1 //! Format attributes and meta items.
4 use rustc_ast::AstLike;
5 use rustc_span::{symbol::sym, Span, Symbol};
7 use self::doc_comment::DocCommentFormatter;
8 use crate::comment::{contains_comment, rewrite_doc_comment, CommentStyle};
9 use crate::config::lists::*;
10 use crate::config::IndentStyle;
11 use crate::expr::rewrite_literal;
12 use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
14 use crate::rewrite::{Rewrite, RewriteContext};
15 use crate::shape::Shape;
16 use crate::source_map::SpanUtils;
17 use crate::types::{rewrite_path, PathContext};
18 use crate::utils::{count_newlines, mk_sp};
22 pub(crate) fn contains_name(attrs: &[ast::Attribute], name: Symbol) -> bool {
23 attrs.iter().any(|attr| attr.has_name(name))
26 pub(crate) fn first_attr_value_str_by_name(
27 attrs: &[ast::Attribute],
32 .find(|attr| attr.has_name(name))
33 .and_then(|attr| attr.value_str())
36 /// Returns attributes on the given statement.
37 pub(crate) fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
41 pub(crate) fn get_span_without_attrs(stmt: &ast::Stmt) -> Span {
43 ast::StmtKind::Local(ref local) => local.span,
44 ast::StmtKind::Item(ref item) => item.span,
45 ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => expr.span,
46 ast::StmtKind::MacCall(ref mac_stmt) => mac_stmt.mac.span(),
47 ast::StmtKind::Empty => stmt.span,
51 /// Returns attributes that are within `outer_span`.
52 pub(crate) fn filter_inline_attrs(
53 attrs: &[ast::Attribute],
55 ) -> Vec<ast::Attribute> {
58 .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
63 fn is_derive(attr: &ast::Attribute) -> bool {
64 attr.has_name(sym::derive)
67 // The shape of the arguments to a function-like attribute.
73 context: &RewriteContext<'_>,
75 match context.config.indent_style() {
76 IndentStyle::Block => {
78 shape.offset_left(left)
82 .block_indent(context.config.tab_spaces())
83 .with_max_width(context.config),
87 IndentStyle::Visual => shape
90 .and_then(|s| s.sub_width(right)),
95 derives: &[ast::Attribute],
97 context: &RewriteContext<'_>,
99 // Collect all items from all attributes
100 let all_items = derives
103 // Parse the derive items and extract the span for each item; if any
104 // attribute is not parseable, none of the attributes will be
106 let item_spans = attr.meta_item_list().map(|meta_item_list| {
109 .map(|nested_meta_item| nested_meta_item.span())
112 let items = itemize_list(
113 context.snippet_provider,
119 |span| Some(context.snippet(*span).to_owned()),
120 // We update derive attribute spans to start after the opening '('
121 // This helps us focus parsing to just what's inside #[derive(...)]
122 context.snippet_provider.span_after(attr.span, "("),
129 // Fail if any attribute failed.
130 .collect::<Option<Vec<_>>>()?
131 // Collect the results into a single, flat, Vec.
134 .collect::<Vec<_>>();
136 // Collect formatting parameters.
137 let prefix = attr_prefix(&derives[0]);
138 let argument_shape = argument_shape(
139 "[derive()]".len() + prefix.len(),
145 let one_line_shape = shape
146 .offset_left("[derive()]".len() + prefix.len())?
147 .sub_width("()]".len())?;
148 let one_line_budget = one_line_shape.width;
150 let tactic = definitive_tactic(
152 ListTactic::HorizontalVertical,
154 argument_shape.width,
156 let trailing_separator = match context.config.indent_style() {
157 // We always add the trailing comma and remove it if it is not needed.
158 IndentStyle::Block => SeparatorTactic::Always,
159 IndentStyle::Visual => SeparatorTactic::Never,
162 // Format the collection of items.
163 let fmt = ListFormatting::new(argument_shape, context.config)
165 .trailing_separator(trailing_separator)
166 .ends_with_newline(false);
167 let item_str = write_list(&all_items, &fmt)?;
169 debug!("item_str: '{}'", item_str);
171 // Determine if the result will be nested, i.e. if we're using the block
172 // indent style and either the items are on multiple lines or we've exceeded
173 // our budget to fit on a single line.
174 let nested = context.config.indent_style() == IndentStyle::Block
175 && (item_str.contains('\n') || item_str.len() > one_line_budget);
177 // Format the final result.
178 let mut result = String::with_capacity(128);
179 result.push_str(prefix);
180 result.push_str("[derive(");
182 let nested_indent = argument_shape.indent.to_string_with_newline(context.config);
183 result.push_str(&nested_indent);
184 result.push_str(&item_str);
185 result.push_str(&shape.indent.to_string_with_newline(context.config));
186 } else if let SeparatorTactic::Always = context.config.trailing_comma() {
187 // Retain the trailing comma.
