How to write a management command that reads from stdin should be documented

[Andrew Northall]

This seems like a fairly common use case, which is supported by Django, but as far as I can tell no mention of it is made in the documentation. It seems like it should be documented.

For an example of how to do it, loaddata and shell read from stdin in Django core:

​https://github.com/django/django/blob/main/django/core/management/commands/loaddata.py
​https://github.com/django/django/blob/main/django/core/management/commands/shell.py

I hear you say, 'but reading from stdin is a Python feature, not a Django feature, why should we document it?'. In my mind, the documentation as it exists now could lead to confusion: it makes specific mention that you should use BaseCommand.stdout and BaseCommand.stderr within a management command to write to stdout or stderr. It is not a big jump to then assume that you should also be using BaseCommand.stdin (which does not exist) to handle incoming data. The API, in this narrow sense, is inconsistent, and this is why the documentation would be helpful.

[Mariusz Felisiak]

Replying to Andrew Northall:

I hear you say, 'but reading from stdin is a Python feature, not a Django feature, why should we document it?'.

Thanks for the ticket, however, we cannot document everything.

In my mind, the documentation as it exists now could lead to confusion: it makes specific mention that you should use BaseCommand.stdout and BaseCommand.stderr within a management command to write to stdout or stderr. It is not a big jump to then assume that you should also be using BaseCommand.stdin (which does not exist) to handle incoming data. The API, in this narrow sense, is inconsistent, and this is why the documentation would be helpful.

I don't see anything inconsistency in API or docs. We don't document nonexistent attributes, and users cannot assume that attributes exist if they are not documented. In management commands you can use sys.stdin like everywhere else, there is nothing specific that they provide. You can start a discussion on DevelopersMailingList if you don't agree.