feat: add Data Transformer support (JSLT/XSLT, Mendix 11.9+)

Adds full MDL support for the new DataTransformers$DataTransformer
document type introduced in Mendix 11.9. Transformers define JSON-to-
JSON (or XML) transformation pipelines using JSLT expressions.

Syntax:

  CREATE DATA TRANSFORMER Module.Name
  SOURCE JSON '{"input": "data"}'
  {
    JSLT $$ { "output": .input } $$;
  };

  LIST DATA TRANSFORMERS [IN Module];
  DESCRIBE DATA TRANSFORMER Module.Name;
  DROP DATA TRANSFORMER Module.Name;

Steps use technology keywords (JSLT, XSLT) directly — no STEP label.
Single-line expressions use '...', multi-line use $$ ... $$ quoting
(same as Java actions). DESCRIBE auto-selects the right format based
on whether the expression contains newlines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

cmd/mxcli/help_topics/rest.txt

@@ -162,3 +162,34 @@ CATALOG QUERIES
   -- Published API surface area
   SELECT ServiceQualifiedName, ResourceName, HttpMethod, Path, Microflow
   FROM CATALOG.PUBLISHED_REST_OPERATIONS;
+
+DATA TRANSFORMERS
+-----------------
+
+  LIST DATA TRANSFORMERS;                           -- List all transformers
+  LIST DATA TRANSFORMERS IN MyModule;               -- Filter by module
+  DESCRIBE DATA TRANSFORMER MyModule.WeatherTransform; -- Re-executable CREATE
+
+  -- Single-line JSLT step
+  CREATE DATA TRANSFORMER MyModule.Flatten
+  SOURCE JSON '{"a": {"b": 1}}'
+  {
+    JSLT '{"value": .a.b}';
+  };
+
+  -- Multi-line JSLT step using $$ quoting
+  CREATE DATA TRANSFORMER MyModule.WeatherTransform
+  SOURCE JSON '{"latitude": 51.9, "current": {"temp": 12.8}}'
+  {
+    JSLT $$
+  {
+    "lat": .latitude,
+    "temp": .current.temp
+  }
+    $$;
+  };
+
+  DROP DATA TRANSFORMER MyModule.WeatherTransform;  -- Delete transformer
+
+  Requires Mendix 11.9+. Steps: JSLT, XSLT.
+  Single-line: JSLT '...'. Multi-line: JSLT $$ ... $$.

