[GitHub] [flink] dawidwys commented on a change in pull request #8345: [FLINK-12402][table] Make validation error message for CallExpression more user friendly

[GitBox <gi...@apache.org>]

dawidwys commented on a change in pull request #8345: [FLINK-12402][table] Make validation error message for CallExpression more user friendly
URL: https://github.com/apache/flink/pull/8345#discussion_r283206493
 
 

 ##########
 File path: flink-table/flink-table-planner/src/main/java/org/apache/flink/table/expressions/rules/ResolveCallByArgumentsRule.java
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 @@ -86,21 +86,31 @@ private Expression performTypeResolution(CallExpression call, List<TypeInformati
 
 		private Expression validateArguments(CallExpression call, PlannerExpression plannerCall) {
 			if (!plannerCall.valid()) {
-				final String errorMessage;
-				ValidationResult validationResult = plannerCall.validateInput();
-				if (validationResult instanceof ValidationFailure) {
-					errorMessage = ((ValidationFailure) validationResult).message();
-				} else {
-					errorMessage = String.format("Invalid arguments %s for function: %s",
-						call.getChildren(),
-						call.getFunctionDefinition().getName());
-				}
-				throw new ValidationException(errorMessage);
+				throw new ValidationException(getValidationErrorMessage(plannerCall));
 			}
-
 			return call;
 		}
 
+		/**
+		 * Return the validation error message of this {@link PlannerExpression} or return the
+		 * validation error message of it's children if it passes the validation. Return an empty
+		 * string if all validation succeeded.
+		 */
+		private String getValidationErrorMessage(PlannerExpression plannerCall) {
 
 Review comment:
   One small comment, let's use the `Optional` to mark that method might not return results.

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