snix_build_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    nixhash::Sha256,
15    store_path::{ParseStorePathError, StorePath, StorePathRef},
16};
17
18use crate::fetchers::Fetch;
19
20/// Struct keeping track of all known Derivations in the current evaluation.
21/// This keeps both the Derivation struct, as well as the "Hash derivation
22/// modulo".
23#[derive(Debug, Default)]
24pub struct KnownPaths {
25    /// All known derivation or FOD hashes.
26    ///
27    /// Keys are derivation paths, values are a tuple of the "hash derivation
28    /// modulo" and the Derivation struct itself.
29    derivations: HashMap<StorePath, (Sha256, Derivation)>,
30
31    /// A map from output path to (one) drv path.
32    /// Note that in the case of FODs, multiple drvs can produce the same output
33    /// path. We use one of them.
34    outputs_to_drvpath: HashMap<StorePath, StorePath>,
35
36    /// A map from output path to fetches (and their names).
37    outputs_to_fetches: HashMap<StorePath, (String, Fetch)>,
38}
39
40impl KnownPaths {
41    /// Fetch the opaque "hash derivation modulo" for a given derivation path.
42    pub fn get_hash_derivation_modulo(&self, drv_path: &StorePathRef) -> Option<&Sha256> {
43        self.derivations
44            .get(drv_path)
45            .map(|(hash_derivation_modulo, _derivation)| hash_derivation_modulo)
46    }
47
48    /// Return a reference to the Derivation for a given drv path.
49    pub fn get_drv_by_drvpath(&self, drv_path: &StorePathRef) -> Option<&Derivation> {
50        self.derivations
51            .get(drv_path)
52            .map(|(_hash_derivation_modulo, derivation)| derivation)
53    }
54
55    /// Return the drv path of the derivation producing the passed output path.
56    /// Note there can be multiple Derivations producing the same output path in
57    /// flight; this function will only return one of them.
58    pub fn get_drv_path_for_output_path(&self, output_path: &StorePathRef) -> Option<&StorePath> {
59        self.outputs_to_drvpath.get(output_path)
60    }
61
62    /// Insert a new [Derivation] into this struct.
63    /// The Derivation struct must pass validation, and its output paths need to
64    /// be fully calculated.
65    /// All input derivations this refers to must also be inserted to this
66    /// struct.
67    pub fn add_derivation(&mut self, drv_path: StorePath, drv: Derivation) {
68        // check input derivations to have been inserted.
69        #[cfg(debug_assertions)]
70        {
71            for input_drv_path in drv.input_derivations.keys() {
72                debug_assert!(self.derivations.contains_key(input_drv_path));
73            }
74        }
75
76        // compute the hash derivation modulo
77        let hash_derivation_modulo = drv.hash_derivation_modulo(|drv_path| {
78            self.get_hash_derivation_modulo(drv_path)
79                .unwrap_or_else(|| panic!("{drv_path} not found"))
80                .to_owned()
81        });
82
83        // For all output paths, update our lookup table.
84        // We only write into the lookup table once.
85        for output in drv.outputs.values() {
86            self.outputs_to_drvpath
87                .entry(output.path.as_ref().expect("missing store path").clone())
88                .or_insert(drv_path.to_owned());
89        }
90
91        // insert the derivation itself
92        #[allow(unused_variables)] // assertions on this only compiled in debug builds
93        let old = self
94            .derivations
95            .insert(drv_path.to_owned(), (hash_derivation_modulo, drv));
96
97        #[cfg(debug_assertions)]
98        {
99            if let Some(old) = old {
100                debug_assert!(
101                    old.0 == hash_derivation_modulo,
102                    "hash derivation modulo for a given derivation should always be calculated the same"
103                );
104            }
105        }
106    }
107
108    /// Insert a new [Fetch] into this struct, which *must* have an expected
109    /// hash (otherwise we wouldn't be able to calculate the store path).
110    /// Fetches without a known hash need to be fetched inside builtins.
111    pub fn add_fetch<'a>(
112        &mut self,
113        fetch: Fetch,
114        name: &'a str,
115    ) -> Result<StorePathRef<'a>, ParseStorePathError> {
116        let store_path = fetch
117            .store_path(name)?
118            .expect("Snix bug: fetch must have an expected hash");
119        // insert the fetch.
120        self.outputs_to_fetches
121            .insert(store_path.to_owned(), (name.to_owned(), fetch));
122
123        Ok(store_path)
124    }
125
126    /// Return the name and fetch producing the passed output path.
