feat: added file loader

Cargo.lock

@@ -4,4 +4,4 @@ version = 4
 
 [[package]]
 name = "envkit"
-version = "0.2.0"
+version = "0.2.1"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "envkit"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2024"
 authors = ["Darwin Cereska <discorddurr@gmail.com>"]
 description = "A dead-simple env loader"

README.md

@@ -1,74 +1,174 @@
 # envkit
 
-`envkit` is a small Rust crate for reading environment variables and converting them into typed values.
+`envkit` is a small Rust crate for reading environment variables as typed values.
 
-It keeps the API minimal:
+It provides a minimal loader API for required values, optional values, defaults,
+prefixed variable names, and simple `.env`-style files.
 
-- `EnvLoader::get` reads a required variable.
-- `EnvLoader::get_or` reads a variable with a fallback.
-- `EnvLoader::get_opt` returns `Option<T>`.
-- `with_prefix` lets you build loaders for namespaced variables like `APP_PORT` or `DB_HOST`.
+## Install
 
-## Supported types
+Add `envkit` to your `Cargo.toml`:
 
-`envkit` currently supports:
+```toml
+[dependencies]
+envkit = "0.2.1"
+```
+
+## Quick Start
+
+```rust
+use envkit::EnvLoader;
+
+fn main() -> Result<(), envkit::error::EnvError> {
+    let env = EnvLoader::new();
+
+    let port: u16 = env.get("PORT")?;
+    let debug: bool = env.get_or("DEBUG", false);
+    let app_name: String = env
+        .get_opt("APP_NAME")
+        .unwrap_or_else(|| "envkit".to_string());
+
+    println!("{app_name} listening on port {port}; debug={debug}");
+    Ok(())
+}
+```
+
+## API
+
+### `EnvLoader::get`
+
+Reads a required environment variable and parses it into the requested type.
+
+```rust
+let env = envkit::EnvLoader::new();
+let port: u16 = env.get("PORT")?;
+```
+
+Returns `EnvError::MissingVar` when the variable is not set and
+`EnvError::Invalid` when parsing fails.
+
+### `EnvLoader::get_or`
+
+Reads an environment variable and returns a fallback when the variable is
+missing or invalid.
+
+```rust
+let debug: bool = env.get_or("DEBUG", false);
+```
+
+### `EnvLoader::get_opt`
+
+Reads an environment variable and returns `None` when the variable is missing or
+invalid.
+
+```rust
+let name: Option<String> = env.get_opt("APP_NAME");
+```
+
+### `EnvLoader::with_prefix`
+
+Creates a loader that prepends a prefix to every key.
+
+```rust
+let app = env.with_prefix("APP_");
+
+let host: String = app.get("HOST")?; // reads APP_HOST
+let port: u16 = app.get_or("PORT", 8080); // reads APP_PORT
+```
+
+### `EnvLoader::load_file`
+
+Loads variables from a file with one `KEY=VALUE` pair per line.
+
+```rust
+let env = envkit::EnvLoader::new();
+env.load_file(".env")?;
+```
+
+Blank lines and lines starting with `#` are ignored. Keys and values are
+trimmed before being written into the process environment.
+
+Example file:
+
+```text
+# .env
+PORT=8080
+DEBUG=true
+APP_NAME=envkit
+```
+
+## Supported Types
+
+Built-in parsing supports:
 
 - `String`
 - `bool`
-- numeric types: `i8`, `i16`, `i32`, `i64`, `i128`, `isize`, `u8`, `u16`, `u32`, `u64`, `u128`, `usize`, `f32`, `f64`
+- signed integers: `i8`, `i16`, `i32`, `i64`, `i128`, `isize`
+- unsigned integers: `u8`, `u16`, `u32`, `u64`, `u128`, `usize`
+- floats: `f32`, `f64`
+- `Vec<T>` where `T` also implements `FromEnv`
 
-Boolean parsing accepts:
+Boolean values accept:
 
 - `true` / `false`
 - `1` / `0`
 - `t` / `f`
+- `yes` / `no`
 
-## Quick start
+Lists are comma-separated and each item is trimmed before parsing:
 
 ```rust
-use envkit::EnvLoader;
-
-fn main() -> Result<(), envkit::error::EnvError> {
-    let loader = EnvLoader;
-
-    let port: u16 = loader.get("PORT")?;
-    let debug: bool = loader.get_or("DEBUG", false);
-    let app_name: String = loader.get_opt("APP_NAME").unwrap_or_else(|| "envkit".to_string());
-
-    println!("port={port}, debug={debug}, app_name={app_name}");
-    Ok(())
-}
+let env = envkit::EnvLoader::new();
+let ports: Vec<u16> = env.get("PORTS")?;
+let flags: Vec<bool> = env.get("FEATURE_FLAGS")?;
 ```
 
