v0.10.0 Phase 2: native vs pluggable DATAGRID dispatch + LEGACYDATAGRID keyword

[ako]

Parent: #529 (unified schema registry, revised phasing)
Depends on: #538 (Phase 1 must land first — object-list support is needed for
pluggable DataGrid columns to actually work)
Milestone: v0.10.0

Goal

DATAGRID MDL keyword dispatches to the right widget per Mendix project version
(native Forms\$DataGrid on 9.x-10.x, pluggable
com.mendix.widget.web.datagrid.Datagrid on 11.0+). Add LEGACYDATAGRID for
migrated 11+ projects that still have native widgets.

Acceptance fixture

mdl-examples/doctype-tests/31-pluggable-datagrid-gallery-v010-examples.mdl
already parses; this issue makes its BSON output correct for Mendix 11
(pluggable Datagrid) and ensures the same MDL still produces native BSON on
Mendix 10.x.

Work

1. Dispatch table (small policy data file)

mdl/backend/widget/dispatch.json (or similar) contains keyword mappings:

{
  "keywordMappings": [
    {
      "keyword": "DATAGRID",
      "versions": [
        { "min": "9.0.0", "max": "10.99.99", "kind": "native",
          "type": "Forms\$DataGrid" },
        { "min": "11.0.0", "kind": "pluggable",
          "widgetId": "com.mendix.widget.web.datagrid.Datagrid" }
      ]
    },
    {
      "keyword": "LEGACYDATAGRID",
      "versions": [
        { "min": "9.0.0", "kind": "native",
          "type": "Forms\$DataGrid",
          "deprecatedFrom": "11.0.0" }
      ]
    }
  ]
}

2. Replace hardcoded case \"datagrid\" in cmd_pages_builder_v3.go

Replace the hardcoded native dispatch with a registry lookup: read the project's
Mendix version, look up the dispatch table, route to native builder OR pluggable
engine based on the binding kind.

3. Add LEGACYDATAGRID keyword

Grammar addition. Behaves like DATAGRID but always routes native, with a
deprecation warning emitted by mxcli check on Mendix 11+.

4. DESCRIBE round-trip

Reader should emit LEGACYDATAGRID keyword for pages where Forms\$DataGrid
BSON is encountered on a Mendix 11+ project, and DATAGRID for the pluggable
variant. On Mendix 10.x, both keywords still emit DATAGRID (only one option).

Acceptance criteria

• Same MDL script with DATAGRID produces native Forms\$DataGrid on
  Mendix 10.24, pluggable com.mendix.widget.web.datagrid.Datagrid on 11.9
• LEGACYDATAGRID keyword always produces native, with deprecation warning
  on Mendix 11+
• Migrated 11.9 project with mixed grids round-trips through DESCRIBE: each
  grid emits the keyword matching its actual BSON stack
• mxcli check --post-migration lists every legacy-stack DATAGRID in the
  project as a migration to-do
• Acceptance fixture 31-pluggable-datagrid-gallery-v010-examples.mdl
  produces correct pluggable BSON on a Mendix 11 project

Out of scope

• Auto-converting native DataGrid BSON to pluggable BSON (different runtime,
  different schemas — manual Studio Pro operation)
• Other dual-stack widgets (LEGACYLISTVIEW, LEGACYDROPDOWN) — those follow the
  same pattern but ship in v0.11+

🤖 Generated with Claude Code

[github-actions]

Issue Triage

Summary:
The issue proposes adding version‑aware dispatch for the DATAGRID MDL keyword (native vs. pluggable) and a new LEGACYDATAGRID keyword to handle migrated Mendix 11+ projects that still use the native widget.

Checklist for feature request completeness

Required info	Present?	Notes
Use case – why the feature is needed / problem it solves	✅	Explained in the “Goal” section: need to dispatch to the correct widget per Mendix version and support migrated projects.
Proposed syntax or behavior (if applicable)	✅	Detailed dispatch table JSON, code changes, grammar addition, DESCRIBE round‑trip behavior, and acceptance criteria.
Mendix version relevance (if version‑specific)	✅	Specifies native for 9.x‑10.x, pluggable for 11.0+, and deprecation of LEGACYDATAGRID from 11.0 onward.

Conclusion:
All required information for a feature request is present. Thank you for the clear and thorough proposal!

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