f2/testlib/env: build initial path via build_env

`build_env` is assumed to be a certain trivial environment, e.g. a
singleton search path.

An environment in general is either empty, contain one or more search
paths separated by a colon.

It seems that the intent was to set the `build_shell` first as a
prepended path in the managed environment then extend via the
`build_env` parts.

This fixes a usecase when the `BUILD_TEST_ENV` is non-trivial.

Change-Id: If5b8ab976d867a57ce0b8d29255f64695e30a8b2
Signed-off-by: Raito Bezarius <raito@lix.systems>

tests/functional2/testlib/fixtures/env.py

@@ -21,12 +21,16 @@ class _ManagedPath:
     """
 
     build_shell: dataclasses.InitVar[str | None]
+    build_env: dataclasses.InitVar[str | None] = None
     """statically linked shell to use within builds which provides coreutils functionality"""
     _path: list[str] = dataclasses.field(default_factory=list)
 
-    def __post_init__(self, build_shell: str | None):
+    def __post_init__(self, build_shell: str | None, build_env: str | None):
         if build_shell:
             self.prepend(build_shell)
+        if build_env:
+            for part in build_env.split(":"):
+                self.append(part)
 
     def to_path(self) -> str:
         """
@@ -177,7 +181,7 @@ class ManagedEnv:
         lix_bin = Path(environ.get("NIX_BIN_DIR", lix_base_folder / "outputs/out/bin"))
 
         self._env = {}
-        self.path = _ManagedPath(build_env)
+        self.path = _ManagedPath(build_shell, build_env)
         self._tmp_path = tmp_path
         self.shell_dir = build_shell or "/bin"
         self.build_env = build_env

tests/functional2/testlib/fixtures/test_env.py

@@ -225,6 +225,13 @@ def test_path_sandbox_entire_store_package():
     assert re.fullmatch(r"^/nix/store/\w{32}-python3-3\.\d{1,2}\.\d{1,2}-[^/]+$", sb_paths[1])
 
 
+def test_path_nontrivial_build_env():
+    path = _ManagedPath("/path/to/build_shell", "/path/to/busybox/bin:/path/to/acl/bin")
+    sb_paths = path.to_sandbox_paths()
+    assert len(sb_paths) == 3
+    assert sb_paths[0] == "/path/to/build_shell"
+
+
 def test_path_which():
     path = _ManagedPath("/path/to/build_shell")
     with pytest.raises(ValueError, match="not in configured path"):