Enum PreviewFeature 

#[repr(u64)]
pub enum PreviewFeature {
    PythonInstallDefault = 1,
    JsonOutput = 2,
    Pylock = 4,
    AddBounds = 8,
    PackageConflicts = 16,
    ExtraBuildDependencies = 32,
    DetectModuleConflicts = 64,
    FormatCommand = 128,
    NativeAuth = 256,
    S3Endpoint = 512,
    CacheSize = 1_024,
    CachePhysicalSpace = 2_048,
    InitProjectFlag = 4_096,
    WorkspaceMetadata = 8_192,
    WorkspaceDir = 16_384,
    WorkspaceList = 32_768,
    SbomExport = 65_536,
    AuthHelper = 131_072,
    TargetWorkspaceDiscovery = 262_144,
    MetadataJson = 524_288,
    GcsEndpoint = 1_048_576,
    AdjustUlimit = 2_097_152,
    SpecialCondaEnvNames = 4_194_304,
    RelocatableEnvsDefault = 8_388_608,
    PublishRequireNormalized = 16_777_216,
    AuditCommand = 33_554_432,
    ProjectDirectoryMustExist = 67_108_864,
    IndexExcludeNewer = 134_217_728,
    AzureEndpoint = 268_435_456,
    TomlBackwardsCompatibility = 536_870_912,
    MalwareCheck = 1_073_741_824,
    VenvSafeClear = 2_147_483_648,
    CheckCommand = 4_294_967_296,
    PackagedInit = 8_589_934_592,
    CentralizedProjectEnvs = 17_179_869_184,
    ToolInstallLocks = 34_359_738_368,
    WorkspaceListScripts = 68_719_476_736,
    IndexHashAlgorithm = 137_438_953_472,
    LockfileFormatCheck = 274_877_906_944,
    LockfileNormalization = 549_755_813_888,
    LockWithoutMetadata = 1_099_511_627_776,
    IndexByName = 2_199_023_255_552,
    ArtifactHashFiltering = 4_398_046_511_104,
    ContentAddressedCache = 8_796_093_022_208,
    MissingExcludeNewerPackageLock = 17_592_186_044_416,
    ResolutionInputs = 35_184_372_088_832,
    BatchExport = 70_368_744_177_664,
    FrozenLockfile = 140_737_488_355_328,
    MinimumLibcVersion = 281_474_976_710_656,
    BuildDependencyCheck = 562_949_953_421_312,
    BuildLazyImports = 1_125_899_906_842_624,
    BuildDependencyHashes = 2_251_799_813_685_248,
    WheelVariants = 4_503_599_627_370_496,
}

Variants

PythonInstallDefault = 1

The uv python install --default option installs python and python3 executables alongside the versioned executable, making a uv-managed Python available without specifying its minor version. When no version is requested and no .python-version file is found, enabling this feature also makes uv python install create these executables by default. See installing Python executables for details about the installation location and handling of existing executables.

JsonOutput = 2

Commands that support --output-format json, such as uv tree, can produce machine-readable output for use by other tools. The JSON schemas are experimental and may change without warning; enabling this feature silences the preview warning.

Pylock = 4

The uv pip install and uv pip sync commands can install dependencies from pylock.toml files, the standardized Python lockfile format. For example, use uv pip install -r pylock.toml or uv pip sync pylock.toml; enabling this feature silences the preview warning.

AddBounds = 8

The add-bounds setting controls the default version bounds added by uv add. Instead of the default lower bound, dependencies can be constrained to a major or minor version range, or pinned to an exact version.

PackageConflicts = 16

Workspace members can declare conflicting dependencies at the package level, in addition to conflicts between extras or dependency groups. This allows members with incompatible requirements to share a lockfile, provided they are not installed together.

ExtraBuildDependencies = 32

The extra-build-dependencies setting augments a package’s declared build dependencies without disabling build isolation. It can supply a missing build dependency or, with match-runtime = true, ensure that a build dependency uses the same version as the project environment.

DetectModuleConflicts = 64

uv warns when multiple packages install conflicting Python modules into the same environment. These conflicts can cause imports to depend on installation order, even when the packages have different distribution names.

FormatCommand = 128

The uv format command formats Python code with Ruff, downloading the formatter when needed. It can also check formatting with --check or show proposed changes with --diff; enabling this feature silences the preview warning.

