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//! This crate provides the trait [FromFile] that can be implemented or derived
//! for any struct or enum. Upon doing so, you'll get a `from_file` method
//! that allows you to skip having read the file the disk & choosing the correct
//! serde method - that will be done based on the file extension.
//!
//! # Quick Preview
//!
//! All examples require that serde Deserialize is also derived.
//! (see below for copy/paste example)
//!
//! ```
//! # #[macro_use]
//! # extern crate serde_derive;
//! # extern crate serde;
//! # #[macro_use]
//! # extern crate from_file_derive;
//! # use from_file::FromFile;
//! #[derive(Deserialize)]
//! struct Person {
//! name: String
//! }
//!
//! impl FromFile for Person {}
//!
//! fn main() {
//! let path = "test/fixtures/person.json";
//! let person = Person::from_file(path).expect("deserialize from file");
//! assert_eq!(person.name, String::from("Shane"));
//! }
//! ```
//!
//! # Quick Preview with `from_file_derive`
//!
//! This requires the additional crate [from_file_derive](https://crates.io/crates/from_file_derive)
//!
//! ```
//! # #[macro_use]
//! # extern crate serde_derive;
//! # extern crate serde;
//! # #[macro_use]
//! # extern crate from_file_derive;
//! # use from_file::FromFile;
//! #[derive(Deserialize, FromFile)]
//! struct Person {
//! name: String
//! }
//!
//! fn main() {
//! let path = "test/fixtures/person.json";
//! let person = Person::from_file(path).expect("deserialize from file");
//! assert_eq!(person.name, String::from("Shane"));
//! }
//! ```
//!
//! # Copy/Paste example
//!
//! ```
//! #[macro_use]
//! extern crate serde_derive;
//! extern crate serde;
//!
//! #[macro_use]
//! extern crate from_file_derive;
//!
//! use from_file::FromFile;
//!
//! #[derive(Deserialize, FromFile)]
//! struct Person {
//! name: String
//! }
//!
//! fn main() {
//! let path = "test/fixtures/person.json";
//! let person = Person::from_file(path).expect("deserialize from file");
//! assert_eq!(person.name, String::from("Shane"));
//! }
//! ```
//!
//! ### Full example with imports and error handing
//!
//! ```rust
//! #[macro_use]
//! extern crate serde_derive;
//!
//! #[macro_use]
//! extern crate from_file_derive;
//! extern crate from_file;
//!
//! use from_file::FromFile;
//!
//! #[derive(Deserialize, FromFile, Debug, PartialEq)]
//! struct Person {
//! name: String,
//! age: usize
//! }
//!
//! fn main() {
//! match Person::from_file("test/fixtures/person.json") {
//! Ok(p) => println!("Got a Person from a file!"),
//! Err(e) => eprintln!("{}", e)
//! }
//! }
//! ```
#[macro_use]
extern crate serde_derive;
extern crate serde;
extern crate serde_json;
extern crate serde_yaml;
use serde::Deserialize;
use std::fs::File;
use std::io::prelude::*;
use std::path::PathBuf;
#[derive(Debug)]
pub enum FromFileError {
InvalidExtension,
InvalidInput,
FileOpen(PathBuf),
FileRead,
SerdeError(String),
}
///
/// Implement this trait to enable your Struct's to be deserialized
/// from a file-path like
///
/// - conf/app.yaml
/// - file:conf/app.yaml
///
pub trait FromFile {
///
/// Support serialising to .yml, .yaml & .json files by
/// looking at the file extension and then choosing the correct
/// serde method
///
/// # Examples
///
/// ```
/// # #[macro_use]
/// # extern crate serde_derive;
/// # extern crate serde;
/// # #[macro_use]
/// # extern crate from_file_derive;
/// # use from_file::FromFile;
/// #[derive(Deserialize)]
/// struct Person {
/// name: String
/// }
///
/// impl FromFile for Person {}
///
