Utility: handle Path::{configuration,home}Directory() failures on Win…

…dows.

These can happen on system accounts without a home folder, for example.
Seems like I didn't read the documentation properly when I made this
into an assert in e1e813e.

Original code had a *silly* check for the appdata path being empty, and
since e1e813e failing in that case, but
the check dates back to e1e813e from
2011, and unfortunately I don't remember what was the logic behind it
back then. Windows XP compatibility or some such? Instead, it's now
morphed into checking the result of SHGetFolderPathW(). Hopefully that
won't cause some other regression again.

src/Corrade/Utility/Path.cpp

@@ -595,9 +595,15 @@ Containers::Optional<Containers::String> homeDirectory() {
     #elif defined(CORRADE_TARGET_WINDOWS) && !defined(CORRADE_TARGET_WINDOWS_RT)
     /** @todo get rid of MAX_PATH */
     wchar_t h[MAX_PATH + 1];
-    /* There doesn't seem to be any possibility how this could fail, so just
-       assert */
-    CORRADE_INTERNAL_ASSERT(SHGetFolderPathW(nullptr, CSIDL_PERSONAL, nullptr, 0, h) == S_OK);
+    /* This could fail for example with E_INVALIDARG for system accounts
+       without a home folder */
+    if(SHGetFolderPathW(nullptr, CSIDL_PERSONAL, nullptr, 0, h) != S_OK) {
+        Error err;
+        err << "Utility::Path::homeDirectory(): can't retrieve CSIDL_PERSONAL:";
+        Utility::Implementation::printWindowsErrorString(err, GetLastError());
+        return {};
+    }
+
     return fromNativeSeparators(Unicode::narrow(h));
 
     /* Other */
@@ -641,11 +647,12 @@ Containers::Optional<Containers::String> configurationDirectory(const Containers
     #elif defined(CORRADE_TARGET_WINDOWS) && !defined(CORRADE_TARGET_WINDOWS_RT)
     /** @todo get rid of MAX_PATH */
     wchar_t path[MAX_PATH];
-    /* There doesn't seem to be any possibility how this could fail, so just
-       assert */
-    CORRADE_INTERNAL_ASSERT(SHGetFolderPathW(nullptr, CSIDL_APPDATA, nullptr, 0, path) == S_OK);
-    if(path[0] == L'\0') {
-        Error{} << "Utility::Path::configurationDirectory(): can't retrieve CSIDL_APPDATA";
+    /* This could fail for example with E_INVALIDARG for system accounts
+       without a home folder */
+    if(SHGetFolderPathW(nullptr, CSIDL_APPDATA, nullptr, 0, path) != S_OK) {
+        Error err;
+        err << "Utility::Path::configurationDirectory(): can't retrieve CSIDL_APPDATA:";
+        Utility::Implementation::printWindowsErrorString(err, GetLastError());
         return {};
     }
     return join(fromNativeSeparators(Unicode::narrow(path)), applicationName);

src/Corrade/Utility/Test/PathTest.cpp

@@ -1530,8 +1530,24 @@ void PathTest::homeDirectory() {
 }
 
 void PathTest::homeDirectoryInvalid() {
-    /* Could be tested by temporarily removing $HOME, but ... ahem */
+    #ifdef CORRADE_TARGET_WINDOWS
+    /* The query fails for system accounts, and system accounts apparently have
+       no access to environment, so checking if %HOMEPATH% is missing:
+       https://serverfault.com/questions/292040/win-service-running-under-localservice-account-cannot-access-environment-variabl */
+    if(std::getenv("HOMEPATH"))
+        CORRADE_SKIP("%HOMEPATH% exists, can't test.");
+
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!Path::homeDirectory());
+    CORRADE_COMPARE_AS(out.str(),
+        "Utility::Path::homeDirectory(): can't retrieve CSIDL_PERSONAL: error 666 (",
+        TestSuite::Compare::StringHasPrefix);
+
+    #else
+    /* On Unix could be tested by temporarily removing $HOME, but ... ahem */
     CORRADE_SKIP("Not sure how to test this.");
+    #endif
 }
 
 void PathTest::homeDirectoryUtf8() {
@@ -1601,9 +1617,25 @@ void PathTest::configurationDirectory() {
 }
 
 void PathTest::configurationDirectoryInvalid() {
-    /* Could be tested by temporarily removing $XDG_CONFIG_HOME and $HOME, but
-       ... ahem */
+    #ifdef CORRADE_TARGET_WINDOWS
+    /* The query fails for system accounts, and system accounts apparently have
+       no access to environment, so checking if %HOMEPATH% is missing:
+       https://serverfault.com/questions/292040/win-service-running-under-localservice-account-cannot-access-environment-variabl */
+    if(std::getenv("APPDATA"))
+        CORRADE_SKIP("%APPDATA% exists, can't test.");
+
+    std::ostringstream out;
+    Error redirectError{&out};
+    CORRADE_VERIFY(!Path::configurationDirectory("Corrade"));
+    CORRADE_COMPARE_AS(out.str(),
+        "Utility::Path::configurationDirectory(): can't retrieve CSIDL_APPDATA: error 666 (",
+        TestSuite::Compare::StringHasPrefix);
+
+    #else
+    /* On Unix could be tested by temporarily removing $XDG_CONFIG_HOME and
+       $HOME, but ... ahem */
     CORRADE_SKIP("Not sure how to test this.");
+    #endif
 }
 
 void PathTest::configurationDirectoryUtf8() {