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::{
  27     count_newlines, extra_offset, first_line_width, last_line_width, mk_sp, paren_overhead,
  28 };
  29
  30 use std::cmp::min;
  31
  32 const SHORT_ITEM_THRESHOLD: usize = 10;
  33
  34 pub fn rewrite_with_parens<T>(
  35     context: &RewriteContext,
  36     ident: &str,
  37     items: &[&T],
  38     shape: Shape,
  39     span: Span,
  40     item_max_width: usize,
  41     force_separator_tactic: Option<SeparatorTactic>,
  42 ) -> Option<String>
  43 where
  44     T: Rewrite + ToExpr + Spanned,
  45 {
  46     Context::new(
  47         context,
  48         items,
  49         ident,
  50         shape,
  51         span,
  52         "(",
  53         ")",
  54         item_max_width,
  55         force_separator_tactic,
  56         None,
  57     ).rewrite(shape)
  58 }
  59
  60 pub fn rewrite_with_angle_brackets<T>(
  61     context: &RewriteContext,
  62     ident: &str,
  63     items: &[&T],
  64     shape: Shape,
  65     span: Span,
  66 ) -> Option<String>
  67 where
  68     T: Rewrite + ToExpr + Spanned,
  69 {
  70     Context::new(
  71         context,
  72         items,
  73         ident,
  74         shape,
  75         span,
  76         "<",
  77         ">",
  78         context.config.max_width(),
  79         None,
  80         None,
  81     ).rewrite(shape)
  82 }
  83
  84 pub fn rewrite_with_square_brackets<T>(
  85     context: &RewriteContext,
  86     name: &str,
  87     items: &[&T],
  88     shape: Shape,
  89     span: Span,
  90     force_separator_tactic: Option<SeparatorTactic>,
  91     delim_token: Option<DelimToken>,
  92 ) -> Option<String>
  93 where
  94     T: Rewrite + ToExpr + Spanned,
  95 {
  96     let (lhs, rhs) = match delim_token {
  97         Some(DelimToken::Paren) => ("(", ")"),
  98         Some(DelimToken::Brace) => ("{", "}"),
  99         _ => ("[", "]"),
 100     };
 101     Context::new(
 102         context,
 103         items,
 104         name,
 105         shape,
 106         span,
 107         lhs,
 108         rhs,
 109         context.config.width_heuristics().array_width,
 110         force_separator_tactic,
 111         Some(("[", "]")),
 112     ).rewrite(shape)
 113 }
 114
 115 struct Context<'a, T: 'a> {
 116     context: &'a RewriteContext<'a>,
 117     items: &'a [&'a T],
 118     ident: &'a str,
 119     prefix: &'static str,
 120     suffix: &'static str,
 121     one_line_shape: Shape,
 122     nested_shape: Shape,
 123     span: Span,
 124     item_max_width: usize,
 125     one_line_width: usize,
 126     force_separator_tactic: Option<SeparatorTactic>,
 127     custom_delims: Option<(&'a str, &'a str)>,
 128 }
 129
 130 impl<'a, T: 'a + Rewrite + ToExpr + Spanned> Context<'a, T> {
 131     pub fn new(
 132         context: &'a RewriteContext,
 133         items: &'a [&'a T],
 134         ident: &'a str,
 135         shape: Shape,
 136         span: Span,
 137         prefix: &'static str,
 138         suffix: &'static str,
 139         item_max_width: usize,
 140         force_separator_tactic: Option<SeparatorTactic>,
 141         custom_delims: Option<(&'a str, &'a str)>,
 142     ) -> Context<'a, T> {
 143         // 2 = `( `, 1 = `(`
 144         let paren_overhead = if context.config.spaces_within_parens_and_brackets() {
 145             2
 146         } else {
 147             1
 148         };
 149         let used_width = extra_offset(ident, shape);
 150         let one_line_width = shape
 151             .width
 152             .checked_sub(used_width + 2 * paren_overhead)
 153             .unwrap_or(0);
 154
 155         // 1 = "(" or ")"
 156         let one_line_shape = shape
 157             .offset_left(last_line_width(ident) + 1)
 158             .and_then(|shape| shape.sub_width(1))
 159             .unwrap_or(Shape { width: 0, ..shape });
 160         let nested_shape = shape_from_indent_style(
 161             context,
 162             shape,
 163             used_width + 2 * paren_overhead,
 164             used_width + paren_overhead,
 165         );
 166         Context {
 167             context,
 168             items,
 169             ident,
 170             one_line_shape,
 171             nested_shape,
 172             span,
 173             prefix,
 174             suffix,
 175             item_max_width,
 176             one_line_width,
 177             force_separator_tactic,
 178             custom_delims,
 179         }
 180     }
 181
 182     fn last_item(&self) -> Option<&&T> {
 183         self.items.last()
 184     }
 185
 186     fn items_span(&self) -> Span {
 187         let span_lo = self.context
 188             .snippet_provider
 189             .span_after(self.span, self.prefix);
 190         mk_sp(span_lo, self.span.hi())
 191     }
 192
 193     fn rewrite_last_item_with_overflow(
 194         &self,
 195         last_list_item: &mut ListItem,
 196         shape: Shape,
 197     ) -> Option<String> {
 198         let last_item = self.last_item()?;
 199         let rewrite = if let Some(expr) = last_item.to_expr() {
 200             match expr.node {
 201                 // When overflowing the closure which consists of a single control flow expression,
 202                 // force to use block if its condition uses multi line.
