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Make uv pip compile attempt to download a specified --python-version if it can. #17249

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Merged
EliteTK merged 18 commits into from
Jan 16, 2026
Merged

Make uv pip compile attempt to download a specified --python-version if it can. #17249

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37d8cb6
Make `uv pip compile` attempt to download --python-version
EliteTK Dec 29, 2025
82fc23b
Move download handling to a separate function
EliteTK Jan 14, 2026
efe864e
Re-attempt a download when falling back to a version without a patch …
EliteTK Jan 14, 2026
2ac4a7f
Avoid errors which would previously have not occurred
EliteTK Jan 14, 2026
c2c8dc4
Add a comment elaborating need to warn on download error
EliteTK Jan 14, 2026
db0e72b
Don't attempt a second download if the first one failed for any reason
EliteTK Jan 14, 2026
5c3dcb7
Download python in the default fallback case too
EliteTK Jan 14, 2026
9cfa37e
Remove stuttery Result type
EliteTK Jan 14, 2026
2aaec3d
Roll everything into a loop
EliteTK Jan 14, 2026
e548074
Fix comments
EliteTK Jan 14, 2026
63f4ef7
Inline attempt_download again
EliteTK Jan 14, 2026
158444b
Restore some more comments
EliteTK Jan 14, 2026
2b70679
Fix error reporting bug?
EliteTK Jan 14, 2026
876704f
Improved error handling comment
EliteTK Jan 15, 2026
260bc11
Elaborate debug messages
EliteTK Jan 15, 2026
e21a148
Rename `installation` -> `result`
EliteTK Jan 15, 2026
f1c06dd
Write out the full error chain
EliteTK Jan 15, 2026
8ac4906
Print first error chain message in bold to match warn_user
EliteTK Jan 16, 2026
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53 changes: 46 additions & 7 deletions crates/uv-python/src/discovery.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
use itertools::{Either, Itertools};
use regex::Regex;
use reqwest_retry::policies::ExponentialBackoff;
use rustc_hash::{FxBuildHasher, FxHashSet};
use same_file::is_same_file;
use std::borrow::Cow;
Expand All @@ -10,6 +11,7 @@ use std::{path::Path, path::PathBuf, str::FromStr};
use thiserror::Error;
use tracing::{debug, instrument, trace};
use uv_cache::Cache;
use uv_client::BaseClient;
use uv_fs::Simplified;
use uv_fs::which::is_executable;
use uv_pep440::{
Expand All @@ -21,7 +23,7 @@ use uv_static::EnvVars;
use uv_warnings::warn_user_once;
use which::{which, which_all};

use crate::downloads::{PlatformRequest, PythonDownloadRequest};
use crate::downloads::{ManagedPythonDownloadList, PlatformRequest, PythonDownloadRequest};
use crate::implementation::ImplementationName;
use crate::installation::PythonInstallation;
use crate::interpreter::Error as InterpreterError;
Expand Down Expand Up @@ -1445,13 +1447,20 @@ pub(crate) fn find_python_installation(
///
/// See [`find_python_installation`] for more details on installation discovery.
#[instrument(skip_all, fields(request))]
pub(crate) fn find_best_python_installation(
pub(crate) async fn find_best_python_installation(
request: &PythonRequest,
environments: EnvironmentPreference,
preference: PythonPreference,
downloads_enabled: bool,
download_list: &ManagedPythonDownloadList,
client: &BaseClient,
retry_policy: &ExponentialBackoff,
cache: &Cache,
reporter: Option<&dyn crate::downloads::Reporter>,
python_install_mirror: Option<&str>,
pypy_install_mirror: Option<&str>,
preview: Preview,
) -> Result<FindPythonResult, Error> {
) -> Result<FindPythonResult, crate::Error> {
debug!("Starting Python discovery for {}", request);

// First, check for an exact match (or the first available version if no Python version was provided)
Expand All @@ -1465,11 +1474,41 @@ pub(crate) fn find_best_python_installation(
// Continue if we can't find a matching Python and ignore non-critical discovery errors
Ok(Err(_)) => {}
Err(ref err) if !err.is_critical() => {}
_ => return result,
_ => return Ok(result?),
}

