The classroom's rules, in one file — and a table that checks them

[mircealungu]

Two commits: a table that checks the rules, and a file that states them.

The problem

The rules for what a student sees were spread across User.cohort_articles_for_user, _classroom_only and the article filters. No file stated any of them. That is the common root of the last fortnight's bugs — the Greek learner staring at a blank app, the 54 students with texts in their class they cannot open, the teacher exemption that made the first bug report misleading.

1. zeeguu/core/classroom.py — the rules, readable

The whole of the classroom's behaviour in the order someone would ask about it. Each rule is one function and the sentence that justifies it:

def student_can_read(student, text):
    """A student reads only in the language they are currently learning.

    The student's own setting decides, not the class's -- which is why a
    Greek learner in an English class sees an empty classroom, and why a class
    can hold texts that nobody in it can open.
    """

def classroom_of(student):
    """The texts a student sees, each with the classes it reached them through.

    One merged list: a student in several classes has one classroom, not one
    per class. A text shared with two of their classes appears once, naming both.
    """

def sees_only_class_texts(user):
    """Whether the app is reduced to the classroom: no feed, no search, no inbox.

    ... the strictest class wins ... Teachers are never restricted, even in a
    class that asks for it: they need the feed and the search to find the texts
    they are going to share.
    """

Both former homes become adapters: cohort_articles_for_user turns the answer into article infos and tags them; _classroom_only forwards.

2. test_classroom_visibility_rules.py — the same rules as a table

#        learning  classes                                sees  mode
("a class in another language is invisible, not empty",
     "da",     {"English Class": "en en"},              0,   FULL_APP),

("a class may hold texts the student cannot see",
     "da",     {"Mixed Class": "da en en"},             1,   FULL_APP),

("Jack's bug: restricted, and every text is in another language",
     "de",     {"CUT!": "en en en en en"},              0,   CLASSROOM_ONLY),

A row is one world. ! on a class name means "students see only the texts I share". Each row builds that world and asks the real code.

No behaviour change, and the table is what says so

298 tests and 20 subtests pass unchanged. The refactor is exactly the kind that is nerve-racking without a spec and dull with one.

The table also found a live fragility on its first run: _tiago_exercises dereferenced user.learned_language.code with no guard, and features_for_user runs on every /user_details — an account with no learned language would have taken down the whole call. Zero such accounts exist today; cohort_articles_for_user already handled the case, so the two halves disagreed. Guarded.

[github-actions]

ArchLens detected architectural changes in the following views: