snix_glue/
known_paths.rs

1//! This module implements logic required for persisting known paths
2//! during an evaluation.
3//!
4//! Snix needs to be able to keep track of each Nix store path that it
5//! knows about during the scope of a single evaluation and its
6//! related builds.
7//!
8//! This data is required to find the derivation needed to actually trigger the
9//! build, if necessary.
10
11use hashbrown::HashMap;
12use nix_compat::{
13    derivation::Derivation,
14    store_path::{BuildStorePathError, StorePath, StorePathRef},
15};
16
17use crate::fetchers::Fetch;
18
19/// Struct keeping track of all known Derivations in the current evaluation.
20/// This keeps both the Derivation struct, as well as the "Hash derivation
21/// modulo".
22#[derive(Debug, Default)]
23pub struct KnownPaths {
24    /// All known derivation or FOD hashes.
25    ///
26    /// Keys are derivation paths, values are a tuple of the "hash derivation
27    /// modulo" and the Derivation struct itself.
28    derivations: HashMap<StorePath<String>, ([u8; 32], Derivation)>,
29
30    /// A map from output path to (one) drv path.
31    /// Note that in the case of FODs, multiple drvs can produce the same output
32    /// path. We use one of them.
33    outputs_to_drvpath: HashMap<StorePath<String>, StorePath<String>>,
34
35    /// A map from output path to fetches (and their names).
36    outputs_to_fetches: HashMap<StorePath<String>, (String, Fetch)>,
37}
38
39impl KnownPaths {
40    /// Fetch the opaque "hash derivation modulo" for a given derivation path.
41    pub fn get_hash_derivation_modulo(&self, drv_path: &StorePath<String>) -> Option<&[u8; 32]> {
42        self.derivations
43            .get(drv_path)
44            .map(|(hash_derivation_modulo, _derivation)| hash_derivation_modulo)
45    }
46
47    /// Return a reference to the Derivation for a given drv path.
48    pub fn get_drv_by_drvpath(&self, drv_path: &StorePath<String>) -> Option<&Derivation> {
49        self.derivations
50            .get(drv_path)
51            .map(|(_hash_derivation_modulo, derivation)| derivation)
52    }
53
54    /// Return the drv path of the derivation producing the passed output path.
55    /// Note there can be multiple Derivations producing the same output path in
56    /// flight; this function will only return one of them.
57    pub fn get_drv_path_for_output_path<S>(
58        &self,
59        output_path: &StorePath<S>,
60    ) -> Option<&StorePath<String>>
61    where
62        S: AsRef<str>,
63    {
64        self.outputs_to_drvpath.get(&output_path.as_ref())
65    }
66
67    /// Insert a new [Derivation] into this struct.
68    /// The Derivation struct must pass validation, and its output paths need to
69    /// be fully calculated.
70    /// All input derivations this refers to must also be inserted to this
71    /// struct.
72    pub fn add_derivation(&mut self, drv_path: StorePath<String>, drv: Derivation) {
73        // check input derivations to have been inserted.
74        #[cfg(debug_assertions)]
75        {
76            for input_drv_path in drv.input_derivations.keys() {
77                debug_assert!(self.derivations.contains_key(input_drv_path));
78            }
79        }
80
81        // compute the hash derivation modulo
82        let hash_derivation_modulo = drv.hash_derivation_modulo(|drv_path| {
83            self.get_hash_derivation_modulo(&drv_path.to_owned())
84                .unwrap_or_else(|| panic!("{drv_path} not found"))
85                .to_owned()
86        });
87
88        // For all output paths, update our lookup table.
89        // We only write into the lookup table once.
90        for output in drv.outputs.values() {
91            self.outputs_to_drvpath
92                .entry(output.path.as_ref().expect("missing store path").clone())
93                .or_insert(drv_path.to_owned());
94        }
95
96        // insert the derivation itself
97        #[allow(unused_variables)] // assertions on this only compiled in debug builds
98        let old = self
99            .derivations
100            .insert(drv_path.to_owned(), (hash_derivation_modulo, drv));
101
102        #[cfg(debug_assertions)]
103        {
104            if let Some(old) = old {
105                debug_assert!(
106                    old.0 == hash_derivation_modulo,
107                    "hash derivation modulo for a given derivation should always be calculated the same"
108                );
109            }
110        }
111    }
112
113    /// Insert a new [Fetch] into this struct, which *must* have an expected
114    /// hash (otherwise we wouldn't be able to calculate the store path).
