Abort expression parsing after encountering a maximum of 10 errors

Fixes #19480

src/core/qgsexpressionparser.yy

@@ -31,6 +31,9 @@
 // don't redeclare malloc/free
 #define YYINCLUDED_STDLIB_H 1
 
+// maximum number of errors encountered before parser aborts
+#define MAX_ERRORS 10
+
 struct expression_parser_context;
 #include "qgsexpressionparser.hpp"
 
@@ -177,7 +180,10 @@ root: expression { parser_ctx->rootNode = $1; }
     | error expression
         {
             delete $2;
-            yyerrok;
+            if ( parser_ctx->parserErrors.count() < MAX_ERRORS )
+              yyerrok;
+            else
+              YYABORT;
         }
    ;
 

tests/src/core/testqgsexpression.cpp

@@ -287,6 +287,14 @@ class TestQgsExpression: public QObject
       QCOMPARE( exp.parserErrors().first().lastColumn, lastColumn );
     }
 
+    void max_errors()
+    {
+      QgsExpression e( "wkt_geom	OBJECTID	id	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	" );
+      QVERIFY( e.hasParserError() );
+      // want parsing to abort after a maximum of 10 errors
+      QCOMPARE( e.parserErrors().count(), 10 );
+    }
+
     void parsing_with_locale()
     {
       // check that parsing of numbers works correctly even when using some other locale