builders 0.5.0

Rust macros for building structs
Documentation 
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// The std::process::Command builder handles args in a way that is potentially
// more convenient than passing a full vector of args to the builder all at
// once.
//
// Look for a field attribute #[builder(each = "...")] on each field. The
// generated code may assume that fields with this attribute have the type Vec
// and should use the word given in the string literal as the name for the
// corresponding builder method which accepts one vector element at a time.
//
// In order for the compiler to know that these builder attributes are
// associated with your macro, they must be declared at the entry point of the
// derive macro. Otherwise the compiler will report them as unrecognized
// attributes and refuse to compile the caller's code.
//
//     #[proc_macro_derive(Builder, attributes(builder))]
//
// These are called inert attributes. The word "inert" indicates that these
// attributes do not correspond to a macro invocation on their own; they are
// simply looked at by other macro invocations.
//
// If the new one-at-a-time builder method is given the same name as the field,
// avoid generating an all-at-once builder method for that field because the
// names would conflict.
//
//
// Resources:
//
//   - Relevant syntax tree type:
//     https://docs.rs/syn/2.0/syn/struct.Attribute.html

use builders::Builder;
use std::collections::HashMap;

#[derive(Builder)]
pub struct Command {
    executable: String,
    #[builder(vec = "arg")]
    args: Vec<String>,
    #[builder(vec = "env")]
    env: Vec<String>,
    #[builder(map = "key")]
    keys: HashMap<i32,String>,
    #[builder(optional = true)]
    current_dir: Option<String>,
}

fn main() {
    let command = Command::builder()
        .executable("cargo".to_owned())
        .arg("build".to_owned())
        .arg("--release".to_owned())
        .key(0,"0")
        .key(10,"10")
        .build()
        .unwrap();

    assert_eq!(command.executable, "cargo");
    assert_eq!(command.args, vec!["build", "--release"]);
    assert_eq!(command.keys.get(&0).unwrap(),"0");
    assert_eq!(command.keys.get(&10).unwrap(),"10");
}