src/overflow.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 //! Rewrite a list some items with overflow.
  12 // FIXME: Replace `ToExpr` with some enum.
  13
  14 use config::lists::*;
  15 use syntax::ast;
  16 use syntax::codemap::Span;
  17 use syntax::parse::token::DelimToken;
  18
  19 use closures;
  20 use codemap::SpanUtils;
  21 use expr::{is_every_expr_simple, is_nested_call, maybe_get_args_offset, ToExpr};
  22 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator};
  23 use rewrite::{Rewrite, RewriteContext};
  24 use shape::Shape;
  25 use spanned::Spanned;
  26 use utils::{count_newlines, extra_offset, first_line_width, last_line_width, mk_sp, paren_overhead};
  27
  28 use std::cmp::min;
  29
  30 const SHORT_ITEM_THRESHOLD: usize = 10;
  31
  32 pub fn rewrite_with_parens<T>(
  33     context: &RewriteContext,
  34     ident: &str,
  35     items: &[&T],
  36     shape: Shape,
  37     span: Span,
  38     item_max_width: usize,
  39     force_separator_tactic: Option<SeparatorTactic>,
  40 ) -> Option<String>
  41 where
  42     T: Rewrite + ToExpr + Spanned,
  43 {
  44     Context::new(
  45         context,
  46         items,
  47         ident,
  48         shape,
  49         span,
  50         "(",
  51         ")",
  52         item_max_width,
  53         force_separator_tactic,
  54         None,
  55     ).rewrite(shape)
  56 }
  57
  58 pub fn rewrite_with_angle_brackets<T>(
  59     context: &RewriteContext,
  60     ident: &str,
  61     items: &[&T],
  62     shape: Shape,
  63     span: Span,
  64 ) -> Option<String>
  65 where
  66     T: Rewrite + ToExpr + Spanned,
  67 {
  68     Context::new(
  69         context,
  70         items,
  71         ident,
  72         shape,
  73         span,
  74         "<",
  75         ">",
  76         context.config.max_width(),
  77         None,
  78         None,
  79     ).rewrite(shape)
  80 }
  81
  82 pub fn rewrite_with_square_brackets<T>(
  83     context: &RewriteContext,
  84     name: &str,
  85     items: &[&T],
  86     shape: Shape,
  87     span: Span,
  88     force_separator_tactic: Option<SeparatorTactic>,
  89     delim_token: Option<DelimToken>,
  90 ) -> Option<String>
  91 where
  92     T: Rewrite + ToExpr + Spanned,
  93 {
  94     let (lhs, rhs) = match delim_token {
  95         Some(DelimToken::Paren) => ("(", ")"),
  96         Some(DelimToken::Brace) => ("{", "}"),
  97         _ => ("[", "]"),
  98     };
  99     Context::new(
 100         context,
 101         items,
 102         name,
 103         shape,
 104         span,
 105         lhs,
 106         rhs,
 107         context.config.width_heuristics().array_width,
 108         force_separator_tactic,
 109         Some(("[", "]")),
 110     ).rewrite(shape)
 111 }
 112
 113 struct Context<'a, T: 'a> {
 114     context: &'a RewriteContext<'a>,
 115     items: &'a [&'a T],
 116     ident: &'a str,
 117     prefix: &'static str,
 118     suffix: &'static str,
 119     one_line_shape: Shape,
 120     nested_shape: Shape,
 121     span: Span,
 122     item_max_width: usize,
 123     one_line_width: usize,
 124     force_separator_tactic: Option<SeparatorTactic>,
 125     custom_delims: Option<(&'a str, &'a str)>,
 126 }
 127
 128 impl<'a, T: 'a + Rewrite + ToExpr + Spanned> Context<'a, T> {
 129     pub fn new(
 130         context: &'a RewriteContext,
 131         items: &'a [&'a T],
 132         ident: &'a str,
 133         shape: Shape,
 134         span: Span,
 135         prefix: &'static str,
 136         suffix: &'static str,
 137         item_max_width: usize,
 138         force_separator_tactic: Option<SeparatorTactic>,
 139         custom_delims: Option<(&'a str, &'a str)>,
 140     ) -> Context<'a, T> {
 141         // 2 = `( `, 1 = `(`
 142         let paren_overhead = if context.config.spaces_within_parens_and_brackets() {
 143             2
 144         } else {
 145             1
 146         };
 147         let used_width = extra_offset(ident, shape);
 148         let one_line_width = shape
 149             .width
 150             .checked_sub(used_width + 2 * paren_overhead)
 151             .unwrap_or(0);
 152
 153         // 1 = "(" or ")"
 154         let one_line_shape = shape
 155             .offset_left(last_line_width(ident) + 1)
 156             .and_then(|shape| shape.sub_width(1))
 157             .unwrap_or(Shape { width: 0, ..shape });
 158         let nested_shape = shape_from_indent_style(
 159             context,
 160             shape,
 161             used_width + 2 * paren_overhead,
 162             used_width + paren_overhead,
 163         );
 164         Context {
 165             context,
 166             items,
 167             ident,
 168             one_line_shape,
 169             nested_shape,
 170             span,
 171             prefix,
 172             suffix,
 173             item_max_width,
 174             one_line_width,
