1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
//! Access to a Git index based registry. See [`RemoteRegistry`] for details.

use crate::core::global_cache_tracker;
use crate::core::{GitReference, PackageId, SourceId};
use crate::sources::git;
use crate::sources::git::fetch::RemoteKind;
use crate::sources::git::resolve_ref;
use crate::sources::registry::download;
use crate::sources::registry::MaybeLock;
use crate::sources::registry::{LoadResponse, RegistryConfig, RegistryData};
use crate::util::cache_lock::CacheLockMode;
use crate::util::errors::CargoResult;
use crate::util::interning::InternedString;
use crate::util::{Filesystem, GlobalContext};
use anyhow::Context as _;
use cargo_util::paths;
use lazycell::LazyCell;
use std::cell::{Cell, Ref, RefCell};
use std::fs::File;
use std::mem;
use std::path::Path;
use std::str;
use std::task::{ready, Poll};
use tracing::{debug, trace};

/// A remote registry is a registry that lives at a remote URL (such as
/// crates.io). The git index is cloned locally, and `.crate` files are
/// downloaded as needed and cached locally.
///
/// This type is primarily accessed through the [`RegistryData`] trait.
///
/// See the [module-level documentation](super) for the index format and layout.
///
/// ## History of Git-based index registry
///
/// Using Git to host this index used to be quite efficient. The full index can
/// be stored efficiently locally on disk, and once it is downloaded, all
/// queries of a registry can happen locally and needn't touch the network.
/// Git-based index was a reasonable design choice at the time when HTTP/2
/// was just introduced.
///
/// However, the full index keeps growing as crates.io grows. It becomes
/// relatively big and slows down the first use of Cargo. Git (specifically
/// libgit2) is not efficient at handling huge amounts of small files either.
/// On the other hand, newer protocols like HTTP/2 are prevalent and capable to
/// serve a bunch of tiny files. Today, it is encouraged to use [`HttpRegistry`],
/// which is the default from 1.70.0. That being said, Cargo will continue
/// supporting Git-based index for a pretty long while.
///
/// [`HttpRegistry`]: super::http_remote::HttpRegistry
pub struct RemoteRegistry<'gctx> {
    /// The name of this source, a unique string (across all sources) used as
    /// the directory name where its cached content is stored.
    name: InternedString,
    /// Path to the registry index (`$CARGO_HOME/registry/index/$REG-HASH`).
    index_path: Filesystem,
    /// Path to the cache of `.crate` files (`$CARGO_HOME/registry/cache/$REG-HASH`).
    cache_path: Filesystem,
    /// The unique identifier of this registry source.
    source_id: SourceId,
    /// This reference is stored so that when a registry needs update, it knows
    /// where to fetch from.
    index_git_ref: GitReference,
    gctx: &'gctx GlobalContext,
    /// A Git [tree object] to help this registry find crate metadata from the
    /// underlying Git repository.
    ///
    /// This is stored here to prevent Git from repeatedly creating a tree object
    /// during each call into `load()`.
    ///
    /// [tree object]: https://git-scm.com/book/en/v2/Git-Internals-Git-Objects#_tree_objects
    tree: RefCell<Option<git2::Tree<'static>>>,
    /// A Git repository that contains the actual index we want.
    repo: LazyCell<git2::Repository>,
    /// The current HEAD commit of the underlying Git repository.
    head: Cell<Option<git2::Oid>>,
    /// This stores sha value of the current HEAD commit for convenience.
    current_sha: Cell<Option<InternedString>>,
    /// Whether this registry needs to update package information.
    ///
    /// See [`RemoteRegistry::mark_updated`] on how to make sure a registry
    /// index is updated only once per session.
    needs_update: bool,
    /// Disables status messages.
    quiet: bool,
}

