mkenv 1.0.2

Lightweight yet useful library to help you define the environment your app needs
Documentation 
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

use std::fmt;

use crate::descriptor::ConfigValueDescriptor;

/// Represents types able to read a value from the process environment.
#[cfg_attr(feature = "nightly", doc(notable_trait))]
pub trait Layer {
    /// The type of the read output.
    type Output;
    /// The type of the error.
    type Error;

    /// Reads and returns the value from the environment, or returns an error.
    fn try_get(&self) -> Result<Self::Output, Self::Error>;

    /// Reads and returns the value from the environment, or panics on error.
    ///
    /// # Panics
    ///
    /// This function panics if it couldn't read the value from the environment, by printing
    /// a formatted message about the variable that failed.
    fn get(&self) -> Self::Output
    where
        Self: ConfigValueDescriptor,
        Self::Error: fmt::Display,
    {
        self.try_get().unwrap_or_else(|e| {
            let val_config = <Self as ConfigValueDescriptor>::get_descriptor(self);
            panic!(
                "couldn't get env var `{}` (expected type `{}`): {e}",
                val_config.var_name,
                std::any::type_name::<Self::Output>(),
            );
        })
    }
}

impl<T: Layer> Layer for &T {
    type Output = <T as Layer>::Output;
    type Error = <T as Layer>::Error;

    fn try_get(&self) -> Result<Self::Output, Self::Error> {
        <T as Layer>::try_get(self)
    }
}