NativeAuth = 256

The uv auth commands store credentials in a system-native location, using Keychain Services on macOS, Credential Manager on Windows, or the Secret Service API on Linux. uv only retrieves credentials that it has stored itself, rather than credentials saved by other applications.

S3Endpoint = 512

uv can authenticate requests to an S3-compatible storage endpoint using AWS Signature Version 4. Set UV_S3_ENDPOINT_URL to identify the endpoint; credentials are obtained from the configured AWS credential sources.

CacheSize = 1_024

The uv cache size command reports the total size of uv’s cache. It supports human-readable output and a machine-readable byte count; enabling this feature silences the preview warning.

CachePhysicalSpace = 2_048

Cache cleanup reports the physical disk space reclaimed, accounting for hardlinks and copy-on-write clones on macOS and Linux. If an entry’s allocated size cannot be measured, uv reports a lower bound; other platforms continue to use a coarser estimate. See clearing the cache for details.

InitProjectFlag = 4_096

The uv init command rejects the deprecated --project option. To choose where to create a project, pass the target directory as a positional argument, such as uv init my-project.

WorkspaceMetadata = 8_192

The uv workspace metadata command exposes structured information about a workspace and its resolved dependencies for use by other tools. Its output is experimental and may change; use --sync to include a mapping from importable modules to the packages that provide them.

WorkspaceDir = 16_384

The uv workspace dir command prints the path to the workspace root. Use --package to print the path to a specific workspace member, for example, with --package my-package.

WorkspaceList = 32_768

The uv workspace list command lists the names of workspace members, with one name per line. Use --paths to display their paths instead, for example, when passing workspace directories to another tool.

SbomExport = 65_536

The uv export --format cyclonedx1.5 command exports a software bill of materials in CycloneDX 1.5 JSON format. This describes the locked dependencies in a format that can be consumed by software inventory and security tools.

AuthHelper = 131_072

The uv auth helper command lets external tools retrieve HTTP credentials through uv. It currently supports the Bazel credential helper protocol, reading a JSON request from standard input and writing a JSON response containing authentication headers when credentials are available.

TargetWorkspaceDiscovery = 262_144

For a local uv run target, uv starts project and workspace discovery from the directory containing the target instead of the current working directory. This feature takes effect before configuration is loaded, so it must be enabled on the command line or through an environment variable.

MetadataJson = 524_288

The uv build backend includes METADATA.json and WHEEL.json files in built wheels alongside the standard METADATA and WHEEL files. These additional files expose package and wheel metadata in JSON format.

GcsEndpoint = 1_048_576

uv can authenticate requests to a Google Cloud Storage endpoint using Google Cloud credentials. Set UV_GCS_ENDPOINT_URL to identify the endpoint; authentication uses GOOGLE_APPLICATION_CREDENTIALS or Application Default Credentials.

AdjustUlimit = 2_097_152

On Unix, uv raises the process’s soft open-file limit at startup, up to the hard limit. This helps avoid “too many open files” errors during concurrent operations, and child processes inherit the raised limit.

SpecialCondaEnvNames = 4_194_304

Conda environments named base or root are classified using their paths, like other named environments. The name alone does not cause uv to treat a user-created environment as the base Conda installation.

RelocatableEnvsDefault = 8_388_608

uv creates relocatable virtual environments by default, using relative paths in their entry point and activation scripts. This allows the environment to be moved without invalidating those scripts, although arbitrary binaries and nonstandard scripts are not guaranteed to be relocatable. Use uv venv --no-relocatable to opt out.

PublishRequireNormalized = 16_777_216

The uv publish command requires distribution filenames to be normalized. Files with non-normalized names are skipped when selecting distributions to upload.

AuditCommand = 33_554_432

The uv audit and uv tool audit commands check project and installed-tool dependencies for known vulnerabilities. Tool audits use the lockfiles recorded by the tool-install-locks feature; enabling both features silences the preview warning for uv tool audit.

ProjectDirectoryMustExist = 67_108_864

The --project option rejects invalid paths instead of warning and continuing in the current directory. Except for uv init, the path must already exist as a directory or point to a pyproject.toml file. This feature takes effect before configuration is loaded, so it must be enabled on the command line or through an environment variable.