impl<'gctx> RemoteRegistry<'gctx> {
    /// Creates a Git-rebased remote registry for `source_id`.
    ///
    /// * `name` --- Name of a path segment where `.crate` tarballs and the
    ///   registry index are stored. Expect to be unique.
    pub fn new(
        source_id: SourceId,
        gctx: &'gctx GlobalContext,
        name: &str,
    ) -> RemoteRegistry<'gctx> {
        RemoteRegistry {
            name: name.into(),
            index_path: gctx.registry_index_path().join(name),
            cache_path: gctx.registry_cache_path().join(name),
            source_id,
            gctx,
            index_git_ref: GitReference::DefaultBranch,
            tree: RefCell::new(None),
            repo: LazyCell::new(),
            head: Cell::new(None),
            current_sha: Cell::new(None),
            needs_update: false,
            quiet: false,
        }
    }

    /// Creates intermediate dirs and initialize the repository.
    fn repo(&self) -> CargoResult<&git2::Repository> {
        self.repo.try_borrow_with(|| {
            trace!("acquiring registry index lock");
            let path = self
                .gctx
                .assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);

            match git2::Repository::open(&path) {
                Ok(repo) => Ok(repo),
                Err(_) => {
                    drop(paths::remove_dir_all(&path));
                    paths::create_dir_all(&path)?;

                    // Note that we'd actually prefer to use a bare repository
                    // here as we're not actually going to check anything out.
                    // All versions of Cargo, though, share the same CARGO_HOME,
                    // so for compatibility with older Cargo which *does* do
                    // checkouts we make sure to initialize a new full
                    // repository (not a bare one).
                    //
                    // We should change this to `init_bare` whenever we feel
                    // like enough time has passed or if we change the directory
                    // that the folder is located in, such as by changing the
                    // hash at the end of the directory.
                    //
                    // Note that in the meantime we also skip `init.templatedir`
                    // as it can be misconfigured sometimes or otherwise add
                    // things that we don't want.
                    let mut opts = git2::RepositoryInitOptions::new();
                    opts.external_template(false);
                    Ok(git2::Repository::init_opts(&path, &opts).with_context(|| {
                        format!("failed to initialize index git repository (in {:?})", path)
                    })?)
                }
            }
        })
    }

    /// Get the object ID of the HEAD commit from the underlying Git repository.
    fn head(&self) -> CargoResult<git2::Oid> {
        if self.head.get().is_none() {
            let repo = self.repo()?;
            let oid = resolve_ref(&self.index_git_ref, repo)?;
            self.head.set(Some(oid));
        }
        Ok(self.head.get().unwrap())
    }

    /// Returns a [`git2::Tree`] object of the current HEAD commit of the
    /// underlying Git repository.
    fn tree(&self) -> CargoResult<Ref<'_, git2::Tree<'_>>> {
        {
            let tree = self.tree.borrow();
            if tree.is_some() {
                return Ok(Ref::map(tree, |s| s.as_ref().unwrap()));
            }
        }
        let repo = self.repo()?;
        let commit = repo.find_commit(self.head()?)?;
        let tree = commit.tree()?;

        // SAFETY:
        // Unfortunately in libgit2 the tree objects look like they've got a
        // reference to the repository object which means that a tree cannot
        // outlive the repository that it came from. Here we want to cache this
        // tree, though, so to accomplish this we transmute it to a static
        // lifetime.
        //
        // Note that we don't actually hand out the static lifetime, instead we
        // only return a scoped one from this function. Additionally the repo
        // we loaded from (above) lives as long as this object
        // (`RemoteRegistry`) so we then just need to ensure that the tree is
        // destroyed first in the destructor, hence the destructor on
        // `RemoteRegistry` below.
        let tree = unsafe { mem::transmute::<git2::Tree<'_>, git2::Tree<'static>>(tree) };
        *self.tree.borrow_mut() = Some(tree);
        Ok(Ref::map(self.tree.borrow(), |s| s.as_ref().unwrap()))
    }

