Scribunto: Do not return early in Gsub if source is String.empty [#731]

400_xowa/src/gplx/xowa/xtns/scribunto/libs/Scrib_lib_ustring__gsub__tst.java

@@ -49,6 +49,12 @@ public class Scrib_lib_ustring__gsub__tst {
 		// TOMBSTONE: tested with local MW and {{#invoke:Test|test16|a|[^]|b}} -> Lua error: Missing close-bracket for character set beginning at pattern character 1.; DATE:2018-07-02
 		// Exec_gsub("a"	, "[^]"			, 1, "b"		, "a;0");		// invalid regx should not fail; should return self; DATE:2013-10-20
 	}
+	@Test public void ReplaceEmptyWithPattern() {
+		Exec_gsub("", "a", -1, "A", ";0");
+	}
+	@Test public void ReplaceEmptyWithFlag() {
+		Exec_gsub("", "$", -1, "A", "A;1");
+	}
 	@Test public void Find__int() {// PURPOSE: gsub with integer arg should not fail; DATE:2013-11-06
 		fxt.Test__proc__kvps__flat(lib, Scrib_lib_ustring.Invk_gsub, Scrib_kv_utl_.base1_many_(1, "[1]", "2", 1), "2;1"); // NOTE: text is integer (lua / php are type-less)
 	}

400_xowa/src/gplx/xowa/xtns/scribunto/libs/patterns/Scrib_pattern_matcher__xowa.java

@@ -52,9 +52,8 @@ class Scrib_pattern_matcher__xowa extends Scrib_pattern_matcher {
 		// get src vars
 		String src_str = src_ucs.Src();
 		int src_len = src_ucs.Len_in_data();
-		if (src_len == 0) {
-			return src_str;
-		}
+		// TOMBSTONE:do not return early if String.empty; allows `string.gsub('', '$', 'a')` ISSUE#:731; DATE:2020-07-20
+		// if (src_len == 0) return src_str;
 		int src_max = src_len + 1;
 		
 		// get pat vars