// Attempt to download the version if downloads are enabled
if downloads_enabled
&& let Some(download_request) = PythonDownloadRequest::from_request(request)
{
let download = download_request
.clone()
.fill()
.map(|request| download_list.find(&request));
if let Some(download) = match download {
Ok(Ok(download)) => Some(download),
Ok(Err(crate::downloads::Error::NoDownloadFound(_))) => None,
Ok(Err(error)) => return Err(error.into()),
Err(error) => return Err(error.into()),
Comment thread
EliteTK marked this conversation as resolved.
Outdated
} {
let installation = PythonInstallation::fetch(
download,
client,
retry_policy,
cache,
reporter,
python_install_mirror,
pypy_install_mirror,
preview,
)
.await?;

return Ok(Ok(installation));
}
}

// If that fails, and a specific patch version was requested try again allowing a
// different patch version
// If both approaches fail, and a specific patch version was requested try
// again allowing a different patch version
Comment thread
EliteTK marked this conversation as resolved.
Outdated
if let Some(request) = match request {
PythonRequest::Version(version) => {
if version.has_patch() {
Expand All @@ -1493,7 +1532,7 @@ pub(crate) fn find_best_python_installation(
// Continue if we can't find a matching Python and ignore non-critical discovery errors
Ok(Err(_)) => {}
Err(ref err) if !err.is_critical() => {}
_ => return result,
_ => return Ok(result?),
}
}

Expand Down
35 changes: 30 additions & 5 deletions crates/uv-python/src/installation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,17 +75,42 @@ impl PythonInstallation {

/// Find an installed [`PythonInstallation`] that satisfies a requested version, if the request cannot
/// be satisfied, fallback to the best available Python installation.
pub fn find_best(
pub async fn find_best(
request: &PythonRequest,
environments: EnvironmentPreference,
preference: PythonPreference,
download_list: &ManagedPythonDownloadList,
python_downloads: PythonDownloads,
client_builder: &BaseClientBuilder<'_>,
cache: &Cache,
reporter: Option<&dyn Reporter>,
python_install_mirror: Option<&str>,
pypy_install_mirror: Option<&str>,
python_downloads_json_url: Option<&str>,
preview: Preview,
) -> Result<Self, Error> {
let installation =
find_best_python_installation(request, environments, preference, cache, preview)??;
installation.warn_if_outdated_prerelease(request, download_list);
let retry_policy = client_builder.retry_policy();
let client = client_builder.clone().retries(0).build();
let download_list =
ManagedPythonDownloadList::new(&client, python_downloads_json_url).await?;
let downloads_enabled = preference.allows_managed()
&& python_downloads.is_automatic()
&& client_builder.connectivity.is_online();
let installation = find_best_python_installation(
request,
environments,
preference,
downloads_enabled,
&download_list,
&client,
&retry_policy,
cache,
reporter,
python_install_mirror,
pypy_install_mirror,
preview,
)
.await??;
installation.warn_if_outdated_prerelease(request, &download_list);
Ok(installation)
}

Expand Down
43 changes: 37 additions & 6 deletions crates/uv-python/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@ mod tests {
use indoc::{formatdoc, indoc};
use temp_env::with_vars;
use test_log::test;
use uv_client::BaseClientBuilder;
use uv_preview::Preview;
use uv_static::EnvVars;

use uv_cache::Cache;

use crate::{
PythonNotFound, PythonRequest, PythonSource, PythonVersion,
implementation::ImplementationName, installation::PythonInstallation,
managed::ManagedPythonInstallations, virtualenv::virtualenv_python_executable,
downloads::ManagedPythonDownloadList, implementation::ImplementationName,
installation::PythonInstallation, managed::ManagedPythonInstallations,
virtualenv::virtualenv_python_executable,
};
use crate::{
PythonPreference,
Expand Down Expand Up @@ -989,13 +991,42 @@ mod tests {
Ok(())
}

fn find_best_python_installation_no_download(
request: &PythonRequest,
environments: EnvironmentPreference,
preference: PythonPreference,
cache: &Cache,
preview: Preview,
) -> Result<Result<PythonInstallation, PythonNotFound>, crate::Error> {
let client_builder = BaseClientBuilder::default();
let download_list = ManagedPythonDownloadList::new_only_embedded()?;
tokio::runtime::Builder::new_current_thread()
.enable_all()
.build()
.expect("Failed to build runtime")
.block_on(find_best_python_installation(
request,
environments,
preference,
false,
&download_list,
&client_builder.clone().retries(0).build(),
&client_builder.retry_policy(),
cache,
None,
None,
None,
preview,
))
}

