Bug: LookupAccountNameW does not use Option for optional arguments

[fgimian]

Which crate is this about?

windows

Crate version

0.42.0

Summary

As per the docs, this function has various optional arguments:

BOOL LookupAccountNameW(
  [in, optional]  LPCWSTR       lpSystemName,
  [in]            LPCWSTR       lpAccountName,
  [out, optional] PSID          Sid,
  [in, out]       LPDWORD       cbSid,
  [out, optional] LPWSTR        ReferencedDomainName,
  [in, out]       LPDWORD       cchReferencedDomainName,
  [out]           PSID_NAME_USE peUse
);

However, these are not marked as such in the Rust crate:

pub unsafe fn LookupAccountNameW<'a, P0, P1>(
    lpsystemname: P0,
    lpaccountname: P1,
    sid: super::Foundation::PSID,
    cbsid: *mut u32, referenceddomainname: ::windows::core::PWSTR,
    cchreferenceddomainname: *mut u32, peuse: *mut SID_NAME_USE) -> super::Foundation::BOOL
where
    P0: ::std::convert::Into<::windows::core::PCWSTR>,
    P1: ::std::convert::Into<::windows::core::PCWSTR>,
{
    #[cfg_attr(windows, link(name = "windows"))]
    extern "system" {
        fn LookupAccountNameW(lpsystemname: ::windows::core::PCWSTR, lpaccountname: ::windows::core::PCWSTR, sid: super::Foundation::PSID, cbsid: *mut u32, referenceddomainname: ::windows::core::PWSTR, cchreferenceddomainname: *mut u32, peuse: *mut SID_NAME_USE) -> super::Foundation::BOOL;
    }
    LookupAccountNameW(lpsystemname.into(), lpaccountname.into(), ::core::mem::transmute(sid), ::core::mem::transmute(cbsid), ::core::mem::transmute(referenceddomainname), ::core::mem::transmute(cchreferenceddomainname), ::core::mem::transmute(peuse))
}

Furthermore, PWSTR doesn't have a From implemntation from Option like PCWSTR so I'm left with something like this:

        let result = LookupAccountNameW(
            None, // Local Computer (this is technically a PCWSTR but is using the From trait defined)
            owner_name,
            PSID::default(),
            &mut owner_sid_size,
            PWSTR::null(),
            &mut domain_name_length,
            &mut sid_type,
        );

I would love to be able to call this function as follows instead (similar to various others):

        let result = LookupAccountNameW(
            None, // Local Computer
            owner_name,
            None,
            &mut owner_sid_size,
            None,
            &mut domain_name_length,
            &mut sid_type,
        );

Toolchain version/configuration

Default host: x86_64-pc-windows-gnu
rustup home:  C:\Users\Fots\scoop\persist\rustup\.rustup

installed toolchains
--------------------

stable-x86_64-pc-windows-gnu (default)
stable-x86_64-pc-windows-msvc

active toolchain
----------------

stable-x86_64-pc-windows-gnu (default)
rustc 1.64.0 (a55dd71d5 2022-09-19)

Reproducible example

N/A

Crate manifest

[package]
name = "file-owners"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
widestring = "1.0.2"

[dependencies.windows]
version = "0.42.0"
features = [
    "Win32_Foundation",
    "Win32_Security",
    "Win32_Security_Authorization",
    "Win32_Storage_FileSystem",
    "Win32_System_Threading",
    "Win32_System_SystemServices",
]

Expected behavior

lpSystemName, Sid and ReferencedDomainName should all be Option<T>s 😄

Actual behavior

Currently, all parameters are marked as required even though several of them are optional.

Additional comments

I'm struggling to know where such issues originate (e.g. win32metadata vs windows-rs). I searched win32metadata for the definition of this function and others that have optional arguments but couldn't see a distinction, so I'm guessing this is handled within windows-rs? 😄

[fgimian]

Similar problem with RegQueryInfoKeyW for the lpClass parameter which is optional 😄

pub unsafe fn RegQueryInfoKeyW<'a, P0>(hkey: P0, lpclass: ::windows::core::PWSTR,...

[kennykerr]

This is a limitation where non-pointer parameters don't consider the optional metadata flag, but it probably should do so for handle types (they're not pointers but often contain pointers).

[fgimian]

This is a limitation where non-pointer parameters don't consider the optional metadata flag, but it probably should do so for handle types (they're not pointers but often contain pointers).

Thanks a lot Kenny. Another idea that may help is also implementing the From trait as you have done for PCWSTR for both PWSTR and PSTR too:

e.g.

impl From<Option<PCWSTR>> for PCWSTR {
    fn from(from: Option<PCWSTR>) -> Self {
        from.unwrap_or_else(Self::null)
    }
}

Thanks heaps
Fotis

[Enyium]

Same for AssocQueryStringW(), which has optional LPCWSTR and LPWSTR.

[kennykerr]

All these parameters should now support None thanks to #2360 - let me know if you have any further issues. Enjoy!