[PATCH v7 2/2] vbscript: fix Mid() empty and null handling

[Francis De Brabandere]

From: Francis De Brabandere

---
 dlls/vbscript/global.c      | 11 +++++++----
 dlls/vbscript/tests/api.vbs | 15 +++++++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/dlls/vbscript/global.c b/dlls/vbscript/global.c
index 058ddabcde1..972d0d2ea0b 100644
--- a/dlls/vbscript/global.c
+++ b/dlls/vbscript/global.c
@@ -1404,9 +1404,6 @@ static HRESULT Global_Mid(BuiltinDisp *This, VARIANT *args, unsigned args_cnt, V

assert(args_cnt == 2 || args_cnt == 3);

-    if(V_VT(args) == VT_EMPTY)
-        return MAKE_VBSERROR(VBSE_ILLEGAL_FUNC_CALL);
-
     if(V_VT(args+1) == VT_NULL || (args_cnt == 3 && V_VT(args+2) == VT_NULL))
         return MAKE_VBSERROR(VBSE_ILLEGAL_NULL_USE);

@@ -1417,7 +1414,7 @@ static HRESULT Global_Mid(BuiltinDisp *This, VARIANT *args, unsigned args_cnt, V
     if(FAILED(hres))
         return hres;

-    if(start < 0)
+    if(start <= 0)
         return MAKE_VBSERROR(VBSE_ILLEGAL_FUNC_CALL);

if(args_cnt == 3) {
@@ -1432,6 +1429,12 @@ static HRESULT Global_Mid(BuiltinDisp *This, VARIANT *args, unsigned args_cnt, V
             return MAKE_VBSERROR(VBSE_ILLEGAL_FUNC_CALL);
     }

+    if(V_VT(args) == VT_EMPTY)
+        return return_string(res, L"");
+
+    if(V_VT(args) == VT_NULL)
+        return return_null(res);
+
     if(V_VT(args) == VT_BSTR) {
         str = V_BSTR(args);
     }else {
diff --git a/dlls/vbscript/tests/api.vbs b/dlls/vbscript/tests/api.vbs
index 296663d9c97..dfa2816bec5 100644
--- a/dlls/vbscript/tests/api.vbs
+++ b/dlls/vbscript/tests/api.vbs
@@ -632,6 +632,16 @@ Sub TestMid2(str, start, ex)
     Call ok(x = ex, "Mid(" & str & ", " & start & ") = " & x & " expected " & ex)
 End Sub

+Sub TestMidNull(str, start, len)
+    x = Mid(str, start, len)
+    Call ok(IsNull(x), "Mid(" & str & ", " & start & ", " & len & ") = " & x & " expected Null")
+End Sub
+
+Sub TestMidNull2(str, start)
+    x = Mid(str, start)
+    Call ok(IsNull(x), "Mid(" & str & ", " & start & ") = " & x & " expected Null")
+End Sub
+
 Sub TestMidError(str, start, len, number)
     On Error Resume Next
     Call Mid(str, start, len)
@@ -654,6 +664,11 @@ TestMid2 "test", 2, "est"
 TestMid2 "test", 4, "t"
 TestMid2 "test", 5, ""
 TestMid2 1234, 5, ""
+TestMid empty, 5, 2, ""
+TestMid2 empty, 5, ""
+
+TestMidNull null, 5, 2
+TestMidNull2 null, 5

TestMidError "test", "a", 1, 13
 TestMidError "test", "a", null, 94