#[test]
fn find_best_python_version_patch_exact() -> Result<()> {
let mut context = TestContext::new()?;
context.add_python_versions(&["3.10.1", "3.11.2", "3.11.4", "3.11.3", "3.12.5"])?;

let python = context.run(|| {
find_best_python_installation(
find_best_python_installation_no_download(
&PythonRequest::parse("3.11.3"),
EnvironmentPreference::Any,
PythonPreference::OnlySystem,
Expand Down Expand Up @@ -1029,7 +1060,7 @@ mod tests {
context.add_python_versions(&["3.10.1", "3.11.2", "3.11.4", "3.11.3", "3.12.5"])?;

let python = context.run(|| {
find_best_python_installation(
find_best_python_installation_no_download(
&PythonRequest::parse("3.11.11"),
EnvironmentPreference::Any,
PythonPreference::OnlySystem,
Expand Down Expand Up @@ -1066,7 +1097,7 @@ mod tests {

let python =
context.run_with_vars(&[(EnvVars::VIRTUAL_ENV, Some(venv.as_os_str()))], || {
find_best_python_installation(
find_best_python_installation_no_download(
&PythonRequest::parse("3.10"),
EnvironmentPreference::Any,
PythonPreference::OnlySystem,
Expand Down Expand Up @@ -1097,7 +1128,7 @@ mod tests {

let python =
context.run_with_vars(&[(EnvVars::VIRTUAL_ENV, Some(venv.as_os_str()))], || {
find_best_python_installation(
find_best_python_installation_no_download(
&PythonRequest::parse("3.10.2"),
EnvironmentPreference::Any,
PythonPreference::OnlySystem,
Expand Down
18 changes: 8 additions & 10 deletions crates/uv/src/commands/pip/compile.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,8 +11,6 @@ use owo_colors::OwoColorize;
use rustc_hash::FxHashSet;
use tracing::debug;

use uv_python::downloads::ManagedPythonDownloadList;

use uv_cache::Cache;
use uv_client::{BaseClientBuilder, FlatIndexClient, RegistryClientBuilder};
use uv_configuration::{
Expand Down Expand Up @@ -297,15 +295,9 @@ pub(crate) async fn pip_compile(
// Find an interpreter to use for building distributions
let environment_preference = EnvironmentPreference::from_system_flag(system, false);
let python_preference = python_preference.with_system_flag(system);
let client = client_builder.clone().retries(0).build();
let download_list = ManagedPythonDownloadList::new(
&client,
install_mirrors.python_downloads_json_url.as_deref(),
)
.await?;
let reporter = PythonDownloadReporter::single(printer);
let interpreter = if let Some(python) = python.as_ref() {
let request = PythonRequest::parse(python);
let reporter = PythonDownloadReporter::single(printer);
PythonInstallation::find_or_download(
Some(&request),
environment_preference,
Expand Down Expand Up @@ -333,10 +325,16 @@ pub(crate) async fn pip_compile(
&request,
environment_preference,
python_preference,
&download_list,
python_downloads,
&client_builder,
&cache,
Some(&reporter),
install_mirrors.python_install_mirror.as_deref(),
install_mirrors.pypy_install_mirror.as_deref(),
install_mirrors.python_downloads_json_url.as_deref(),
preview,
)
.await
}?
.into_interpreter();

Expand Down
33 changes: 33 additions & 0 deletions crates/uv/tests/it/pip_compile.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18110,3 +18110,36 @@ fn compile_missing_python() -> Result<()> {

Ok(())
}

#[cfg(feature = "python-managed")]
#[test]
fn compile_missing_python_version() -> Result<()> {
let context = TestContext::new("3.12")
.with_python_download_cache()
.with_managed_python_dirs();

let requirements_in = context.temp_dir.child("requirements.in");
requirements_in.write_str("anyio==3.7.0")?;

uv_snapshot!(context
.pip_compile()
.arg("--python-version").arg("3.13")
.arg("requirements.in"), @r"
success: true
exit_code: 0
----- stdout -----
# This file was autogenerated by uv via the following command:
# uv pip compile --cache-dir [CACHE_DIR] --python-version 3.13 requirements.in
anyio==3.7.0
# via -r requirements.in
idna==3.6
# via anyio
sniffio==1.3.1
# via anyio

----- stderr -----
Resolved 3 packages in [TIME]
");

Ok(())
}
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