127    /// Note there can also be (multiple) Derivations producing the same output path.
128    pub fn get_fetch_for_output_path(
129        &self,
130        output_path: &StorePathRef<'_>,
131    ) -> Option<(String, Fetch)> {
132        self.outputs_to_fetches
133            .get(output_path)
134            .map(|(name, fetch)| (name.to_owned(), fetch.to_owned()))
135    }
136
137    /// Returns an iterator over all known derivations and their store path.
138    pub fn get_derivations<'a>(
139        &'a self,
140    ) -> impl Iterator<Item = (StorePathRef<'a>, &'a Derivation)> {
141        self.derivations.iter().map(|(k, v)| (k.as_ref(), &v.1))
142    }
143}
144
145#[cfg(test)]
146mod tests {
147    use std::sync::LazyLock;
148
149    use hex_literal::hex;
150    use nix_compat::{
151        derivation::Derivation,
152        nixbase32,
153        nixhash::{NixHash, Sha256},
154        store_path::StorePath,
155    };
156    use url::Url;
157
158    use super::KnownPaths;
159    use crate::fetchers::Fetch;
160
161    static BAR_DRV: LazyLock<Derivation> = LazyLock::new(|| {
162        Derivation::from_aterm_bytes(include_bytes!(
163            "../test-data/ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv"
164        ))
165        .expect("must parse")
166    });
167
168    static FOO_DRV: LazyLock<Derivation> = LazyLock::new(|| {
169        Derivation::from_aterm_bytes(include_bytes!(
170            "../test-data/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv"
171        ))
172        .expect("must parse")
173    });
174
175    static BAR_DRV_PATH: LazyLock<StorePath> = LazyLock::new(|| {
176        StorePath::from_bytes(b"ss2p4wmxijn652haqyd7dckxwl4c7hxx-bar.drv").expect("must parse")
177    });
178
179    static FOO_DRV_PATH: LazyLock<StorePath> = LazyLock::new(|| {
180        StorePath::from_bytes(b"ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv").expect("must parse")
181    });
182
183    static BAR_OUT_PATH: LazyLock<StorePath> = LazyLock::new(|| {
184        StorePath::from_bytes(b"mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar").expect("must parse")
185    });
186
187    static FOO_OUT_PATH: LazyLock<StorePath> = LazyLock::new(|| {
188        StorePath::from_bytes(b"fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo").expect("must parse")
189    });
190
191    static FETCH_URL: LazyLock<Fetch> = LazyLock::new(|| {
192        Fetch::URL {
193        url: Url::parse("https://raw.githubusercontent.com/aaptel/notmuch-extract-patch/f732a53e12a7c91a06755ebfab2007adc9b3063b/notmuch-extract-patch").unwrap(),
194        exp_hash: Some(NixHash::from_sri("sha256-Xa1Jbl2Eq5+L0ww+Ph1osA3Z/Dxe/RkN1/dITQCdXFk=").unwrap())
195    }
196    });
197
198    static FETCH_URL_OUT_PATH: LazyLock<StorePath> = LazyLock::new(|| {
199        StorePath::from_bytes(b"06qi00hylriyfm0nl827crgjvbax84mz-notmuch-extract-patch").unwrap()
200    });
201
202    static FETCH_TARBALL: LazyLock<Fetch> = LazyLock::new(|| {
203        Fetch::Tarball {
204        url: Url::parse("https://github.com/NixOS/nixpkgs/archive/91050ea1e57e50388fa87a3302ba12d188ef723a.tar.gz").unwrap(),
205        exp_nar_sha256: Some(nixbase32::decode_fixed("1hf6cgaci1n186kkkjq106ryf8mmlq9vnwgfwh625wa8hfgdn4dm").unwrap())
206    }
207    });
208
209    static FETCH_TARBALL_OUT_PATH: LazyLock<StorePath> = LazyLock::new(|| {
210        StorePath::from_bytes(b"7adgvk5zdfq4pwrhsm3n9lzypb12gw0g-source").unwrap()
211    });
212
213    /// Ensure that we don't allow adding a derivation that depends on another,
214    /// not-yet-added derivation.
215    #[test]
216    #[should_panic]
217    fn drv_reject_if_missing_input_drv() {
218        let mut known_paths = KnownPaths::default();
219
220        // FOO_DRV depends on BAR_DRV, which wasn't added.
