rust/src/lists.rs

858 lines
29 KiB
Rust

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::cmp;
use std::iter::Peekable;
use syntax::codemap::{BytePos, CodeMap};
use comment::{find_comment_end, rewrite_comment, FindUncommented};
use config::{Config, IndentStyle};
use rewrite::RewriteContext;
use shape::{Indent, Shape};
use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
/// Formatting tactic for lists. This will be cast down to a
/// `DefinitiveListTactic` depending on the number and length of the items and
/// their comments.
#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum ListTactic {
// One item per row.
Vertical,
// All items on one row.
Horizontal,
// Try Horizontal layout, if that fails then vertical.
HorizontalVertical,
// HorizontalVertical with a soft limit of n characters.
LimitedHorizontalVertical(usize),
// Pack as many items as possible per row over (possibly) many rows.
Mixed,
}
impl_enum_serialize_and_deserialize!(ListTactic, Vertical, Horizontal, HorizontalVertical, Mixed);
#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum SeparatorTactic {
Always,
Never,
Vertical,
}
impl_enum_serialize_and_deserialize!(SeparatorTactic, Always, Never, Vertical);
impl SeparatorTactic {
pub fn from_bool(b: bool) -> SeparatorTactic {
if b {
SeparatorTactic::Always
} else {
SeparatorTactic::Never
}
}
}
pub struct ListFormatting<'a> {
pub tactic: DefinitiveListTactic,
pub separator: &'a str,
pub trailing_separator: SeparatorTactic,
pub separator_place: SeparatorPlace,
pub shape: Shape,
// Non-expressions, e.g. items, will have a new line at the end of the list.
// Important for comment styles.
pub ends_with_newline: bool,
// Remove newlines between list elements for expressions.
pub preserve_newline: bool,
pub config: &'a Config,
}
impl<'a> ListFormatting<'a> {
pub fn needs_trailing_separator(&self) -> bool {
match self.trailing_separator {
// We always put separator in front.
SeparatorTactic::Always => true,
SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
SeparatorTactic::Never => {
self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
}
}
}
}
impl AsRef<ListItem> for ListItem {
fn as_ref(&self) -> &ListItem {
self
}
}
#[derive(PartialEq, Eq)]
pub enum ListItemCommentStyle {
// Try to keep the comment on the same line with the item.
SameLine,
// Put the comment on the previous or the next line of the item.
DifferentLine,
// No comment available.
None,
}
pub struct ListItem {
// None for comments mean that they are not present.
pub pre_comment: Option<String>,
pub pre_comment_style: ListItemCommentStyle,
// Item should include attributes and doc comments. None indicates a failed
// rewrite.
pub item: Option<String>,
pub post_comment: Option<String>,
// Whether there is extra whitespace before this item.
pub new_lines: bool,
}
impl ListItem {
pub fn inner_as_ref(&self) -> &str {
self.item.as_ref().map_or("", |s| s)
}
pub fn is_different_group(&self) -> bool {
self.inner_as_ref().contains('\n') || self.pre_comment.is_some()
|| self.post_comment
.as_ref()
.map_or(false, |s| s.contains('\n'))
}
pub fn is_multiline(&self) -> bool {
self.inner_as_ref().contains('\n')
|| self.pre_comment
.as_ref()
.map_or(false, |s| s.contains('\n'))
|| self.post_comment
.as_ref()
.map_or(false, |s| s.contains('\n'))
}
pub fn has_comment(&self) -> bool {
self.pre_comment
.as_ref()
.map_or(false, |comment| comment.trim_left().starts_with("//"))
|| self.post_comment
.as_ref()
.map_or(false, |comment| comment.trim_left().starts_with("//"))
}
pub fn from_str<S: Into<String>>(s: S) -> ListItem {
ListItem {
pre_comment: None,
pre_comment_style: ListItemCommentStyle::None,
item: Some(s.into()),
post_comment: None,
new_lines: false,
}
}
}
/// The definitive formatting tactic for lists.
#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum DefinitiveListTactic {
Vertical,
Horizontal,
Mixed,
/// Special case tactic for `format!()`, `write!()` style macros.
SpecialMacro(usize),
}
impl DefinitiveListTactic {
pub fn ends_with_newline(&self, indent_style: IndentStyle) -> bool {
match indent_style {
IndentStyle::Block => *self != DefinitiveListTactic::Horizontal,
IndentStyle::Visual => false,
}
}
}
/// The type of separator for lists.
