jj_lib/
extensions_map.rs

1// Copyright 2024 The Jujutsu Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#![allow(missing_docs)]
16
17use std::any::Any;
18use std::any::TypeId;
19use std::collections::HashMap;
20
21/// Type-safe map that stores objects of arbitrary types.
22///
23/// This allows extensions to store and retrieve their own types unknown to
24/// jj_lib safely.
25#[derive(Default)]
26pub struct ExtensionsMap {
27    values: HashMap<TypeId, Box<dyn Any>>,
28}
29
30impl ExtensionsMap {
31    /// Creates an empty ExtensionsMap.
32    pub fn empty() -> Self {
33        Default::default()
34    }
35
36    /// Returns the specified type if it has already been inserted.
37    pub fn get<V: Any>(&self) -> Option<&V> {
38        self.values
39            .get(&TypeId::of::<V>())
40            .map(|v| v.downcast_ref::<V>().unwrap())
41    }
42
43    /// Inserts a new instance of the specified type.
44    ///
45    /// Requires that this type has not been inserted before.
46    pub fn insert<V: Any>(&mut self, value: V) {
47        assert!(self
48            .values
49            .insert(TypeId::of::<V>(), Box::new(value))
50            .is_none());
51    }
52}
53
54#[cfg(test)]
55mod tests {
56    use super::*;
57
58    struct TestTypeA;
59    impl TestTypeA {
60        fn get_a(&self) -> &'static str {
61            "a"
62        }
63    }
64
65    struct TestTypeB;
66    impl TestTypeB {
67        fn get_b(&self) -> &'static str {
68            "b"
69        }
70    }
71
72    #[test]
73    fn test_empty() {
74        let extensions_map = ExtensionsMap::empty();
75        assert!(extensions_map.get::<TestTypeA>().is_none());
76        assert!(extensions_map.get::<TestTypeB>().is_none());
77    }
78
79    #[test]
80    fn test_retrieval() {
81        let mut extensions_map = ExtensionsMap::empty();
82        extensions_map.insert(TestTypeA);
83        extensions_map.insert(TestTypeB);
84        assert_eq!(
85            extensions_map
86                .get::<TestTypeA>()
87                .map(|a| a.get_a())
88                .unwrap_or(""),
89            "a"
90        );
91        assert_eq!(
92            extensions_map
93                .get::<TestTypeB>()
94                .map(|b| b.get_b())
95                .unwrap_or(""),
96            "b"
97        );
98    }
99}
jj_lib/extensions_map.rs

jj_lib/
extensions_map.rs
