src/cargo/macros.rs

   1 use std::fmt;
   2
   3 macro_rules! compact_debug {
   4     (
   5         impl fmt::Debug for $ty:ident {
   6             fn fmt(&$this:ident, f: &mut fmt::Formatter) -> fmt::Result {
   7                 let (default, default_name) = $e:expr;
   8                 [debug_the_fields($($field:ident)*)]
   9             }
  10         }
  11     ) => (
  12
  13         impl fmt::Debug for $ty {
  14             fn fmt(&$this, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  15                 // Try printing a pretty version where we collapse as many fields as
  16                 // possible, indicating that they're equivalent to a function call
  17                 // that's hopefully enough to indicate what each value is without
  18                 // actually dumping everything so verbosely.
  19                 let mut s = f.debug_struct(stringify!($ty));
  20                 let (default, default_name) = $e;
  21                 let mut any_default = false;
  22
  23                 // Exhaustively match so when fields are added we get a compile
  24                 // failure
  25                 let $ty { $($field),* } = $this;
  26                 $(
  27                     if *$field == default.$field {
  28                         any_default = true;
  29                     } else {
  30                         s.field(stringify!($field), $field);
  31                     }
  32                 )*
  33
  34                 if any_default {
  35                     s.field("..", &crate::macros::DisplayAsDebug(default_name));
  36                 }
  37                 s.finish()
  38             }
  39         }
  40     )
  41 }
  42
  43 pub struct DisplayAsDebug<T>(pub T);
  44
  45 impl<T: fmt::Display> fmt::Debug for DisplayAsDebug<T> {
  46     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  47         fmt::Display::fmt(&self.0, f)
  48     }
  49 }