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub enum Separator {
Comma,
VerticalBar,
}
impl Separator {
pub fn len(&self) -> usize {
match *self {
// 2 = `, `
Separator::Comma => 2,
// 3 = ` | `
Separator::VerticalBar => 3,
}
}
}
/// Where to put separator.
#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum SeparatorPlace {
Front,
Back,
}
impl_enum_serialize_and_deserialize!(SeparatorPlace, Front, Back);
impl SeparatorPlace {
pub fn is_front(&self) -> bool {
*self == SeparatorPlace::Front
}
pub fn is_back(&self) -> bool {
*self == SeparatorPlace::Back
}
pub fn from_tactic(
default: SeparatorPlace,
tactic: DefinitiveListTactic,
sep: &str,
) -> SeparatorPlace {
match tactic {
DefinitiveListTactic::Vertical => default,
_ => if sep == "," {
SeparatorPlace::Back
} else {
default
},
}
}
}
pub fn definitive_tactic<I, T>(
items: I,
tactic: ListTactic,
sep: Separator,
width: usize,
) -> DefinitiveListTactic
where
I: IntoIterator<Item = T> + Clone,
T: AsRef<ListItem>,
{
let pre_line_comments = items
.clone()
.into_iter()
.any(|item| item.as_ref().has_comment());
let limit = match tactic {
_ if pre_line_comments => return DefinitiveListTactic::Vertical,
ListTactic::Mixed => return DefinitiveListTactic::Mixed,
ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
ListTactic::Vertical => return DefinitiveListTactic::Vertical,
ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
ListTactic::HorizontalVertical => width,
};
let (sep_count, total_width) = calculate_width(items.clone());
let total_sep_len = sep.len() * sep_count.checked_sub(1).unwrap_or(0);
let real_total = total_width + total_sep_len;
if real_total <= limit && !pre_line_comments
&& !items.into_iter().any(|item| item.as_ref().is_multiline())
{
DefinitiveListTactic::Horizontal
} else {
DefinitiveListTactic::Vertical
}
}
// Format a list of commented items into a string.
// TODO: add unit tests
pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
where
I: IntoIterator<Item = T> + Clone,
T: AsRef<ListItem>,
{
let tactic = formatting.tactic;
let sep_len = formatting.separator.len();
// Now that we know how we will layout, we can decide for sure if there
// will be a trailing separator.
let mut trailing_separator = formatting.needs_trailing_separator();
let mut result = String::with_capacity(128);
let cloned_items = items.clone();
let mut iter = items.into_iter().enumerate().peekable();
let mut item_max_width: Option<usize> = None;
let sep_place =
SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
let mut line_len = 0;
let indent_str = &formatting.shape.indent.to_string(formatting.config);
while let Some((i, item)) = iter.next() {
let item = item.as_ref();
let inner_item = item.item.as_ref()?;
let first = i == 0;
let last = iter.peek().is_none();
let mut separate = match sep_place {
SeparatorPlace::Front => !first,
SeparatorPlace::Back => !last || trailing_separator,
};
let item_sep_len = if separate { sep_len } else { 0 };
// Item string may be multi-line. Its length (used for block comment alignment)
// should be only the length of the last line.
let item_last_line = if item.is_multiline() {
inner_item.lines().last().unwrap_or("")
} else {
inner_item.as_ref()
};
let mut item_last_line_width = item_last_line.len() + item_sep_len;
if item_last_line.starts_with(&**indent_str) {
item_last_line_width -= indent_str.len();
}
match tactic {
DefinitiveListTactic::Horizontal if !first => {
result.push(' ');
}
DefinitiveListTactic::SpecialMacro(num_args_before) => {
if i == 0 {
// Nothing
} else if i < num_args_before {
result.push(' ');
} else if i <= num_args_before + 1 {
result.push('\n');
result.push_str(indent_str);
} else {
result.push(' ');
}
}
DefinitiveListTactic::Vertical if !first => {
result.push('\n');
result.push_str(indent_str);
}
DefinitiveListTactic::Mixed => {
let total_width = total_item_width(item) + item_sep_len;
// 1 is space between separator and item.