-## Prefixed variables
+## Custom Types
+
+Implement `FromEnv` for your own types when you want domain-specific parsing.
 
 ```rust
-use envkit::EnvLoader;
+use envkit::{error::EnvError, FromEnv};
 
-fn main() -> Result<(), envkit::error::EnvError> {
-    let loader = EnvLoader;
-    let app = loader.with_prefix("APP_");
+enum LogFormat {
+    Json,
+    Pretty,
+}
 
-    let host: String = app.get("HOST")?;
-    let port: u16 = app.get_or("PORT", 8080);
-
-    println!("host={host}, port={port}");
-    Ok(())
+impl FromEnv for LogFormat {
+    fn from_env(value: &str) -> Result<Self, EnvError> {
+        match value.trim().to_lowercase().as_str() {
+            "json" => Ok(Self::Json),
+            "pretty" => Ok(Self::Pretty),
+            other => Err(EnvError::invalid(
+                "LogFormat",
+                other,
+                "expected `json` or `pretty`",
+            )),
+        }
+    }
 }
 ```
 
-If you use the prefixed loader above, it reads `APP_HOST` and `APP_PORT`.
-
 ## Errors
 
-`envkit` returns `EnvError` for two cases:
+`envkit` returns `EnvError` values:
 
-- `MissingVar` when the environment variable is not present
-- `Invalid` when parsing fails
+- `EnvError::MissingVar(key)` when a required environment variable is not set.
+- `EnvError::Invalid { key, value, message }` when a value cannot be parsed.
+- `EnvError::FileError { path, message }` when a file cannot be read or contains
+  an invalid line.
 
 ## Examples
 
-See the `examples/` folder for runnable usage samples.
+Run the included examples with:
+
+```bash
+cargo run --example basic
+cargo run --example prefixed
+```
+
+The examples seed their own environment variables so they can be run directly.
 
 ## Development
 

examples/basic.rs

@@ -1,15 +1,26 @@
 use envkit::EnvLoader;
 
 fn main() -> Result<(), envkit::error::EnvError> {
-    let loader = EnvLoader;
+    unsafe {
+        std::env::set_var("PORT", "8080");
+        std::env::set_var("DEBUG", "true");
+        std::env::set_var("APP_NAME", "envkit");
+        std::env::set_var("ALLOWED_PORTS", "8080, 8081, 8082");
+    }
+
+    let loader = EnvLoader::new();
 
     let port: u16 = loader.get("PORT")?;
     let debug: bool = loader.get_or("DEBUG", false);
-    let app_name: String = loader.get_opt("APP_NAME").unwrap_or_else(|| "envkit".to_string());
+    let app_name: String = loader
+        .get_opt("APP_NAME")
+        .unwrap_or_else(|| "envkit".to_string());
+    let allowed_ports: Vec<u16> = loader.get("ALLOWED_PORTS")?;
 
-    println!("port={port}");
-    println!("debug={debug}");
-    println!("app_name={app_name}");
+    println!("{app_name}");
+    println!("port: {port}");
+    println!("debug: {debug}");
+    println!("allowed ports: {allowed_ports:?}");
 
     Ok(())
 }

examples/prefixed.rs

@@ -1,16 +1,22 @@
 use envkit::EnvLoader;
 
 fn main() -> Result<(), envkit::error::EnvError> {
-    let loader = EnvLoader;
+    unsafe {
+        std::env::set_var("APP_HOST", "127.0.0.1");
+        std::env::set_var("APP_PORT", "3000");
+        std::env::set_var("APP_ENABLED", "yes");
+    }
+
+    let loader = EnvLoader::new();
     let app = loader.with_prefix("APP_");
 
     let host: String = app.get("HOST")?;
     let port: u16 = app.get_or("PORT", 8080);
     let enabled: bool = app.get_or("ENABLED", false);
 
-    println!("host={host}");
-    println!("port={port}");
-    println!("enabled={enabled}");
+    println!("host: {host}");
+    println!("port: {port}");
+    println!("enabled: {enabled}");
 
