shivaam commented on issue #60142:
URL: https://github.com/apache/airflow/issues/60142#issuecomment-4204186516
Thanks for the feedback @bugraoz93!
I looked into supporting both positional and `--flag` styles for required
params. Unfortunately argparse doesn't natively support this — a parameter is
either positional (`dag_id`) or a flag (`--dag-id`), never both.
**Why it's not straightforward:**
The closest workaround is registering all params as `--flags`, adding a
`nargs='*'` catch-all for bare values, and using `parse_intermixed_args` to map
positionals into unfilled flag slots after parsing. But this means we lose
argparse's built-in validation, type checking, help formatting, and
`required=True` for those params — we'd essentially reimplement positional
argument handling ourselves on top of argparse.
**Options:**
1. **Keep it positional for required params** (current PR) — the simplest,
most conventional choice. Required params are positional, optional params are
flags. All argparse features work, clean help output.
2. **Two-pass parsing** — maintain two parsers per command: one with
required params as positional, one with them as `--flags required=True`. Try
positional first, fall back to flags. Users can use either style, just not
mixed in the same invocation:
```bash
# both work:
airflowctl xcom add my_dag my_task my_key
airflowctl xcom add --dag-id=my_dag --task-id=my_task --key=my_key
# but not mixed:
airflowctl xcom add my_dag --task-id=my_task my_key # would fail
```
No argparse hacks needed (both parsers are standard), but doubles the
parser setup and mixed usage isn't supported.
3. **Cap positional count** — first 1-2 required params (like `dag_id`) are
positional, rest stay as `--flag required=True`. Common CLI pattern (like `git
checkout <branch> --force`). No hacks, all argparse features work.
I'd recommend Option 1 for simplicity. Happy to go with whichever you prefer!
---
<details>
<summary>Details on the <code>parse_intermixed_args</code> workaround (and
why I didn't recommend it)</summary>
The idea is to register all required params as `--flags` only (no argparse
positionals), add a single `nargs='*'` argument to collect any bare values,
then map those bare values into whichever flag slots the user didn't fill:
```python
PARAM_ORDER = ['dag_id', 'task_id', 'key']
parser.add_argument('--dag-id', dest='dag_id', default=None)
parser.add_argument('--task-id', dest='task_id', default=None)
parser.add_argument('--key', default=None)
parser.add_argument('positionals', nargs='*')
args = parser.parse_intermixed_args(argv)
# map bare values into unfilled flag slots, left to right
unfilled = [d for d in PARAM_ORDER if getattr(args, d) is None]
for i, val in enumerate(args.positionals):
setattr(args, unfilled[i], val)
```
`parse_intermixed_args` (Python 3.7+) allows flags and bare values to be
freely interspersed, so all of these would work:
```bash
airflowctl xcom add d t k # all positional
airflowctl xcom add --dag-id=d --task-id=t --key=k # all flags
airflowctl xcom add d --task-id=t k # mixed
airflowctl xcom add --task-id=t my_dag my_key # gap-filling
```
The problem is what we lose:
- **Validation** — can't use `required=True` on flags (argparse would reject
positional-only usage), so we validate manually after gap-filling
- **Type checking** — `type=int`, `choices=[...]` etc. don't apply to the
`nargs='*'` catch-all, so we type-check manually
- **Help output** — shows `[positionals ...]` instead of named params like
`DAG_ID TASK_ID`, and no indication which flags are required vs optional
- **`argparse.REMAINDER`** and **mutually exclusive groups with
positionals** — unsupported with `parse_intermixed_args`
This effectively means using argparse for flag parsing only and
reimplementing positional handling on top of it.
</details>
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