188 result.push_str(&item_str);
189 } else if item_str.ends_with(',') {
190 // Remove the trailing comma.
191 result.push_str(&item_str[..item_str.len() - 1]);
193 result.push_str(&item_str);
195 result.push_str(")]");
200 /// Returns the first group of attributes that fills the given predicate.
201 /// We consider two doc comments are in different group if they are separated by normal comments.
202 fn take_while_with_pred<'a, P>(
203 context: &RewriteContext<'_>,
204 attrs: &'a [ast::Attribute],
206 ) -> &'a [ast::Attribute]
208 P: Fn(&ast::Attribute) -> bool,
211 let mut iter = attrs.iter().peekable();
213 while let Some(attr) = iter.next() {
219 if let Some(next_attr) = iter.peek() {
220 // Extract comments between two attributes.
221 let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
222 let snippet = context.snippet(span_between_attr);
223 if count_newlines(snippet) >= 2 || snippet.contains('/') {
232 /// Rewrite the any doc comments which come before any other attributes.
233 fn rewrite_initial_doc_comments(
234 context: &RewriteContext<'_>,
235 attrs: &[ast::Attribute],
237 ) -> Option<(usize, Option<String>)> {
238 if attrs.is_empty() {
239 return Some((0, None));
241 // Rewrite doc comments
242 let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_doc_comment());
243 if !sugared_docs.is_empty() {
244 let snippet = sugared_docs
246 .map(|a| context.snippet(a.span))
251 Some(rewrite_doc_comment(
253 shape.comment(context.config),
262 impl Rewrite for ast::NestedMetaItem {
263 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
265 ast::NestedMetaItem::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
266 ast::NestedMetaItem::Literal(ref l) => rewrite_literal(context, l, shape),
271 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
272 // Look at before and after comment and see if there are any empty lines.
273 let comment_begin = comment.find('/');
274 let len = comment_begin.unwrap_or_else(|| comment.len());
275 let mlb = count_newlines(&comment[..len]) > 1;
276 let mla = if comment_begin.is_none() {
282 .take_while(|c| c.is_whitespace())
283 .filter(|&c| c == '\n')
287 (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
290 impl Rewrite for ast::MetaItem {
291 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
292 Some(match self.kind {
293 ast::MetaItemKind::Word => {
294 rewrite_path(context, PathContext::Type, None, &self.path, shape)?
296 ast::MetaItemKind::List(ref list) => {
297 let path = rewrite_path(context, PathContext::Type, None, &self.path, shape)?;
298 let has_trailing_comma = crate::expr::span_ends_with_comma(context, self.span);
299 overflow::rewrite_with_parens(
306 context.config.attr_fn_like_width(),
307 Some(if has_trailing_comma {
308 SeparatorTactic::Always
310 SeparatorTactic::Never
314 ast::MetaItemKind::NameValue(ref literal) => {
315 let path = rewrite_path(context, PathContext::Type, None, &self.path, shape)?;
317 let lit_shape = shape.shrink_left(path.len() + 3)?;
318 // `rewrite_literal` returns `None` when `literal` exceeds max
319 // width. Since a literal is basically unformattable unless it
320 // is a string literal (and only if `format_strings` is set),
321 // we might be better off ignoring the fact that the attribute
322 // is longer than the max width and continue on formatting.
323 // See #2479 for example.
324 let value = rewrite_literal(context, literal, lit_shape)
325 .unwrap_or_else(|| context.snippet(literal.span).to_owned());
326 format!("{} = {}", path, value)
332 impl Rewrite for ast::Attribute {
333 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
334 let snippet = context.snippet(self.span);
335 if self.is_doc_comment() {
336 rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
338 let should_skip = self
340 .map(|s| context.skip_context.skip_attribute(s.name.as_str()))
342 let prefix = attr_prefix(self);
344 if should_skip || contains_comment(snippet) {
345 return Some(snippet.to_owned());
348 if let Some(ref meta) = self.meta() {
349 // This attribute is possibly a doc attribute needing normalization to a doc comment
350 if context.config.normalize_doc_attributes() && meta.has_name(sym::doc) {
351 if let Some(ref literal) = meta.value_str() {
352 let comment_style = match self.style {
353 ast::AttrStyle::Inner => CommentStyle::Doc,
354 ast::AttrStyle::Outer => CommentStyle::TripleSlash,
357 let literal_str = literal.as_str();
358 let doc_comment_formatter =
359 DocCommentFormatter::new(literal_str, comment_style);
360 let doc_comment = format!("{}", doc_comment_formatter);
361 return rewrite_doc_comment(
363 shape.comment(context.config),
370 let shape = shape.offset_left(prefix.len() + 1)?;
372 meta.rewrite(context, shape)
373 .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
376 Some(snippet.to_owned())
382 impl Rewrite for [ast::Attribute] {
383 fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
385 return Some(String::new());
388 // The current remaining attributes.
