1 // Copyright 2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Format attributes and meta items.
15 use syntax::codemap::Span;
17 use comment::{combine_strs_with_missing_comments, contains_comment, rewrite_doc_comment};
18 use expr::rewrite_literal;
19 use lists::{itemize_list, write_list, ListFormatting};
20 use rewrite::{Rewrite, RewriteContext};
22 use utils::{count_newlines, mk_sp};
26 /// Returns attributes on the given statement.
27 pub fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
29 ast::StmtKind::Local(ref local) => &local.attrs,
30 ast::StmtKind::Item(ref item) => &item.attrs,
31 ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
32 ast::StmtKind::Mac(ref mac) => &mac.2,
36 /// Returns attributes that are within `outer_span`.
37 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
40 .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
45 fn is_derive(attr: &ast::Attribute) -> bool {
46 attr.check_name("derive")
49 /// Returns the arguments of `#[derive(...)]`.
50 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
51 attr.meta_item_list().map(|meta_item_list| {
54 .map(|nested_meta_item| context.snippet(nested_meta_item.span))
59 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
60 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
61 let mut result = String::with_capacity(128);
62 result.push_str("#[derive(");
64 let initial_budget = shape.width.checked_sub(11)?;
65 let mut budget = initial_budget;
66 let num = derive_args.len();
67 for (i, a) in derive_args.iter().enumerate() {
69 let width = a.len() + 2;
72 // Remove trailing whitespace.
77 result.push_str(&(shape.indent + 9).to_string(context.config));
78 budget = initial_budget;
80 budget = budget.checked_sub(width).unwrap_or(0);
87 result.push_str(")]");
91 /// Returns the first group of attributes that fills the given predicate.
92 /// We consider two doc comments are in different group if they are separated by normal comments.
93 fn take_while_with_pred<'a, P>(
94 context: &RewriteContext,
95 attrs: &'a [ast::Attribute],
97 ) -> &'a [ast::Attribute]
99 P: Fn(&ast::Attribute) -> bool,
101 let mut last_index = 0;
102 let mut iter = attrs.iter().enumerate().peekable();
103 while let Some((i, attr)) = iter.next() {
107 if let Some(&(_, next_attr)) = iter.peek() {
108 // Extract comments between two attributes.
109 let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
110 let snippet = context.snippet(span_between_attr);
111 if count_newlines(snippet) >= 2 || snippet.contains('/') {
120 &attrs[..last_index + 1]
124 /// Rewrite the same kind of attributes at the same time. This includes doc
125 /// comments and derives.
126 fn rewrite_first_group_attrs(
127 context: &RewriteContext,
128 attrs: &[ast::Attribute],
130 ) -> Option<(usize, String)> {
131 if attrs.is_empty() {
132 return Some((0, String::new()));
134 // Rewrite doc comments
135 let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
136 if !sugared_docs.is_empty() {
137 let snippet = sugared_docs
139 .map(|a| context.snippet(a.span))
144 rewrite_doc_comment(&snippet, shape, context.config)?,
147 // Rewrite `#[derive(..)]`s.
148 if context.config.merge_derives() {
149 let derives = take_while_with_pred(context, attrs, is_derive);
150 if !derives.is_empty() {
151 let mut derive_args = vec![];
152 for derive in derives {
153 derive_args.append(&mut get_derive_args(context, derive)?);
155 return Some((derives.len(), format_derive(context, &derive_args, shape)?));
158 // Rewrite the first attribute.
159 Some((1, attrs[0].rewrite(context, shape)?))
162 impl Rewrite for ast::NestedMetaItem {
163 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
165 ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
166 ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
171 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
172 // Look at before and after comment and see if there are any empty lines.
173 let comment_begin = comment.chars().position(|c| c == '/');
174 let len = comment_begin.unwrap_or_else(|| comment.len());
175 let mlb = count_newlines(&comment[..len]) > 1;
176 let mla = if comment_begin.is_none() {
179 let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
180 let len = comment_end.unwrap();
185 .filter(|c| *c == '\n')
188 (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
191 impl Rewrite for ast::MetaItem {
192 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
193 Some(match self.node {
194 ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
195 ast::MetaItemKind::List(ref list) => {
196 let name = self.name.as_str();
197 // 1 = `(`, 2 = `]` and `)`
198 let item_shape = shape
200 .shrink_left(name.len() + 1)
201 .and_then(|s| s.sub_width(2))?;
202 let items = itemize_list(
203 context.snippet_provider,
207 |nested_meta_item| nested_meta_item.span.lo(),
208 |nested_meta_item| nested_meta_item.span.hi(),
209 |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
214 let item_vec = items.collect::<Vec<_>>();
215 let fmt = ListFormatting {
216 tactic: DefinitiveListTactic::Mixed,
218 trailing_separator: SeparatorTactic::Never,
219 separator_place: SeparatorPlace::Back,
221 ends_with_newline: false,
222 preserve_newline: false,
223 config: context.config,
225 format!("{}({})", name, write_list(&item_vec, &fmt)?)
227 ast::MetaItemKind::NameValue(ref literal) => {
228 let name = self.name.as_str();
230 let lit_shape = shape.shrink_left(name.len() + 3)?;
231 // `rewrite_literal` returns `None` when `literal` exceeds max
232 // width. Since a literal is basically unformattable unless it
233 // is a string literal (and only if `format_strings` is set),
234 // we might be better off ignoring the fact that the attribute
235 // is longer than the max width and contiue on formatting.
236 // See #2479 for example.
237 let value = rewrite_literal(context, literal, lit_shape)
238 .unwrap_or_else(|| context.snippet(literal.span).to_owned());
239 format!("{} = {}", name, value)
245 impl Rewrite for ast::Attribute {
246 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
247 let prefix = match self.style {
248 ast::AttrStyle::Inner => "#!",
249 ast::AttrStyle::Outer => "#",
251 let snippet = context.snippet(self.span);
252 if self.is_sugared_doc {
253 let doc_shape = Shape {
254 width: cmp::min(shape.width, context.config.comment_width())
255 .checked_sub(shape.indent.width())
259 rewrite_doc_comment(snippet, doc_shape, context.config)
261 if contains_comment(snippet) {
262 return Some(snippet.to_owned());
265 let shape = shape.offset_left(prefix.len() + 1)?;
268 .and_then(|meta| meta.rewrite(context, shape))
269 .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
275 impl<'a> Rewrite for [ast::Attribute] {
276 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
278 return Some(String::new());
280 let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
281 if self.len() == 1 || first_group_len == self.len() {
282 Some(first_group_str)
284 let rest_str = self[first_group_len..].rewrite(context, shape)?;
285 let missing_span = mk_sp(
286 self[first_group_len - 1].span.hi(),
287 self[first_group_len].span.lo(),
289 // Preserve an empty line before/after doc comments.
290 if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
291 let snippet = context.snippet(missing_span);
292 let (mla, mlb) = has_newlines_before_after_comment(snippet);
293 let comment = ::comment::recover_missing_comment_in_span(
295 shape.with_max_width(context.config),
299 let comment = if comment.is_empty() {
302 format!("{}{}\n{}", mla, comment, mlb)
308 shape.indent.to_string(context.config),
312 combine_strs_with_missing_comments(