DataGrid2 SELECTION binding may not persist; document pluggable vs built-in widget support scope

[ako]

Problem

SELECTION binding on DATAGRID2 (pluggable widget) may not persist after mxcli exec. GALLERY (built-in widget) works as a workaround, but this difference is undocumented — users don't know the supported scope for pluggable vs built-in widgets.

Current behavior

The MDL SELECTION syntax and code path are the same for both (mdl/grammar/domains/MDLPage.g4:334; mdl/executor/widget_engine.go:432-433 → SetSelection at mdl/backend/mpr/widget_builder.go:111-127). But DataGrid2 is pluggable (.def.json), so its itemSelection property nesting/PropertyKey may differ from Gallery's template, and SetSelection may miss the target and fail silently. There is no DataGrid2 selection-binding test.

Request

1. Documentation: clearly specify MDL support scope for pluggable widgets (DataGrid2) vs built-in widgets (Gallery), including the SELECTION-binding workaround.
2. (Stretch) Make DataGrid2 SELECTION binding persist, with a regression test.

Touch points

• Verify the DataGrid2 .def.json Selection property path; align SetSelection (mdl/backend/mpr/widget_builder.go) if it differs.
• Add a test alongside mdl/executor/roundtrip_mxcheck_datagrid_test.go.
• Document scope (skill / docs-site).

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Source: customer feedback batch (2026-06). Reporter: Miwa. Reporter severity: 5/5.
Filed after codebase investigation at 297e0b0a.

[github-actions]

Issue Triage

Summary
The issue reports that the SELECTION binding on the pluggable DataGrid2 widget does not persist after running mxcli exec (while the built‑in Gallery widget works), and asks for documentation of the supported scope and a fix with a regression test.

Checklist of required bug‑report information

Required info	Present?	Details
mxcli version	❌	Not mentioned
Mendix version	❌	Not mentioned
Scenario (what the user was trying to do)	⚠️	Mentions mxcli exec and SELECTION binding, but no concrete MDL script or command line shown
Expected output	❌	Not described
Experienced output (error, wrong result, crash)	❌	Not described
AI bug report (mxcli diag --bundle or session log)	❌	Not provided

What’s needed
To help us investigate, could you please add:

1. The exact mxcli --version (or commit/build) you used.
2. The Mendix version of the project you’re processing (e.g., 10.6.0).
3. A minimal MDL snippet or the exact mxcli exec command that reproduces the issue, plus what you expected to happen.
4. What actually happened (any error messages, wrong output, or silent failure).
5. If possible, the output of mxcli diag --bundle (or at least the session log) so we can see the internal state.

Once we have those details, we’ll be able to reproduce the problem and work on a fix or documentation update. Thank you for bringing this to our attention!

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Automated triage via OpenRouter — workflow source

[ako]

Resolved. Both parts of the request are addressed.

Behavior (the "stretch") — done. DataGrid2 selection: single and a DataView bound to its selection (datasource: selection dgProducts) now persist and build. Verified end-to-end on Mendix 11.12, on both engines (modelsdk default + legacy):

• describe page round-trips Selection: Single on the grid and DataSource: selection dgProducts on the DataView;
• mxcli docker check → 0 errors.

So the Gallery workaround is no longer needed — DataGrid2 and Gallery both support selection binding. (The Selection-casing/persistence fixes landed via 73c7ddec / c2b9b070.)

Documentation — done. docs-site/src/language/data-binding.md ("Selection Source") documents the master-detail pattern with a DataGrid master + DataView … SELECTION dgProducts detail. Selection binding is also in create-page.md and master-detail-pages.md.

Regression test — added. fcf19752 adds mdl-examples/bug-tests/628-datagrid2-selection.mdl (on the check-mdl guard) documenting the verified DataGrid2 master-detail repro.