ft: Add method to Specfile to Instantiate from string

[p0tat0chip]

TODO:

• Write new tests or update the old ones to cover new functionality.
• Update doc-strings where appropriate.
• Update or write new documentation in packit/packit.dev.

Fixes

Related to #248

RELEASE NOTES BEGIN

Now supports creating specfile instance from a string.

RELEASE NOTES END

[softwarefactory-project-zuul]

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✔️ specfile-tests-rpm-deps SUCCESS in 1m 07s
✔️ specfile-tests-pip-deps SUCCESS in 1m 01s

[softwarefactory-project-zuul]

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[nforro]

Thank you for the contribution!
However, I think this problem could be handled in a more elegant way, without using temporary files, and together with #206. The idea is to replace the internal Specfile._path attribute with a file-like object that could be either passed directly to the constructor or instantiated from a path using open() or from a string using StringIO.
The implementation would simply replace instances of Specfile._path.read_text() with something like Specfile._stream.read() and instances of Specfile._path.write_text() with something like Specfile._stream.write() if the file-like object is writable. It would also need to handle seeking, truncating, flushing etc. accordingly.

[p0tat0chip]

I tried implementing as described and converted even the path to a fileobject (self._stream = self._path.open("r+"))
But two tests were failing:

FAILED tests/integration/test_specfile.py::test_copy - TypeError: cannot pickle 'TextIOWrapper' instances
FAILED tests/integration/test_specfile.py::test_parse_if_necessary - TypeError: cannot pickle 'TextIOWrapper' instances

and this will fail for objects instantiated from string and open() as well. Not really sure how to handle this.

[nforro]

Right, that will require doing something similar to what is done in SpecParser:

specfile/specfile/spec_parser.py

Lines 81 to 90 in 01f6a7c

	def __deepcopy__(self, memo: Dict[int, Any]) -> "SpecParser":
	result = self.__class__.__new__(self.__class__)
	memo[self.id()] = result
	for k, v in self.__dict__.items():
	if k in ["spec", "tainted"]:
	continue
	setattr(result, k, copy.deepcopy(v, memo))
	result.spec = None
	result.tainted = False
	return result

The _stream attribute will have to be skipped when deepcopying a Specfile instance, but the question is what should the copy get. For Specfile instantiated from a path it could be calling open() again on the same path, for Specfile instantiated from a string it could be creating a new StringIO instance and supplying it with the content of the original StringIO. For Specfile instantiated with a file-like object perhaps we could just disable deepcopying.

[softwarefactory-project-zuul]

Build failed.
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❌ pre-commit FAILURE in 1m 57s
❌ specfile-tests-rpm-deps FAILURE in 1m 05s
❌ specfile-tests-pip-deps FAILURE in 58s

[p0tat0chip]

The tests are passing now. Currently:

• Return a new StringIO instance for the ones instantiated from it.
• Return a copy for the ones instantiated from path. They are still file-like objects from open().
• Ignore and return None for file-like objects without path.

will write new tests for them.

[softwarefactory-project-zuul]

Build failed.
https://softwarefactory-project.io/zuul/t/packit-service/buildset/776c81427af644f5906c1d9d36901524

❌ pre-commit FAILURE in 1m 59s
✔️ specfile-tests-rpm-deps SUCCESS in 1m 00s
✔️ specfile-tests-pip-deps SUCCESS in 59s