 175             force_separator_tactic,
 176             custom_delims,
 177         }
 178     }
 179
 180     fn last_item(&self) -> Option<&&T> {
 181         self.items.last()
 182     }
 183
 184     fn items_span(&self) -> Span {
 185         let span_lo = self.context
 186             .snippet_provider
 187             .span_after(self.span, self.prefix);
 188         mk_sp(span_lo, self.span.hi())
 189     }
 190
 191     fn rewrite_last_item_with_overflow(
 192         &self,
 193         last_list_item: &mut ListItem,
 194         shape: Shape,
 195     ) -> Option<String> {
 196         let last_item = self.last_item()?;
 197         let rewrite = if let Some(expr) = last_item.to_expr() {
 198             match expr.node {
 199                 // When overflowing the closure which consists of a single control flow expression,
 200                 // force to use block if its condition uses multi line.
 201                 ast::ExprKind::Closure(..) => {
 202                     // If the argument consists of multiple closures, we do not overflow
 203                     // the last closure.
 204                     if closures::args_have_many_closure(self.items) {
 205                         None
 206                     } else {
 207                         closures::rewrite_last_closure(self.context, expr, shape)
 208                     }
 209                 }
 210                 _ => expr.rewrite(self.context, shape),
 211             }
 212         } else {
 213             last_item.rewrite(self.context, shape)
 214         };
 215
 216         if let Some(rewrite) = rewrite {
 217             let rewrite_first_line = Some(rewrite[..first_line_width(&rewrite)].to_owned());
 218             last_list_item.item = rewrite_first_line;
 219             Some(rewrite)
 220         } else {
 221             None
 222         }
 223     }
 224
 225     fn default_tactic(&self, list_items: &[ListItem]) -> DefinitiveListTactic {
 226         definitive_tactic(
 227             list_items,
 228             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 229             Separator::Comma,
 230             self.one_line_width,
 231         )
 232     }
 233
 234     fn try_overflow_last_item(&self, list_items: &mut Vec<ListItem>) -> DefinitiveListTactic {
 235         // 1 = "("
 236         let combine_arg_with_callee = self.items.len() == 1 && self.items[0].to_expr().is_some()
 237             && self.ident.len() + 1 <= self.context.config.tab_spaces();
 238         let overflow_last = combine_arg_with_callee || can_be_overflowed(self.context, self.items);
 239
 240         // Replace the last item with its first line to see if it fits with
 241         // first arguments.
 242         let placeholder = if overflow_last {
 243             let old_value = *self.context.force_one_line_chain.borrow();
 244             if !combine_arg_with_callee {
 245                 if let Some(expr) = self.last_item().and_then(|item| item.to_expr()) {
 246                     if let ast::ExprKind::MethodCall(..) = expr.node {
 247                         self.context.force_one_line_chain.replace(true);
 248                     }
 249                 }
 250             }
 251             let result = last_item_shape(
 252                 self.items,
 253                 list_items,
 254                 self.one_line_shape,
 255                 self.item_max_width,
 256             ).and_then(|arg_shape| {
 257                 self.rewrite_last_item_with_overflow(
 258                     &mut list_items[self.items.len() - 1],
 259                     arg_shape,
 260                 )
 261             });
 262             self.context.force_one_line_chain.replace(old_value);
 263             result
 264         } else {
 265             None
 266         };
 267
 268         let mut tactic = definitive_tactic(
 269             &*list_items,
 270             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 271             Separator::Comma,
 272             self.one_line_width,
 273         );
 274
 275         // Replace the stub with the full overflowing last argument if the rewrite
 276         // succeeded and its first line fits with the other arguments.
 277         match (overflow_last, tactic, placeholder) {
 278             (true, DefinitiveListTactic::Horizontal, Some(ref overflowed))
 279                 if self.items.len() == 1 =>
 280             {
 281                 // When we are rewriting a nested function call, we restrict the
 282                 // bugdet for the inner function to avoid them being deeply nested.
 283                 // However, when the inner function has a prefix or a suffix
 284                 // (e.g. `foo() as u32`), this budget reduction may produce poorly
 285                 // formatted code, where a prefix or a suffix being left on its own
 286                 // line. Here we explicitlly check those cases.
