[stdlib] Implement NamedTemporaryFile in tempfile module

[artemiogr97]

Implementation of NamedTemporaryFile a wrapper around a FileHandle that can be used as a context manager that is deleted after closing it if needed.

[artemiogr97]

@JoeLoser, @laszlokindrat, I'm having some issues with this:
The implementation that I had in #2352 used to work in an older release, in the current release I had the following compiler error:

for _ in range(TMP_MAX):  #error here: field 'self._file_handle' destroyed out of the middle of a value, preventing the overall value from being destroyed
    var potential_name = final_dir / (
        prefix + _get_random_name() + suffix
    )
    if os.path.exists(potential_name):
        continue
    try:
        self.name = potential_name
        self._file_handle = FileHandle(potential_name, mode=mode)
        return
    except:
        continue

I had to put the if condition inside the for to be able to compile:

for _ in range(TMP_MAX):
            var potential_name = final_dir / (
                prefix + _get_random_name() + suffix
            )
            try:
                if os.path.exists(potential_name) == False:
                    self.name = potential_name
                    self._file_handle = FileHandle(potential_name, mode=mode)
                    return
            except:
                continue

But now there is a runtime error which I don't really understand, I also had the same tests on my old PR and everything was ok.

[laszlokindrat]

@artemiogr97 I think this is unblocked now. Are you still planning to work on this?

[artemiogr97]

@laszlokindrat yes, I was planning to check again this week

[laszlokindrat]

@laszlokindrat yes, I was planning to check again this week

Awesome, thanks, please ping me when you have something ready for review.

[artemiogr97]

@JoeLoser, @laszlokindrat, I'm having some issues with this: The implementation that I had in #2352 used to work in an older release, in the current release I had the following compiler error:

for _ in range(TMP_MAX):  #error here: field 'self._file_handle' destroyed out of the middle of a value, preventing the overall value from being destroyed
    var potential_name = final_dir / (
        prefix + _get_random_name() + suffix
    )
    if os.path.exists(potential_name):
        continue
    try:
        self.name = potential_name
        self._file_handle = FileHandle(potential_name, mode=mode)
        return
    except:
        continue

I had to put the if condition inside the for to be able to compile:

for _ in range(TMP_MAX):
            var potential_name = final_dir / (
                prefix + _get_random_name() + suffix
            )
            try:
                if os.path.exists(potential_name) == False:
                    self.name = potential_name
                    self._file_handle = FileHandle(potential_name, mode=mode)
                    return
            except:
                continue

But now there is a runtime error which I don't really understand, I also had the same tests on my old PR and everything was ok.

Turns out that adding an else after the for loop makes the compiler happier, style-wise I prefer the first implementation that I had so I changed it again

[laszlokindrat]

Great, thank you! I mostly have nits and questions. Could you please add a changelog entry, and update the PR title and description with a summary of the patch?

[laszlokindrat]

Q: Just to confirm, providing these wrappers is necessary because we need to allow this to be used both within a context manager and as a normal object, right? (And also because in python this is actually a function).

This is fine, but I wonder if we could introduce a trait for things that implement these FileHandle-like interfaces.

[artemiogr97]

yes, I don't know if there is a better way to do this in mojo for now, just as a reference the python implementation does not wraps all the methods of the underlying object, it reimplements __getattr__ to directly return the methods of the real file object: https://github.com/python/cpython/blob/e83ce850f433fd8bbf8ff4e8d7649b942639db31/Lib/tempfile.py#L489-L506

I guess it would make sense to define some traits for IO stuff, the equivalent of the classes defined here: https://docs.python.org/3/library/io.html

[JoeLoser]

This is great, thank you for working on this! @Dan13llljws is excited to use this new functionality soon 😄

[JoeLoser]

!sync

[JoeLoser]

!sync

[modularbot]

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[modularbot]

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