[GR-15169] Propagate messages from parser to the user.

PullRequest: graalpython/661

Author: ppisl

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/PythonParserImpl.java

@@ -259,6 +259,8 @@ public String unescapeJavaString(String str) {
 
     private static PException handleParserError(ParserErrorCallback errors, Source source, Exception e) {
         SourceSection section = PythonErrorStrategy.getPosition(source, e);
-        throw errors.raiseInvalidSyntax(source, section);
+        // from parser we are getting RuntimeExceptions
+        String message = e instanceof RuntimeException && e.getMessage() != null ? e.getMessage() : "invalid syntax";
+        throw errors.raiseInvalidSyntax(source, section, message);
     }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/antlr/DescriptiveBailErrorListener.java

@@ -63,7 +63,7 @@ public void syntaxError(Recognizer<?, ?> recognizer, Object offendingSymbol,
 
         String entireMessage = String.format("source: %s, line: %s, index: %s, error message: %s %s",
                         recognizer.getInputStream().getSourceName(), line, charPositionInLine, msg,
-                        e == null ? "<null>" : e.getMessage());
+                        e == null || e.getMessage() == null ? "invalid syntax" : e.getMessage());
 
         if (e != null) {
             PIncompleteSourceException handleRecognitionException = handleRecognitionException(e.getExpectedTokens(), entireMessage, e, line);