Improve project handling in uv venv (#6835)

- Respect `UV_PROJECT_ENVIRONMENT` when in project root
- Add `--no-project` and `--no-workspace` to opt-out of above and
`requires-python` detection
- Rename `[NAME]` to `[PATH]` in CLI

crates/uv-cli/src/lib.rs

@@ -322,6 +322,10 @@ pub enum Commands {
     /// By default, creates a virtual environment named `.venv` in the working
     /// directory. An alternative path may be provided positionally.
     ///
+    /// If in a project, the default environment name can be changed with
+    /// the `UV_PROJECT_ENVIRONMENT` environment variable; this only applies
+    /// when run from the project root directory.
+    ///
     /// If a virtual environment exists at the target path, it will be removed
     /// and a new, empty virtual environment will be created.
     ///
@@ -1961,6 +1965,14 @@ pub struct VenvArgs {
     #[arg(long, overrides_with("system"), hide = true)]
     pub no_system: bool,
 
+    /// Avoid discovering a project or workspace.
+    ///
+    /// By default, uv searches for projects in the current directory or any parent directory to
+    /// determine the default path of the virtual environment and check for Python version
+    /// constraints, if any.
+    #[arg(long, alias = "no-workspace")]
+    pub no_project: bool,
+
     /// Install seed packages (one or more of: `pip`, `setuptools`, and `wheel`) into the virtual environment.
     ///
     /// Note `setuptools` and `wheel` are not included in Python 3.12+ environments.
@@ -1980,8 +1992,11 @@ pub struct VenvArgs {
     pub allow_existing: bool,
 
     /// The path to the virtual environment to create.
-    #[arg(default_value = ".venv")]
-    pub name: PathBuf,
+    ///
+    /// Default to `.venv` in the working directory.
+    ///
+    /// Relative paths are resolved relative to the working directory.
+    pub path: Option<PathBuf>,
 
     /// Provide an alternative prompt prefix for the virtual environment.
     ///

crates/uv/src/commands/venv.rs

@@ -1,5 +1,5 @@
 use std::fmt::Write;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::vec;
 
@@ -41,7 +41,7 @@ use crate::printer::Printer;
 /// Create a virtual environment.
 #[allow(clippy::unnecessary_wraps, clippy::fn_params_excessive_bools)]
 pub(crate) async fn venv(
-    path: &Path,
+    path: Option<PathBuf>,
     python_request: Option<&str>,
     python_preference: PythonPreference,
     python_downloads: PythonDownloads,
@@ -59,6 +59,7 @@ pub(crate) async fn venv(
     concurrency: Concurrency,
     native_tls: bool,
     no_config: bool,
+    no_project: bool,
     cache: &Cache,
     printer: Printer,
     relocatable: bool,
@@ -82,6 +83,7 @@ pub(crate) async fn venv(
         concurrency,
         native_tls,
         no_config,
+        no_project,
         cache,
         printer,
         relocatable,
@@ -118,7 +120,7 @@ enum VenvError {
 /// Create a virtual environment.
 #[allow(clippy::fn_params_excessive_bools)]
 async fn venv_impl(
-    path: &Path,
+    path: Option<PathBuf>,
     python_request: Option<&str>,
     link_mode: LinkMode,
     index_locations: &IndexLocations,
@@ -136,10 +138,39 @@ async fn venv_impl(
     concurrency: Concurrency,
     native_tls: bool,
     no_config: bool,
+    no_project: bool,
     cache: &Cache,
     printer: Printer,
     relocatable: bool,
 ) -> miette::Result<ExitStatus> {
+    let project = if no_project {
+        None
+    } else {
+        match VirtualProject::discover(&CWD, &DiscoveryOptions::default()).await {
+            Ok(project) => Some(project),
+            Err(WorkspaceError::MissingProject(_)) => None,
+            Err(WorkspaceError::MissingPyprojectToml) => None,
+            Err(WorkspaceError::NonWorkspace(_)) => None,
+            Err(err) => {
+                warn_user_once!("{err}");
+                None
+            }
+        }
+    };
+
+    // Determine the default path; either the virtual environment for the project or `.venv`
+    let path = path.unwrap_or(
+        project
+            .as_ref()
+            .and_then(|project| {
+                // Only use the project environment path if we're invoked from the root
+                // This isn't strictly necessary and we may want to change it later, but this
+                // avoids a breaking change when adding project environment support to `uv venv`.
+                (project.workspace().install_path() == &*CWD).then(|| project.workspace().venv())
+            })
+            .unwrap_or(PathBuf::from(".venv")),
+    );
+
     let client_builder = BaseClientBuilder::default()
         .connectivity(connectivity)
         .native_tls(native_tls);
@@ -159,17 +190,6 @@ async fn venv_impl(
 