 203                 ast::ExprKind::Closure(..) => {
 204                     // If the argument consists of multiple closures, we do not overflow
 205                     // the last closure.
 206                     if closures::args_have_many_closure(self.items) {
 207                         None
 208                     } else {
 209                         closures::rewrite_last_closure(self.context, expr, shape)
 210                     }
 211                 }
 212                 _ => expr.rewrite(self.context, shape),
 213             }
 214         } else {
 215             last_item.rewrite(self.context, shape)
 216         };
 217
 218         if let Some(rewrite) = rewrite {
 219             let rewrite_first_line = Some(rewrite[..first_line_width(&rewrite)].to_owned());
 220             last_list_item.item = rewrite_first_line;
 221             Some(rewrite)
 222         } else {
 223             None
 224         }
 225     }
 226
 227     fn default_tactic(&self, list_items: &[ListItem]) -> DefinitiveListTactic {
 228         definitive_tactic(
 229             list_items,
 230             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 231             Separator::Comma,
 232             self.one_line_width,
 233         )
 234     }
 235
 236     fn try_overflow_last_item(&self, list_items: &mut Vec<ListItem>) -> DefinitiveListTactic {
 237         // 1 = "("
 238         let combine_arg_with_callee = self.items.len() == 1 && self.items[0].to_expr().is_some()
 239             && self.ident.len() + 1 <= self.context.config.tab_spaces();
 240         let overflow_last = combine_arg_with_callee || can_be_overflowed(self.context, self.items);
 241
 242         // Replace the last item with its first line to see if it fits with
 243         // first arguments.
 244         let placeholder = if overflow_last {
 245             let old_value = *self.context.force_one_line_chain.borrow();
 246             if !combine_arg_with_callee {
 247                 if let Some(expr) = self.last_item().and_then(|item| item.to_expr()) {
 248                     if let ast::ExprKind::MethodCall(..) = expr.node {
 249                         self.context.force_one_line_chain.replace(true);
 250                     }
 251                 }
 252             }
 253             let result = last_item_shape(
 254                 self.items,
 255                 list_items,
 256                 self.one_line_shape,
 257                 self.item_max_width,
 258             ).and_then(|arg_shape| {
 259                 self.rewrite_last_item_with_overflow(
 260                     &mut list_items[self.items.len() - 1],
 261                     arg_shape,
 262                 )
 263             });
 264             self.context.force_one_line_chain.replace(old_value);
 265             result
 266         } else {
 267             None
 268         };
 269
 270         let mut tactic = definitive_tactic(
 271             &*list_items,
 272             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 273             Separator::Comma,
 274             self.one_line_width,
 275         );
 276
 277         // Replace the stub with the full overflowing last argument if the rewrite
 278         // succeeded and its first line fits with the other arguments.
 279         match (overflow_last, tactic, placeholder) {
 280             (true, DefinitiveListTactic::Horizontal, Some(ref overflowed))
 281                 if self.items.len() == 1 =>
 282             {
 283                 // When we are rewriting a nested function call, we restrict the
 284                 // budget for the inner function to avoid them being deeply nested.
 285                 // However, when the inner function has a prefix or a suffix
 286                 // (e.g. `foo() as u32`), this budget reduction may produce poorly
 287                 // formatted code, where a prefix or a suffix being left on its own
 288                 // line. Here we explicitlly check those cases.