    /// Gets the current version of the registry index.
    ///
    /// It is usually sha of the HEAD commit from the underlying Git repository.
    fn current_version(&self) -> Option<InternedString> {
        if let Some(sha) = self.current_sha.get() {
            return Some(sha);
        }
        let sha = InternedString::new(&self.head().ok()?.to_string());
        self.current_sha.set(Some(sha));
        Some(sha)
    }

    /// Whether the registry is up-to-date. See [`Self::mark_updated`] for more.
    fn is_updated(&self) -> bool {
        self.gctx.updated_sources().contains(&self.source_id)
    }

    /// Marks this registry as up-to-date.
    ///
    /// This makes sure the index is only updated once per session since it is
    /// an expensive operation. This generally only happens when the resolver
    /// is run multiple times, such as during `cargo publish`.
    fn mark_updated(&self) {
        self.gctx.updated_sources().insert(self.source_id);
    }
}

impl<'gctx> RegistryData for RemoteRegistry<'gctx> {
    fn prepare(&self) -> CargoResult<()> {
        self.repo()?;
        self.gctx
            .deferred_global_last_use()?
            .mark_registry_index_used(global_cache_tracker::RegistryIndex {
                encoded_registry_name: self.name,
            });
        Ok(())
    }

    fn index_path(&self) -> &Filesystem {
        &self.index_path
    }

    fn assert_index_locked<'a>(&self, path: &'a Filesystem) -> &'a Path {
        self.gctx
            .assert_package_cache_locked(CacheLockMode::DownloadExclusive, path)
    }

    /// Read the general concept for `load()` on [`RegistryData::load`].
    ///
    /// `index_version` is a string representing the version of the file used
    /// to construct the cached copy.
    ///
    /// Older versions of Cargo used the single value of the hash of the HEAD
    /// commit as a `index_version`. This is technically correct but a little
    /// too conservative. If a new commit is fetched all cached files need to
    /// be regenerated even if a particular file was not changed.
    ///
    /// However if an old cargo has written such a file we still know how to
    /// read it, as long as we check for that hash value.
    ///
    /// Cargo now uses a hash of the file's contents as provided by git.
    fn load(
        &mut self,
        _root: &Path,
        path: &Path,
        index_version: Option<&str>,
    ) -> Poll<CargoResult<LoadResponse>> {
        if self.needs_update {
            return Poll::Pending;
        }
        // Check if the cache is valid.
        let git_commit_hash = self.current_version();
        if index_version.is_some() && index_version == git_commit_hash.as_deref() {
            // This file was written by an old version of cargo, but it is
            // still up-to-date.
            return Poll::Ready(Ok(LoadResponse::CacheValid));
        }
        // Note that the index calls this method and the filesystem is locked
        // in the index, so we don't need to worry about an `update_index`
        // happening in a different process.
        fn load_helper(
            registry: &RemoteRegistry<'_>,
            path: &Path,
            index_version: Option<&str>,
        ) -> CargoResult<LoadResponse> {
            let repo = registry.repo()?;
            let tree = registry.tree()?;
            let entry = tree.get_path(path);
            let entry = entry?;
            let git_file_hash = Some(entry.id().to_string());

            // Check if the cache is valid.
            if index_version.is_some() && index_version == git_file_hash.as_deref() {
                return Ok(LoadResponse::CacheValid);
            }

            let object = entry.to_object(repo)?;
            let Some(blob) = object.as_blob() else {
                anyhow::bail!("path `{}` is not a blob in the git repo", path.display())
            };

