Update the interface for declaring Python download preferences

crates/uv-cli/src/lib.rs

@@ -15,7 +15,7 @@ use uv_configuration::{
     ConfigSettingEntry, IndexStrategy, KeyringProviderType, PackageNameSpecifier, TargetTriple,
 };
 use uv_normalize::{ExtraName, PackageName};
-use uv_python::{PythonFetch, PythonPreference, PythonVersion};
+use uv_python::{PythonDownloads, PythonPreference, PythonVersion};
 use uv_resolver::{AnnotationStyle, ExcludeNewer, PrereleaseMode, ResolutionMode};
 
 pub mod compat;
@@ -119,9 +119,17 @@ pub struct GlobalArgs {
     )]
     pub python_preference: Option<PythonPreference>,
 
-    /// Whether to automatically download Python when required.
+    /// Allow automatically downloading Python when required.
+    #[arg(global = true, long, help_heading = "Python options", hide = true)]
+    pub allow_python_downloads: bool,
+
+    /// Disable automatic downloads of Python.
     #[arg(global = true, long, help_heading = "Python options")]
-    pub python_fetch: Option<PythonFetch>,
+    pub no_python_downloads: bool,
+
+    /// Deprecated version of [`Self::python_downloads`].
+    #[arg(global = true, long, hide = true)]
+    pub python_fetch: Option<PythonDownloads>,
 
     /// Do not print any output.
     #[arg(global = true, long, short, conflicts_with = "verbose")]
@@ -258,7 +266,7 @@ pub enum Commands {
     ///
     /// When preview is enabled, i.e., via `--preview` or by using a preview
     /// command, uv will download Python if a version cannot be found. This
-    /// behavior can be disabled with the `--python-fetch` option.
+    /// behavior can be disabled with the `--python-downloads` option.
     ///
     /// The `--python` option allows requesting a different interpreter.
     ///

crates/uv-python/src/discovery.rs

@@ -79,12 +79,25 @@ pub enum PythonPreference {
 #[serde(deny_unknown_fields, rename_all = "kebab-case")]
 #[cfg_attr(feature = "clap", derive(clap::ValueEnum))]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
-pub enum PythonFetch {
-    /// Automatically fetch managed Python installations when needed.
+pub enum PythonDownloads {
+    /// Automatically download managed Python installations when needed.
     #[default]
+    #[serde(alias = "auto")]
     Automatic,
-    /// Do not automatically fetch managed Python installations; require explicit installation.
+    /// Do not automatically download managed Python installations; require explicit installation.
     Manual,
+    /// Do not ever allow Python downloads.
+    Never,
+}
+
+impl From<bool> for PythonDownloads {
+    fn from(value: bool) -> Self {
+        if value {
+            PythonDownloads::Automatic
+        } else {
+            PythonDownloads::Never
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
@@ -1298,7 +1311,7 @@ impl PythonPreference {
     }
 }
 
-impl PythonFetch {
+impl PythonDownloads {
     pub fn is_automatic(self) -> bool {
         matches!(self, Self::Automatic)
     }

crates/uv-python/src/installation.rs

@@ -15,7 +15,7 @@ use crate::implementation::LenientImplementationName;
 use crate::managed::{ManagedPythonInstallation, ManagedPythonInstallations};
 use crate::platform::{Arch, Libc, Os};
 use crate::{
-    downloads, Error, Interpreter, PythonFetch, PythonPreference, PythonSource, PythonVersion,
+    downloads, Error, Interpreter, PythonDownloads, PythonPreference, PythonSource, PythonVersion,
 };
 
 /// A Python interpreter and accompanying tools.
@@ -77,11 +77,11 @@ impl PythonInstallation {
     /// Find or fetch a [`PythonInstallation`].
     ///
     /// Unlike [`PythonInstallation::find`], if the required Python is not installed it will be installed automatically.
-    pub async fn find_or_fetch<'a>(
+    pub async fn find_or_download<'a>(
         request: Option<PythonRequest>,
         environments: EnvironmentPreference,
         preference: PythonPreference,
-        python_fetch: PythonFetch,
+        python_downloads: PythonDownloads,
         client_builder: &BaseClientBuilder<'a>,
         cache: &Cache,
         reporter: Option<&dyn Reporter>,
@@ -94,7 +94,7 @@ impl PythonInstallation {
             // If missing and allowed, perform a fetch
             Err(Error::MissingPython(err))
                 if preference.allows_managed()
-                    && python_fetch.is_automatic()
+                    && python_downloads.is_automatic()
                     && client_builder.connectivity.is_online() =>
             {
                 if let Some(request) = PythonDownloadRequest::from_request(&request) {

crates/uv-python/src/lib.rs

@@ -2,7 +2,7 @@
 use thiserror::Error;
 
 pub use crate::discovery::{
-    find_python_installations, EnvironmentPreference, Error as DiscoveryError, PythonFetch,
+    find_python_installations, EnvironmentPreference, Error as DiscoveryError, PythonDownloads,
     PythonNotFound, PythonPreference, PythonRequest, PythonSource, VersionRequest,
 };
 pub use crate::environment::PythonEnvironment;

