MDL parser fails to parse inline if...then...else expression in SET statement

[engalar]

Summary

DESCRIBE MICROFLOW correctly emits Mendix inline if...then...else expressions (used in SET assignments), but mxcli exec fails to parse them back. This makes the DESCRIBE → exec roundtrip impossible for any microflow containing a conditional expression assignment.

Steps to Reproduce

Using a microflow that contains a SET action with an inline conditional expression (e.g. ConversationalUI.DS_TokenMonitor_UsageList):

# 1. Capture DESCRIBE output
mxcli -p app.mpr -c "DESCRIBE MICROFLOW ConversationalUI.DS_TokenMonitor_UsageList;" > a.mdl

# 2. Drop the original
mxcli -p app.mpr -c "DROP MICROFLOW ConversationalUI.DS_TokenMonitor_UsageList;"

# 3. Re-create — this fails
mxcli exec a.mdl -p app.mpr

DESCRIBE Output (a.mdl) — the problematic fragment

SET $EndOfCurrentBin = if $EndOfCurrentBin > $TokenMonitorSettings/DateTo then
  $TokenMonitorSettings/DateTo
else
  $EndOfCurrentBin;

This is valid Mendix expression syntax (lowercase if...then...else), but mxcli exec rejects it.

Actual Error

Parse error: line 31:49 no viable alternative at input '$EndOfCurrentBin>'
Parse error: line 31:80 extraneous input 'then' expecting {<EOF>, CREATE, ALTER, DROP, ...}
Parse error: line 33:0 extraneous input 'else' expecting {<EOF>, CREATE, ALTER, DROP, ...}

The parser interprets the if keyword as starting a top-level IF...THEN...END IF block, then fails when it encounters the expression $EndOfCurrentBin > ... instead of a condition.

Expected Behavior

mxcli exec should parse and write the inline if...then...else Mendix expression correctly:

-- Mendix expression syntax: lowercase if, inline, terminates at ;
SET $Var = if <condition> then <expr1> else <expr2>;

Root Cause

The MDL grammar treats if as a statement-level keyword (→ IF...THEN...END IF block) and does not handle the Mendix expression-level if...then...else construct inside expression positions (RHS of SET, CHANGE attribute values, DECLARE default values, etc.).

Environment

• Mendix version: 11.6.4
• Affected module: ConversationalUI (Marketplace v3.0.0) — any microflow with a conditional expression in a SET action

Impact

High. Mendix uses inline if...then...else widely in generated and hand-written microflows. Any such microflow produces a DESCRIBE output that cannot be re-executed, fully breaking the roundtrip. The dropped microflow is also not restored, leaving references dangling (CE1613).