     // (3) `Requires-Python` in `pyproject.toml`
     if interpreter_request.is_none() {
-        let project = match VirtualProject::discover(&CWD, &DiscoveryOptions::default()).await {
-            Ok(project) => Some(project),
-            Err(WorkspaceError::MissingProject(_)) => None,
-            Err(WorkspaceError::MissingPyprojectToml) => None,
-            Err(WorkspaceError::NonWorkspace(_)) => None,
-            Err(err) => {
-                warn_user_once!("{err}");
-                None
-            }
-        };
-
         if let Some(project) = project {
             interpreter_request = find_requires_python(project.workspace())
                 .into_diagnostic()?
@@ -229,7 +249,7 @@ async fn venv_impl(
 
     // Create the virtual environment.
     let venv = uv_virtualenv::create_venv(
-        path,
+        &path,
         interpreter,
         prompt,
         system_site_packages,

crates/uv/src/lib.rs

@@ -1,7 +1,6 @@
 use std::ffi::OsString;
 use std::fmt::Write;
 use std::io::stdout;
-use std::path::PathBuf;
 use std::process::ExitCode;
 
 use anstream::eprintln;
@@ -680,7 +679,7 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
 
             // Since we use ".venv" as the default name, we use "." as the default prompt.
             let prompt = args.prompt.or_else(|| {
-                if args.name == PathBuf::from(".venv") {
+                if args.path.is_none() {
                     Some(".".to_string())
                 } else {
                     None
@@ -688,7 +687,7 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
             });
 
             commands::venv(
-                &args.name,
+                args.path,
                 args.settings.python.as_deref(),
                 globals.python_preference,
                 globals.python_downloads,
@@ -706,6 +705,7 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
                 globals.concurrency,
                 globals.native_tls,
                 cli.no_config,
+                args.no_project,
                 &cache,
                 printer,
                 args.relocatable,

crates/uv/src/settings.rs

@@ -1614,10 +1614,11 @@ impl PipCheckSettings {
 pub(crate) struct VenvSettings {
     pub(crate) seed: bool,
     pub(crate) allow_existing: bool,
-    pub(crate) name: PathBuf,
+    pub(crate) path: Option<PathBuf>,
     pub(crate) prompt: Option<String>,
     pub(crate) system_site_packages: bool,
     pub(crate) relocatable: bool,
+    pub(crate) no_project: bool,
     pub(crate) settings: PipSettings,
 }
 
@@ -1630,7 +1631,7 @@ impl VenvSettings {
             no_system,
             seed,
             allow_existing,
-            name,
+            path,
             prompt,
             system_site_packages,
             relocatable,
@@ -1639,6 +1640,7 @@ impl VenvSettings {
             keyring_provider,
             allow_insecure_host,
             exclude_newer,
+            no_project,
             link_mode,
             compat_args: _,
         } = args;
@@ -1646,9 +1648,10 @@ impl VenvSettings {
         Self {
             seed,
             allow_existing,
-            name,
+            path,
             prompt,
             system_site_packages,
+            no_project,
             relocatable,
             settings: PipSettings::combine(
                 PipOptions {

crates/uv/tests/common/mod.rs

@@ -335,8 +335,8 @@ impl TestContext {
 
         // Make virtual environment activation cross-platform and shell-agnostic
         filters.push((
-            r"Activate with: (?:.*)\\Scripts\\activate".to_string(),
-            "Activate with: source .venv/bin/activate".to_string(),
+            r"Activate with: (.*)\\Scripts\\activate".to_string(),
+            "Activate with: source $1/bin/activate".to_string(),
         ));
         filters.push((
             r"Activate with: source .venv/bin/activate(?:\.\w+)".to_string(),

crates/uv/tests/venv.rs

@@ -52,10 +52,10 @@ fn create_venv() {
 }
 
 #[test]
-fn create_venv_uv_project_environment() -> Result<()> {
+fn create_venv_project_environment() -> Result<()> {
     let context = TestContext::new_with_versions(&["3.12"]);
 