 289                 if count_newlines(overflowed) == 1 {
 290                     let rw = self.items
 291                         .last()
 292                         .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 293                     let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
 294                     if no_newline {
 295                         list_items[self.items.len() - 1].item = rw;
 296                     } else {
 297                         list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 298                     }
 299                 } else {
 300                     list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 301                 }
 302             }
 303             (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
 304                 list_items[self.items.len() - 1].item = placeholder;
 305             }
 306             _ if self.items.len() >= 1 => {
 307                 list_items[self.items.len() - 1].item = self.items
 308                     .last()
 309                     .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 310
 311                 // Use horizontal layout for a function with a single argument as long as
 312                 // everything fits in a single line.
 313                 // `self.one_line_width == 0` means vertical layout is forced.
 314                 if self.items.len() == 1 && self.one_line_width != 0 && !list_items[0].has_comment()
 315                     && !list_items[0].inner_as_ref().contains('\n')
 316                     && ::lists::total_item_width(&list_items[0]) <= self.one_line_width
 317                 {
 318                     tactic = DefinitiveListTactic::Horizontal;
 319                 } else {
 320                     tactic = self.default_tactic(list_items);
 321
 322                     if tactic == DefinitiveListTactic::Vertical {
 323                         if let Some((all_simple, num_args_before)) =
 324                             maybe_get_args_offset(self.ident, self.items)
 325                         {
 326                             let one_line = all_simple
 327                                 && definitive_tactic(
 328                                     &list_items[..num_args_before],
 329                                     ListTactic::HorizontalVertical,
 330                                     Separator::Comma,
 331                                     self.nested_shape.width,
 332                                 )
 333                                     == DefinitiveListTactic::Horizontal
 334                                 && definitive_tactic(
 335                                     &list_items[num_args_before + 1..],
 336                                     ListTactic::HorizontalVertical,
 337                                     Separator::Comma,
 338                                     self.nested_shape.width,
 339                                 )
 340                                     == DefinitiveListTactic::Horizontal;
 341
 342                             if one_line {
 343                                 tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
 344                             };
 345                         } else if is_every_expr_simple(self.items) && no_long_items(list_items) {
 346                             tactic = DefinitiveListTactic::Mixed;
 347                         }
 348                     }
 349                 }
 350             }
 351             _ => (),
 352         }
 353
 354         tactic
 355     }
 356
 357     fn rewrite_items(&self) -> Option<(bool, String)> {
 358         let span = self.items_span();
 359         let items = itemize_list(
 360             self.context.snippet_provider,
 361             self.items.iter(),
 362             self.suffix,
 363             ",",
 364             |item| item.span().lo(),
 365             |item| item.span().hi(),
 366             |item| item.rewrite(self.context, self.nested_shape),
 367             span.lo(),
 368             span.hi(),
 369             true,
 370         );
 371         let mut list_items: Vec<_> = items.collect();
 372
 373         // Try letting the last argument overflow to the next line with block
 374         // indentation. If its first line fits on one line with the other arguments,
 375         // we format the function arguments horizontally.
 376         let tactic = self.try_overflow_last_item(&mut list_items);
 377
 378         let fmt = ListFormatting {
 379             tactic,
 380             separator: ",",
 381             trailing_separator: if let Some(tactic) = self.force_separator_tactic {
 382                 tactic
 383             } else if !self.context.use_block_indent() {
 384                 SeparatorTactic::Never
 385             } else if tactic == DefinitiveListTactic::Mixed {
 386                 // We are using mixed layout because everything did not fit within a single line.
