Round-trip harness: untracked describe → exec losses on the Studio Pro fixture (microflows, entities, pages, snippets, menus, roles, JS actions)

[ako]

Found by the round-trip harness (#703) on the committed Studio Pro fixture testdata/pedapp (PedApp, Mendix 11.13). Plan item 0.4 in PROPOSAL_mdl_beta_syntax_freeze.md §8.1.

The harness runs describe → exec (unchanged) → compares every unit. Only 42 of 223 documents keep the GetPut law ("executing describe output writes nothing"). #704 and #705 cover part of what it finds. This issue lists the untracked classes, so each allowlist entry in mdl/roundtrip/pedapp_roundtrip_test.go names an issue. Split into per-class issues or PRs as they are picked up; each fix strikes its entries from the allowlist (the test fails until it does).

Reproduce: go test -tags integration -run TestPedAppRoundTrip -v ./mdl/roundtrip/. Each failure prints the changed BSON paths.

A. Microflows and nanoflows: the whole-document rebuild is lossy (16 microflows, 13 nanoflows)

Every Studio Pro microflow and nanoflow with a flow changes when its own describe output is re-run:

• curve control vectors are reset (-30;0 -> 0;0);
• merges and flows are dropped (VAL_Feedback 32 → 27 flows);
• case values change type (EnumerationCase ↔ NoCase/InheritanceCase);
• error-handler flags and connection indexes change;
• annotation flows become sequence flows.

This is the architecture problem in ADR-0012 decision 3 (UpdateMicroflow rebuild + positional ID re-pairing). It is fixed by diff-then-patch create or modify (plan 4.2g), not per statement. Nanoflow ExportLevel and annotation links are #705 item 2.

B. Entities: stored properties dropped on rebuild (7 entities)

• AccessRules[*]/MemberAccesses[*]/Association and .../Attribute (empty pointers Studio Pro writes) are removed.
• MaybeGeneralization/HasChangedByAttr, HasChangedDateAttr, HasCreatedDateAttr, HasOwnerAttr (false) are removed.

C. Pages: widget properties changed or dropped (16 pages)

Beyond the translations in #705 item 1:

• layout-grid column weights change (12 -> -1, -2 -> -1, 4 -> -1), and row VerticalAlignment resets;
• SourceVariable on inputs is dropped;
• DisabledDuringExecution false -> true (also A page rewrite overwrites a stored DisabledDuringExecution = false with true #549);
• the pluggable Image widget's stored Type is replaced by mxcli's template, a different property schema;
• tab-container properties (DefaultPagePointer, ActivePage*, Badge) are dropped;
• design properties are dropped (Appearance/DesignProperties 3 -> 1);
• a legacy Forms$DataGrid is described as datagrid, which create builds as the pluggable Datagrid.

D. Snippets: content dropped (4 snippets)

Beyond Type (#705 item 4):

• Atlas_Core.FeedbackWidget loses all its widgets (Widgets: removed);
• Atlas_Core.LanguageSelectorWidget changes its data source sort and caption expression.

E. Menus: sub-items dropped (2 menus)

Atlas_Core.Phone_Menu, Atlas_Core.Tablet_Menu: nested Items are removed, and DisabledDuringExecution and AlternativeText are dropped.

F. describe emits plain create for user roles and JavaScript actions (2 user roles, 43 JavaScript actions)

Re-running fails with "already exists". #705 item 5 covers associations, Java actions and module roles; user roles and JavaScript actions are not listed there. Note the JavaScript action body is "omitted by DESCRIBE", so a create or modify would also have to carry the stored source rather than write the placeholder.

G. describe output that does not parse (40 building blocks, 24 JavaScript actions)

• Building blocks: describe says they are read-only, then prints a bare { … } widget body, which is a parse error. It should print only comments, or a statement that parses.
• JavaScript actions with a type parameter print create javascript action M.X<TypeParameter> …, which does not parse.
• JavaScript action parameters print the trailing comma after the -- comment, so it is commented out (DataWidgets.Set_Filter).