-    // `uv venv` ignores UV_PROJECT_ENVIRONMENT
+    // `uv venv` ignores `UV_PROJECT_ENVIRONMENT` when it's not a project
     uv_snapshot!(context.filters(), context.venv().env("UV_PROJECT_ENVIRONMENT", "foo"), @r###"
     success: true
     exit_code: 0
@@ -74,14 +74,44 @@ fn create_venv_uv_project_environment() -> Result<()> {
         .child("foo")
         .assert(predicates::path::missing());
 
-    context.temp_dir.child("pyproject.toml").touch()?;
+    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"]
+            "#,
+    )?;
 
-    // Even if there's a `pyproject.toml`
+    // But, if we're in a project we'll respect it
     uv_snapshot!(context.filters(), context.venv().env("UV_PROJECT_ENVIRONMENT", "foo"), @r###"
     success: true
     exit_code: 0
     ----- stdout -----
 
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtualenv at: foo
+    Activate with: source foo/bin/activate
+    "###
+    );
+
+    context
+        .temp_dir
+        .child("foo")
+        .assert(predicates::path::is_dir());
+
+    // Unless we're in a child directory
+    let child = context.temp_dir.child("child");
+    child.create_dir_all()?;
+
+    uv_snapshot!(context.filters(), context.venv().env("UV_PROJECT_ENVIRONMENT", "foo").current_dir(child.path()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
     ----- stderr -----
     Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
     Creating virtualenv at: .venv
@@ -89,10 +119,52 @@ fn create_venv_uv_project_environment() -> Result<()> {
     "###
     );
 
+    // In which case, we'll use the default name of `.venv`
+    child.child("foo").assert(predicates::path::missing());
+    child.child(".venv").assert(predicates::path::is_dir());
+
+    // Or, if a name is provided
+    uv_snapshot!(context.filters(), context.venv().arg("bar"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtualenv at: bar
+    Activate with: source bar/bin/activate
+    "###
+    );
+
     context
         .temp_dir
-        .child("foo")
-        .assert(predicates::path::missing());
+        .child("bar")
+        .assert(predicates::path::is_dir());
+
+    // Or, of they opt-out with `--no-workspace` or `--no-project`
+    uv_snapshot!(context.filters(), context.venv().arg("--no-workspace"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtualenv at: .venv
+    Activate with: source .venv/bin/activate
+    "###
+    );
+
+    uv_snapshot!(context.filters(), context.venv().arg("--no-project"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+    Creating virtualenv at: .venv
+    Activate with: source .venv/bin/activate
+    "###
+    );
 
     Ok(())
 }

docs/reference/cli.md

@@ -5956,6 +5956,8 @@ Create a virtual environment.
 
 By default, creates a virtual environment named `.venv` in the working directory. An alternative path may be provided positionally.
 
+If in a project, the default environment name can be changed with the `UV_PROJECT_ENVIRONMENT` environment variable; this only applies when run from the project root directory.
+
 If a virtual environment exists at the target path, it will be removed and a new, empty virtual environment will be created.
 
 When using uv, the virtual environment does not need to be activated. uv will find a virtual environment (named `.venv`) in the working directory or any parent directories.
@@ -5963,12 +5965,16 @@ When using uv, the virtual environment does not need to be activated. uv will fi
 <h3 class="cli-reference">Usage</h3>
 
 ```
-uv venv [OPTIONS] [NAME]
+uv venv [OPTIONS] [PATH]
 ```
 
 <h3 class="cli-reference">Arguments</h3>
 
-<dl class="cli-reference"><dt><code>NAME</code></dt><dd><p>The path to the virtual environment to create</p>
+<dl class="cli-reference"><dt><code>PATH</code></dt><dd><p>The path to the virtual environment to create.</p>
+
+<p>Default to <code>.venv</code> in the working directory.</p>
+
+<p>Relative paths are resolved relative to the working directory.</p>
 
 </dd></dl>
 
@@ -6105,6 +6111,10 @@ uv venv [OPTIONS] [NAME]
 
 <p>For example, spinners or progress bars.</p>
 
+</dd><dt><code>--no-project</code></dt><dd><p>Avoid discovering a project or workspace.</p>
+
+<p>By default, uv searches for projects in the current directory or any parent directory to determine the default path of the virtual environment and check for Python version constraints, if any.</p>
+
 </dd><dt><code>--no-python-downloads</code></dt><dd><p>Disable automatic downloads of Python.</p>
 
 </dd><dt><code>--offline</code></dt><dd><p>Disable network access.</p>