if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
result.push('\n');
result.push_str(indent_str);
line_len = 0;
if formatting.ends_with_newline {
if last {
separate = true;
} else {
trailing_separator = true;
}
}
}
if line_len > 0 {
result.push(' ');
line_len += 1;
}
line_len += total_width;
}
_ => {}
}
// Pre-comments
if let Some(ref comment) = item.pre_comment {
// Block style in non-vertical mode.
let block_mode = tactic != DefinitiveListTactic::Vertical;
// Width restriction is only relevant in vertical mode.
let comment =
rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
result.push_str(&comment);
if tactic == DefinitiveListTactic::Vertical {
// We cannot keep pre-comments on the same line if the comment if normalized.
let keep_comment = if formatting.config.normalize_comments()
|| item.pre_comment_style == ListItemCommentStyle::DifferentLine
{
false
} else {
// We will try to keep the comment on the same line with the item here.
// 1 = ` `
let total_width = total_item_width(item) + item_sep_len + 1;
total_width <= formatting.shape.width
};
if keep_comment {
result.push(' ');
} else {
result.push('\n');
result.push_str(indent_str);
}
} else {
result.push(' ');
}
item_max_width = None;
}
if separate && sep_place.is_front() && !first {
result.push_str(formatting.separator.trim());
result.push(' ');
}
result.push_str(&inner_item[..]);
// Post-comments
if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
let comment = item.post_comment.as_ref().unwrap();
let formatted_comment = rewrite_comment(
comment,
true,
Shape::legacy(formatting.shape.width, Indent::empty()),
formatting.config,
)?;
result.push(' ');
result.push_str(&formatted_comment);
}
if separate && sep_place.is_back() {
result.push_str(formatting.separator);
}
if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
let comment = item.post_comment.as_ref().unwrap();
let overhead = last_line_width(&result) + first_line_width(comment.trim());
let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
if item_max_width.is_none() && !last && !inner_item.contains('\n') {
*item_max_width = Some(max_width_of_item_with_post_comment(
&cloned_items,
i,
overhead,
formatting.config.max_width(),
));
}
let overhead = if starts_with_newline(comment) {
0
} else if let Some(max_width) = *item_max_width {
max_width + 2
} else {
// 1 = space between item and comment.
item_last_line_width + 1
};
let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
let offset = formatting.shape.indent + overhead;
let comment_shape = Shape::legacy(width, offset);
// Use block-style only for the last item or multiline comments.
let block_style = !formatting.ends_with_newline && last
|| comment.trim().contains('\n')
|| comment.trim().len() > width;
rewrite_comment(
comment.trim_left(),
block_style,
comment_shape,
formatting.config,
)
};
let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
if !starts_with_newline(comment) {
let mut comment_alignment =
post_comment_alignment(item_max_width, inner_item.len());
if first_line_width(&formatted_comment) + last_line_width(&result)
+ comment_alignment + 1 > formatting.config.max_width()
{
item_max_width = None;
formatted_comment = rewrite_post_comment(&mut item_max_width)?;
comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
}
for _ in 0..(comment_alignment + 1) {
result.push(' ');
}
// An additional space for the missing trailing separator.
