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use core::fmt::Write as _;
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#[test]
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fn one_digit() {
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let input = "verify\nthis";
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let expected = " 2: verify\n this";
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let mut output = String::new();
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indented(&mut output).ind(2).write_str(input).unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn two_digits() {
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let input = "verify\nthis";
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let expected = " 12: verify\n this";
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let mut output = String::new();
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indented(&mut output).ind(12).write_str(input).unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn no_digits() {
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let input = "verify\nthis";
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let expected = " verify\n this";
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let mut output = String::new();
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indented(&mut output).write_str(input).unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn with_str() {
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let input = "verify\nthis";
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let expected = "...verify\n...this";
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let mut output = String::new();
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indented(&mut output)
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.with_str("...")
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.write_str(input)
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.unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn dyn_write() {
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let input = "verify\nthis";
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let expected = " verify\n this";
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let mut output = String::new();
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let writer: &mut dyn core::fmt::Write = &mut output;
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indented(writer).write_str(input).unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn nice_api() {
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let input = "verify\nthis";
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let expected = " 1: verify\n this";
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let output = &mut String::new();
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let n = 1;
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write!(
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indented(output).with_format(Format::Custom {
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inserter: &mut move |line_no, f| {
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if line_no == 0 {
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write!(f, "{: >4}: ", n)
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} else {
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write!(f, " ")
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}
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}
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}),
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"{}",
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input
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)
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.unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn nice_api_2() {
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let input = "verify\nthis";
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let expected = " verify\n this";
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let output = &mut String::new();
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write!(
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indented(output).with_format(Format::Uniform { indentation: " " }),
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"{}",
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input
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)
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.unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn trailing_newlines() {
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let input = "verify\nthis\n";
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let expected = " verify\n this\n";
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let output = &mut String::new();
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write!(indented(output).with_str(" "), "{}", input).unwrap();
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assert_eq!(expected, output);
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}
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#[test]
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fn several_interpolations() {
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let input = "verify\nthis\n";
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let expected = " verify\n this\n and verify\n this\n";
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let output = &mut String::new();
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write!(indented(output).with_str(" "), "{} and {}", input, input).unwrap();
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assert_eq!(expected, output);
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}
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}
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#[cfg(all(test, feature = "std"))]
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mod tests_std {
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use super::*;
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use core::fmt::Write as _;
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#[test]
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fn dedent() {
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let mut s = String::new();
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let mut f = CodeFormatter::new(&mut s, " ");
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write!(
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f,
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r#"
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struct Foo;
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impl Foo {{
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fn foo() {{
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todo!()
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}}
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}}
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"#,
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)
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.unwrap();
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assert_eq!(
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s,
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"struct Foo;\n\nimpl Foo {\n fn foo() {\n todo!()\n }\n}\n"
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);
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let mut s = String::new();
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let mut f = CodeFormatter::new(&mut s, " ");
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write!(
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f,
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r#"
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struct Foo;
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impl Foo {{
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fn foo() {{
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todo!()
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}}
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}}"#,
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)
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.unwrap();
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assert_eq!(
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s,
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"struct Foo;\n\nimpl Foo {\n fn foo() {\n todo!()\n }\n}\n"
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);
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}
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#[test]
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fn indent() {
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let mut s = String::new();
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let mut f = CodeFormatter::new(&mut s, " ");
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f.indent(1);
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write!(
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f,
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r#"
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struct Foo;
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impl Foo {{
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fn foo() {{
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todo!()
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}}
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}}
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"#,
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)
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.unwrap();
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assert_eq!(s, " struct Foo;\n\n impl Foo {\n fn foo() {\n todo!()\n }\n }\n");
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}
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|
|
#[test]
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fn inline() {
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let mut s = String::new();
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let mut f = CodeFormatter::new(&mut s, " ");
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write!(
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f,
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r#"struct Foo;
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fn foo() {{
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}}"#,
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)
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.unwrap();
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assert_eq!(s, "struct Foo;\n fn foo() {\n }");
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}
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|
|
#[test]
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fn split_prefix() {
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let mut s = String::new();
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let mut f = CodeFormatter::new(&mut s, " ");
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writeln!(f).unwrap();
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assert_eq!(s, "\n");
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}
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}
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