smart_format/combinator/
conditional.rs

1use core::fmt;
2
3/// Conditionally displays a value. If the condition is false, writes nothing.
4pub struct If<T> {
5    inner: T,
6    condition: bool,
7}
8
9impl<T> If<T> {
10    pub(crate) fn new(inner: T, condition: bool) -> Self {
11        If { inner, condition }
12    }
13}
14
15impl<T: fmt::Display> fmt::Display for If<T> {
16    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
17        if self.condition {
18            self.inner.fmt(f)
19        } else {
20            Ok(())
21        }
22    }
23}
24
25/// Chooses between two values based on a condition.
26/// If `use_fallback` is false, displays `inner`; otherwise displays `fallback`.
27pub struct Or<T, U> {
28    inner: T,
29    use_fallback: bool,
30    fallback: U,
31}
32
33impl<T, U> Or<T, U> {
34    pub(crate) fn new(inner: T, use_fallback: bool, fallback: U) -> Self {
35        Or {
36            inner,
37            use_fallback,
38            fallback,
39        }
40    }
41}
42
43impl<T: fmt::Display, U: fmt::Display> fmt::Display for Or<T, U> {
44    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
45        if self.use_fallback {
46            self.fallback.fmt(f)
47        } else {
48            self.inner.fmt(f)
49        }
50    }
51}
52
53#[cfg(test)]
54mod tests {
55    use crate::combinator::SmartFormat;
56
57    #[test]
58    fn if_true_displays() {
59        assert_eq!("hello", "hello".display_if(true).to_string());
60    }
61
62    #[test]
63    fn if_false_is_empty() {
64        assert_eq!("", "hello".display_if(false).to_string());
65    }
66
67    #[test]
68    fn if_chain_with_wrap() {
69        let result = "hello".display_if(true).display_wrap("[", "]").to_string();
70        assert_eq!("[hello]", result);
71    }
72
73    #[test]
74    fn if_false_chain_with_wrap() {
75        let result = "hello".display_if(false).display_wrap("[", "]").to_string();
76        assert_eq!("[]", result);
77    }
78
79    #[test]
80    fn or_uses_self() {
81        assert_eq!(
82            "hello",
83            "hello".display_or_if(false, "fallback").to_string()
84        );
85    }
86
87    #[test]
88    fn or_uses_fallback() {
89        assert_eq!(
90            "fallback",
91            "hello".display_or_if(true, "fallback").to_string()
92        );
93    }
94
95    #[test]
96    fn or_with_different_types() {
97        let n: i32 = 42;
98        assert_eq!("42", n.display_or_if(false, "N/A").to_string());
99        assert_eq!("N/A", n.display_or_if(true, "N/A").to_string());
100    }
101}
smart_format/combinator/conditional.rs

smart_format/combinator/
conditional.rs
