Add a GitHub Actions warning to the `uv venv` behavior change

.github/workflows/ci.yml

@@ -777,6 +777,29 @@ jobs:
             fi
           done
 
+  uv-venv-annotation-test-linux:
+    timeout-minutes: 10
+    needs: build-binary-linux-libc
+    name: "`uv venv` annotation test | linux"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: "Download binary"
+        uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
+        with:
+          name: uv-linux-libc-${{ github.sha }}
+
+      - name: "Prepare binary"
+        run: |
+          chmod +x ./uv
+          chmod +x ./uvx
+
+      - name: "Run `uv venv` twice"
+        run: |
+          ./uv venv
+          ./uv venv
+
   smoke-test-linux:
     timeout-minutes: 10
     needs: build-binary-linux-libc

Cargo.lock

@@ -6010,6 +6010,7 @@ dependencies = [
  "uv-pypi-types",
  "uv-python",
  "uv-shell",
+ "uv-static",
  "uv-version",
  "uv-warnings",
 ]
@@ -6021,6 +6022,7 @@ dependencies = [
  "anstream",
  "owo-colors",
  "rustc-hash",
+ "uv-static",
 ]
 
 [[package]]

crates/uv-static/src/env_vars.rs

@@ -534,7 +534,7 @@ impl EnvVars {
     #[attr_hidden]
     pub const GIT_CEILING_DIRECTORIES: &'static str = "GIT_CEILING_DIRECTORIES";
 
-    /// Used for trusted publishing via `uv publish`.
+    /// Used to detect if running in GitHub Actions, e.g., for trusted publishing via `uv publish`.
     pub const GITHUB_ACTIONS: &'static str = "GITHUB_ACTIONS";
 
     /// Used for trusted publishing via `uv publish`. Contains the oidc token url.

crates/uv-virtualenv/Cargo.toml

@@ -26,6 +26,7 @@ uv-fs = { workspace = true }
 uv-pypi-types = { workspace = true }
 uv-python = { workspace = true }
 uv-shell = { workspace = true }
+uv-static = { workspace = true }
 uv-version = { workspace = true }
 uv-warnings = { workspace = true }
 

crates/uv-virtualenv/src/virtualenv.rs

@@ -19,7 +19,7 @@ use uv_python::managed::{PythonMinorVersionLink, create_link_to_executable};
 use uv_python::{Interpreter, VirtualEnvironment};
 use uv_shell::escape_posix_for_single_quotes;
 use uv_version::version;
-use uv_warnings::warn_user_once;
+use uv_warnings::{warn_ci_once, warn_user_once};
 
 use crate::{Error, Prompt};
 
@@ -135,6 +135,9 @@ pub(crate) fn create(
                                 location.user_display(),
                                 "--clear".green(),
                             );
+                            warn_ci_once!(
+                                "`uv venv` replaced an existing {name}; this behavior is deprecated. In the future, uv will require `--clear` or `UV_VENV_CLEAR=1` to replace an existing {name}.",
+                            );
                         }
                     }
                 }

crates/uv-warnings/Cargo.toml

@@ -16,6 +16,8 @@ doctest = false
 workspace = true
 
 [dependencies]
+uv-static = { workspace = true }
+
 anstream = { workspace = true }
 owo-colors = { workspace = true }
 rustc-hash = { workspace = true }

crates/uv-warnings/src/lib.rs

@@ -7,6 +7,8 @@ pub use anstream;
 #[doc(hidden)]
 pub use owo_colors;
 use rustc_hash::FxHashSet;
+#[doc(hidden)]
+pub use uv_static::EnvVars;
 
 /// Whether user-facing warnings are enabled.
 pub static ENABLED: AtomicBool = AtomicBool::new(false);
@@ -56,3 +58,46 @@ macro_rules! warn_user_once {
         }
     }};
 }
+
+/// Create a warning for a visibility in a CI provider, if warnings are enabled. Only shows the
+/// warning once in a given uv invocation, with uniqueness determined by the content of the message.
+#[macro_export]
+macro_rules! warn_ci_once {
+    ($($arg:tt)*) => {{
+        use $crate::anstream::eprintln;
+        use $crate::owo_colors::OwoColorize;
+
+        if $crate::ENABLED.load(std::sync::atomic::Ordering::Relaxed) {
+            if let Ok(mut states) = $crate::WARNINGS.lock() {
+                if let Some(provider) = $crate::CIProvider::from_env() {
+                    let message = provider.format(&format!("{}", format_args!($($arg)*)));
+                    if states.insert(message.clone()) {
+                        eprintln!("{message}");
+                    }
+                }
+            }
+        }
+    }};
+}
+
+pub enum CIProvider {
+    GitHubActions,
+}
+
+impl CIProvider {
+    pub fn from_env() -> Option<Self> {
+        if std::env::var_os(EnvVars::GITHUB_ACTIONS).is_some() {
+            Some(Self::GitHubActions)
+        } else {
+            None
+        }
+    }
+
+    pub fn format(&self, message: &str) -> String {
+        match self {
+            Self::GitHubActions => {
+                format!("::warning ::{message}")
+            }
+        }
+    }
+}