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};
24 /// Returns attributes on the given statement.
25 pub fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
27 ast::StmtKind::Local(ref local) => &local.attrs,
28 ast::StmtKind::Item(ref item) => &item.attrs,
29 ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
30 ast::StmtKind::Mac(ref mac) => &mac.2,
34 /// Returns attributes that are within `outer_span`.
35 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
38 .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
43 fn is_derive(attr: &ast::Attribute) -> bool {
44 attr.check_name("derive")
47 /// Returns the arguments of `#[derive(...)]`.
48 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
49 attr.meta_item_list().map(|meta_item_list| {
52 .map(|nested_meta_item| context.snippet(nested_meta_item.span))
57 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
58 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
59 let mut result = String::with_capacity(128);
60 result.push_str("#[derive(");
62 let initial_budget = shape.width.checked_sub(11)?;
63 let mut budget = initial_budget;
64 let num = derive_args.len();
65 for (i, a) in derive_args.iter().enumerate() {
67 let width = a.len() + 2;
70 // Remove trailing whitespace.
75 result.push_str(&(shape.indent + 9).to_string(context.config));
76 budget = initial_budget;
78 budget = budget.checked_sub(width).unwrap_or(0);
85 result.push_str(")]");
89 /// Returns the first group of attributes that fills the given predicate.
90 /// We consider two doc comments are in different group if they are separated by normal comments.
91 fn take_while_with_pred<'a, P>(
92 context: &RewriteContext,
93 attrs: &'a [ast::Attribute],
95 ) -> &'a [ast::Attribute]
97 P: Fn(&ast::Attribute) -> bool,
100 let mut iter = attrs.iter().peekable();
102 while let Some(attr) = iter.next() {
108 if let Some(next_attr) = iter.peek() {
109 // Extract comments between two attributes.
110 let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
111 let snippet = context.snippet(span_between_attr);
112 if count_newlines(snippet) >= 2 || snippet.contains('/') {
121 /// Rewrite the same kind of attributes at the same time. This includes doc
122 /// comments and derives.
123 fn rewrite_first_group_attrs(
124 context: &RewriteContext,
125 attrs: &[ast::Attribute],
127 ) -> Option<(usize, String)> {
128 if attrs.is_empty() {
129 return Some((0, String::new()));
131 // Rewrite doc comments
132 let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
133 if !sugared_docs.is_empty() {
134 let snippet = sugared_docs
136 .map(|a| context.snippet(a.span))
141 rewrite_doc_comment(&snippet, shape.comment(context.config), context.config)?,
144 // Rewrite `#[derive(..)]`s.
145 if context.config.merge_derives() {
146 let derives = take_while_with_pred(context, attrs, is_derive);
147 if !derives.is_empty() {
148 let mut derive_args = vec![];
149 for derive in derives {
150 derive_args.append(&mut get_derive_args(context, derive)?);
152 return Some((derives.len(), format_derive(context, &derive_args, shape)?));
155 // Rewrite the first attribute.
156 Some((1, attrs[0].rewrite(context, shape)?))
159 impl Rewrite for ast::NestedMetaItem {
160 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
162 ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
163 ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
168 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
169 // Look at before and after comment and see if there are any empty lines.
170 let comment_begin = comment.find('/');
171 let len = comment_begin.unwrap_or_else(|| comment.len());
172 let mlb = count_newlines(&comment[..len]) > 1;
173 let mla = if comment_begin.is_none() {
179 .take_while(|c| c.is_whitespace())
180 .filter(|&c| c == '\n')
183 (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
186 fn allow_mixed_tactic_for_nested_metaitem_list(list: &[ast::NestedMetaItem]) -> bool {
187 list.iter().all(|nested_metaitem| {
188 if let ast::NestedMetaItemKind::MetaItem(ref inner_metaitem) = nested_metaitem.node {
189 match inner_metaitem.node {
190 ast::MetaItemKind::List(..) | ast::MetaItemKind::NameValue(..) => false,
199 impl Rewrite for ast::MetaItem {
200 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
201 Some(match self.node {
202 ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
203 ast::MetaItemKind::List(ref list) => {
204 let name = self.name.as_str();
205 // 1 = `(`, 2 = `]` and `)`
206 let item_shape = shape
208 .shrink_left(name.len() + 1)
209 .and_then(|s| s.sub_width(2))?;
210 let items = itemize_list(
211 context.snippet_provider,
215 |nested_meta_item| nested_meta_item.span.lo(),
216 |nested_meta_item| nested_meta_item.span.hi(),
217 |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
222 let item_vec = items.collect::<Vec<_>>();
223 let tactic = if allow_mixed_tactic_for_nested_metaitem_list(list) {
224 DefinitiveListTactic::Mixed
226 ::lists::definitive_tactic(
228 ListTactic::HorizontalVertical,
229 ::lists::Separator::Comma,
233 let fmt = ListFormatting {
236 trailing_separator: SeparatorTactic::Never,
237 separator_place: SeparatorPlace::Back,
239 ends_with_newline: false,
240 preserve_newline: false,
241 config: context.config,
243 format!("{}({})", name, write_list(&item_vec, &fmt)?)
245 ast::MetaItemKind::NameValue(ref literal) => {
246 let name = self.name.as_str();
248 let lit_shape = shape.shrink_left(name.len() + 3)?;
249 // `rewrite_literal` returns `None` when `literal` exceeds max
250 // width. Since a literal is basically unformattable unless it
251 // is a string literal (and only if `format_strings` is set),
252 // we might be better off ignoring the fact that the attribute
253 // is longer than the max width and contiue on formatting.
254 // See #2479 for example.
255 let value = rewrite_literal(context, literal, lit_shape)
256 .unwrap_or_else(|| context.snippet(literal.span).to_owned());
257 format!("{} = {}", name, value)
263 impl Rewrite for ast::Attribute {
264 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
265 let prefix = match self.style {
266 ast::AttrStyle::Inner => "#!",
267 ast::AttrStyle::Outer => "#",
269 let snippet = context.snippet(self.span);
270 if self.is_sugared_doc {
271 rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
273 if contains_comment(snippet) {
274 return Some(snippet.to_owned());
277 let shape = shape.offset_left(prefix.len() + 1)?;
280 .and_then(|meta| meta.rewrite(context, shape))
281 .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
287 impl<'a> Rewrite for [ast::Attribute] {
288 fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
290 return Some(String::new());
292 let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
293 if self.len() == 1 || first_group_len == self.len() {
294 Some(first_group_str)
296 let rest_str = self[first_group_len..].rewrite(context, shape)?;
297 let missing_span = mk_sp(
298 self[first_group_len - 1].span.hi(),
299 self[first_group_len].span.lo(),
301 // Preserve an empty line before/after doc comments.
302 if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
303 let snippet = context.snippet(missing_span);
304 let (mla, mlb) = has_newlines_before_after_comment(snippet);
305 let comment = ::comment::recover_missing_comment_in_span(
307 shape.with_max_width(context.config),
311 let comment = if comment.is_empty() {
314 format!("{}{}\n{}", mla, comment, mlb)
320 shape.indent.to_string(context.config),
324 combine_strs_with_missing_comments(