1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use crate::observer::{error_proxy_impl, is_stopped_proxy_impl};
use crate::prelude::*;
use observable::observable_proxy_impl;

#[derive(Clone)]
pub struct DefaultIfEmptyOp<S>
where
  S: Observable,
{
  pub(crate) source: S,
  pub(crate) is_empty: bool,
  pub(crate) default_value: S::Item,
}

#[doc(hidden)]
macro observable_impl($subscription:ty, $($marker:ident +)* $lf: lifetime) {
  fn actual_subscribe<O: Observer<Self::Item, Self::Err> + $($marker +)* $lf>(
    self,
    subscriber: Subscriber<O, $subscription>,
  ) -> Self::Unsub {
    let subscriber = Subscriber {
      observer: DefaultIfEmptyObserver {
        observer: subscriber.observer,
        is_empty: self.is_empty,
        default_value: self.default_value,
      },
      subscription: subscriber.subscription,
    };
    self.source.actual_subscribe(subscriber)
  }
}

observable_proxy_impl!(DefaultIfEmptyOp, S);

impl<'a, S> LocalObservable<'a> for DefaultIfEmptyOp<S>
where
  S: LocalObservable<'a>,
  S::Item: Clone + 'a,
{
  type Unsub = S::Unsub;
  observable_impl!(LocalSubscription, 'a);
}

impl<S> SharedObservable for DefaultIfEmptyOp<S>
where
  S: SharedObservable,
  S::Item: Clone + Send + Sync + 'static,
{
  type Unsub = S::Unsub;
  observable_impl!(SharedSubscription, Send + Sync + 'static);
}

pub struct DefaultIfEmptyObserver<O, Item> {
  observer: O,
  is_empty: bool,
  default_value: Item,
}

impl<Item, Err, O> Observer<Item, Err> for DefaultIfEmptyObserver<O, Item>
where
  O: Observer<Item, Err>,
  Item: Clone,
{
  fn next(&mut self, value: Item) {
    self.observer.next(value);
    if self.is_empty {
      self.is_empty = false;
    }
  }

  fn complete(&mut self) {
    if self.is_empty {
      self.observer.next(self.default_value.clone());
    }
    self.observer.complete()
  }

  error_proxy_impl!(Err, observer);

  is_stopped_proxy_impl!(observer);
}

#[cfg(test)]
mod test {
  use crate::prelude::*;

  #[test]
  fn base_function() {
    let mut completed = false;
    let mut value = 0;

    observable::of(10)
      .default_if_empty(5)
      .subscribe_complete(|v| value = v, || completed = true);

    assert_eq!(value, 10);
    assert_eq!(completed, true);
  }

  #[test]
  fn base_empty_function() {
    let mut completed = false;
    let mut value = 0;

    observable::empty()
      .default_if_empty(5)
      .subscribe_complete(|v| value = v, || completed = true);

    assert_eq!(value, 5);
    assert_eq!(completed, true);
  }

  #[test]
  fn into_shared() {
    observable::from_iter(0..100)
      .default_if_empty(5)
      .to_shared()
      .subscribe(|_| {});
  }

  #[test]
  fn into_shared_empty() {
    observable::empty()
      .default_if_empty(5)
      .to_shared()
      .subscribe(|_| {});
  }
}