if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
{
result.push(' ');
}
} else {
result.push('\n');
result.push_str(indent_str);
}
if formatted_comment.contains('\n') {
item_max_width = None;
}
result.push_str(&formatted_comment);
} else {
item_max_width = None;
}
if formatting.preserve_newline && !last && tactic == DefinitiveListTactic::Vertical
&& item.new_lines
{
item_max_width = None;
result.push('\n');
}
}
Some(result)
}
fn max_width_of_item_with_post_comment<I, T>(
items: &I,
i: usize,
overhead: usize,
max_budget: usize,
) -> usize
where
I: IntoIterator<Item = T> + Clone,
T: AsRef<ListItem>,
{
let mut max_width = 0;
let mut first = true;
for item in items.clone().into_iter().skip(i) {
let item = item.as_ref();
let inner_item_width = item.inner_as_ref().len();
if !first
&& (item.is_different_group() || !item.post_comment.is_some()
|| inner_item_width + overhead > max_budget)
{
return max_width;
}
if max_width < inner_item_width {
max_width = inner_item_width;
}
if item.new_lines {
return max_width;
}
first = false;
}
max_width
}
fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
item_max_width
.and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
.unwrap_or(0)
}
pub struct ListItems<'a, I, F1, F2, F3>
where
I: Iterator,
{
codemap: &'a CodeMap,
inner: Peekable<I>,
get_lo: F1,
get_hi: F2,
get_item_string: F3,
prev_span_end: BytePos,
next_span_start: BytePos,
terminator: &'a str,
separator: &'a str,
leave_last: bool,
}
impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
where
I: Iterator<Item = T>,
F1: Fn(&T) -> BytePos,
F2: Fn(&T) -> BytePos,
F3: Fn(&T) -> Option<String>,
{
type Item = ListItem;
fn next(&mut self) -> Option<Self::Item> {
let white_space: &[_] = &[' ', '\t'];
self.inner.next().map(|item| {
let mut new_lines = false;
// Pre-comment
let pre_snippet = self.codemap
.span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
.unwrap();
let trimmed_pre_snippet = pre_snippet.trim();
let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
let has_block_comment = trimmed_pre_snippet.starts_with("/*");
let (pre_comment, pre_comment_style) = if has_single_line_comment {
(
Some(trimmed_pre_snippet.to_owned()),
ListItemCommentStyle::DifferentLine,
)
} else if has_block_comment {
let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
if pre_snippet
.chars()
.rev()
.take(comment_end + 1)
.any(|c| c == '\n')
{
(
Some(trimmed_pre_snippet.to_owned()),
ListItemCommentStyle::DifferentLine,
)
} else {
(
Some(trimmed_pre_snippet.to_owned()),
ListItemCommentStyle::SameLine,
)
}
} else {
(None, ListItemCommentStyle::None)
};
// Post-comment
let next_start = match self.inner.peek() {
Some(next_item) => (self.get_lo)(next_item),
None => self.next_span_start,
};
let post_snippet = self.codemap
.span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
.unwrap();
let comment_end = match self.inner.peek() {
Some(..) => {
let mut block_open_index = post_snippet.find("/*");
// check if it really is a block comment (and not `//*` or a nested comment)
if let Some(i) = block_open_index {
match post_snippet.find('/') {
Some(j) if j < i => block_open_index = None,
_ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
_ => (),
}
}
let newline_index = post_snippet.find('\n');
if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
match (block_open_index, newline_index) {
// Separator before comment, with the next item on same line.
// Comment belongs to next item.
(Some(i), None) if i > separator_index => separator_index + 1,
// Block-style post-comment before the separator.
(Some(i), None) => cmp::max(
find_comment_end(&post_snippet[i..]).unwrap() + i,
separator_index + 1,
),
// Block-style post-comment. Either before or after the separator.
(Some(i), Some(j)) if i < j => cmp::max(
find_comment_end(&post_snippet[i..]).unwrap() + i,
separator_index + 1,
),
// Potential *single* line comment.
(_, Some(j)) if j > separator_index => j + 1,
_ => post_snippet.len(),
}
} else if let Some(newline_index) = newline_index {
// Match arms may not have trailing comma. In any case, for match arms,
// we will assume that the post comment belongs to the next arm if they
// do not end with trailing comma.
newline_index + 1
} else {
0
}
}
None => post_snippet
.find_uncommented(self.terminator)
.unwrap_or_else(|| post_snippet.len()),
};
if !post_snippet.is_empty() && comment_end > 0 {
// Account for extra whitespace between items. This is fiddly
// because of the way we divide pre- and post- comments.
// Everything from the separator to the next item.
let test_snippet = &post_snippet[comment_end - 1..];
let first_newline = test_snippet
.find('\n')
.unwrap_or_else(|| test_snippet.len());
// From the end of the first line of comments.
let test_snippet = &test_snippet[first_newline..];
let first = test_snippet
.find(|c: char| !c.is_whitespace())
.unwrap_or_else(|| test_snippet.len());
// From the end of the first line of comments to the next non-whitespace char.
let test_snippet = &test_snippet[..first];
if count_newlines(test_snippet) > 1 {
// There were multiple line breaks which got trimmed to nothing.
new_lines = true;
}
}
// Cleanup post-comment: strip separators and whitespace.