crates/uv-settings/src/combine.rs

@@ -4,7 +4,7 @@ use std::path::PathBuf;
 use distribution_types::IndexUrl;
 use install_wheel_rs::linker::LinkMode;
 use uv_configuration::{ConfigSettings, IndexStrategy, KeyringProviderType, TargetTriple};
-use uv_python::{PythonFetch, PythonPreference, PythonVersion};
+use uv_python::{PythonDownloads, PythonPreference, PythonVersion};
 use uv_resolver::{AnnotationStyle, ExcludeNewer, PrereleaseMode, ResolutionMode};
 
 use crate::{FilesystemOptions, PipOptions};
@@ -70,7 +70,7 @@ impl_combine_or!(ResolutionMode);
 impl_combine_or!(String);
 impl_combine_or!(TargetTriple);
 impl_combine_or!(PythonPreference);
-impl_combine_or!(PythonFetch);
+impl_combine_or!(PythonDownloads);
 impl_combine_or!(bool);
 
 impl<T> Combine for Option<Vec<T>> {

crates/uv-settings/src/settings.rs

@@ -11,7 +11,7 @@ use uv_configuration::{
 };
 use uv_macros::{CombineOptions, OptionsMetadata};
 use uv_normalize::{ExtraName, PackageName};
-use uv_python::{PythonFetch, PythonPreference, PythonVersion};
+use uv_python::{PythonDownloads, PythonPreference, PythonVersion};
 use uv_resolver::{AnnotationStyle, ExcludeNewer, PrereleaseMode, ResolutionMode};
 
 /// A `pyproject.toml` with an (optional) `[tool.uv]` section.
@@ -143,16 +143,16 @@ pub struct GlobalOptions {
         possible_values = true
     )]
     pub python_preference: Option<PythonPreference>,
-    /// Whether to automatically download Python when required.
+    /// Whether to allow Python downloads.
     #[option(
         default = "\"automatic\"",
         value_type = "str",
         example = r#"
-            python-fetch = "manual"
+            python-downloads = "manual"
         "#,
         possible_values = true
     )]
-    pub python_fetch: Option<PythonFetch>,
+    pub python_downloads: Option<PythonDownloads>,
 }
 
 /// Settings relevant to all installer operations.

crates/uv/src/commands/project/add.rs

@@ -15,7 +15,7 @@ use uv_dispatch::BuildDispatch;
 use uv_distribution::DistributionDatabase;
 use uv_fs::CWD;
 use uv_normalize::PackageName;
-use uv_python::{PythonFetch, PythonPreference, PythonRequest};
+use uv_python::{PythonDownloads, PythonPreference, PythonRequest};
 use uv_requirements::{NamedRequirementsResolver, RequirementsSource, RequirementsSpecification};
 use uv_resolver::FlatIndex;
 use uv_types::{BuildIsolation, HashStrategy};
@@ -51,7 +51,7 @@ pub(crate) async fn add(
     python: Option<String>,
     settings: ResolverInstallerSettings,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     preview: PreviewMode,
     connectivity: Connectivity,
     concurrency: Concurrency,
@@ -93,7 +93,7 @@ pub(crate) async fn add(
         project.workspace(),
         python.as_deref().map(PythonRequest::parse),
         python_preference,
-        python_fetch,
+        python_downloads,
         connectivity,
         native_tls,
         cache,

crates/uv/src/commands/project/init.rs

@@ -11,7 +11,7 @@ use uv_client::{BaseClientBuilder, Connectivity};
 use uv_configuration::PreviewMode;
 use uv_fs::{absolutize_path, Simplified, CWD};
 use uv_python::{
-    EnvironmentPreference, PythonFetch, PythonInstallation, PythonPreference, PythonRequest,
+    EnvironmentPreference, PythonDownloads, PythonInstallation, PythonPreference, PythonRequest,
     VersionRequest,
 };
 use uv_resolver::RequiresPython;
@@ -35,7 +35,7 @@ pub(crate) async fn init(
     no_workspace: bool,
     preview: PreviewMode,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     connectivity: Connectivity,
     native_tls: bool,
     cache: &Cache,
@@ -86,7 +86,7 @@ pub(crate) async fn init(
             python,
             no_workspace,
             python_preference,
-            python_fetch,
+            python_downloads,
             connectivity,
             native_tls,
             cache,
@@ -160,7 +160,7 @@ async fn init_project(
     python: Option<String>,
     no_workspace: bool,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     connectivity: Connectivity,
     native_tls: bool,
     cache: &Cache,
@@ -213,11 +213,11 @@ async fn init_project(
                 let client_builder = BaseClientBuilder::new()
                     .connectivity(connectivity)
                     .native_tls(native_tls);
-                let interpreter = PythonInstallation::find_or_fetch(
+                let interpreter = PythonInstallation::find_or_download(
                     Some(request),
                     EnvironmentPreference::Any,
                     python_preference,
-                    python_fetch,
+                    python_downloads,
                     &client_builder,
                     cache,
                     Some(&reporter),
@@ -240,11 +240,11 @@ async fn init_project(
         let client_builder = BaseClientBuilder::new()
             .connectivity(connectivity)
             .native_tls(native_tls);
-        let interpreter = PythonInstallation::find_or_fetch(
+        let interpreter = PythonInstallation::find_or_download(
             Some(request),
             EnvironmentPreference::Any,
             python_preference,
-            python_fetch,
+            python_downloads,
             &client_builder,
             cache,
             Some(&reporter),