/// fn main() {
/// let path = "test/fixtures/person.json";
/// let person = Person::from_file(path).expect("deserialize from file");
/// assert_eq!(person.name, String::from("Shane"));
/// }
/// ```
///
fn from_file(input: &str) -> Result<Self, FromFileError>
where
for<'de> Self: Deserialize<'de> + Sized,
{
let pb = PathBuf::from(input);
let ext = pb
.extension()
.and_then(|ext| ext.to_str())
.ok_or(FromFileError::InvalidExtension)?;
match ext {
"json" => <Self as FromFile>::from_json_file(input),
"yml" | "yaml" => <Self as FromFile>::from_yml_file(input),
_ => Err(FromFileError::InvalidExtension),
}
}
///
/// From a string like `file:config.yaml`, try to read the file
/// and if it exists, parse into a strongly typed struct `Self`
///
fn from_yml_file(input: &str) -> Result<Self, FromFileError>
where
for<'de> Self: Deserialize<'de> + Sized,
{
<Self as FromFile>::get_file_path(input)
.and_then(<Self as FromFile>::file_read)
.and_then(<Self as FromFile>::from_yaml_string)
}
///
/// From a string like `file:config.yaml`, try to read the file
/// and if it exists, parse into a strongly typed struct `Self`
///
fn from_json_file(input: &str) -> Result<Self, FromFileError>
where
for<'de> Self: Deserialize<'de> + Sized,
{
<Self as FromFile>::get_file_path(input)
.and_then(<Self as FromFile>::file_read)
.and_then(<Self as FromFile>::from_json_string)
}
///
/// Parse strings like file:config.yaml to extract the file path only
///
fn get_file_path(input: &str) -> Result<String, FromFileError> {
let split: Vec<&str> = input.split(":").collect();
match split.len() {
1 => Ok(split[0].into()),
2 => Ok(split[1].into()),
_ => Err(FromFileError::InvalidInput),
}
}
///
/// Attempt to Read the file's contents into a string
///
fn file_read(input: String) -> Result<String, FromFileError> {
let mut maybe_path = std::env::current_dir().expect("can read current dir");
maybe_path.push(&input);
let mut file = File::open(&input).map_err(|_| FromFileError::FileOpen(maybe_path))?;
let mut contents = String::new();
file.read_to_string(&mut contents)
.map_err(|_| FromFileError::FileRead)?;
Ok(contents)
}
///
/// Parse any YAML string directly into a Self
///
fn from_yaml_string(contents: String) -> Result<Self, FromFileError>
where
for<'de> Self: Deserialize<'de>,
{
serde_yaml::from_str(&contents).map_err(|e| FromFileError::SerdeError(e.to_string()))
}
///
/// Parse json string directly into a Self
///
fn from_json_string(contents: String) -> Result<Self, FromFileError>
where
for<'de> Self: Deserialize<'de>,
{
serde_json::from_str(&contents).map_err(|e| FromFileError::SerdeError(e.to_string()))
}
}
impl std::fmt::Display for FromFileError {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
match self {
FromFileError::InvalidExtension => write!(f, "FromFileError::InvalidExtension"),
FromFileError::InvalidInput => write!(f, "FromFileError::InvalidInput"),
FromFileError::FileOpen(path) => {
write!(f, "FromFileError::FileOpen - couldn't open {:?}", path)
}
FromFileError::FileRead => write!(f, "FromFileError::FileRead"),
FromFileError::SerdeError(e) => write!(f, "FromFileError::SerdeError - {}", e),
}
}
}
#[cfg(test)]
mod tests {
use super::FromFile;
#[test]
fn test_from_file() {
#[derive(Deserialize, Debug, PartialEq)]
struct Person {
name: String,
}
impl FromFile for Person {}
let p1 = Person::from_file("test/fixtures/person.json").expect("file->Person");
assert_eq!(
p1,
Person {
name: "Shane".into()
}
);
let p1 = Person::from_file("test/fixtures/person.yaml").expect("file->Person");
assert_eq!(
p1,
Person {
name: "Shane".into()
}
);
}
}