 287                 if count_newlines(overflowed) == 1 {
 288                     let rw = self.items
 289                         .last()
 290                         .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 291                     let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
 292                     if no_newline {
 293                         list_items[self.items.len() - 1].item = rw;
 294                     } else {
 295                         list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 296                     }
 297                 } else {
 298                     list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 299                 }
 300             }
 301             (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
 302                 list_items[self.items.len() - 1].item = placeholder;
 303             }
 304             _ if self.items.len() >= 1 => {
 305                 list_items[self.items.len() - 1].item = self.items
 306                     .last()
 307                     .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 308
 309                 // Use horizontal layout for a function with a single argument as long as
 310                 // everything fits in a single line.
 311                 // `self.one_line_width == 0` means vertical layout is forced.
 312                 if self.items.len() == 1 && self.one_line_width != 0 && !list_items[0].has_comment()
 313                     && !list_items[0].inner_as_ref().contains('\n')
 314                     && ::lists::total_item_width(&list_items[0]) <= self.one_line_width
 315                 {
 316                     tactic = DefinitiveListTactic::Horizontal;
 317                 } else {
 318                     tactic = self.default_tactic(list_items);
 319
 320                     if tactic == DefinitiveListTactic::Vertical {
 321                         if let Some((all_simple, num_args_before)) =
 322                             maybe_get_args_offset(self.ident, self.items)
 323                         {
 324                             let one_line = all_simple
 325                                 && definitive_tactic(
 326                                     &list_items[..num_args_before],
 327                                     ListTactic::HorizontalVertical,
 328                                     Separator::Comma,
 329                                     self.nested_shape.width,
 330                                 )
 331                                     == DefinitiveListTactic::Horizontal
 332                                 && definitive_tactic(
 333                                     &list_items[num_args_before + 1..],
 334                                     ListTactic::HorizontalVertical,
 335                                     Separator::Comma,
 336                                     self.nested_shape.width,
 337                                 )
 338                                     == DefinitiveListTactic::Horizontal;
 339
 340                             if one_line {
 341                                 tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
 342                             };
 343                         } else if is_every_expr_simple(self.items) && no_long_items(list_items) {
 344                             tactic = DefinitiveListTactic::Mixed;
 345                         }
 346                     }
 347                 }
 348             }
 349             _ => (),
 350         }
 351
 352         tactic
 353     }
 354
 355     fn rewrite_items(&self) -> Option<(bool, String)> {
 356         let span = self.items_span();
 357         let items = itemize_list(
 358             self.context.snippet_provider,
 359             self.items.iter(),
 360             self.suffix,
 361             ",",
 362             |item| item.span().lo(),
 363             |item| item.span().hi(),
 364             |item| item.rewrite(self.context, self.nested_shape),
 365             span.lo(),
 366             span.hi(),
 367             true,
 368         );
 369         let mut list_items: Vec<_> = items.collect();
 370
 371         // Try letting the last argument overflow to the next line with block
 372         // indentation. If its first line fits on one line with the other arguments,
 373         // we format the function arguments horizontally.
 374         let tactic = self.try_overflow_last_item(&mut list_items);
 375
 376         let fmt = ListFormatting {
 377             tactic,
 378             separator: ",",
 379             trailing_separator: if let Some(tactic) = self.force_separator_tactic {
 380                 tactic
 381             } else if !self.context.use_block_indent() {
 382                 SeparatorTactic::Never
 383             } else if tactic == DefinitiveListTactic::Mixed {
 384                 // We are using mixed layout because everything did not fit within a single line.