            Ok(LoadResponse::Data {
                raw_data: blob.content().to_vec(),
                index_version: git_file_hash,
            })
        }

        match load_helper(&self, path, index_version) {
            Ok(result) => Poll::Ready(Ok(result)),
            Err(_) if !self.is_updated() => {
                // If git returns an error and we haven't updated the repo,
                // return pending to allow an update to try again.
                self.needs_update = true;
                Poll::Pending
            }
            Err(e)
                if e.downcast_ref::<git2::Error>()
                    .map(|e| e.code() == git2::ErrorCode::NotFound)
                    .unwrap_or_default() =>
            {
                // The repo has been updated and the file does not exist.
                Poll::Ready(Ok(LoadResponse::NotFound))
            }
            Err(e) => Poll::Ready(Err(e)),
        }
    }

    fn config(&mut self) -> Poll<CargoResult<Option<RegistryConfig>>> {
        debug!("loading config");
        self.prepare()?;
        self.gctx
            .assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);
        match ready!(self.load(Path::new(""), Path::new(RegistryConfig::NAME), None)?) {
            LoadResponse::Data { raw_data, .. } => {
                trace!("config loaded");
                let cfg: RegistryConfig = serde_json::from_slice(&raw_data)?;
                Poll::Ready(Ok(Some(cfg)))
            }
            _ => Poll::Ready(Ok(None)),
        }
    }

    fn block_until_ready(&mut self) -> CargoResult<()> {
        if !self.needs_update {
            return Ok(());
        }

        self.needs_update = false;

        if self.is_updated() {
            return Ok(());
        }
        self.mark_updated();

        if self.gctx.offline() {
            return Ok(());
        }
        if self.gctx.cli_unstable().no_index_update {
            return Ok(());
        }

        debug!("updating the index");

        // Ensure that we'll actually be able to acquire an HTTP handle later on
        // once we start trying to download crates. This will weed out any
        // problems with `.cargo/config` configuration related to HTTP.
        //
        // This way if there's a problem the error gets printed before we even
        // hit the index, which may not actually read this configuration.
        self.gctx.http()?;

        self.prepare()?;
        self.head.set(None);
        *self.tree.borrow_mut() = None;
        self.current_sha.set(None);
        let _path = self
            .gctx
            .assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);
        if !self.quiet {
            self.gctx
                .shell()
                .status("Updating", self.source_id.display_index())?;
        }

        // Fetch the latest version of our `index_git_ref` into the index
        // checkout.
        let url = self.source_id.url();
        let repo = self.repo.borrow_mut().unwrap();
        git::fetch(
            repo,
            url.as_str(),
            &self.index_git_ref,
            self.gctx,
            RemoteKind::Registry,
        )
        .with_context(|| format!("failed to fetch `{}`", url))?;

        Ok(())
    }

    /// Read the general concept for `invalidate_cache()` on
    /// [`RegistryData::invalidate_cache`].
    ///
    /// To fully invalidate, undo [`RemoteRegistry::mark_updated`]'s work.
    fn invalidate_cache(&mut self) {
        self.needs_update = true;
    }

    fn set_quiet(&mut self, quiet: bool) {
        self.quiet = quiet;
    }

    fn is_updated(&self) -> bool {
        self.is_updated()
    }

    fn download(&mut self, pkg: PackageId, checksum: &str) -> CargoResult<MaybeLock> {
        let registry_config = loop {
            match self.config()? {
                Poll::Pending => self.block_until_ready()?,
                Poll::Ready(cfg) => break cfg.unwrap(),
            }
        };

        download::download(
            &self.cache_path,
            &self.gctx,
            self.name,
            pkg,
            checksum,
            registry_config,
        )
    }

    fn finish_download(
        &mut self,
        pkg: PackageId,
        checksum: &str,
        data: &[u8],
    ) -> CargoResult<File> {
        download::finish_download(
            &self.cache_path,
            &self.gctx,
            self.name.clone(),
            pkg,
            checksum,
            data,
        )
    }

    fn is_crate_downloaded(&self, pkg: PackageId) -> bool {
        download::is_crate_downloaded(&self.cache_path, &self.gctx, pkg)
    }
}

/// Implemented to just be sure to drop `tree` field before our other fields.
/// See SAFETY inside [`RemoteRegistry::tree()`] for more.
impl<'gctx> Drop for RemoteRegistry<'gctx> {
    fn drop(&mut self) {
        self.tree.borrow_mut().take();
    }
}