fix: DESCRIBE CONSTANT emits COMMENT field

Bug #25: Constants created with COMMENT 'text' were stored correctly
but DESCRIBE CONSTANT did not emit the COMMENT line. Also fixed the
CREATE CONSTANT handler to store stmt.Comment into the model's
Documentation field.

Author: engalar

mdl/executor/cmd_constants.go

@@ -141,16 +141,6 @@ func (e *Executor) describeConstant(name ast.QualifiedName) error {
 
 // outputConstantMDL outputs a constant definition in MDL format.
 func (e *Executor) outputConstantMDL(c *model.Constant, moduleName string) error {
-	// Output documentation if present
-	if c.Documentation != "" {
-		lines := strings.Split(c.Documentation, "\n")
-		fmt.Fprintln(e.output, "/**")
-		for _, line := range lines {
-			fmt.Fprintf(e.output, " * %s\n", line)
-		}
-		fmt.Fprintln(e.output, " */")
-	}
-
 	// Format default value based on type
 	defaultValueStr := formatDefaultValue(c.Type, c.DefaultValue)
 
@@ -159,6 +149,10 @@ func (e *Executor) outputConstantMDL(c *model.Constant, moduleName string) error
 	fmt.Fprintf(e.output, "  DEFAULT %s", defaultValueStr)
 
 	// Add options if present
+	if c.Documentation != "" {
+		escaped := strings.ReplaceAll(c.Documentation, "'", "''")
+		fmt.Fprintf(e.output, "\n  COMMENT '%s'", escaped)
+	}
 	if c.ExposedToClient {
 		fmt.Fprintf(e.output, "\n  EXPOSED TO CLIENT")
 	}
@@ -310,8 +304,12 @@ func (e *Executor) createConstant(stmt *ast.CreateConstantStmt) error {
 			modName := h.GetModuleName(modID)
 			if strings.EqualFold(modName, stmt.Name.Module) && strings.EqualFold(c.Name, stmt.Name.Name) {
 				if stmt.CreateOrModify {
-					// Update existing constant
-					c.Documentation = stmt.Documentation
+					// Update existing constant — COMMENT takes precedence over doc-comment
+					if stmt.Comment != "" {
+						c.Documentation = stmt.Comment
+					} else {
+						c.Documentation = stmt.Documentation
+					}
 					c.Type = constType
 					c.DefaultValue = defaultValue
 					c.ExposedToClient = stmt.ExposedToClient
@@ -327,10 +325,16 @@ func (e *Executor) createConstant(stmt *ast.CreateConstantStmt) error {
 		}
 	}
 
+	// COMMENT 'text' takes precedence; fall back to /** */ doc-comment
+	doc := stmt.Comment
+	if doc == "" {
+		doc = stmt.Documentation
+	}
+
 	constant := &model.Constant{
 		ContainerID:     module.ID,
 		Name:            stmt.Name.Name,
-		Documentation:   stmt.Documentation,
+		Documentation:   doc,
 		Type:            constType,
 		DefaultValue:    defaultValue,
 		ExposedToClient: stmt.ExposedToClient,