Strip conda/mamba activation vars from Python worker processes

When the calling process has a conda/mamba environment active,
variables like CONDA_PREFIX, CONDA_DEFAULT_ENV, and CONDA_SHLVL are
inherited by subprocesses. This can interfere with environment
activation in tools like pixi, causing the worker to resolve the wrong
Python interpreter (e.g., the caller's miniforge Python instead of the
pixi-managed one).

Fix by unsetting those three variables from every Python worker's
environment in Environment.python(). Variables explicitly set by the
caller via the builder's env() are left untouched.

Infrastructure: Service gains an env(**vars: str | None) method, and
process.builder() now treats a None value as a deletion request rather
than a set.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ctrueden

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "appose"
-version = "0.11.1.dev0"
+version = "0.12.0.dev0"
 description = "Appose: multi-language interprocess cooperation with shared memory."
 license = "BSD-2-Clause"
 authors = [{name = "Appose developers"}]

src/appose/environment.py

@@ -146,7 +146,17 @@ def python(self, *args) -> Service:
             "-c",
             "import appose.python_worker; appose.python_worker.main()",
         ]
-        return self.service(python_exes, *python_args).syntax(PythonSyntax())
+        # NB: Unset conda/mamba variables so they don't bleed into the worker
+        # process and cause the wrong Python interpreter to be resolved.
+        # Only clear variables not explicitly set by the caller via env().
+        conda_vars = ("CONDA_PREFIX", "CONDA_DEFAULT_ENV", "CONDA_SHLVL")
+        explicit = self.env_vars()
+        conda_unset = {var: None for var in conda_vars if var not in explicit}
+        return (
+            self.service(python_exes, *python_args)
+            .syntax(PythonSyntax())
+            .env(**conda_unset)
+        )
 
     def groovy(
         self,

src/appose/service.py

@@ -47,10 +47,12 @@ class Service:
     _service_count: int = 0
 
     def __init__(
-        self, cwd: str | Path, env_vars: dict[str, str] | None = None, *args: str
+        self, cwd: str | Path, env_vars: dict[str, str | None] | None = None, *args: str
     ) -> None:
         self._cwd: Path = Path(cwd)
-        self._env_vars: dict[str, str] = env_vars.copy() if env_vars is not None else {}
+        self._env_vars: dict[str, str | None] = (
+            env_vars.copy() if env_vars is not None else {}
+        )
         self._args: list[str] = list(args)
         self._tasks: dict[str, "Task"] = {}
         self._service_id: int = Service._service_count
@@ -102,6 +104,20 @@ def init(self, script: str) -> "Service":
         self._init_script = script
         return self
 
+    def env(self, **vars: str | None) -> "Service":
+        """
+        Set environment variables to pass to the worker process.
+
+        Args:
+            **vars: Key/value pairs to add to the worker's environment.
+                A value of None causes the variable to be unset in the worker.
+
+        Returns:
+            This service object, for chaining method calls.
+        """
+        self._env_vars.update(vars)
+        return self
+
     def start(self) -> "Service":
         """
         Explicitly launch the worker process associated with this service.

src/appose/util/process.py

@@ -33,7 +33,11 @@ def builder(
     """
     env = os.environ.copy()
     if env_vars:
-        env.update(env_vars)
+        for key, value in env_vars.items():
+            if value is None:
+                env.pop(key, None)
+            else:
+                env[key] = value
 
     cwd = str(working_dir) if working_dir else None