 387                 SeparatorTactic::Always
 388             } else {
 389                 self.context.config.trailing_comma()
 390             },
 391             separator_place: SeparatorPlace::Back,
 392             shape: self.nested_shape,
 393             ends_with_newline: match tactic {
 394                 DefinitiveListTactic::Vertical | DefinitiveListTactic::Mixed => {
 395                     self.context.use_block_indent()
 396                 }
 397                 _ => false,
 398             },
 399             preserve_newline: false,
 400             config: self.context.config,
 401         };
 402
 403         write_list(&list_items, &fmt)
 404             .map(|items_str| (tactic == DefinitiveListTactic::Horizontal, items_str))
 405     }
 406
 407     fn wrap_items(&self, items_str: &str, shape: Shape, is_extendable: bool) -> String {
 408         let shape = Shape {
 409             width: shape
 410                 .width
 411                 .checked_sub(last_line_width(self.ident))
 412                 .unwrap_or(0),
 413             ..shape
 414         };
 415
 416         let (prefix, suffix) = match self.custom_delims {
 417             Some((lhs, rhs)) => (lhs, rhs),
 418             _ => (self.prefix, self.suffix),
 419         };
 420         let paren_overhead = paren_overhead(self.context);
 421         let fits_one_line = items_str.len() + paren_overhead <= shape.width;
 422         let extend_width = if items_str.is_empty() {
 423             paren_overhead
 424         } else {
 425             paren_overhead / 2
 426         };
 427         let nested_indent_str = self.nested_shape
 428             .indent
 429             .to_string_with_newline(self.context.config);
 430         let indent_str = shape
 431             .block()
 432             .indent
 433             .to_string_with_newline(self.context.config);
 434         let mut result = String::with_capacity(
 435             self.ident.len() + items_str.len() + 2 + indent_str.len() + nested_indent_str.len(),
 436         );
 437         result.push_str(self.ident);
 438         result.push_str(prefix);
 439         if !self.context.use_block_indent()
 440             || (self.context.inside_macro() && !items_str.contains('\n') && fits_one_line)
 441             || (is_extendable && extend_width <= shape.width)
 442         {
 443             if self.context.config.spaces_within_parens_and_brackets() && !items_str.is_empty() {
 444                 result.push(' ');
 445                 result.push_str(items_str);
 446                 result.push(' ');
 447             } else {
 448                 result.push_str(items_str);
 449             }
 450         } else {
 451             if !items_str.is_empty() {
 452                 result.push_str(&nested_indent_str);
 453                 result.push_str(items_str);
 454             }
 455             result.push_str(&indent_str);
 456         }
 457         result.push_str(suffix);
 458         result
 459     }
 460
 461     fn rewrite(&self, shape: Shape) -> Option<String> {
 462         let (extendable, items_str) = self.rewrite_items()?;
 463
 464         // If we are using visual indent style and failed to format, retry with block indent.
 465         if !self.context.use_block_indent() && need_block_indent(&items_str, self.nested_shape)
 466             && !extendable
 467         {
 468             self.context.use_block.replace(true);
 469             let result = self.rewrite(shape);
 470             self.context.use_block.replace(false);
 471             return result;
 472         }
 473
 474         Some(self.wrap_items(&items_str, shape, extendable))
 475     }
 476 }
 477
 478 fn need_block_indent(s: &str, shape: Shape) -> bool {
 479     s.lines().skip(1).any(|s| {
 480         s.find(|c| !char::is_whitespace(c))
 481             .map_or(false, |w| w + 1 < shape.indent.width())
 482     })
 483 }
 484
 485 fn can_be_overflowed<'a, T>(context: &RewriteContext, items: &[&T]) -> bool
 486 where
 487     T: Rewrite + Spanned + ToExpr + 'a,
 488 {
 489     items
 490         .last()
 491         .map_or(false, |x| x.can_be_overflowed(context, items.len()))
 492 }
 493
 494 /// Returns a shape for the last argument which is going to be overflowed.
 495 fn last_item_shape<T>(
 496     lists: &[&T],
 497     items: &[ListItem],
 498     shape: Shape,
 499     args_max_width: usize,
 500 ) -> Option<Shape>
 501 where
 502     T: Rewrite + Spanned + ToExpr,
 503 {
 504     let is_nested_call = lists
 505         .iter()
 506         .next()
 507         .and_then(|item| item.to_expr())
 508         .map_or(false, is_nested_call);
 509     if items.len() == 1 && !is_nested_call {
 510         return Some(shape);
 511     }
 512     let offset = items.iter().rev().skip(1).fold(0, |acc, i| {
 513         // 2 = ", "
 514         acc + 2 + i.inner_as_ref().len()
 515     });
 516     Shape {
 517         width: min(args_max_width, shape.width),
 518         ..shape
 519     }.offset_left(offset)
 520 }
 521
 522 fn shape_from_indent_style(
 523     context: &RewriteContext,
 524     shape: Shape,
 525     overhead: usize,
 526     offset: usize,
 527 ) -> Shape {
 528     if context.use_block_indent() {
 529         // 1 = ","
 530         shape
 531             .block()
 532             .block_indent(context.config.tab_spaces())
 533             .with_max_width(context.config)
 534             .sub_width(1)
 535             .unwrap()
 536     } else {
 537         let shape = shape.visual_indent(offset);
 538         if let Some(shape) = shape.sub_width(overhead) {
 539             shape
 540         } else {
 541             Shape { width: 0, ..shape }
 542         }
 543     }
 544 }
 545
 546 fn no_long_items(list: &[ListItem]) -> bool {
 547     list.iter()
 548         .all(|item| !item.has_comment() && item.inner_as_ref().len() <= SHORT_ITEM_THRESHOLD)
 549 }