docs(inline): correct inline post-processing example and fix Peewee parity (#1738)

[jbbqqf]

Summary

The inline_model_form_converter docstrings in
flask_admin.contrib.sqla.view and flask_admin.contrib.peewee.view
advertise a post_process method on a converter subclass. That method
name is never invoked anywhere in the codebase, so following the
documented example is silently a no-op. The hook the SQLAlchemy
converter actually calls is InlineFormAdmin.postprocess_form (see
flask_admin/contrib/sqla/form.py:1014,1139); the examples/sqla_custom_inline_forms/main.py:132
example uses that real hook.

Fixes #1738.

Context

• flask_admin/contrib/sqla/view.py:213-224 (pre-change) and
  flask_admin/contrib/peewee/view.py:112-123 (pre-change) showed:

  class MyInlineModelConverter(InlineModelConverter):
      def post_process(self, form_class, info):
          ...

  Grepping the repo for post_process returns only those two docstring
  occurrences -- nothing in the code path ever calls a method by that
  name.

• The real contract is on InlineBaseFormAdmin:
  flask_admin/model/form.py:120-134 defines
  postprocess_form(self, form_class) and the SQLA converter invokes it
  at flask_admin/contrib/sqla/form.py:1014 and :1139.

• The Peewee inline converter (flask_admin/contrib/peewee/form.py:287-350)
  never invoked postprocess_form at all, so the documented pattern was
  effectively broken on the Peewee backend as well.

Changes

• flask_admin/contrib/sqla/view.py, flask_admin/contrib/peewee/view.py:
  rewrite the inline_model_form_converter docstring example to use
  InlineFormAdmin.postprocess_form (the hook the converter actually
  invokes) and to pass the subclass through inline_models.
• flask_admin/contrib/peewee/form.py: call
  info.postprocess_form(child_form) inside
  InlineModelConverter.contribute, mirroring the long-standing SQLA
  behavior so the documented hook works on both backends.
• flask_admin/tests/sqla/test_inlineform.py:
  add test_inline_form_postprocess_form_hook that subclasses
  InlineFormAdmin, contributes an extra StringField via
  postprocess_form, and asserts the field lands on the generated
  inline form class. Pins the documented contract.
• flask_admin/tests/peeweemodel/test_basic.py:
  add a matching regression test that fails on origin/main (the hook
  was never called) and passes on this branch.
• doc/changelog.rst: add [unreleased] entries for the documentation
  fix and the Peewee bug fix.

Reproduce BEFORE/AFTER yourself (copy-paste)

# --- one-time setup ---
git clone https://github.com/pallets-eco/flask-admin.git /tmp/fa-1738 && cd /tmp/fa-1738
uv venv .venv --python 3.12
source .venv/bin/activate
uv pip install -e ".[sqlalchemy,peewee]" pytest flask-sqlalchemy-lite

# --- BEFORE: origin/master, Peewee `postprocess_form` hook is never called ---
git checkout origin/master
git fetch https://github.com/jbbqqf/flask-admin.git docs/1738-inline-postprocess-form
git checkout FETCH_HEAD -- flask_admin/tests/peeweemodel/test_basic.py
pytest flask_admin/tests/peeweemodel/test_basic.py::test_inline_form_postprocess_form_hook -v
# Expected: FAILED -- "InlineFormAdmin.postprocess_form should contribute
#                      extra fields on the Peewee backend just like it
#                      does on the SQLAlchemy backend."
git checkout origin/master -- flask_admin/tests/peeweemodel/test_basic.py

# --- AFTER: this branch, both SQLA and Peewee fire the documented hook ---
git checkout FETCH_HEAD
pytest \
  flask_admin/tests/peeweemodel/test_basic.py::test_inline_form_postprocess_form_hook \
  flask_admin/tests/sqla/test_inlineform.py::test_inline_form_postprocess_form_hook \
  -v
# Expected: 4 passed, 1 skipped (SQLALite-with-session_deprecated is skipped
#           by the conftest fixture; the SQLA + Peewee cases all pass).

What I ran locally

• New tests, focused:

  pytest flask_admin/tests/peeweemodel/test_basic.py::test_inline_form_postprocess_form_hook \
         flask_admin/tests/sqla/test_inlineform.py::test_inline_form_postprocess_form_hook -v
  # 4 passed, 1 skipped
  

• Whole inline test file:

  pytest flask_admin/tests/sqla/test_inlineform.py -q
  # 18 passed, 6 skipped
  

• Broader regression sweep (excluding the Postgres-only test module, which
  needs psycopg2):

  pytest flask_admin/tests/peeweemodel/ flask_admin/tests/sqla/ \
         flask_admin/tests/test_base.py flask_admin/tests/test_model.py \
         --ignore=flask_admin/tests/sqla/test_postgres.py -q
  # 335 passed, 81 skipped, 13 xfailed
  

• Lint:

  ruff check flask_admin/contrib/peewee/form.py flask_admin/contrib/peewee/view.py \
             flask_admin/contrib/sqla/view.py \
             flask_admin/tests/peeweemodel/test_basic.py \
             flask_admin/tests/sqla/test_inlineform.py
  # All checks passed!
  

Edge cases

#	Scenario	Input	Expected	Verified by
1	SQLA backend, subclass InlineFormAdmin and contribute extra field via postprocess_form	inline_models = (UserInfoInlineForm(UserInfo),)	view._create_form_class.info.args[0] has extra attribute	new test_inline_form_postprocess_form_hook[SQLAProvider-*]
2	Peewee backend, same subclass-and-contribute pattern	inline_models = (Model2InlineForm(Model2),)	generated inline form class has extra attribute	new test_inline_form_postprocess_form_hook (peewee)
3	Plain inline_models = (Model,) with no InlineFormAdmin subclass	existing behavior	continues to work unchanged	existing test_inline_form / test_inline_form_required / test_inline_form_self / test_inline_form_base_class all still pass
4	Peewee InlineFormAdmin returning a custom form via get_form() (skips the auto-generated path)	info.get_form() returns non-None	still passes through postprocess_form after assignment	code path now uniformly calls postprocess_form after the if child_form is None branch, matching the SQLA backend's structure

Risk / blast radius

• Docstring-only change for SQLA: no behavior change.
• Peewee InlineModelConverter.contribute: now calls
  info.postprocess_form(child_form). The default
  InlineFormAdmin.postprocess_form (flask_admin/model/form.py:134)
  returns the form class unchanged, so existing call sites that never
  overrode the hook see no diff. Behavior changes only for users who
  do override the hook -- which is the previously-documented but
  broken case we're fixing.
• All non-Postgres tests pass locally; the Postgres test module fails
  to import only because psycopg2 isn't installed in my dev env (it's
  unrelated to this diff).

Release note

Fix the SQLAlchemy/Peewee `inline_model_form_converter` docstring example
to point at the real `InlineFormAdmin.postprocess_form` hook, and wire
the Peewee backend to call that hook so the documented pattern actually
works there.

---

PR drafted with assistance from Claude Code (Anthropic). The change was
reviewed manually against flask-admin's source -- file:line references in
the body were checked against the cloned tree, and the copy-paste
BEFORE/AFTER reproducer block is the one I used during development;
reviewers can paste it verbatim.