[SHELL32] Do not return -1 if a file is not valid or not found - ExtractIconEx() (#2113)

ExtractIconEx() returns the number of successfully extracted icons from a file. The routine may return 0 in case no icons could be extracted but it could also return 0 if the file is not a valid PE image file or the file couldn't be found.

PrivateExtractIcons and the internal USER32 routine, ICO_ExtractIconExW(), return -1 in such scenarios. The behaviour is correct however we do not want that ExtractIconEx() returns -1 as well as it doesn't comply with the general documentation. In such cases, simply return 0 as no successful icons have been extracted due to related file failures.

CORE-16535

modules/rostests/apitests/shell32/ExtractIconEx.cpp

@@ -0,0 +1,37 @@
+/*
+ * PROJECT:     ReactOS API Tests
+ * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:     Tests for ExtractIconEx routine
+ * COPYRIGHT:   Copyright 2019 Bișoc George (fraizeraust99 at gmail dot com)
+ */
+
+#include "shelltest.h"
+
+typedef struct
+{
+    PCWSTR pszFilePath;
+    UINT nIcons;
+} EXTRACTICONTESTS;
+
+EXTRACTICONTESTS IconTests[] =
+{
+    /* Executable file with icon */
+    {L"%SystemRoot%\\System32\\cmd.exe", 1},
+
+    /* Executable file without icon */
+    {L"%SystemRoot%\\System32\\autochk.exe", 0},
+
+    /* Non-existing files */
+    {L"%SystemRoot%\\non-existent-file.sdf", 0}
+};
+
+START_TEST(ExtractIconEx)
+{
+    UINT i, nReturnedIcons;
+
+    for (i = 0; i < _countof(IconTests); ++i)
+    {
+        nReturnedIcons = ExtractIconExW(IconTests[i].pszFilePath, 0, NULL, NULL, IconTests[i].nIcons);
+        ok(nReturnedIcons == IconTests[i].nIcons, "ExtractIconExW(%u): Expected %u icons, got %u\n", i, IconTests[i].nIcons, nReturnedIcons);
+    }
+}