extra env vars in help text when using default_env=True

[asmacdo]

🐛 Bug report

When using default_env=True, the action="version" argument gets environment variable support even though this doesn't make semantic sense. The version action is purely informational (prints and exits), similar to help, which is already auto-excluded from environment variable parsing.

Additionally, subcommand selection via environment variables is also questionable, though there may be legitimate use cases for this.

To reproduce

from jsonargparse import ArgumentParser

parser = ArgumentParser(
    prog="cli",
    description="Minimal CLI example",
    default_env=True,
)
parser.add_argument("--version", action="version", version="1.0.0")

subcommands = parser.add_subcommands()
subparser = ArgumentParser()
subcommands.add_subcommand("greet", subparser, help="Greet someone")

parser.print_help()

Output:

usage: cli [-h] [--version] {greet} ...

Minimal CLI example

options:
  ARG:   -h, --help     Show this help message and exit.
  ARG:   --version
  ENV:   CLI_VERSION
                        show program's version number and exit

subcommands:
  For more details of each subcommand, add it as an argument followed by
  --help.

  ENV:   CLI_SUBCOMMAND

  Available subcommands:
    ARG:   greet
  ENV:   CLI_GREET
                        Greet someone

Problems:

Heres a simlar cases too:

• ENV: CLI_VERSION - Setting version via environment variable doesn't make semantic sense for a meta-action that just prints and exits
• ENV: CLI_SUBCOMMAND - Subcommand selection via environment variable is unusual and may not be desirable
• ENV: CLI_GREET - Individual subcommands showing in the help as environment variables may be confusing

Note that -h, --help is already correctly excluded from environment variable parsing.

Expected behavior

Immediate fix (bug):

The action="version" argument should be automatically excluded from environment variable parsing, just like help actions already are.

More general solution (feature):

For broader control, it would be useful to have an enable_env parameter (similar to the existing enable_path parameter) that allows selectively disabling environment variable parsing:

parser = ArgumentParser(prog="cli", description="Minimal CLI example", default_env=True)
parser.add_argument("--version", action="version", version="1.0.0", enable_env=False)

subcommands = parser.add_subcommands(enable_env=False)  # Disable for subcommand selection

This would:

1. Suppress the corresponding ENV: lines in help output
2. Skip processing those environment variables during parsing

Use cases for enable_env:

• Meta arguments: --version, custom help flags
• Arguments where environment variable support would be confusing
• Inverse use case: default_env=False with selective enable_env=True for specific arguments

Environment

• jsonargparse version: latest (main branch)
• Python version: 3.x
• How jsonargparse was installed: git clone
• OS: Linux

---

@mauvilsa I'd be happy to put together a PR (especially for the the broader feature) if you agree this is worth addressing! It may be related to other default_env issues.

[mauvilsa]

Thank you for reporting!

* `ENV: CLI_VERSION` - Setting version via environment variable doesn't make semantic sense for a meta-action that just prints and exits

I agree, for version it should behave the same as for --help.

* `ENV: CLI_SUBCOMMAND` - Subcommand selection via environment variable is unusual and may not be desirable

Running a parser with subcommands with input from environment variables is an official feature. This should not be changed. See unit test

jsonargparse/jsonargparse_tests/test_subcommands.py

Lines 179 to 184 in 36679f3

	@patch.dict(os.environ, {"APP_SUBCOMMAND": "a", **env})
	def test_subcommands_parse_env(subcommands_parser):
	cfg = subcommands_parser.parse_env().as_dict()
	assert cfg["o1"] == "o1_env"
	assert cfg["subcommand"] == "a"
	assert cfg["a"] == {"ap1": "ap1_env", "ao1": "ao1_env"}

* `ENV: CLI_GREET` - Individual subcommands showing in the help as environment variables may be confusing

I also agree. I think that after "Available subcommands:" it should look the same as for default_env=False, so no ENV: lines, but also no ARG: prefixes.

parser.add_argument(..., enable_env=False)
subcommands = parser.add_subcommands(enable_env=False)

I don't see the need for this. jsonargparse is already complex enough, so I would be hesitant to add more parameters unless there is a very clear need. Having env vars for all arguments is not a problem. The variable names are just shown in the help. If they never get used, then it is fine.

I'd be happy to put together a PR

That would be great!