     Ok(())
 }

src/error.rs

@@ -6,6 +6,9 @@ pub enum EnvError {
 
     /// An environment variable was expected, but it was not found.
     MissingVar(String),
+
+    /// A file was expected to be found, but it was not found or could not be read.
+    FileError { path: String, message: String }
 }
 
 impl EnvError {
@@ -28,4 +31,12 @@ impl EnvError {
     where T: Into<String> {
         Self::MissingVar(key.into())
     }
+
+    /// Creates a new `EnvError::FileMissing` with the given path and message.
+    pub fn file_error<P: Into<String>, M: Into<String>>(path: P, message: M) -> Self {
+        Self::FileError {
+            path: path.into(),
+            message: message.into()
+        }
+    }
 }

src/lib.rs

@@ -49,6 +49,35 @@ impl FromEnv for String {
 pub struct EnvLoader;
 
 impl EnvLoader {
+    /// Creates a new `EnvLoader`.
+    pub fn new() -> Self {
+        Self
+    }
+
+    /// Loads environment variables from a file. The file should have one variable per line, in the format `KEY=VALUE`. Lines starting with `#` are treated as comments and ignored.
+    pub fn load_file(&self, path: &str) -> Result<(), EnvError> {
+        // Load the file
+        let contents = std::fs::read_to_string(path).map_err(|e| EnvError::file_error(path, e.to_string()))?;
+
+        // Parse the file
+        for line in contents.lines() {
+            let line = line.trim();
+            if line.is_empty() || line.starts_with("#") { continue }
+            let parts: Vec<&str> = line.splitn(2, '=').collect();
+            if parts.len() != 2 {
+                return Err(EnvError::file_error(path, format!("Invalid line: {}", line)));
+            }
+
+            // Trim the key and value
+            let key = parts[0].trim();
+            let value = parts[1].trim();
+
+            // Set the environment variable
+            unsafe { std::env::set_var(key, value) }
+        }
+        Ok(())
+    }
+
     /// Creates a new `EnvLoader` with the given prefix.
     pub fn with_prefix<P: Into<String>>(&self, prefix: P) -> PrefixedEnvLoader {
         PrefixedEnvLoader {

tests/test_main.rs

@@ -1,43 +1,160 @@
-#[cfg(test)]
-mod test_main {
-    use envkit::*;
+use envkit::{EnvLoader, error::EnvError};
+use std::path::PathBuf;
+use std::time::{SystemTime, UNIX_EPOCH};
 
-    #[test]
-    /// Tests that `get` successfully retrieves an existing environment variable.
-    fn test_get() {
-        let env = EnvLoader;
+fn unique_key(name: &str) -> String {
+    let nanos = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .expect("system time should be after the Unix epoch")
+        .as_nanos();
 
-        unsafe {
-            std::env::set_var("TEST_VAR", "test_value");
-        }
+    format!("ENVKIT_TEST_{name}_{nanos}")
+}
 
-        assert_eq!(env.get::<String>("TEST_VAR"), Ok("test_value".to_string()));
+#[test]
+fn get_reads_required_typed_values() {
+    let env = EnvLoader::new();
+    let name_key = unique_key("NAME");
+    let port_key = unique_key("PORT");
+    let debug_key = unique_key("DEBUG");
+    let list_key = unique_key("PORTS");
+
+    unsafe {
+        std::env::set_var(&name_key, "envkit");
+        std::env::set_var(&port_key, "3000");
+        std::env::set_var(&debug_key, "yes");
+        std::env::set_var(&list_key, "3000, 3001, 3002");
     }
 
-    #[test]
-    /// Tests that `get_or` returns the default value when the environment variable is missing.
-    fn test_get_or() {
-        let env = EnvLoader;
+    assert_eq!(env.get::<String>(&name_key), Ok("envkit".to_string()));
+    assert_eq!(env.get::<u16>(&port_key), Ok(3000));
+    assert_eq!(env.get::<bool>(&debug_key), Ok(true));
+    assert_eq!(env.get::<Vec<u16>>(&list_key), Ok(vec![3000, 3001, 3002]));
 