389 let mut attrs = self;
390 let mut result = String::new();
392 // This is not just a simple map because we need to handle doc comments
393 // (where we take as many doc comment attributes as possible) and possibly
394 // merging derives into a single attribute.
396 if attrs.is_empty() {
400 // Handle doc comments.
401 let (doc_comment_len, doc_comment_str) =
402 rewrite_initial_doc_comments(context, attrs, shape)?;
403 if doc_comment_len > 0 {
404 let doc_comment_str = doc_comment_str.expect("doc comments, but no result");
405 result.push_str(&doc_comment_str);
407 let missing_span = attrs
408 .get(doc_comment_len)
409 .map(|next| mk_sp(attrs[doc_comment_len - 1].span.hi(), next.span.lo()));
410 if let Some(missing_span) = missing_span {
411 let snippet = context.snippet(missing_span);
412 let (mla, mlb) = has_newlines_before_after_comment(snippet);
413 let comment = crate::comment::recover_missing_comment_in_span(
415 shape.with_max_width(context.config),
419 let comment = if comment.is_empty() {
422 format!("{}{}\n{}", mla, comment, mlb)
424 result.push_str(&comment);
425 result.push_str(&shape.indent.to_string(context.config));
428 attrs = &attrs[doc_comment_len..];
433 // Handle derives if we will merge them.
434 if context.config.merge_derives() && is_derive(&attrs[0]) {
435 let derives = take_while_with_pred(context, attrs, is_derive);
436 let derive_str = format_derive(derives, shape, context)?;
437 result.push_str(&derive_str);
439 let missing_span = attrs
441 .map(|next| mk_sp(attrs[derives.len() - 1].span.hi(), next.span.lo()));
442 if let Some(missing_span) = missing_span {
443 let comment = crate::comment::recover_missing_comment_in_span(
445 shape.with_max_width(context.config),
449 result.push_str(&comment);
450 if let Some(next) = attrs.get(derives.len()) {
451 if next.is_doc_comment() {
452 let snippet = context.snippet(missing_span);
453 let (_, mlb) = has_newlines_before_after_comment(snippet);
454 result.push_str(mlb);
458 result.push_str(&shape.indent.to_string(context.config));
461 attrs = &attrs[derives.len()..];
466 // If we get here, then we have a regular attribute, just handle one
469 let formatted_attr = attrs[0].rewrite(context, shape)?;
470 result.push_str(&formatted_attr);
472 let missing_span = attrs
474 .map(|next| mk_sp(attrs[0].span.hi(), next.span.lo()));
475 if let Some(missing_span) = missing_span {
476 let comment = crate::comment::recover_missing_comment_in_span(
478 shape.with_max_width(context.config),
482 result.push_str(&comment);
483 if let Some(next) = attrs.get(1) {
484 if next.is_doc_comment() {
485 let snippet = context.snippet(missing_span);
486 let (_, mlb) = has_newlines_before_after_comment(snippet);
487 result.push_str(mlb);
491 result.push_str(&shape.indent.to_string(context.config));
499 fn attr_prefix(attr: &ast::Attribute) -> &'static str {
501 ast::AttrStyle::Inner => "#!",
502 ast::AttrStyle::Outer => "#",
506 pub(crate) trait MetaVisitor<'ast> {
507 fn visit_meta_item(&mut self, meta_item: &'ast ast::MetaItem) {
508 match meta_item.kind {
509 ast::MetaItemKind::Word => self.visit_meta_word(meta_item),
510 ast::MetaItemKind::List(ref list) => self.visit_meta_list(meta_item, list),
511 ast::MetaItemKind::NameValue(ref lit) => self.visit_meta_name_value(meta_item, lit),
517 _meta_item: &'ast ast::MetaItem,
518 list: &'ast [ast::NestedMetaItem],
521 self.visit_nested_meta_item(nm);
525 fn visit_meta_word(&mut self, _meta_item: &'ast ast::MetaItem) {}
527 fn visit_meta_name_value(&mut self, _meta_item: &'ast ast::MetaItem, _lit: &'ast ast::Lit) {}
529 fn visit_nested_meta_item(&mut self, nm: &'ast ast::NestedMetaItem) {
531 ast::NestedMetaItem::MetaItem(ref meta_item) => self.visit_meta_item(meta_item),
532 ast::NestedMetaItem::Literal(ref lit) => self.visit_literal(lit),
536 fn visit_literal(&mut self, _lit: &'ast ast::Lit) {}