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
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

//! Unpack multiple levels of `Result<T, E>` and `Option<T>` at once
//!
//! ```
//! use unwrap_all::unwrap_all;
//!
//! let nested: Option<Result<Option<Result<usize, ()>>, ()>> = Some(Ok(Some(Ok(42))));
//! let unpacked = unwrap_all!(4, nested);
//! assert_eq!(42, unpacked);
//! ```
//!
//! This crate should work with `no_std` too.

extern crate proc_macro;
use proc_macro::TokenStream as TokenStreamRustc;

use proc_macro2::{/*Delimiter, Ident, Literal, */ Spacing, /*Span, TokenStream,*/ TokenTree,};

/// Use it like this: `unwrap_all!(n_times, object)`
///
/// ```
/// use unwrap_all::unwrap_all;
///
/// let nested = Some(Ok::<usize, ()>(42));
/// let unpacked = unwrap_all!(2, nested);
///
/// assert_eq!(42, unpacked);
/// ```
#[proc_macro]
pub fn unwrap_all(input: TokenStreamRustc) -> TokenStreamRustc {
    let tokens = proc_macro2::TokenStream::from(input);
    let mut iter = tokens.clone().into_iter();

    let n_times = match iter.next().unwrap() {
        TokenTree::Literal(lit) => lit
            .to_string()
            .parse::<usize>()
            .expect("first argument must be unsigned {{integer}}"),
        _ => panic!("expected {{number}} - wrong token: {:?}", tokens),
    };

    match iter.next().unwrap() {
        TokenTree::Punct(punct) => {
            assert_eq!(punct.as_char(), ',');
            assert_eq!(punct.spacing(), Spacing::Alone);
        }
        _ => panic!("expected ',' - wrong token {:?}", tokens),
    }

    let unwraps = (0..n_times).flat_map(|_| {
        use quote::quote;

        quote! {
            .unwrap()
        }
    });

    let output: proc_macro2::TokenStream = iter.chain(unwraps).collect();

    proc_macro::TokenStream::from(output)
}

/// Running this function will give you a panic with the message `1 - must fail: 23`, where the `1` tells you how many levels in the panic was caused.
///
/// ```
/// use unwrap_all::expect_all;
///
/// fn must_fail() {
///     let var = Some(Err::<usize, isize>(23));
///     let _result: usize = expect_all!(2, "must fail", var);
/// }
/// ```
#[proc_macro]
pub fn expect_all(input: TokenStreamRustc) -> TokenStreamRustc {
    let tokens = proc_macro2::TokenStream::from(input);
    let mut iter = tokens.clone().into_iter();

    let n_times = match iter.next().unwrap() {
        TokenTree::Literal(lit) => lit
            .to_string()
            .parse::<usize>()
            .expect("first argument must be unsigned {{integer}}"),
        _ => panic!("expected {{number}} - wrong token: {:?}", tokens),
    };

    match iter.next().unwrap() {
        TokenTree::Punct(punct) => {
            assert_eq!(punct.as_char(), ',');
            assert_eq!(punct.spacing(), Spacing::Alone);
        }
        _ => panic!("expected ',' - wrong token {:?}", tokens),
    }

    // --------- message
    let message = match iter.next().unwrap() {
        TokenTree::Literal(lit) => {
            let s = lit.to_string();

            assert!(
                s.starts_with('"') && s.ends_with('"'),
                "message literal must be quoted"
            );

            s.trim_matches('"').to_owned()
            //.parse::<String>()
            //.expect("first argument must be {{String}}")
        }
        _ => panic!("expected {{String}} - wrong token: {:?}", tokens),
    };

    match iter.next().unwrap() {
        TokenTree::Punct(punct) => {
            assert_eq!(punct.as_char(), ',');
            assert_eq!(punct.spacing(), Spacing::Alone);
        }
        _ => panic!("expected ',' - wrong token {:?}", tokens),
    }

    let expects = (0..n_times).flat_map(move |level| {
        use quote::quote;

        let message = format!("{} - {}", level, message);

        quote! {
            .expect(#message)
        }
    });

    let output: proc_macro2::TokenStream = iter.chain(expects).collect();

    proc_macro::TokenStream::from(output)
}