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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
#![cfg(feature = "rust_decimal")]
//! Conversions to and from [rust_decimal](https://docs.rs/rust_decimal)'s [`Decimal`] type.
//!
//! This is useful for converting Python's decimal.Decimal into and from a native Rust type.
//!
//! # Setup
//!
//! To use this feature, add to your **`Cargo.toml`**:
//!
//! ```toml
//! [dependencies]
#![doc = concat!("pyo3 = { version = \"", env!("CARGO_PKG_VERSION"),  "\", features = [\"rust_decimal\"] }")]
//! rust_decimal = "1.0"
//! ```
//!
//! Note that you must use a compatible version of rust_decimal and PyO3.
//! The required rust_decimal version may vary based on the version of PyO3.
//!
//! # Example
//!
//! Rust code to create a function that adds one to a Decimal
//!
//! ```rust
//! use rust_decimal::Decimal;
//! use pyo3::prelude::*;
//!
//! #[pyfunction]
//! fn add_one(d: Decimal) -> Decimal {
//!     d + Decimal::ONE
//! }
//!
//! #[pymodule]
//! fn my_module(m: &Bound<'_, PyModule>) -> PyResult<()> {
//!     m.add_function(wrap_pyfunction!(add_one, m)?)?;
//!     Ok(())
//! }
//! ```
//!
//! Python code that validates the functionality
//!
//!
//! ```python
//! from my_module import add_one
//! from decimal import Decimal
//!
//! d = Decimal("2")
//! value = add_one(d)
//!
//! assert d + 1 == value
//! ```

use crate::exceptions::PyValueError;
use crate::sync::GILOnceCell;
use crate::types::any::PyAnyMethods;
use crate::types::string::PyStringMethods;
use crate::types::PyType;
use crate::{
    intern, Bound, FromPyObject, IntoPy, Py, PyAny, PyObject, PyResult, Python, ToPyObject,
};
use rust_decimal::Decimal;
use std::str::FromStr;

impl FromPyObject<'_> for Decimal {
    fn extract_bound(obj: &Bound<'_, PyAny>) -> PyResult<Self> {
        // use the string representation to not be lossy
        if let Ok(val) = obj.extract() {
            Ok(Decimal::new(val, 0))
        } else {
            Decimal::from_str(&obj.str()?.to_cow()?)
                .map_err(|e| PyValueError::new_err(e.to_string()))
        }
    }
}

static DECIMAL_CLS: GILOnceCell<Py<PyType>> = GILOnceCell::new();

fn get_decimal_cls(py: Python<'_>) -> PyResult<&PyType> {
    DECIMAL_CLS
        .get_or_try_init(py, || {
            py.import_bound(intern!(py, "decimal"))?
                .getattr(intern!(py, "Decimal"))?
                .extract()
        })
        .map(|ty| ty.as_ref(py))
}

impl ToPyObject for Decimal {
    fn to_object(&self, py: Python<'_>) -> PyObject {
        // TODO: handle error gracefully when ToPyObject can error
        // look up the decimal.Decimal
        let dec_cls = get_decimal_cls(py).expect("failed to load decimal.Decimal");
        // now call the constructor with the Rust Decimal string-ified
        // to not be lossy
        let ret = dec_cls
            .call1((self.to_string(),))
            .expect("failed to call decimal.Decimal(value)");
        ret.to_object(py)
    }
}

impl IntoPy<PyObject> for Decimal {
    fn into_py(self, py: Python<'_>) -> PyObject {
        self.to_object(py)
    }
}

#[cfg(test)]
mod test_rust_decimal {
    use super::*;
    use crate::err::PyErr;
    use crate::types::dict::PyDictMethods;
    use crate::types::PyDict;

    #[cfg(not(target_arch = "wasm32"))]
    use proptest::prelude::*;

    macro_rules! convert_constants {
        ($name:ident, $rs:expr, $py:literal) => {
            #[test]
            fn $name() {
                Python::with_gil(|py| {
                    let rs_orig = $rs;
                    let rs_dec = rs_orig.into_py(py);
                    let locals = PyDict::new_bound(py);
                    locals.set_item("rs_dec", &rs_dec).unwrap();
                    // Checks if Rust Decimal -> Python Decimal conversion is correct
                    py.run_bound(
                        &format!(
                            "import decimal\npy_dec = decimal.Decimal({})\nassert py_dec == rs_dec",
                            $py
                        ),
                        None,
                        Some(&locals),
                    )
                    .unwrap();
                    // Checks if Python Decimal -> Rust Decimal conversion is correct
                    let py_dec = locals.get_item("py_dec").unwrap().unwrap();
                    let py_result: Decimal = py_dec.extract().unwrap();
                    assert_eq!(rs_orig, py_result);
                })
            }
        };
    }

    convert_constants!(convert_zero, Decimal::ZERO, "0");
    convert_constants!(convert_one, Decimal::ONE, "1");
    convert_constants!(convert_neg_one, Decimal::NEGATIVE_ONE, "-1");
    convert_constants!(convert_two, Decimal::TWO, "2");
    convert_constants!(convert_ten, Decimal::TEN, "10");
    convert_constants!(convert_one_hundred, Decimal::ONE_HUNDRED, "100");
    convert_constants!(convert_one_thousand, Decimal::ONE_THOUSAND, "1000");

    #[cfg(not(target_arch = "wasm32"))]
    proptest! {
        #[test]
        fn test_roundtrip(
            lo in any::<u32>(),
            mid in any::<u32>(),
            high in any::<u32>(),
            negative in any::<bool>(),
            scale in 0..28u32
        ) {
            let num = Decimal::from_parts(lo, mid, high, negative, scale);
            Python::with_gil(|py| {
                let rs_dec = num.into_py(py);
                let locals = PyDict::new_bound(py);
                locals.set_item("rs_dec", &rs_dec).unwrap();
                py.run_bound(
                    &format!(
                       "import decimal\npy_dec = decimal.Decimal(\"{}\")\nassert py_dec == rs_dec",
                     num),
                None, Some(&locals)).unwrap();
                let roundtripped: Decimal = rs_dec.extract(py).unwrap();
                assert_eq!(num, roundtripped);
            })
        }

        #[test]
        fn test_integers(num in any::<i64>()) {
            Python::with_gil(|py| {
                let py_num = num.into_py(py);
                let roundtripped: Decimal = py_num.extract(py).unwrap();
                let rs_dec = Decimal::new(num, 0);
                assert_eq!(rs_dec, roundtripped);
            })
        }
    }

    #[test]
    fn test_nan() {
        Python::with_gil(|py| {
            let locals = PyDict::new_bound(py);
            py.run_bound(
                "import decimal\npy_dec = decimal.Decimal(\"NaN\")",
                None,
                Some(&locals),
            )
            .unwrap();
            let py_dec = locals.get_item("py_dec").unwrap().unwrap();
            let roundtripped: Result<Decimal, PyErr> = py_dec.extract();
            assert!(roundtripped.is_err());
        })
    }

    #[test]
    fn test_infinity() {
        Python::with_gil(|py| {
            let locals = PyDict::new_bound(py);
            py.run_bound(
                "import decimal\npy_dec = decimal.Decimal(\"Infinity\")",
                None,
                Some(&locals),
            )
            .unwrap();
            let py_dec = locals.get_item("py_dec").unwrap().unwrap();
            let roundtripped: Result<Decimal, PyErr> = py_dec.extract();
            assert!(roundtripped.is_err());
        })
    }
}