src/attr.rs

   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.
   4 //
   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.
  10
  11 //! Format attributes and meta items.
  12
  13 use config::lists::*;
  14 use config::IndentStyle;
  15 use syntax::ast;
  16 use syntax::codemap::Span;
  17
  18 use comment::{combine_strs_with_missing_comments, contains_comment, rewrite_doc_comment};
  19 use expr::rewrite_literal;
  20 use lists::{itemize_list, write_list, ListFormatting};
  21 use rewrite::{Rewrite, RewriteContext};
  22 use shape::Shape;
  23 use types::{rewrite_path, PathContext};
  24 use utils::{count_newlines, mk_sp};
  25
  26 /// Returns attributes on the given statement.
  27 pub fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
  28     match stmt.node {
  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,
  33     }
  34 }
  35
  36 /// Returns attributes that are within `outer_span`.
  37 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
  38     attrs
  39         .iter()
  40         .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
  41         .cloned()
  42         .collect()
  43 }
  44
  45 fn is_derive(attr: &ast::Attribute) -> bool {
  46     attr.check_name("derive")
  47 }
  48
  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| {
  52         meta_item_list
  53             .iter()
  54             .map(|nested_meta_item| context.snippet(nested_meta_item.span))
  55             .collect()
  56     })
  57 }
  58
  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(");
  63     // 11 = `#[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() {
  68         // 2 = `, ` or `)]`
  69         let width = a.len() + 2;
  70         if width > budget {
  71             if i > 0 {
  72                 // Remove trailing whitespace.
  73                 result.pop();
  74             }
  75             result.push('\n');
  76             // 9 = `#[derive(`
  77             result.push_str(&(shape.indent + 9).to_string(context.config));
  78             budget = initial_budget;
  79         } else {
  80             budget = budget.saturating_sub(width);
  81         }
  82         result.push_str(a);
  83         if i != num - 1 {
  84             result.push_str(", ")
  85         }
  86     }
  87     result.push_str(")]");
  88     Some(result)
  89 }
  90
  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],
  96     pred: P,
  97 ) -> &'a [ast::Attribute]
  98 where
  99     P: Fn(&ast::Attribute) -> bool,
 100 {
 101     let mut len = 0;
 102     let mut iter = attrs.iter().peekable();
 103
 104     while let Some(attr) = iter.next() {
 105         if pred(attr) {
 106             len += 1;
 107         } else {
 108             break;
 109         }
 110         if let Some(next_attr) = iter.peek() {
 111             // Extract comments between two attributes.
 112             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 113             let snippet = context.snippet(span_between_attr);
 114             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 115                 break;
 116             }
 117         }
 118     }
 119
 120     &attrs[..len]
 121 }
 122
 123 /// Rewrite the same kind of attributes at the same time. This includes doc
 124 /// comments and derives.
 125 fn rewrite_first_group_attrs(
 126     context: &RewriteContext,
 127     attrs: &[ast::Attribute],
 128     shape: Shape,
 129 ) -> Option<(usize, String)> {
 130     if attrs.is_empty() {
 131         return Some((0, String::new()));
 132     }
 133     // Rewrite doc comments
 134     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 135     if !sugared_docs.is_empty() {
 136         let snippet = sugared_docs
 137             .iter()
 138             .map(|a| context.snippet(a.span))
 139             .collect::<Vec<_>>()
 140             .join("\n");
 141         return Some((
 142             sugared_docs.len(),
 143             rewrite_doc_comment(&snippet, shape.comment(context.config), context.config)?,
 144         ));
 145     }
 146     // Rewrite `#[derive(..)]`s.
 147     if context.config.merge_derives() {
 148         let derives = take_while_with_pred(context, attrs, is_derive);
 149         if !derives.is_empty() {
 150             let mut derive_args = vec![];
 151             for derive in derives {
 152                 derive_args.append(&mut get_derive_args(context, derive)?);
 153             }
 154             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 155         }
 156     }
 157     // Rewrite the first attribute.
 158     Some((1, attrs[0].rewrite(context, shape)?))
 159 }
 160
 161 impl Rewrite for ast::NestedMetaItem {
 162     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 163         match self.node {
 164             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 165             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 166         }
 167     }
 168 }
 169
 170 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 171     // Look at before and after comment and see if there are any empty lines.
 172     let comment_begin = comment.find('/');
 173     let len = comment_begin.unwrap_or_else(|| comment.len());
 174     let mlb = count_newlines(&comment[..len]) > 1;
 175     let mla = if comment_begin.is_none() {
 176         mlb
 177     } else {
 178         comment
 179             .chars()
 180             .rev()
 181             .take_while(|c| c.is_whitespace())
 182             .filter(|&c| c == '\n')
 183             .count() > 1
 184     };
 185     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 186 }
 187
 188 fn allow_mixed_tactic_for_nested_metaitem_list(list: &[ast::NestedMetaItem]) -> bool {
 189     list.iter().all(|nested_metaitem| {
 190         if let ast::NestedMetaItemKind::MetaItem(ref inner_metaitem) = nested_metaitem.node {
 191             match inner_metaitem.node {
 192                 ast::MetaItemKind::List(..) | ast::MetaItemKind::NameValue(..) => false,
 193                 _ => true,
 194             }
 195         } else {
 196             true
 197         }
 198     })
 199 }
 200
 201 impl Rewrite for ast::MetaItem {
 202     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 203         Some(match self.node {
 204             ast::MetaItemKind::Word => {
 205                 rewrite_path(context, PathContext::Type, None, &self.ident, shape)?