IndexExcludeNewer = 134_217_728

Each configured package index can set its own exclude-newer cutoff, overriding the global cutoff for packages served by that index. Set the value to false to disable the cutoff for an index; package-specific exclude-newer-package values still take precedence.

AzureEndpoint = 268_435_456

uv can authenticate requests to an Azure Blob Storage endpoint using Azure credentials. Set UV_AZURE_ENDPOINT_URL to identify the endpoint; authentication uses the default Azure credential chain, including Azure CLI credentials and workload identity.

TomlBackwardsCompatibility = 536_870_912

When building source distributions, the uv build backend rewrites pyproject.toml as TOML 1.0 for compatibility with older build tools. The original file is included as pyproject.toml.orig in the source distribution.

MalwareCheck = 1_073_741_824

The uv sync command and other installation commands can check packages for malware using OSV before installing them. This checks for known malicious packages, while uv audit checks dependencies for known vulnerabilities.

VenvSafeClear = 2_147_483_648

The uv venv --clear option refuses to clear a directory that does not contain a pyvenv.cfg file. This helps avoid removing unrelated files when the target is not a virtual environment; use --force to explicitly allow clearing such a directory.

CheckCommand = 4_294_967_296

The uv check command runs Python type checking with ty. It uses the project’s environment to resolve imports and can synchronize that environment before checking; enabling this feature silences the preview warning.

PackagedInit = 8_589_934_592

The uv init command creates a packaged application by default, with a src/ layout, a build system, and a script entry point. This gives new applications an installable package structure without requiring --package.

CentralizedProjectEnvs = 17_179_869_184

uv stores default project virtual environments in its cache and attempts to link .venv to the cached environment. Switching interpreters selects separate cached environments that can be reused later. Explicit environment paths and environments selected with --active are not centralized.

ToolInstallLocks = 34_359_738_368

uv stores a uv.lock file alongside each installed tool and reuses it for subsequent installations and upgrades. The lockfile records the tool’s resolved dependencies and also provides the dependency information used by uv tool audit.

WorkspaceListScripts = 68_719_476_736

The uv workspace list --scripts command lists standalone Python scripts with inline metadata under the workspace root. It prints script paths relative to the workspace root, allowing tools to discover scripts separately from workspace members.

IndexHashAlgorithm = 137_438_953_472

Each configured package index can require a hash algorithm with the hash-algorithm setting. uv records that algorithm’s hash in the lockfile and fails if a distribution does not advertise it, instead of selecting another available algorithm.

LockfileFormatCheck = 274_877_906_944

Commands using --locked or --check reject non-canonical lockfile formatting, even if the lockfile can be parsed. This makes formatting part of the lockfile check in addition to checking whether the resolution is up to date.

LockfileNormalization = 549_755_813_888

uv combines equivalent dependency declarations when writing lockfiles. This reduces duplicated declarations in the recorded requirements, constraints, overrides, exclusions, and dependency groups.

LockWithoutMetadata = 1_099_511_627_776

uv omits the package.metadata tables from uv.lock, except for remote URL and Git dependencies. Their metadata is retained so uv can check whether those sources are requested or stale without network access.

IndexByName = 2_199_023_255_552

The --index and --default-index options accept the names of configured package indexes as well as URLs. For example, --index internal selects the configured index named internal, so its URL does not need to be repeated on the command line.

ArtifactHashFiltering = 4_398_046_511_104

The uv pip compile --generate-hashes command restricts the generated hashes to artifacts allowed by the selected binary and build policies. For example, when source builds are disabled, hashes for source distributions are omitted.

ContentAddressedCache = 8_796_093_022_208

uv identifies cached wheel archives by a digest of their contents. Matching archive contents can share a cache entry, reducing duplication when the same wheel contents are encountered more than once.

MissingExcludeNewerPackageLock = 17_592_186_044_416

uv omits exclude-newer-package entries from the lockfile when the corresponding packages are absent from the resolved dependencies. This keeps cutoffs for unrelated packages out of uv.lock.

ResolutionInputs = 35_184_372_088_832

uv omits redundant runtime constraints and unused overrides, exclusions, dependency metadata, and package-specific upload cutoffs from the lockfile. It records which settings were consulted during resolution, including backtracking, so settings that affected resolution can be retained even when their packages are absent from the final dependency graph.

