ilyagr.bsky.social
just playing with tangled
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}