221        known_paths.add_derivation(FOO_DRV_PATH.clone(), FOO_DRV.clone());
222    }
223
224    #[test]
225    fn drv_happy_path() {
226        let mut known_paths = KnownPaths::default();
227
228        // get_drv_by_drvpath should return None for non-existing Derivations,
229        // same as get_hash_derivation_modulo and get_drv_path_for_output_path
230        assert_eq!(None, known_paths.get_drv_by_drvpath(&BAR_DRV_PATH.as_ref()));
231        assert_eq!(
232            None,
233            known_paths.get_hash_derivation_modulo(&BAR_DRV_PATH.as_ref())
234        );
235        assert_eq!(
236            None,
237            known_paths.get_drv_path_for_output_path(&BAR_OUT_PATH.as_ref())
238        );
239
240        // Add BAR_DRV
241        known_paths.add_derivation(BAR_DRV_PATH.clone(), BAR_DRV.clone());
242
243        // We should get it back
244        assert_eq!(
245            Some(&BAR_DRV.clone()),
246            known_paths.get_drv_by_drvpath(&BAR_DRV_PATH.as_ref())
247        );
248
249        // Test get_drv_path_for_output_path
250        assert_eq!(
251            Some(&BAR_DRV_PATH.clone()),
252            known_paths.get_drv_path_for_output_path(&BAR_OUT_PATH.as_ref())
253        );
254
255        // It should be possible to get the hash derivation modulo.
256        assert_eq!(
257            Some(&Sha256::new(hex!(
258                "c79aebd0ce3269393d4a1fde2cbd1d975d879b40f0bf40a48f550edc107fd5df"
259            ))),
260            known_paths.get_hash_derivation_modulo(&BAR_DRV_PATH.as_ref())
261        );
262
263        // Now insert FOO_DRV too. It shouldn't panic, as BAR_DRV is already
264        // added.
265        known_paths.add_derivation(FOO_DRV_PATH.clone(), FOO_DRV.clone());
266
267        assert_eq!(
268            Some(&FOO_DRV.clone()),
269            known_paths.get_drv_by_drvpath(&FOO_DRV_PATH.as_ref())
270        );
271        assert_eq!(
272            Some(&Sha256::new(hex!(
273                "af030d36d63d3d7f56a71adaba26b36f5fa1f9847da5eed953ed62e18192762f"
274            ))),
275            known_paths.get_hash_derivation_modulo(&FOO_DRV_PATH.as_ref())
276        );
277
278        // Test get_drv_path_for_output_path
279        assert_eq!(
280            Some(&FOO_DRV_PATH.clone()),
281            known_paths.get_drv_path_for_output_path(&FOO_OUT_PATH.as_ref())
282        );
283    }
284
285    #[test]
286    fn fetch_happy_path() {
287        let mut known_paths = KnownPaths::default();
288
289        // get_fetch_for_output_path should return None for new fetches.
290        assert!(
291            known_paths
292                .get_fetch_for_output_path(&FETCH_TARBALL_OUT_PATH.as_ref())
293                .is_none()
294        );
295
296        // add_fetch should return the properly calculated store paths.
297        assert_eq!(
298            *FETCH_TARBALL_OUT_PATH,
299            known_paths
300                .add_fetch(FETCH_TARBALL.clone(), "source")
301                .unwrap()
302                .to_owned()
303        );
304
305        assert_eq!(
306            *FETCH_URL_OUT_PATH,
307            known_paths
308                .add_fetch(FETCH_URL.clone(), "notmuch-extract-patch")
309                .unwrap()
310                .to_owned()
311        );
312    }
313
314    #[test]
315    fn get_derivations_working() {
316        let mut known_paths = KnownPaths::default();
317
318        // Add BAR_DRV
319        known_paths.add_derivation(BAR_DRV_PATH.clone(), BAR_DRV.clone());
320
321        // We should be able to find BAR_DRV_PATH and BAR_DRV as a pair in get_derivations.
322        assert_eq!(
323            Some((BAR_DRV_PATH.as_ref(), &BAR_DRV.clone())),
324            known_paths
325                .get_derivations()
326                .find(|(s, d)| (s, *d) == (&BAR_DRV_PATH.as_ref(), &*BAR_DRV))
327        );
328    }
329
330    // TODO: add test panicking about missing digest
331}
snix_build_glue/known_paths.rs

snix_build_glue/
known_paths.rs