crates/uv/src/commands/project/lock.rs

@@ -18,7 +18,7 @@ use uv_dispatch::BuildDispatch;
 use uv_fs::CWD;
 use uv_git::ResolvedRepositoryReference;
 use uv_normalize::{PackageName, DEV_DEPENDENCIES};
-use uv_python::{Interpreter, PythonEnvironment, PythonFetch, PythonPreference, PythonRequest};
+use uv_python::{Interpreter, PythonDownloads, PythonEnvironment, PythonPreference, PythonRequest};
 use uv_requirements::upgrade::{read_lock_requirements, LockedRequirements};
 use uv_resolver::{
     FlatIndex, Lock, OptionsBuilder, PythonRequirement, RequiresPython, ResolverMarkers,
@@ -50,7 +50,7 @@ pub(crate) async fn lock(
     settings: ResolverSettings,
     preview: PreviewMode,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     connectivity: Connectivity,
     concurrency: Concurrency,
     native_tls: bool,
@@ -69,7 +69,7 @@ pub(crate) async fn lock(
         &workspace,
         python.as_deref().map(PythonRequest::parse),
         python_preference,
-        python_fetch,
+        python_downloads,
         connectivity,
         native_tls,
         cache,

crates/uv/src/commands/project/mod.rs

@@ -20,8 +20,8 @@ use uv_fs::Simplified;
 use uv_installer::{SatisfiesResult, SitePackages};
 use uv_normalize::PackageName;
 use uv_python::{
-    request_from_version_file, EnvironmentPreference, Interpreter, PythonEnvironment, PythonFetch,
-    PythonInstallation, PythonPreference, PythonRequest, VersionRequest,
+    request_from_version_file, EnvironmentPreference, Interpreter, PythonDownloads,
+    PythonEnvironment, PythonInstallation, PythonPreference, PythonRequest, VersionRequest,
 };
 use uv_requirements::{NamedRequirementsResolver, RequirementsSpecification};
 use uv_resolver::{
@@ -202,7 +202,7 @@ impl FoundInterpreter {
         workspace: &Workspace,
         python_request: Option<PythonRequest>,
         python_preference: PythonPreference,
-        python_fetch: PythonFetch,
+        python_downloads: PythonDownloads,
         connectivity: Connectivity,
         native_tls: bool,
         cache: &Cache,
@@ -251,11 +251,11 @@ impl FoundInterpreter {
         let reporter = PythonDownloadReporter::single(printer);
 
         // Locate the Python interpreter to use in the environment
-        let python = PythonInstallation::find_or_fetch(
+        let python = PythonInstallation::find_or_download(
             python_request,
             EnvironmentPreference::OnlySystem,
             python_preference,
-            python_fetch,
+            python_downloads,
             &client_builder,
             cache,
             Some(&reporter),
@@ -329,7 +329,7 @@ pub(crate) async fn get_or_init_environment(
     workspace: &Workspace,
     python: Option<PythonRequest>,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     connectivity: Connectivity,
     native_tls: bool,
     cache: &Cache,
@@ -339,7 +339,7 @@ pub(crate) async fn get_or_init_environment(
         workspace,
         python,
         python_preference,
-        python_fetch,
+        python_downloads,
         connectivity,
         native_tls,
         cache,

crates/uv/src/commands/project/remove.rs

@@ -5,7 +5,7 @@ use uv_cache::Cache;
 use uv_client::Connectivity;
 use uv_configuration::{Concurrency, ExtrasSpecification, PreviewMode};
 use uv_fs::CWD;
-use uv_python::{PythonFetch, PythonPreference, PythonRequest};
+use uv_python::{PythonDownloads, PythonPreference, PythonRequest};
 use uv_warnings::{warn_user, warn_user_once};
 use uv_workspace::pyproject::DependencyType;
 use uv_workspace::pyproject_mut::PyProjectTomlMut;
@@ -29,7 +29,7 @@ pub(crate) async fn remove(
     python: Option<String>,
     settings: ResolverInstallerSettings,
     python_preference: PythonPreference,
-    python_fetch: PythonFetch,
+    python_downloads: PythonDownloads,
     preview: PreviewMode,
     connectivity: Connectivity,
     concurrency: Concurrency,
@@ -101,7 +101,7 @@ pub(crate) async fn remove(
         project.workspace(),
         python.as_deref().map(PythonRequest::parse),
         python_preference,
-        python_fetch,
+        python_downloads,
         connectivity,
         native_tls,
         cache,