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Tidy up

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This commit is contained in:
Laurenz 2025-03-11 14:17:27 +01:00
parent 3c6a284387
commit 62f7c37dc8
1 changed files with 24 additions and 29 deletions
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53
crates/typst-kit/src/package.rs
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@ -193,40 +193,35 @@ impl PackageStorage {
}
};
// Temporary place where the package will be extracted before being
// moved to the target directory. To avoid name clashing we use a PRNG
// to get a unique directory name.
let tempdir = Tempdir::create(cache_dir.join(format!(
"{}/{}/.tmp-{}-{}",
spec.namespace,
spec.name,
// The directory in which the package's version lives.
let base_dir = cache_dir.join(format!("{}/{}", spec.namespace, spec.name));
// The place at which the specific package version will live in the end.
let package_dir = base_dir.join(format!("{}", spec.version));
// To prevent multiple Typst instances from interferring, we download
// into a temporary directory first and then move this directory to
// its final destination.
//
// In the `rename` function's documentation it is stated:
// > This will not work if the new name is on a different mount point.
//
// By locating the temporary directory directly next to where the
// package directory will live, we are (trying our best) making sure
// that `tempdir` and `package_dir` are on the same mount point.
let tempdir = Tempdir::create(base_dir.join(format!(
".tmp-{}-{}",
spec.version,
fastrand::u32(..),
)))
.map_err(|err| error("failed to create temporary package directory", err))?;
// Decompress the archive into the temporary directory.
let decompressed = flate2::read::GzDecoder::new(data.as_slice());
tar::Archive::new(decompressed)
.unpack(&tempdir)
.map_err(|err| PackageError::MalformedArchive(Some(eco_format!("{err}"))))?;
// The place into which we'll move the extracted package.
let package_dir =
cache_dir.join(format!("{}/{}/{}", spec.namespace, spec.name, spec.version));
// As to not overcomplicate the code to combat an already rare case
// where multiple instances try to download the same package version
// concurrently, we are abusing the behavior of the `rename` FS
// operation without the help of file locking.
//
// From the function's documentation it is stated that:
//
// > This will not work if the new name is on a different mount point.
//
// By extracting package into the same base directory where all packages
// live we are (trying our best) making sure that `extracted_package_dir`
// and `package_dir` are on the same mount point.
//
// When trying to move (i.e., `rename`) the directory from one place to
// another and the target/destination directory is empty, then the
// operation will succeed (if it's atomic, or hardware doesn't fail, or
@ -234,11 +229,11 @@ impl PackageStorage {
// empty, i.e., another instance already successfully moved the package,
// then we can safely ignore the `DirectoryNotEmpty` error.
//
// This means that we do not check the integrity of the existing moved
// package in a very rare case where it is broken, as it does not
// (currently) justify the additional code complexity. If such situation
// occur and it will be reported, then we probably would consider a
// more comprehensive solution (i.e., file locking or checksums).
// This means that we do not check the integrity of an existing moved
// package, just like we don't check the integrity if the package
// directory already existed in the first place. If situations with
// broken packages still occur even with the rename safeguard, we might
// consider more complex solutions like file locking or checksums.
match fs::rename(&tempdir, &package_dir) {
Ok(()) => Ok(()),
Err(err) if err.kind() == io::ErrorKind::DirectoryNotEmpty => Ok(()),