Allow for passing stdin to child

[CompeyDev]

This PR adds functionality for passing stdin contents to a child process.

Things to finish before merge:

• Update FromLua implementation for Process options (Rust)
• Implement writer for stdin (Rust)
• Update SpawnOptions type (Luau)
• Include tests (Luau)
• Proper error handling

Closes #89.

[CompeyDev]

Tests seem to fail because certain linux commands cannot be found on Windows. We can fix this by setting up MinGW on the CI for Windows targets only.

Here is how it would look like:

- name: Set up MinGW
  uses: egor-tensin/setup-mingw@v2
  with:
    platform: x64
  if: ${{matrix.runner-os == 'windows-latest'}}

We might also want to set the cargo-target within the matrix to x86_64-pc-windows-gnu.

CC @filiptibell

[filiptibell]

Thank you for the PR! I left a few comments then this should be all good 👍

[filiptibell]

Everything looks good code-wise but the windows tests still seem to fail - any idea why that is?

[CompeyDev]

Everything looks good code-wise but the windows tests still seem to fail - any idea why that is?

Windows includes additional symbols with echo (not just a newline, but other things such as return carriages, etc. IIRC). I'm not exactly sure what they are, and it's kind of difficult for me to debug them either, considering I don't have access to a Windows instance.

@SnorlaxAssist Could you help out with this? Char codes of these special characters are 239 and 191. What are their significance?

[SnorlaxAssist]

Windows does include additional symbols, although that isn't the problem. The issue is on windows, you would be executing the command powershell -c echo then stdin input would go through but not finish executing, by not "pressing enter" to confirm the command.

So then you would get something like this

cmdlet Write-Output at command pipeline position 1
Supply values for the following parameters:
InputObject[0]: InputObject[1]: Hello from child process!

You can do something like this to confirm the execution & below is the stdout value I got from my virtual machine.

-- Passing stdin strings should work
local input = echoMessage
if IS_WINDOWS then
	-- Confirm input on Windows.
	-- Arg 0 would be default from process.spawn
	-- Confirm message input, and execute with a blank 2nd input.
	input ..= "\n\n"
end
local stdinChild = process.spawn((((not IS_WINDOWS) and "xargs") or "powershell"), {
	"echo",
}, {
	stdin = input,
})
--[[
stdout would includes the stdin value I believe, might be an stdout/stdin bug, not too sure
stdout:
1: Hello from child process!
2: 
3: Hello from child process!
4: 
]]
assert(
	...

[CompeyDev]

Unfortunately, that does not pass either! I don't think it has anything to do with what you previously mentioned as lune literally gets a handle to the process and injects to its stdin, it does not run another shell command to pipe stdin (which may require user input, such as an enter).

I think this has something to do with some special chars with codes 239 and 191 getting prepended to the stdout (which I noticed in the CI a bit ago).

[SnorlaxAssist]

Where exactly are you finding those special characters? I don't see those characters in the test & at the output on a VM.

[SnorlaxAssist]

try this

local stdinChild = process.spawn(not IS_WINDOWS and "xargs" or "powershell", {
	"echo",
}, {
	stdin = echoMessage .. (IS_WINDOWS and "\n\n" or ""),
})

local stdinChildOut = stdinChild.stdout
if IS_WINDOWS then
	stdinChildOut = stdinChildOut:sub(#stdinChildOut - #echoMessage - 1, #stdinChildOut)
end
assert(
	stdinChildOut == echoMessage .. trailingAddition,
	"Stdin passing did not return proper output"
)

[SnorlaxAssist]

Btw, on CI the output looks like this

1: Hello from child process!
2: 
3: Hello from child process!
4: 

I assume line 1 is the input & line 3 is the output from child process. and at the end of line 3-4 is \r\n on windows.

[filiptibell]

Seems like those latest test changes worked! Could you merge in latest changes from main?

EDIT: GitHub let me squash merge without any issues anyway 🎉 thank you once again for the PR!