user32: fix return value in DialogBoxParamA if no resource can be found + simple test

[Louis. Lenders]

Skipped content of type multipart/alternative-------------- next part --------------
diff --git a/dlls/user32/dialog.c b/dlls/user32/dialog.c
index 7d64790..10f3c32 100644
--- a/dlls/user32/dialog.c
+++ b/dlls/user32/dialog.c
@@ -800,7 +800,12 @@ INT_PTR WINAPI DialogBoxParamA( HINSTANC
     HRSRC hrsrc;
     LPCDLGTEMPLATEA ptr;
 
-    if (!(hrsrc = FindResourceA( hInst, name, (LPSTR)RT_DIALOG ))) return 0;
+    if (!(hrsrc = FindResourceA( hInst, name, (LPSTR)RT_DIALOG )))
+    {
+        SetLastError(ERROR_RESOURCE_NAME_NOT_FOUND);
+        ERR("FindResource %s failed, returning -1\n",debugstr_a(name));
+        return -1;
+    }
     if (!(ptr = (LPCDLGTEMPLATEA)LoadResource(hInst, hrsrc))) return 0;
     hwnd = DIALOG_CreateIndirect( hInst, ptr, owner, dlgProc, param, FALSE, TRUE );
     if (hwnd) return DIALOG_DoDialogBox( hwnd, owner );
diff --git a/dlls/user32/tests/dialog.c b/dlls/user32/tests/dialog.c
index eeea474..b322d7c 100644
--- a/dlls/user32/tests/dialog.c
+++ b/dlls/user32/tests/dialog.c
@@ -861,6 +861,14 @@ static void test_GetDlgItemText(void)
     ok(string[0] == '\0', "string retrieved using GetDlgItemText should have been NULL terminated\n");
 }
 
+static void test_DialogBoxParamA(void)
+{
+    int ret;
+    SetLastError(0xdeadbeef);
+    ret = DialogBoxParamA(GetModuleHandle(NULL), "NAME_DOES_NOT_EXSIST" , NULL, NULL, 0);
+    ok(-1 == ret, "DialogBoxParamA returned %d, expected -1\n", ret); 
+    ok(ERROR_RESOURCE_NAME_NOT_FOUND == GetLastError(),"GetLastError returned %d instead of 1814\n",GetLastError());
+}
 
 START_TEST(dialog)
 {
@@ -873,4 +881,5 @@ START_TEST(dialog)
     WM_NEXTDLGCTLTest();
     InitialFocusTest();
     test_GetDlgItemText();
+    test_DialogBoxParamA();
 }