 385                 SeparatorTactic::Always
 386             } else {
 387                 self.context.config.trailing_comma()
 388             },
 389             separator_place: SeparatorPlace::Back,
 390             shape: self.nested_shape,
 391             ends_with_newline: match tactic {
 392                 DefinitiveListTactic::Vertical | DefinitiveListTactic::Mixed => {
 393                     self.context.use_block_indent()
 394                 }
 395                 _ => false,
 396             },
 397             preserve_newline: false,
 398             config: self.context.config,
 399         };
 400
 401         write_list(&list_items, &fmt)
 402             .map(|items_str| (tactic == DefinitiveListTactic::Horizontal, items_str))
 403     }
 404
 405     fn wrap_items(&self, items_str: &str, shape: Shape, is_extendable: bool) -> String {
 406         let shape = Shape {
 407             width: shape
 408                 .width
 409                 .checked_sub(last_line_width(self.ident))
 410                 .unwrap_or(0),
 411             ..shape
 412         };
 413
 414         let (prefix, suffix) = match self.custom_delims {
 415             Some((lhs, rhs)) => (lhs, rhs),
 416             _ => (self.prefix, self.suffix),
 417         };
 418         let paren_overhead = paren_overhead(self.context);
 419         let fits_one_line = items_str.len() + paren_overhead <= shape.width;
 420         let extend_width = if items_str.is_empty() {
 421             paren_overhead
 422         } else {
 423             paren_overhead / 2
 424         };
 425         let nested_indent_str = self.nested_shape
 426             .indent
 427             .to_string_with_newline(self.context.config);
 428         let indent_str = shape
 429             .block()
 430             .indent
 431             .to_string_with_newline(self.context.config);
 432         let mut result = String::with_capacity(
 433             self.ident.len() + items_str.len() + 2 + indent_str.len() + nested_indent_str.len(),
 434         );
 435         result.push_str(self.ident);
 436         result.push_str(prefix);
 437         if !self.context.use_block_indent()
 438             || (self.context.inside_macro() && !items_str.contains('\n') && fits_one_line)
 439             || (is_extendable && extend_width <= shape.width)
 440         {
 441             if self.context.config.spaces_within_parens_and_brackets() && !items_str.is_empty() {
 442                 result.push(' ');
 443                 result.push_str(items_str);
 444                 result.push(' ');
 445             } else {
 446                 result.push_str(items_str);
 447             }
 448         } else {
 449             if !items_str.is_empty() {
 450                 result.push_str(&nested_indent_str);
 451                 result.push_str(items_str);
 452             }
 453             result.push_str(&indent_str);
 454         }
 455         result.push_str(suffix);
 456         result
 457     }
 458
 459     fn rewrite(&self, shape: Shape) -> Option<String> {
 460         let (extendable, items_str) = self.rewrite_items()?;
 461
 462         // If we are using visual indent style and failed to format, retry with block indent.
 463         if !self.context.use_block_indent() && need_block_indent(&items_str, self.nested_shape)
 464             && !extendable
 465         {
 466             self.context.use_block.replace(true);
 467             let result = self.rewrite(shape);
 468             self.context.use_block.replace(false);
 469             return result;
 470         }
 471
 472         Some(self.wrap_items(&items_str, shape, extendable))
 473     }
 474 }
 475
 476 fn need_block_indent(s: &str, shape: Shape) -> bool {
 477     s.lines().skip(1).any(|s| {
 478         s.find(|c| !char::is_whitespace(c))
 479             .map_or(false, |w| w + 1 < shape.indent.width())
 480     })
 481 }
 482
 483 fn can_be_overflowed<'a, T>(context: &RewriteContext, items: &[&T]) -> bool
 484 where
 485     T: Rewrite + Spanned + ToExpr + 'a,
 486 {
 487     items
 488         .last()
 489         .map_or(false, |x| x.can_be_overflowed(context, items.len()))
 490 }
 491
 492 /// Returns a shape for the last argument which is going to be overflowed.
 493 fn last_item_shape<T>(
 494     lists: &[&T],
 495     items: &[ListItem],
 496     shape: Shape,
 497     args_max_width: usize,
 498 ) -> Option<Shape>
 499 where
 500     T: Rewrite + Spanned + ToExpr,
 501 {
 502     let is_nested_call = lists
 503         .iter()
 504         .next()
 505         .and_then(|item| item.to_expr())
 506         .map_or(false, is_nested_call);
 507     if items.len() == 1 && !is_nested_call {
 508         return Some(shape);
 509     }
 510     let offset = items.iter().rev().skip(1).fold(0, |acc, i| {
 511         // 2 = ", "
 512         acc + 2 + i.inner_as_ref().len()
 513     });
 514     Shape {
 515         width: min(args_max_width, shape.width),
 516         ..shape
 517     }.offset_left(offset)
 518 }
 519
 520 fn shape_from_indent_style(
 521     context: &RewriteContext,
 522     shape: Shape,
 523     overhead: usize,
 524     offset: usize,
 525 ) -> Shape {
 526     if context.use_block_indent() {
 527         // 1 = ","
 528         shape
 529             .block()
 530             .block_indent(context.config.tab_spaces())
 531             .with_max_width(context.config)
 532             .sub_width(1)
 533             .unwrap()
 534     } else {
 535         let shape = shape.visual_indent(offset);
 536         if let Some(shape) = shape.sub_width(overhead) {
 537             shape
 538         } else {
 539             Shape { width: 0, ..shape }
 540         }
 541     }
 542 }
 543
 544 fn no_long_items(list: &[ListItem]) -> bool {
 545     list.iter()
 546         .all(|item| !item.has_comment() && item.inner_as_ref().len() <= SHORT_ITEM_THRESHOLD)
 547 }