self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
let post_snippet = post_snippet[..comment_end].trim();
let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
post_snippet[1..].trim_matches(white_space)
} else if post_snippet.ends_with(',') {
post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
} else {
post_snippet
};
let post_comment = if !post_snippet_trimmed.is_empty() {
Some(post_snippet_trimmed.to_owned())
} else {
None
};
ListItem {
pre_comment: pre_comment,
pre_comment_style: pre_comment_style,
item: if self.inner.peek().is_none() && self.leave_last {
None
} else {
(self.get_item_string)(&item)
},
post_comment: post_comment,
new_lines: new_lines,
}
})
}
}
// Creates an iterator over a list's items with associated comments.
pub fn itemize_list<'a, T, I, F1, F2, F3>(
codemap: &'a CodeMap,
inner: I,
terminator: &'a str,
separator: &'a str,
get_lo: F1,
get_hi: F2,
get_item_string: F3,
prev_span_end: BytePos,
next_span_start: BytePos,
leave_last: bool,
) -> ListItems<'a, I, F1, F2, F3>
where
I: Iterator<Item = T>,
F1: Fn(&T) -> BytePos,
F2: Fn(&T) -> BytePos,
F3: Fn(&T) -> Option<String>,
{
ListItems {
codemap: codemap,
inner: inner.peekable(),
get_lo: get_lo,
get_hi: get_hi,
get_item_string: get_item_string,
prev_span_end: prev_span_end,
next_span_start: next_span_start,
terminator: terminator,
separator: separator,
leave_last: leave_last,
}
}
/// Returns the count and total width of the list items.
fn calculate_width<I, T>(items: I) -> (usize, usize)
where
I: IntoIterator<Item = T>,
T: AsRef<ListItem>,
{
items
.into_iter()
.map(|item| total_item_width(item.as_ref()))
.fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
}
pub fn total_item_width(item: &ListItem) -> usize {
comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
+ comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
+ item.item.as_ref().map_or(0, |str| str.len())
}
fn comment_len(comment: Option<&str>) -> usize {
match comment {
Some(s) => {
let text_len = s.trim().len();
if text_len > 0 {
// We'll put " /*" before and " */" after inline comments.
text_len + 6
} else {
text_len
}
}
None => 0,
}
}
// Compute horizontal and vertical shapes for a struct-lit-like thing.
pub fn struct_lit_shape(
shape: Shape,
context: &RewriteContext,
prefix_width: usize,
suffix_width: usize,
) -> Option<(Option<Shape>, Shape)> {
let v_shape = match context.config.indent_style() {
IndentStyle::Visual => shape
.visual_indent(0)
.shrink_left(prefix_width)?
.sub_width(suffix_width)?,
IndentStyle::Block => {
let shape = shape.block_indent(context.config.tab_spaces());
Shape {
width: context.budget(shape.indent.width()),
..shape
}
}
};
let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
if let Some(w) = shape_width {
let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
} else {
Some((None, v_shape))
}
}
// Compute the tactic for the internals of a struct-lit-like thing.
pub fn struct_lit_tactic(
h_shape: Option<Shape>,
context: &RewriteContext,
items: &[ListItem],
) -> DefinitiveListTactic {
if let Some(h_shape) = h_shape {
let prelim_tactic = match (context.config.indent_style(), items.len()) {
(IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
_ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
_ => ListTactic::Vertical,
};
definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
} else {
DefinitiveListTactic::Vertical
}
}
// Given a tactic and possible shapes for horizontal and vertical layout,
// come up with the actual shape to use.
pub fn shape_for_tactic(
tactic: DefinitiveListTactic,
h_shape: Option<Shape>,
v_shape: Shape,
) -> Shape {
match tactic {
DefinitiveListTactic::Horizontal => h_shape.unwrap(),
_ => v_shape,
}
}
// Create a ListFormatting object for formatting the internals of a
// struct-lit-like thing, that is a series of fields.
pub fn struct_lit_formatting<'a>(
shape: Shape,
tactic: DefinitiveListTactic,
context: &'a RewriteContext,
force_no_trailing_comma: bool,
) -> ListFormatting<'a> {
let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
&& tactic == DefinitiveListTactic::Vertical;
ListFormatting {
tactic: tactic,
separator: ",",
trailing_separator: if force_no_trailing_comma {
SeparatorTactic::Never
} else {
context.config.trailing_comma()
},
separator_place: SeparatorPlace::Back,
shape: shape,
ends_with_newline: ends_with_newline,
preserve_newline: true,
config: context.config,
}
}