 206             }
 207             ast::MetaItemKind::List(ref list) => {
 208                 let path = rewrite_path(context, PathContext::Type, None, &self.ident, shape)?;
 209                 let item_shape = match context.config.indent_style() {
 210                     IndentStyle::Block => shape
 211                         .block_indent(context.config.tab_spaces())
 212                         .with_max_width(context.config),
 213                     // 1 = `(`, 2 = `]` and `)`
 214                     IndentStyle::Visual => shape
 215                         .visual_indent(0)
 216                         .shrink_left(path.len() + 1)
 217                         .and_then(|s| s.sub_width(2))?,
 218                 };
 219                 let items = itemize_list(
 220                     context.snippet_provider,
 221                     list.iter(),
 222                     ")",
 223                     ",",
 224                     |nested_meta_item| nested_meta_item.span.lo(),
 225                     |nested_meta_item| nested_meta_item.span.hi(),
 226                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 227                     self.span.lo(),
 228                     self.span.hi(),
 229                     false,
 230                 );
 231                 let item_vec = items.collect::<Vec<_>>();
 232                 let tactic = if allow_mixed_tactic_for_nested_metaitem_list(list) {
 233                     DefinitiveListTactic::Mixed
 234                 } else {
 235                     ::lists::definitive_tactic(
 236                         &item_vec,
 237                         ListTactic::HorizontalVertical,
 238                         ::lists::Separator::Comma,
 239                         item_shape.width,
 240                     )
 241                 };
 242                 let fmt = ListFormatting {
 243                     tactic,
 244                     separator: ",",
 245                     trailing_separator: SeparatorTactic::Never,
 246                     separator_place: SeparatorPlace::Back,
 247                     shape: item_shape,
 248                     ends_with_newline: false,
 249                     preserve_newline: false,
 250                     nested: false,
 251                     config: context.config,
 252                 };
 253                 let item_str = write_list(&item_vec, &fmt)?;
 254                 // 3 = "()" and "]"
 255                 let one_line_budget = shape.offset_left(path.len())?.sub_width(3)?.width;
 256                 if context.config.indent_style() == IndentStyle::Visual
 257                     || (!item_str.contains('\n') && item_str.len() <= one_line_budget)
 258                 {
 259                     format!("{}({})", path, item_str)
 260                 } else {
 261                     let indent = shape.indent.to_string_with_newline(context.config);
 262                     let nested_indent = item_shape.indent.to_string_with_newline(context.config);
 263                     format!("{}({}{}{})", path, nested_indent, item_str, indent)
 264                 }
 265             }
 266             ast::MetaItemKind::NameValue(ref literal) => {
 267                 let path = rewrite_path(context, PathContext::Type, None, &self.ident, shape)?;
 268                 // 3 = ` = `
 269                 let lit_shape = shape.shrink_left(path.len() + 3)?;
 270                 // `rewrite_literal` returns `None` when `literal` exceeds max
 271                 // width. Since a literal is basically unformattable unless it
 272                 // is a string literal (and only if `format_strings` is set),
 273                 // we might be better off ignoring the fact that the attribute
 274                 // is longer than the max width and contiue on formatting.
 275                 // See #2479 for example.
 276                 let value = rewrite_literal(context, literal, lit_shape)
 277                     .unwrap_or_else(|| context.snippet(literal.span).to_owned());
 278                 format!("{} = {}", path, value)
 279             }
 280         })
 281     }
 282 }
 283
 284 impl Rewrite for ast::Attribute {
 285     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 286         let prefix = match self.style {
 287             ast::AttrStyle::Inner => "#!",
 288             ast::AttrStyle::Outer => "#",
 289         };
 290         let snippet = context.snippet(self.span);
 291         if self.is_sugared_doc {
 292             rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
 293         } else {
 294             if contains_comment(snippet) {
 295                 return Some(snippet.to_owned());
 296             }
 297             // 1 = `[`
 298             let shape = shape.offset_left(prefix.len() + 1)?;
 299             Some(
 300                 self.meta()
 301                     .and_then(|meta| meta.rewrite(context, shape))
 302                     .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
 303             )
 304         }
 305     }
 306 }
 307
 308 impl<'a> Rewrite for [ast::Attribute] {
 309     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 310         if self.is_empty() {
 311             return Some(String::new());
 312         }
 313         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 314         if self.len() == 1 || first_group_len == self.len() {
 315             Some(first_group_str)
 316         } else {
 317             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 318             let missing_span = mk_sp(
 319                 self[first_group_len - 1].span.hi(),
 320                 self[first_group_len].span.lo(),
 321             );
 322             // Preserve an empty line before/after doc comments.
 323             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 324                 let snippet = context.snippet(missing_span);
 325                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
 326                 let comment = ::comment::recover_missing_comment_in_span(
 327                     missing_span,
 328                     shape.with_max_width(context.config),
 329                     context,
 330                     0,
 331                 )?;
 332                 let comment = if comment.is_empty() {
 333                     format!("\n{}", mlb)
 334                 } else {
 335                     format!("{}{}\n{}", mla, comment, mlb)
 336                 };
 337                 Some(format!(
 338                     "{}{}{}{}",
 339                     first_group_str,
 340                     comment,
 341                     shape.indent.to_string(context.config),
 342                     rest_str
 343                 ))
 344             } else {
 345                 combine_strs_with_missing_comments(
 346                     context,
 347                     &first_group_str,
 348                     &rest_str,
 349                     missing_span,
 350                     shape,
 351                     false,
 352                 )
 353             }
 354         }
 355     }
 356 }