XFA - Don't fail xfa loading because of a JS subexpression in SOM expressions

- Fix for one pdf in bug 1717668 (PDFIUM-292-0.pdf).

src/core/xfa/som.js

@@ -60,7 +60,10 @@ function parseIndex(index) {
   return parseInt(index, 10) || 0;
 }
 
-function parseExpression(expr, dotDotAllowed) {
+// For now expressions containaing .[...] or .(...) are not
+// evaluated so don't parse them.
+// TODO: implement that stuff and the remove the noExpr param.
+function parseExpression(expr, dotDotAllowed, noExpr = true) {
   let match = expr.match(namePattern);
   if (!match) {
     return null;
@@ -108,10 +111,22 @@ function parseExpression(expr, dotDotAllowed) {
         operator = operators.dotHash;
         break;
       case "[":
+        if (noExpr) {
+          warn(
+            "XFA - SOM expression contains a FormCalc subexpression which is not supported for now."
+          );
+          return null;
+        }
         // TODO: FormCalc expression so need to use the parser
         operator = operators.dotBracket;
         break;
       case "(":
+        if (noExpr) {
+          warn(
+            "XFA - SOM expression contains a JavaScript subexpression which is not supported for now."
+          );
+          return null;
+        }
         // TODO:
         // Javascript expression: should be a boolean operation with a path
         // so maybe we can have our own parser for that stuff or