src/imports.rs

   1 // Copyright 2015 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 use visitor::FmtVisitor;
  12 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic, ListTactic};
  13 use utils::{span_after, format_visibility};
  14
  15 use syntax::ast;
  16 use syntax::parse::token;
  17 use syntax::print::pprust;
  18 use syntax::codemap::Span;
  19
  20 // TODO (some day) remove unused imports, expand globs, compress many single imports into a list import
  21
  22 fn rewrite_single_use_list(path_str: String, vpi: ast::PathListItem, vis: &str) -> String {
  23     if let ast::PathListItem_::PathListIdent{ name, .. } = vpi.node {
  24         let name_str = token::get_ident(name).to_string();
  25         if path_str.len() == 0 {
  26             format!("{}use {};", vis, name_str)
  27         } else {
  28             format!("{}use {}::{};", vis, path_str, name_str)
  29         }
  30     } else {
  31         if path_str.len() != 0 {
  32             format!("{}use {};", vis, path_str)
  33         } else {
  34             // This catches the import: use {self}, which is a compiler error, so we just
  35             // leave it alone.
  36             format!("{}use {{self}};", vis)
  37         }
  38     }
  39 }
  40
  41 impl<'a> FmtVisitor<'a> {
  42     // Basically just pretty prints a multi-item import.
  43     // Returns None when the import can be removed.
  44     pub fn rewrite_use_list(&self,
  45                             block_indent: usize,
  46                             one_line_budget: usize, // excluding indentation
  47                             multi_line_budget: usize,
  48                             path: &ast::Path,
  49                             path_list: &[ast::PathListItem],
  50                             visibility: ast::Visibility,
  51                             span: Span)
  52                             -> Option<String> {
  53         let path_str = pprust::path_to_string(path);
  54         let vis = format_visibility(visibility);
  55
  56         match path_list.len() {
  57             0 => return None,
  58             1 => return Some(rewrite_single_use_list(path_str, path_list[0], vis)),
  59             _ => ()
  60         }
  61
  62         // 2 = ::
  63         let path_separation_w = if path_str.len() > 0 { 2 } else { 0 };
  64         // 5 = "use " + {
  65         let indent = path_str.len() + 5 + path_separation_w + vis.len();
  66
  67         // 2 = } + ;
  68         let used_width = indent + 2;
  69
  70         // Break as early as possible when we've blown our budget.
  71         let remaining_line_budget = one_line_budget.checked_sub(used_width).unwrap_or(0);
  72         let remaining_multi_budget = multi_line_budget.checked_sub(used_width).unwrap_or(0);
  73
  74         let fmt = ListFormatting {
  75             tactic: ListTactic::Mixed,
  76             separator: ",",
  77             trailing_separator: SeparatorTactic::Never,
  78             indent: block_indent + indent,
  79             h_width: remaining_line_budget,
  80             v_width: remaining_multi_budget,
  81             ends_with_newline: true,
  82         };
  83
  84         let mut items = itemize_list(self.codemap,
  85                                      vec![ListItem::from_str("")], /* Dummy value, explanation
  86                                                                     * below */
  87                                      path_list.iter(),
  88                                      ",",
  89                                      "}",
  90                                      |vpi| vpi.span.lo,
  91                                      |vpi| vpi.span.hi,
  92                                      |vpi| match vpi.node {
  93                                          ast::PathListItem_::PathListIdent{ name, .. } => {
  94                                              token::get_ident(name).to_string()
  95                                          }
  96                                          ast::PathListItem_::PathListMod{ .. } => {
  97                                              "self".to_owned()
  98                                          }
  99                                      },
 100                                      span_after(span, "{", self.codemap),
 101                                      span.hi);
 102
 103         // We prefixed the item list with a dummy value so that we can
 104         // potentially move "self" to the front of the vector without touching
 105         // the rest of the items.
 106         // FIXME: Make more efficient by using a linked list? That would
 107         // require changes to the signatures of itemize_list and write_list.
 108         let has_self = move_self_to_front(&mut items);
 109         let first_index = if has_self { 0 } else { 1 };
 110
 111         if self.config.reorder_imports {
 112             items[1..].sort_by(|a, b| a.item.cmp(&b.item));
 113         }
 114
 115         let list = write_list(&items[first_index..], &fmt);
 116
 117         Some(if path_str.len() == 0 {
 118             format!("{}use {{{}}};", vis, list)
 119         } else {
 120             format!("{}use {}::{{{}}};", vis, path_str, list)
 121         })
 122     }
 123 }
 124
 125 // Returns true when self item was found.
 126 fn move_self_to_front(items: &mut Vec<ListItem>) -> bool {
 127     match items.iter().position(|item| item.item == "self") {
 128         Some(pos) => {
 129             items[0] = items.remove(pos);
 130             true
 131         },
 132         None => false
 133     }
 134 }