cmd/mxcli/lsp_completions_gen.go

@@ -298,3 +298,51 @@ CREATE OR REPLACE PUBLISHED REST SERVICE Module.OrderAPI (
 -- Remove entirely
 DROP PUBLISHED REST SERVICE Module.OrderAPI;
 ```
+
+## Data Transformers (JSLT)
+
+Data Transformers apply transformation steps (JSLT or XSLT) to JSON or XML payloads. Useful for reshaping API responses before import mapping, or normalising data from third-party sources. Requires Mendix 11.9+.
+
+```sql
+-- Create a transformer that extracts key fields from a weather API response.
+-- The SOURCE JSON defines a sample payload used for schema inference and testing.
+CREATE DATA TRANSFORMER Integration.WeatherTransform
+SOURCE JSON '{
+  "latitude": 51.9,
+  "longitude": 4.5,
+  "timezone": "Europe/Amsterdam",
+  "current": {
+    "time": "2024-01-15T14:00",
+    "temperature_2m": 12.8,
+    "wind_speed_10m": 18.3,
+    "weather_code": 3
+  }
+}'
+{
+  JSLT $$
+{
+  "lat":        .latitude,
+  "lon":        .longitude,
+  "timezone":   .timezone,
+  "temp":       .current.temperature_2m,
+  "wind_speed": .current.wind_speed_10m,
+  "code":       .current.weather_code
+}
+  $$;
+};
+
+-- List all data transformers in the Integration module
+LIST DATA TRANSFORMERS IN Integration;
+
+-- Inspect a transformer (outputs a re-executable CREATE statement)
+DESCRIBE DATA TRANSFORMER Integration.WeatherTransform;
+
+-- Remove a transformer
+DROP DATA TRANSFORMER Integration.WeatherTransform;
+```
+
+**Notes:**
+- Steps execute in order; the output of each step feeds the next.
+- `JSLT '...'` for short single-line expressions; `JSLT $$ ... $$` for multi-line.
+- `XSLT $$ ... $$` is also supported for XML-to-XML transformations.
+- Requires Mendix 11.9+. Use `SHOW FEATURES` to confirm support before using.

docs-site/src/examples/rest-integration.md

@@ -527,6 +527,30 @@ CREATE PUBLISHED REST SERVICE Module.MyAPI (
 **Path parameters:** Must match a microflow parameter exactly (case-sensitive). E.g., `'{id}'` requires the microflow to have parameter `$id`.
 **Operation modifiers:** `DEPRECATED`, `IMPORT MAPPING Module.Name`, `EXPORT MAPPING Module.Name`, `COMMIT Yes|No`
 
+## Data Transformers
+
+Requires Mendix 11.9+. Steps: `JSLT`, `XSLT`. Single-line: `JSLT '...'`. Multi-line: `JSLT $$ ... $$`.
+
+| Statement | Syntax | Notes |
+|-----------|--------|-------|
+| List transformers | `LIST DATA TRANSFORMERS [IN Module];` | |
+| Describe transformer | `DESCRIBE DATA TRANSFORMER Module.Name;` | Re-executable CREATE |
+| Create transformer | See syntax below | |
+| Drop transformer | `DROP DATA TRANSFORMER Module.Name;` | |
+
+```sql
+CREATE DATA TRANSFORMER Module.WeatherTransform
+SOURCE JSON '{"latitude": 51.9, "current": {"temp": 12.8}}'
+{
+  JSLT $$
+{
+  "lat": .latitude,
+  "temp": .current.temp
+}
+  $$;
+};
+```
+
 ## JSON Structures
 
 | Statement | Syntax | Notes |

docs/01-project/MDL_QUICK_REFERENCE.md

@@ -0,0 +1,63 @@
+-- ============================================================================
+-- Data Transformer Examples
+-- ============================================================================
+--
+-- Demonstrates creating, describing, listing, and dropping data transformers.
+--
+-- Prerequisites:
+--   - Mendix 11.9+ (Data Transformers require >= 11.9)
+--
+-- ============================================================================
+
+CREATE MODULE DtTest;
+
+-- ############################################################################
+-- PART 1: SIMPLE SINGLE-LINE JSLT TRANSFORMER
+-- ############################################################################
+
+-- Flatten a nested JSON object using a single-line JSLT expression.
+CREATE DATA TRANSFORMER DtTest.FlattenNested
+SOURCE JSON '{"wrapper": {"value": 42, "label": "hello"}}'
+{
+  JSLT '{"value": .wrapper.value, "label": .wrapper.label}';
+};
+
+-- ############################################################################
+-- PART 2: MULTI-LINE JSLT TRANSFORMER WITH $$ QUOTING