BatchExport = 70_368_744_177_664

The uv export --batch option exports multiple dependency selections from a TOML manifest containing [[export]] entries. Each entry specifies an output-file and its own package, extra, and dependency group selections; output paths are relative to the manifest.

FrozenLockfile = 140_737_488_355_328

Frozen project commands can use uv.lock without the workspace’s pyproject.toml file. Discovery requires a lockfile with revision 5 or later, which records the workspace information needed to select dependencies without the manifest.

MinimumLibcVersion = 281_474_976_710_656

The minimum-libc-version setting specifies the oldest glibc or musl versions that must be supported during universal resolution. Use it with required-environments to require compatible wheels for the selected Linux environments without excluding wheels for newer libc versions.

BuildDependencyCheck = 562_949_953_421_312

Before a nonisolated uv build, uv checks that the selected environment satisfies declared, backend-reported, and transitive build requirements. This reports missing or incompatible build dependencies before building; use --skip-dependency-check to skip the check.

BuildLazyImports = 1_125_899_906_842_624

uv enables lazy imports when invoking build backends on CPython 3.15 and later. This can reduce the work performed by imports during a build, but can also change import-time side effects in third-party build backends.

BuildDependencyHashes = 2_251_799_813_685_248

The --require-build-hashes option requires hashes for every build dependency, including transitive dependencies. It applies when build dependencies are downloaded during builds, project resolution, and installation. See project build dependency hashes for configuration and exceptions.

WheelVariants = 4_503_599_627_370_496

Enables experimental support for wheel variants. Variant wheels are not yet selectable.

Implementations

impl PreviewFeature

pub const fn metadata() -> &'static [(Self, &'static str, &'static [&'static str])]

Returns each enum variant, its documentation, and its aliases.

Trait Implementations

impl BitAnd for PreviewFeature

type Output = BitFlags<PreviewFeature>

The resulting type after applying the & operator.

fn bitand(self, other: Self) -> Self::Output

Performs the & operation.

impl BitFlag for PreviewFeature

fn empty() -> BitFlags<Self>

Create a BitFlags with no flags set (in other words, with a value of 0).

fn all() -> BitFlags<Self>

Create a BitFlags with all flags set.

fn from_bits(bits: Self::Numeric) -> Result<BitFlags<Self>, FromBitsError<Self>>

Create a BitFlags if the raw value provided does not contain any illegal flags.

fn from_bits_truncate(bits: Self::Numeric) -> BitFlags<Self>

Create a BitFlags from an underlying bitwise value. If any invalid bits are set, ignore them.

unsafe fn from_bits_unchecked(bits: Self::Numeric) -> BitFlags<Self>

Create a BitFlags unsafely, without checking if the bits form a valid bit pattern for the type.

impl BitOr for PreviewFeature

type Output = BitFlags<PreviewFeature>

The resulting type after applying the | operator.

fn bitor(self, other: Self) -> Self::Output

Performs the | operation.

impl BitXor for PreviewFeature

type Output = BitFlags<PreviewFeature>

The resulting type after applying the ^ operator.

fn bitxor(self, other: Self) -> Self::Output

Performs the ^ operation.

impl Clone for PreviewFeature

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for PreviewFeature

impl Debug for PreviewFeature

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for PreviewFeature

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for PreviewFeature

impl FromStr for PreviewFeature

type Err = PreviewFeatureParseError

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

impl Not for PreviewFeature

type Output = BitFlags<PreviewFeature>

The resulting type after applying the ! operator.

fn not(self) -> Self::Output

Performs the unary ! operation.

impl PartialEq for PreviewFeature

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl RawBitFlags for PreviewFeature

const EMPTY: <Self as RawBitFlags>::Numeric = 0

A value with no bits set.

const DEFAULT: <Self as RawBitFlags>::Numeric = 0

The value used by the Default implementation. Equivalent to EMPTY, unless customized.

const ALL_BITS: <Self as RawBitFlags>::Numeric

A value with all flag bits set.

const BITFLAGS_TYPE_NAME: &'static str = "BitFlags<PreviewFeature>"

The name of the type for debug formatting purposes.

type Numeric = u64

The underlying integer type.

fn bits(self) -> <Self as RawBitFlags>::Numeric

Return the bits as a number type.

impl StructuralPartialEq for PreviewFeature