fix(benchmark): ensure tox allows the environment variables we use to…

… change the core

benchmark/benchmark.py

@@ -58,11 +58,16 @@ def __exit__(
  self.foutput.close()
 
  @contextlib.contextmanager
- def set_env(self, env_vars: dict[str, str] | None) -> Iterator[None]:
+ def set_env(self, *env_varss: dict[str, str] | None) -> Iterator[None]:
+ """Set environment variables.
+
+ All the arguments are dicts of name:value, or None. All are applied
+ to the environment variables.
+ """
  old_env_vars = self.env_vars
- if env_vars:
-  self.env_vars = dict(old_env_vars)
- self.env_vars.update(env_vars)
+ self.env_vars = dict(old_env_vars)
+ for env_vars in env_varss:
+ self.env_vars.update(env_vars or {})
  try:
  yield
  finally:
@@ -185,6 +190,7 @@ class ProjectToTest:
  # Where can we clone the project from?
  git_url: str = ""
  slug: str = ""
+ env_vars: Env_VarsType = {}
 
  def __init__(self) -> None:
  url_must_exist(self.git_url)
@@ -270,6 +276,12 @@ def run_with_coverage(self, env: Env, cov_ver: Coverage) -> float:
 class ToxProject(ProjectToTest):
  """A project using tox to run the test suite."""
 
+ env_vars: Env_VarsType = {
+ **(ProjectToTest.env_vars or {}),
+ # Allow some environment variables into the tox execution.
+ "TOX_OVERRIDE": "testenv.pass_env+=COVERAGE_DEBUG,COVERAGE_CORE",
+ }
+
  def prep_environment(self, env: Env) -> None:
  env.shell.run_command(f"{env.python} -m pip install tox")
  self.run_tox(env, env.pyver.toxenv, "--notest")
@@ -441,13 +453,11 @@ def run_with_coverage(self, env: Env, cov_ver: Coverage) -> float:
  f".tox/{env.pyver.toxenv}/bin/python -m pip install {cov_ver.pip_args}"
  )
  with self.tweak_coverage_settings(cov_ver.tweaks):
- self.pre_check(env) # NOTE: Not properly factored, and only used from here.
+ self.pre_check(env) # NOTE: Not properly factored, and only used here.
  duration = self.run_tox(
  env, env.pyver.toxenv, "--skip-pkg-install -- --cov"
  )
- self.post_check(
- env
- ) # NOTE: Not properly factored, and only used from here.
+ self.post_check(env) # NOTE: Not properly factored, and only used here.
  return duration
 
 
@@ -932,7 +942,7 @@ def run(self, num_runs: int = 3) -> None:
  print(banner)
  env.shell.print_banner(banner)
  with change_dir(proj.dir):
- with env.shell.set_env(cov_ver.env_vars):
+ with env.shell.set_env(proj.env_vars, cov_ver.env_vars):
  try:
  if cov_ver.pip_args is None:
  dur = proj.run_no_coverage(env)