115    /// Fetches without a known hash need to be fetched inside builtins.
116    pub fn add_fetch<'a>(
117        &mut self,
118        fetch: Fetch,
119        name: &'a str,
120    ) -> Result<StorePathRef<'a>, BuildStorePathError> {
121        let store_path = fetch
122            .store_path(name)?
123            .expect("Snix bug: fetch must have an expected hash");
124        // insert the fetch.
125        self.outputs_to_fetches
126            .insert(store_path.to_owned(), (name.to_owned(), fetch));
127
128        Ok(store_path)
129    }
130
131    /// Return the name and fetch producing the passed output path.
132    /// Note there can also be (multiple) Derivations producing the same output path.
133    pub fn get_fetch_for_output_path<S>(
134        &self,
135        output_path: &StorePath<S>,
136    ) -> Option<(String, Fetch)>
137    where
138        S: AsRef<str>,
139    {
140        self.outputs_to_fetches
141            .get(&output_path.as_ref())
142            .map(|(name, fetch)| (name.to_owned(), fetch.to_owned()))
143    }
144
145    /// Returns an iterator over all known derivations and their store path.
146    pub fn get_derivations(&self) -> impl Iterator<Item = (&StorePath<String>, &Derivation)> {
147        self.derivations.iter().map(|(k, v)| (k, &v.1))
148    }
149}
150
151#[cfg(test)]
152mod tests {
153    use std::sync::LazyLock;
154
155    use hex_literal::hex;
156    use nix_compat::{derivation::Derivation, nixbase32, nixhash::NixHash, store_path::StorePath};
157    use url::Url;
158
159    use super::KnownPaths;
160    use crate::fetchers::Fetch;
161
162    static BAR_DRV: LazyLock<Derivation> = LazyLock::new(|| {
163        Derivation::from_aterm_bytes(include_bytes!(
164            "tests/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv"
165        ))
166        .expect("must parse")
167    });
168
169    static FOO_DRV: LazyLock<Derivation> = LazyLock::new(|| {
170        Derivation::from_aterm_bytes(include_bytes!(
171            "tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv"
172        ))
173        .expect("must parse")
174    });
175
176    static BAR_DRV_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
177        StorePath::from_bytes(b"ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv").expect("must parse")
178    });
179
180    static FOO_DRV_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
181        StorePath::from_bytes(b"ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv").expect("must parse")
182    });
183
184    static BAR_OUT_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
185        StorePath::from_bytes(b"mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar").expect("must parse")
186    });
187
188    static FOO_OUT_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
189        StorePath::from_bytes(b"fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo").expect("must parse")
190    });
191
192    static FETCH_URL: LazyLock<Fetch> = LazyLock::new(|| {
193        Fetch::URL {
194        url: Url::parse("https://raw.githubusercontent.com/aaptel/notmuch-extract-patch/f732a53e12a7c91a06755ebfab2007adc9b3063b/notmuch-extract-patch").unwrap(),
195        exp_hash: Some(NixHash::from_sri("sha256-Xa1Jbl2Eq5+L0ww+Ph1osA3Z/Dxe/RkN1/dITQCdXFk=").unwrap())
196    }
197    });
198
199    static FETCH_URL_OUT_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
200        StorePath::from_bytes(b"06qi00hylriyfm0nl827crgjvbax84mz-notmuch-extract-patch").unwrap()
201    });
202
203    static FETCH_TARBALL: LazyLock<Fetch> = LazyLock::new(|| {
204        Fetch::Tarball {
205        url: Url::parse("https://github.com/NixOS/nixpkgs/archive/91050ea1e57e50388fa87a3302ba12d188ef723a.tar.gz").unwrap(),
206        exp_nar_sha256: Some(nixbase32::decode_fixed("1hf6cgaci1n186kkkjq106ryf8mmlq9vnwgfwh625wa8hfgdn4dm").unwrap())
207    }
208    });
209
210    static FETCH_TARBALL_OUT_PATH: LazyLock<StorePath<String>> = LazyLock::new(|| {
211        StorePath::from_bytes(b"7adgvk5zdfq4pwrhsm3n9lzypb12gw0g-source").unwrap()
212    });
213
214    /// Ensure that we don't allow adding a derivation that depends on another,
215    /// not-yet-added derivation.
