rust_decouple/
core.rs

1use std::{env, fmt::Display, str::FromStr};
2
3pub struct Environment;
4pub struct VecEnvironment;
5
6#[derive(Debug, PartialEq)]
7pub enum FromEnvironmentError {
8    VariableNotFoundError(String),
9    ParseVariableError(String, String),
10}
11
12impl Display for FromEnvironmentError {
13    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
14        match self {
15            Self::VariableNotFoundError(v) => write!(f, "Couldn't find variable `{}`", v),
16            Self::ParseVariableError(variable, value) => {
17                write!(f, "Couldn't parse `{}` from value: '{}'", variable, value)
18            }
19        }
20    }
21}
22
23impl Environment {
24    /// Retrieve the environment variable parsed as `T`
25    /// Panic if variable is not found and default value is not provided
26    pub fn from<T: FromStr>(var_name: &str, default: Option<T>) -> Result<T, FromEnvironmentError> {
27        let value = env::var(var_name);
28        if value.is_err() && default.is_none() {
29            return Err(FromEnvironmentError::VariableNotFoundError(
30                var_name.to_string(),
31            ));
32        } else if let Some(default_value) = default {
33            return Ok(default_value);
34        }
35
36        let value = value.unwrap();
37        T::from_str(value.as_ref())
38            .map_err(|_| FromEnvironmentError::ParseVariableError(var_name.to_string(), value))
39    }
40}
41
42impl VecEnvironment {
43    pub fn from<T: FromStr>(
44        var_name: &str,
45        default: Option<Vec<T>>,
46    ) -> Result<Vec<T>, FromEnvironmentError> {
47        let value = env::var(var_name);
48        if value.is_err() && default.is_none() {
49            return Err(FromEnvironmentError::VariableNotFoundError(
50                var_name.to_string(),
51            ));
52        } else if let Some(default_value) = default {
53            return Ok(default_value);
54        }
55
56        let value = value.unwrap();
57        value
58            .split(",")
59            .map(T::from_str)
60            .collect::<Result<Vec<T>, _>>()
61            .map_err(|_| FromEnvironmentError::ParseVariableError(var_name.to_string(), value))
62    }
63}
64
65#[cfg(test)]
66mod tests {
67    use std::env;
68
69    use crate::core::{Environment, FromEnvironmentError, VecEnvironment};
70
71    #[test]
72    fn parse_env_var_u8_correctly() {
73        env::set_var("RIGHT_VALUE", "123");
74        let result: Result<u8, _> = Environment::from("RIGHT_VALUE", None);
75        assert_eq!(result.unwrap(), 123);
76    }
77
78    #[test]
79    fn parse_env_var_f64_correctly() {
80        env::set_var("RIGHT_F64_VALUE", "12.345");
81        let result: Result<f64, _> = Environment::from("RIGHT_F64_VALUE", None);
82        assert_eq!(result.unwrap(), 12.345)
83    }
84
85    #[test]
86    fn parse_not_set_env_var_with_default_value_correctly() {
87        env::remove_var("NOT_SET_VALUE");
88        let result: Result<u8, _> = Environment::from("NOT_SET_VALUE", Some(42));
89        assert_eq!(result.unwrap(), 42);
90    }
91
92    #[test]
93    fn parse_not_set_env_var_with_no_default_value_panics() {
94        env::remove_var("NOT_SET_VALUE_2");
95        let result = Environment::from::<u8>("NOT_SET_VALUE_2", None);
96        assert!(result.is_err_and(
97            |e| e == FromEnvironmentError::VariableNotFoundError("NOT_SET_VALUE_2".to_string())
98        ))
99    }
100
101    #[test]
102    fn parse_wrong_typed_value_panics() {
103        env::set_var("WRONG_TYPED_VALUE", "12r3");
104        let result = Environment::from::<u8>("WRONG_TYPED_VALUE", None);
105        assert!(result.is_err_and(|e| e
106            == FromEnvironmentError::ParseVariableError(
107                "WRONG_TYPED_VALUE".to_string(),
108                "12r3".to_string()
109            )))
110    }
111
112    #[test]
113    fn parse_vec_of_string_values_correctly() {
114        env::set_var("VEC_STRING_VAL", "hello,world");
115        let result: Vec<String> = VecEnvironment::from("VEC_STRING_VAL", None).unwrap();
116        assert_eq!(result, vec!["hello", "world"]);
117    }
118
119    #[test]
120    fn parse_vec_of_usize_correctly() {
121        env::set_var("VEC_USIZE_VAR", "0,1,2,3,4,5");
122        let result: Vec<usize> = VecEnvironment::from("VEC_USIZE_VAR", None).unwrap();
123        assert_eq!(result, vec![0, 1, 2, 3, 4, 5]);
124    }
125
126    #[test]
127    fn parse_not_set_vec_of_u8_with_default_value_correctly() {
128        env::remove_var("VEC_U8_WITH_DEFAULT");
129        let result = VecEnvironment::from("VEC_U8_WITH_DEFAULT", Some(vec![5u8, 42])).unwrap();
130        assert_eq!(result, vec![5, 42]);
131    }
132}
rust_decouple/core.rs

rust_decouple/
core.rs