+-- ############################################################################
+
+-- Extract key fields from a weather API response using a multi-line JSLT step.
+CREATE DATA TRANSFORMER DtTest.WeatherTransform
+SOURCE JSON '{"latitude": 51.9, "longitude": 4.5, "timezone": "Europe/Amsterdam", "current": {"time": "2024-01-15T14:00", "temperature_2m": 12.8, "wind_speed_10m": 18.3, "weather_code": 3}}'
+{
+  JSLT $$
+{
+  "lat":        .latitude,
+  "lon":        .longitude,
+  "timezone":   .timezone,
+  "temp":       .current.temperature_2m,
+  "wind_speed": .current.wind_speed_10m,
+  "code":       .current.weather_code
+}
+  $$;
+};
+
+-- ############################################################################
+-- PART 3: LIST AND DESCRIBE
+-- ############################################################################
+
+-- List all data transformers in the project
+LIST DATA TRANSFORMERS;
+
+-- List data transformers in a specific module
+LIST DATA TRANSFORMERS IN DtTest;
+
+-- Describe a transformer (outputs a re-executable CREATE statement)
+DESCRIBE DATA TRANSFORMER DtTest.WeatherTransform;
+
+-- ############################################################################
+-- PART 4: DROP
+-- ############################################################################
+
+DROP DATA TRANSFORMER DtTest.FlattenNested;
+DROP DATA TRANSFORMER DtTest.WeatherTransform;

mdl-examples/doctype-tests/23-data-transformer-examples.mdl

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package ast
+
+// CreateDataTransformerStmt represents:
+//
+//	CREATE DATA TRANSFORMER Module.Name SOURCE JSON '...' { JSLT '...'; };
+type CreateDataTransformerStmt struct {
+	Name       QualifiedName
+	SourceType string // "JSON" or "XML"
+	SourceJSON string // the source content
+	Steps      []DataTransformerStepDef
+}
+
+func (s *CreateDataTransformerStmt) isStatement() {}
+
+// DataTransformerStepDef represents a single step: JSLT '...' or XSLT '...'
+type DataTransformerStepDef struct {
+	Technology string // "JSLT", "XSLT"
+	Expression string
+}
+
+// DropDataTransformerStmt represents: DROP DATA TRANSFORMER Module.Name
+type DropDataTransformerStmt struct {
+	Name QualifiedName
+}
+
+func (s *DropDataTransformerStmt) isStatement() {}

mdl/ast/ast_datatransformer.go

@@ -79,6 +79,7 @@ const (
 	ShowImageCollections      // SHOW IMAGE COLLECTIONS [IN module]
 	ShowRestClients           // SHOW REST CLIENTS [IN module]
 	ShowPublishedRestServices // SHOW PUBLISHED REST SERVICES [IN module]
+	ShowDataTransformers     // LIST DATA TRANSFORMERS [IN module]
 	ShowConstantValues        // SHOW CONSTANT VALUES [IN module]
 	ShowContractEntities      // SHOW CONTRACT ENTITIES FROM Module.Service
 	ShowContractActions       // SHOW CONTRACT ACTIONS FROM Module.Service
@@ -193,6 +194,8 @@ func (t ShowObjectType) String() string {
 		return "REST CLIENTS"
 	case ShowPublishedRestServices:
 		return "PUBLISHED REST SERVICES"
+	case ShowDataTransformers:
+		return "DATA TRANSFORMERS"
 	case ShowConstantValues:
 		return "CONSTANT VALUES"
 	case ShowContractEntities:
@@ -280,6 +283,7 @@ const (
 	DescribeImageCollection      // DESCRIBE IMAGE COLLECTION Module.Name
 	DescribeRestClient           // DESCRIBE REST CLIENT Module.Name
 	DescribePublishedRestService // DESCRIBE PUBLISHED REST SERVICE Module.Name
+	DescribeDataTransformer      // DESCRIBE DATA TRANSFORMER Module.Name
 	DescribeContractEntity       // DESCRIBE CONTRACT ENTITY Service.EntityName [FORMAT mdl]
 	DescribeContractAction       // DESCRIBE CONTRACT ACTION Service.ActionName [FORMAT mdl]
 	DescribeContractMessage      // DESCRIBE CONTRACT MESSAGE Service.MessageName
@@ -344,6 +348,8 @@ func (t DescribeObjectType) String() string {
 		return "REST CLIENT"
 	case DescribePublishedRestService:
 		return "PUBLISHED REST SERVICE"
+	case DescribeDataTransformer:
+		return "DATA TRANSFORMER"
 	case DescribeContractEntity:
 		return "CONTRACT ENTITY"
 	case DescribeContractAction: