python: Stop falling back to conda activate base for nameless toolchains (#56785)

Stops the `conda activate base` fallback in
`PythonToolchainProvider::activation_script` for two cases:

1. A Conda toolchain whose `environment.name` is `None`.
2. A Conda toolchain whose name is `Some(...)` but `shell.try_quote`
rejects it.

Previously both cases pushed `conda activate base` into the activation
script. With miniforge installed and no env explicitly selected, every
terminal silently activated `(base)`. The user didn't pick `base`;
injecting it is contamination.

Both branches now log a warning and emit no activation line. Users who
want `(base)` can select it as the toolchain explicitly.

Two unit tests cover the new behavior:
`test_conda_activation_skips_when_name_missing` (name=None) and
`test_conda_activation_skips_unquotable_name` (name=Some but unquotable,
exercised with an embedded NUL byte that `shlex::try_quote` rejects).
The existing `test_conda_activation_script_injection` still verifies
that quotable names get activated.

Release Notes:

- Fixed Zed silently injecting `conda activate base` into terminals when
a Conda manager (miniforge/miniconda) was installed but no specific
environment was selected.

crates/languages/src/python.rs

@@ -1495,18 +1495,23 @@ impl ToolchainLister for PythonToolchainProvider {
                         }
                     }
 
+                    // Only inject `{manager} activate <name>` when we have a
+                    // safely-quotable name. Never silently fall back to
+                    // `activate base`: a user with miniforge installed but a
+                    // local uv/venv project should not have their terminal
+                    // hijacked just because we couldn't resolve a name.
                     if let Some(name) = &toolchain.environment.name {
                         if let Some(quoted_name) = shell.try_quote(name) {
                             activation_script.push(format!("{manager} activate {quoted_name}"));
                         } else {
                             log::warn!(
-                                "Could not safely quote environment name {:?}, falling back to base",
+                                "Conda environment name {:?} could not be safely quoted; \
+                                 skipping terminal activation",
                                 name
                             );
-                            activation_script.push(format!("{manager} activate base"));
                         }
                     } else {
-                        activation_script.push(format!("{manager} activate base"));
+                        log::warn!("Conda toolchain has no name; skipping terminal activation");
                     }
                 }
                 Some(
@@ -2793,6 +2798,143 @@ mod tests {
         );
     }
 
+    #[gpui::test]
+    async fn test_conda_activation_skips_when_name_missing(cx: &mut TestAppContext) {
+        use language::{LanguageName, Toolchain, ToolchainLister};
+        use settings::{CondaManager, VenvSettings};
+        use task::ShellKind;
+
+        use crate::python::PythonToolchainProvider;
+
+        cx.executor().allow_parking();
+
+        cx.update(|cx| {
+            let test_settings = SettingsStore::test(cx);
+            cx.set_global(test_settings);
+            cx.update_global::<SettingsStore, _>(|store, cx| {
+                store.update_user_settings(cx, |s| {
+                    s.terminal
+                        .get_or_insert_with(Default::default)
+                        .project
+                        .detect_venv = Some(VenvSettings::On {
+                        activate_script: None,
+                        venv_name: None,
+                        directories: None,
+                        conda_manager: Some(CondaManager::Conda),
+                    });
+                });
+            });
+        });
+
+        let fs = project::FakeFs::new(cx.executor());
+        let provider = PythonToolchainProvider::new(fs);
+        let manager_executable = std::env::current_exe().unwrap();
+
+        let data = serde_json::json!({
+            "name": serde_json::Value::Null,
+            "kind": "Conda",
+            "executable": "/tmp/conda/bin/python",
+            "version": serde_json::Value::Null,
+            "prefix": serde_json::Value::Null,
+            "arch": serde_json::Value::Null,
+            "displayName": serde_json::Value::Null,
+            "project": serde_json::Value::Null,
+            "symlinks": serde_json::Value::Null,
+            "manager": {
+                "executable": manager_executable,
+                "version": serde_json::Value::Null,
+                "tool": "Conda",
+            },
+        });
+
+        let toolchain = Toolchain {
+            name: "test".into(),
+            path: "/tmp/conda".into(),
+            language_name: LanguageName::new_static("Python"),
+            as_json: data,
+        };
+
+        let script = cx
+            .update(|cx| provider.activation_script(&toolchain, ShellKind::Posix, cx))
+            .await;
+
+        assert!(
+            script.is_empty(),
+            "Nameless conda toolchains must not fall back to `conda activate base`, actual: {:?}",
+            script
+        );
+    }
+
+    #[gpui::test]
+    async fn test_conda_activation_skips_unquotable_name(cx: &mut TestAppContext) {
+        use language::{LanguageName, Toolchain, ToolchainLister};
+        use settings::{CondaManager, VenvSettings};
+        use task::ShellKind;
+
+        use crate::python::PythonToolchainProvider;
+
+        cx.executor().allow_parking();
+
+        cx.update(|cx| {
+            let test_settings = SettingsStore::test(cx);
+            cx.set_global(test_settings);
+            cx.update_global::<SettingsStore, _>(|store, cx| {
+                store.update_user_settings(cx, |s| {
+                    s.terminal
+                        .get_or_insert_with(Default::default)
+                        .project
+                        .detect_venv = Some(VenvSettings::On {
+                        activate_script: None,
+                        venv_name: None,
+                        directories: None,
+                        conda_manager: Some(CondaManager::Conda),
+                    });
+                });
+            });
+        });
+
+        let fs = project::FakeFs::new(cx.executor());
+        let provider = PythonToolchainProvider::new(fs);
+        // shlex::try_quote rejects strings containing a NUL byte, so this name
+        // is guaranteed to fail the Posix quoting path.
+        let unquotable_name = "foo\0bar";
+        let manager_executable = std::env::current_exe().unwrap();
+
+        let data = serde_json::json!({
+            "name": unquotable_name,
+            "kind": "Conda",
+            "executable": "/tmp/conda/bin/python",
+            "version": serde_json::Value::Null,
+            "prefix": serde_json::Value::Null,
+            "arch": serde_json::Value::Null,
+            "displayName": serde_json::Value::Null,
+            "project": serde_json::Value::Null,
+            "symlinks": serde_json::Value::Null,
+            "manager": {
+                "executable": manager_executable,
+                "version": serde_json::Value::Null,
+                "tool": "Conda",
+            },
+        });
+
+        let toolchain = Toolchain {
+            name: "test".into(),
+            path: "/tmp/conda".into(),
+            language_name: LanguageName::new_static("Python"),
+            as_json: data,
+        };
+
+        let script = cx
+            .update(|cx| provider.activation_script(&toolchain, ShellKind::Posix, cx))
+            .await;
+
+        assert!(
+            !script.iter().any(|s| s.contains("conda activate")),
+            "Unquotable conda env names must not emit any `conda activate` line, actual: {:?}",
+            script
+        );
+    }
+
     #[gpui::test]
     async fn test_python_autoindent(cx: &mut TestAppContext) {
         cx.executor().set_block_on_ticks(usize::MAX..=usize::MAX);