Make project and interpreter lock acquisition non-fatal (#14404)

## Summary

If we fail to acquire a lock on an environment, uv shouldn't fail; we
should just warn. In some cases, users run uv with read-only permissions
for their projects, etc.

For now, I kept any locks acquired _in the cache_ as hard failures,
since we always need write-access to the cache.

Closes https://github.com/astral-sh/uv/issues/14411.

crates/uv-build-frontend/src/lib.rs

@@ -25,7 +25,7 @@ use tempfile::TempDir;
 use tokio::io::AsyncBufReadExt;
 use tokio::process::Command;
 use tokio::sync::{Mutex, Semaphore};
-use tracing::{Instrument, debug, info_span, instrument};
+use tracing::{Instrument, debug, info_span, instrument, warn};
 
 use uv_cache_key::cache_digest;
 use uv_configuration::PreviewMode;
@@ -456,8 +456,12 @@ impl SourceBuild {
                 "uv-setuptools-{}.lock",
                 cache_digest(&canonical_source_path)
             ));
-            source_tree_lock =
+            source_tree_lock = LockedFile::acquire(lock_path, self.source_tree.to_string_lossy())
-                Some(LockedFile::acquire(lock_path, self.source_tree.to_string_lossy()).await?);
+                .await
+                .inspect_err(|err| {
+                    warn!("Failed to acquire build lock: {err}");
+                })
+                .ok();
         }
         Ok(source_tree_lock)
     }

crates/uv/src/commands/pip/install.rs

@@ -5,7 +5,7 @@ use std::path::PathBuf;
 use anyhow::Context;
 use itertools::Itertools;
 use owo_colors::OwoColorize;
-use tracing::{Level, debug, enabled};
+use tracing::{Level, debug, enabled, warn};
 
 use uv_cache::Cache;
 use uv_client::{BaseClientBuilder, FlatIndexClient, RegistryClientBuilder};
@@ -236,7 +236,13 @@ pub(crate) async fn pip_install(
         }
     }
 
-    let _lock = environment.lock().await?;
+    let _lock = environment
+        .lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     // Determine the markers to use for the resolution.
     let interpreter = environment.interpreter();

crates/uv/src/commands/pip/sync.rs

@@ -3,7 +3,7 @@ use std::fmt::Write;
 
 use anyhow::{Context, Result};
 use owo_colors::OwoColorize;
-use tracing::debug;
+use tracing::{debug, warn};
 
 use uv_cache::Cache;
 use uv_client::{BaseClientBuilder, FlatIndexClient, RegistryClientBuilder};
@@ -211,7 +211,13 @@ pub(crate) async fn pip_sync(
         }
     }
 
-    let _lock = environment.lock().await?;
+    let _lock = environment
+        .lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     let interpreter = environment.interpreter();
 

crates/uv/src/commands/pip/uninstall.rs

@@ -3,7 +3,7 @@ use std::fmt::Write;
 use anyhow::Result;
 use itertools::{Either, Itertools};
 use owo_colors::OwoColorize;
-use tracing::debug;
+use tracing::{debug, warn};
 
 use uv_cache::Cache;
 use uv_client::BaseClientBuilder;
@@ -100,7 +100,13 @@ pub(crate) async fn pip_uninstall(
         }
     }
 
-    let _lock = environment.lock().await?;
+    let _lock = environment
+        .lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     // Index the current `site-packages` directory.
     let site_packages = uv_installer::SitePackages::from_environment(&environment)?;

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

@@ -10,7 +10,7 @@ use anyhow::{Context, Result, bail};
 use itertools::Itertools;
 use owo_colors::OwoColorize;
 use rustc_hash::{FxBuildHasher, FxHashMap};
-use tracing::debug;
+use tracing::{debug, warn};
 use url::Url;
 
 use uv_cache::Cache;
@@ -319,7 +319,13 @@ pub(crate) async fn add(
         }
     };
 
-    let _lock = target.acquire_lock().await?;
+    let _lock = target
+        .acquire_lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     let client_builder = BaseClientBuilder::new()
         .connectivity(network_settings.connectivity)