216    #[test]
217    #[should_panic]
218    fn drv_reject_if_missing_input_drv() {
219        let mut known_paths = KnownPaths::default();
220
221        // FOO_DRV depends on BAR_DRV, which wasn't added.
222        known_paths.add_derivation(FOO_DRV_PATH.clone(), FOO_DRV.clone());
223    }
224
225    #[test]
226    fn drv_happy_path() {
227        let mut known_paths = KnownPaths::default();
228
229        // get_drv_by_drvpath should return None for non-existing Derivations,
230        // same as get_hash_derivation_modulo and get_drv_path_for_output_path
231        assert_eq!(None, known_paths.get_drv_by_drvpath(&BAR_DRV_PATH));
232        assert_eq!(None, known_paths.get_hash_derivation_modulo(&BAR_DRV_PATH));
233        assert_eq!(
234            None,
235            known_paths.get_drv_path_for_output_path(&BAR_OUT_PATH.as_ref())
236        );
237
238        // Add BAR_DRV
239        known_paths.add_derivation(BAR_DRV_PATH.clone(), BAR_DRV.clone());
240
241        // We should get it back
242        assert_eq!(
243            Some(&BAR_DRV.clone()),
244            known_paths.get_drv_by_drvpath(&BAR_DRV_PATH)
245        );
246
247        // Test get_drv_path_for_output_path
248        assert_eq!(
249            Some(&BAR_DRV_PATH.clone()),
250            known_paths.get_drv_path_for_output_path(&BAR_OUT_PATH)
251        );
252
253        // It should be possible to get the hash derivation modulo.
254        assert_eq!(
255            Some(&hex!(
256                "c79aebd0ce3269393d4a1fde2cbd1d975d879b40f0bf40a48f550edc107fd5df"
257            )),
258            known_paths.get_hash_derivation_modulo(&BAR_DRV_PATH.clone())
259        );
260
261        // Now insert FOO_DRV too. It shouldn't panic, as BAR_DRV is already
262        // added.
263        known_paths.add_derivation(FOO_DRV_PATH.clone(), FOO_DRV.clone());
264
265        assert_eq!(
266            Some(&FOO_DRV.clone()),
267            known_paths.get_drv_by_drvpath(&FOO_DRV_PATH)
268        );
269        assert_eq!(
270            Some(&hex!(
271                "af030d36d63d3d7f56a71adaba26b36f5fa1f9847da5eed953ed62e18192762f"
272            )),
273            known_paths.get_hash_derivation_modulo(&FOO_DRV_PATH.clone())
274        );
275
276        // Test get_drv_path_for_output_path
277        assert_eq!(
278            Some(&FOO_DRV_PATH.clone()),
279            known_paths.get_drv_path_for_output_path(&FOO_OUT_PATH)
280        );
281    }
282
283    #[test]
284    fn fetch_happy_path() {
285        let mut known_paths = KnownPaths::default();
286
287        // get_fetch_for_output_path should return None for new fetches.
288        assert!(
289            known_paths
290                .get_fetch_for_output_path(&FETCH_TARBALL_OUT_PATH)
291                .is_none()
292        );
293
294        // add_fetch should return the properly calculated store paths.
295        assert_eq!(
296            *FETCH_TARBALL_OUT_PATH,
297            known_paths
298                .add_fetch(FETCH_TARBALL.clone(), "source")
299                .unwrap()
300                .to_owned()
301        );
302
303        assert_eq!(
304            *FETCH_URL_OUT_PATH,
305            known_paths
306                .add_fetch(FETCH_URL.clone(), "notmuch-extract-patch")
307                .unwrap()
308                .to_owned()
309        );
310    }
311
312    #[test]
313    fn get_derivations_working() {
314        let mut known_paths = KnownPaths::default();
315
316        // Add BAR_DRV
317        known_paths.add_derivation(BAR_DRV_PATH.clone(), BAR_DRV.clone());
318
319        // We should be able to find BAR_DRV_PATH and BAR_DRV as a pair in get_derivations.
320        assert_eq!(
321            Some((&BAR_DRV_PATH.clone(), &BAR_DRV.clone())),
322            known_paths
323                .get_derivations()
324                .find(|(s, d)| (*s, *d) == (&BAR_DRV_PATH, &BAR_DRV))
325        );
326    }
327
328    // TODO: add test panicking about missing digest
329}
snix_glue/known_paths.rs

snix_glue/
known_paths.rs
