bevy_macro_utils/
bevy_manifest.rs

1extern crate proc_macro;
2
3use alloc::collections::BTreeMap;
4use parking_lot::{lock_api::RwLockReadGuard, MappedRwLockReadGuard, RwLock, RwLockWriteGuard};
5use proc_macro::TokenStream;
6use std::{
7    env,
8    path::{Path, PathBuf},
9    time::SystemTime,
10};
11use toml_edit::{Document, Item};
12
13/// The path to the `Cargo.toml` file for the Bevy project.
14#[derive(Debug)]
15pub struct BevyManifest {
16    manifest: Document<Box<str>>,
17    modified_time: SystemTime,
18}
19
20const BEVY: &str = "bevy";
21
22impl BevyManifest {
23    /// Returns a global shared instance of the [`BevyManifest`] struct.
24    pub fn shared() -> MappedRwLockReadGuard<'static, BevyManifest> {
25        static MANIFESTS: RwLock<BTreeMap<PathBuf, BevyManifest>> = RwLock::new(BTreeMap::new());
26        let manifest_path = Self::get_manifest_path();
27        let modified_time = Self::get_manifest_modified_time(&manifest_path)
28            .expect("The Cargo.toml should have a modified time");
29
30        if let Ok(manifest) =
31            RwLockReadGuard::try_map(MANIFESTS.read(), |manifests| manifests.get(&manifest_path))
32            && manifest.modified_time == modified_time
33        {
34            return manifest;
35        }
36
37        let manifest = BevyManifest {
38            manifest: Self::read_manifest(&manifest_path),
39            modified_time,
40        };
41
42        let key = manifest_path.clone();
43        let mut manifests = MANIFESTS.write();
44        manifests.insert(key, manifest);
45
46        RwLockReadGuard::map(RwLockWriteGuard::downgrade(manifests), |manifests| {
47            manifests.get(&manifest_path).unwrap()
48        })
49    }
50
51    fn get_manifest_path() -> PathBuf {
52        env::var_os("CARGO_MANIFEST_DIR")
53            .map(|path| {
54                let mut path = PathBuf::from(path);
55                path.push("Cargo.toml");
56                assert!(
57                    path.exists(),
58                    "Cargo manifest does not exist at path {}",
59                    path.display()
60                );
61                path
62            })
63            .expect("CARGO_MANIFEST_DIR is not defined.")
64    }
65
66    fn get_manifest_modified_time(
67        cargo_manifest_path: &Path,
68    ) -> Result<SystemTime, std::io::Error> {
69        std::fs::metadata(cargo_manifest_path).and_then(|metadata| metadata.modified())
70    }
71
72    fn read_manifest(path: &Path) -> Document<Box<str>> {
73        let manifest = std::fs::read_to_string(path)
74            .unwrap_or_else(|_| panic!("Unable to read cargo manifest: {}", path.display()))
75            .into_boxed_str();
76        Document::parse(manifest)
77            .unwrap_or_else(|_| panic!("Failed to parse cargo manifest: {}", path.display()))
78    }
79
80    /// Attempt to retrieve the [path](syn::Path) of a particular package in
81    /// the [manifest](BevyManifest) by [name](str).
82    pub fn maybe_get_path(&self, name: &str) -> Option<syn::Path> {
83        let find_in_deps = |deps: &Item| -> Option<syn::Path> {
84            let package = if deps.get(name).is_some() {
85                return Some(Self::parse_str(name));
86            } else if deps.get(BEVY).is_some() {
87                BEVY
88            } else {
89                // Note: to support bevy crate aliases, we could do scanning here to find a crate with a "package" name that
90                // matches our request, but that would then mean we are scanning every dependency (and dev dependency) for every
91                // macro execution that hits this branch (which includes all built-in bevy crates). Our current stance is that supporting
92                // remapped crate names in derive macros is not worth that "compile time" price of admission. As a workaround, people aliasing
93                // bevy crate names can use "use REMAPPED as bevy_X" or "use REMAPPED::x as bevy_x".
94                return None;
95            };
96
97            let mut path = Self::parse_str::<syn::Path>(&format!("::{package}"));
98            if let Some(module) = name.strip_prefix("bevy_") {
99                path.segments.push(Self::parse_str(module));
100            }
101            Some(path)
102        };
103
104        let deps = self.manifest.get("dependencies");
105        let deps_dev = self.manifest.get("dev-dependencies");
106
107        deps.and_then(find_in_deps)
108            .or_else(|| deps_dev.and_then(find_in_deps))
109    }
110
111    /// Attempt to parse the provided [path](str) as a [syntax tree node](syn::parse::Parse)
112    pub fn try_parse_str<T: syn::parse::Parse>(path: &str) -> Option<T> {
113        syn::parse(path.parse::<TokenStream>().ok()?).ok()
114    }
115
116    /// Returns the path for the crate with the given name.
117    pub fn get_path(&self, name: &str) -> syn::Path {
118        self.maybe_get_path(name)
119            .unwrap_or_else(|| Self::parse_str(name))
120    }
121
122    /// Attempt to parse provided [path](str) as a [syntax tree node](syn::parse::Parse).
123    ///
124    /// # Panics
125    ///
126    /// Will panic if the path is not able to be parsed. For a non-panicking option, see [`try_parse_str`]
127    ///
128    /// [`try_parse_str`]: Self::try_parse_str
129    pub fn parse_str<T: syn::parse::Parse>(path: &str) -> T {
130        Self::try_parse_str(path).unwrap()
131    }
132}
bevy_macro_utils/bevy_manifest.rs

bevy_macro_utils/
bevy_manifest.rs
