Don't error on empty string

Author: kevinresol

src/why/searchsyntax/Parser.hx

@@ -77,7 +77,10 @@ class Parser extends tink.parse.ParserBase<Pos, Error> {
 		#end
 	}
 
-	static function doParse(source, ?pos):Outcome<Array<Term>, Error> {
+	static function doParse(source:String, ?pos):Outcome<Array<Term>, Error> {
+		if(source.trim().length == 0)
+			return Success([]);
+		
 		final offset = 0;
 		final reporter = new RuntimeReporter(pos);
 		final parser = new Parser(source, reporter, offset);

tests/ParserTest.hx

@@ -25,8 +25,13 @@ class ParserTest {
 
 	#else
 
+	public function empty() {
+		final result = Parser.parse('');
+		asserts.assert(result.length == 0);
+		return asserts.done();
+	}
+	
 	public function basic() {
-		Parser.parse('?date:2022-02-02');
 		final result = Parser.parse('?date:>=2022-02-02');
 		asserts.assert(result.length == 1);
 		asserts.assert(result[0].modifiers.length == 1);