-        unsafe {
-            std::env::remove_var("MISSING_VAR");
-            std::env::set_var("TEST_VAR", "test_value");
-        }
-        
-        assert_eq!(env.get_or::<String>("MISSING_VAR", "default".to_string()), "default".to_string());
-        assert_eq!(env.get_or::<String>("TEST_VAR", "default".to_string()), "test_value".to_string());
-    }
-
-    #[test]
-    /// Tests that `get_opt` returns `Some` when the environment variable exists.
-    fn test_get_opt() {
-        let env = EnvLoader;
-       
-        unsafe {
-            std::env::set_var("OPTIONAL_VAR", "optional_value");
-        } 
-
-        assert_eq!(env.get_opt::<String>("OPTIONAL_VAR"), Some("optional_value".to_string()));
-        assert_eq!(env.get_opt::<bool>("DEV"), None);
+    unsafe {
+        std::env::remove_var(name_key);
+        std::env::remove_var(port_key);
+        std::env::remove_var(debug_key);
+        std::env::remove_var(list_key);
     }
 }
+
+#[test]
+fn get_reports_missing_and_invalid_values() {
+    let env = EnvLoader::new();
+    let missing_key = unique_key("MISSING");
+    let invalid_key = unique_key("INVALID");
+
+    unsafe {
+        std::env::remove_var(&missing_key);
+        std::env::set_var(&invalid_key, "not-a-port");
+    }
+
+    assert_eq!(
+        env.get::<String>(&missing_key),
+        Err(EnvError::MissingVar(missing_key.clone()))
+    );
+
+    assert!(matches!(
+        env.get::<u16>(&invalid_key),
+        Err(EnvError::Invalid { key, value, .. })
+            if key == "u16" && value == "not-a-port"
+    ));
+
+    unsafe {
+        std::env::remove_var(invalid_key);
+    }
+}
+
+#[test]
+fn get_or_and_get_opt_handle_fallbacks() {
+    let env = EnvLoader::new();
+    let present_key = unique_key("PRESENT");
+    let missing_key = unique_key("DEFAULT");
+    let invalid_key = unique_key("BAD_BOOL");
+
+    unsafe {
+        std::env::set_var(&present_key, "42");
+        std::env::remove_var(&missing_key);
+        std::env::set_var(&invalid_key, "maybe");
+    }
+
+    assert_eq!(env.get_or::<u8>(&present_key, 7), 42);
+    assert_eq!(env.get_or::<u8>(&missing_key, 7), 7);
+    assert_eq!(env.get_or::<bool>(&invalid_key, false), false);
+
+    assert_eq!(env.get_opt::<u8>(&present_key), Some(42));
+    assert_eq!(env.get_opt::<u8>(&missing_key), None);
+    assert_eq!(env.get_opt::<bool>(&invalid_key), None);
+
+    unsafe {
+        std::env::remove_var(present_key);
+        std::env::remove_var(invalid_key);
+    }
+}
+
+#[test]
+fn prefixed_loader_reads_namespaced_variables() {
+    let env = EnvLoader::new();
+    let prefix = unique_key("APP_");
+    let host_key = format!("{prefix}HOST");
+    let enabled_key = format!("{prefix}ENABLED");
+
+    unsafe {
+        std::env::set_var(&host_key, "127.0.0.1");
+        std::env::set_var(&enabled_key, "1");
+    }
+
+    let app = env.with_prefix(prefix);
+
+    assert_eq!(app.get::<String>("HOST"), Ok("127.0.0.1".to_string()));
+    assert_eq!(app.get::<bool>("ENABLED"), Ok(true));
+    assert_eq!(app.get_or::<u16>("PORT", 8080), 8080);
+
+    unsafe {
+        std::env::remove_var(host_key);
+        std::env::remove_var(enabled_key);
+    }
+}
+
+#[test]
+fn load_file_sets_environment_variables() {
+    let env = EnvLoader::new();
+    let prefix = unique_key("FILE_");
+    let port_key = format!("{prefix}PORT");
+    let debug_key = format!("{prefix}DEBUG");
+    let names_key = format!("{prefix}NAMES");
+    let path = temp_env_file(&prefix, &port_key, &debug_key, &names_key);
+
+    env.load_file(path.to_str().expect("test path should be UTF-8"))
+        .expect("env file should load");
+
+    assert_eq!(env.get::<u16>(&port_key), Ok(8080));
+    assert_eq!(env.get::<bool>(&debug_key), Ok(true));
+    assert_eq!(
+        env.get::<Vec<String>>(&names_key),
+        Ok(vec!["api".to_string(), "worker".to_string()])
+    );
+
+    std::fs::remove_file(path).expect("test env file should be removable");
+    unsafe {
+        std::env::remove_var(port_key);
+        std::env::remove_var(debug_key);
+        std::env::remove_var(names_key);
+    }
+}
+
+fn temp_env_file(prefix: &str, port_key: &str, debug_key: &str, names_key: &str) -> PathBuf {
+    let path = std::env::temp_dir().join(format!("{prefix}.env"));
+    let contents = format!(
+        r#"
+# comments and blank lines are ignored
+{port_key} = 8080
+{debug_key}= yes
+{names_key}= api, worker
+"#
+    );
+
+    std::fs::write(&path, contents).expect("test env file should be writable");
+    path
+}