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

@@ -1244,7 +1244,12 @@ impl ProjectEnvironment {
         preview: PreviewMode,
     ) -> Result<Self, ProjectError> {
         // Lock the project environment to avoid synchronization issues.
-        let _lock = ProjectInterpreter::lock(workspace).await?;
+        let _lock = ProjectInterpreter::lock(workspace)
+            .await
+            .inspect_err(|err| {
+                warn!("Failed to acquire project environment lock: {err}");
+            })
+            .ok();
 
         let upgradeable = preview.is_enabled()
             && python
@@ -1462,7 +1467,13 @@ impl ScriptEnvironment {
         preview: PreviewMode,
     ) -> Result<Self, ProjectError> {
         // Lock the script environment to avoid synchronization issues.
-        let _lock = ScriptInterpreter::lock(script).await?;
+        let _lock = ScriptInterpreter::lock(script)
+            .await
+            .inspect_err(|err| {
+                warn!("Failed to acquire script environment lock: {err}");
+            })
+            .ok();
+
         let upgradeable = python_request
             .as_ref()
             .is_none_or(|request| !request.includes_patch());

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

@@ -5,7 +5,7 @@ use std::str::FromStr;
 
 use anyhow::{Context, Result};
 use owo_colors::OwoColorize;
-use tracing::debug;
+use tracing::{debug, warn};
 
 use uv_cache::Cache;
 use uv_configuration::{
@@ -281,7 +281,13 @@ pub(crate) async fn remove(
         }
     };
 
-    let _lock = target.acquire_lock().await?;
+    let _lock = target
+        .acquire_lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     // Determine the lock mode.
     let mode = if locked {

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

@@ -240,7 +240,13 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
             .await?
             .into_environment()?;
 
-            let _lock = environment.lock().await?;
+            let _lock = environment
+                .lock()
+                .await
+                .inspect_err(|err| {
+                    warn!("Failed to acquire environment lock: {err}");
+                })
+                .ok();
 
             // Determine the lock mode.
             let mode = if frozen {
@@ -386,7 +392,13 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
                         )
                     });
 
-                let _lock = environment.lock().await?;
+                let _lock = environment
+                    .lock()
+                    .await
+                    .inspect_err(|err| {
+                        warn!("Failed to acquire environment lock: {err}");
+                    })
+                    .ok();
 
                 match update_environment(
                     environment,
@@ -699,7 +711,13 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
                         .map(|lock| (lock, project.workspace().install_path().to_owned()));
                 }
             } else {
-                let _lock = venv.lock().await?;
+                let _lock = venv
+                    .lock()
+                    .await
+                    .inspect_err(|err| {
+                        warn!("Failed to acquire environment lock: {err}");
+                    })
+                    .ok();
 
                 // Determine the lock mode.
                 let mode = if frozen {

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

@@ -6,6 +6,7 @@ use std::sync::Arc;
 use anyhow::{Context, Result};
 use itertools::Itertools;
 use owo_colors::OwoColorize;
+use tracing::warn;
 
 use uv_cache::Cache;
 use uv_client::{BaseClientBuilder, FlatIndexClient, RegistryClientBuilder};
@@ -169,7 +170,13 @@ pub(crate) async fn sync(
         ),
     };
 
-    let _lock = environment.lock().await?;
+    let _lock = environment
+        .lock()
+        .await
+        .inspect_err(|err| {
+            warn!("Failed to acquire environment lock: {err}");
+        })
+        .ok();
 
     // Notify the user of any environment changes.
     match &environment {

crates/uv/tests/it/sync.rs

@@ -3,13 +3,14 @@ use assert_cmd::prelude::*;
 use assert_fs::{fixture::ChildPath, prelude::*};
 use indoc::{formatdoc, indoc};
 use insta::assert_snapshot;
-
-use crate::common::{TestContext, download_to_disk, packse_index_url, uv_snapshot, venv_bin_path};
 use predicates::prelude::predicate;
 use tempfile::tempdir_in;
+
 use uv_fs::Simplified;
 use uv_static::EnvVars;
 
+use crate::common::{TestContext, download_to_disk, packse_index_url, uv_snapshot, venv_bin_path};
+
 #[test]
 fn sync() -> Result<()> {
     let context = TestContext::new("3.12");
@@ -9989,3 +9990,54 @@ fn sync_url_with_query_parameters() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+#[cfg(unix)]
+fn read_only() -> Result<()> {
+    use std::os::unix::fs::PermissionsExt;
+
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["iniconfig"]
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + iniconfig==2.0.0
+    "###);
+
+    assert!(context.temp_dir.child("uv.lock").exists());
+
+    // Remove the flock.
+    fs_err::remove_file(context.venv.child(".lock"))?;
+
+    // Make the virtual environment read and execute (but not write).
+    fs_err::set_permissions(&context.venv, std::fs::Permissions::from_mode(0o555))?;
+
+    uv_snapshot!(context.filters(), context.sync(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 2 packages in [TIME]
+    Audited 1 package in [TIME]
+    ");
+
+    Ok(())
+}