Misleading makemigrations "App count not be found" error message with nested apps

[Matthew Schinckel]

I have a couple of nested apps, or apps that are not available directly in the top-level namespace.

When you use makemigrations, and pass the full dotted path to this command, the error message is somewhat misleading:

App 'integrations.systems.generic.importers' could not be found. Is it in INSTALLED_APPS?

In this case, I have that exact string in my INSTALLED_APPS, but makemigrations is expecting just the app_label. Perhaps we could improve the error message when dots are detected in the app_label, suggesting how to fix it: or even look at just the last part of the path?

[Windson yang]

Maybe you should add an example project?

[oliver]

Current code generating that error message is as follows when using makemigraions command.

       # Make sure the app they asked for exists
        app_labels = set(app_labels)
        bad_app_labels = set()
        for app_label in app_labels:
            try:
                apps.get_app_config(app_label)
            except LookupError:
                bad_app_labels.add(app_label)
        if bad_app_labels:
            for app_label in bad_app_labels:
                self.stderr.write("App '%s' could not be found. Is it in INSTALLED_APPS?" % app_label)
            sys.exit(2)

and below is the part that checks the validity of the app name when using startapp and createproject command

        if not name.isidentifier():
            raise CommandError(
                "'{name}' is not a valid {app} name. Please make sure the "
                "name is a valid identifier.".format(
                    name=name,
                    app=app_or_project,
                )
            )

How about using the code validating app name to current code as follows?
​https://github.com/django/django/pull/10052

       # Make sure the app they asked for is a valid app name and exist.
        app_labels = set(app_labels)
        bad_app_labels = set()
        for app_label in app_labels:
            try:
                apps.get_app_config(app_label)
            except LookupError:
                bad_app_labels.add(app_label)
        if bad_app_labels:
            for app_label in bad_app_labels:
                if not app_label.isidentifier():
                    self.stderr.write(
                        "'%s' is not a valid app name. Please make sure the "
                        "name is a valid identifier." % app_label
                    )
                else:
                    self.stderr.write("App '%s' could not be found. Is it in INSTALLED_APPS?" % app_label)
            sys.exit(2)

[Tim Graham]

​PR

[oliver]

​https://github.com/django/django/pull/10057

I change the target branch to master and add a test.

[Tim Graham <timograham@…>]

In 78972af3:

Fixed #29469 -- Added a helpful makemigrations error if app_label contains dots.

[Tim Graham <timograham@…>]

In d03b130c:

[2.1.x] Fixed #29469 -- Added a helpful makemigrations error if app_label contains dots.

Backport of 78972af367a1da54aa7e539e4b1ffa2b56571e77 from master

[Tim Graham <timograham@…>]

In c3c7d15:

Refs #29469 -- Reused get_app_config() error message in makemigrations error.