Exception: Unknown klass <class 'ast.Constant'> in CrystalTypes

[viraptor]

When running via python 3.9.9, I tested the app on https://github.com/viraptor/arpy/blob/master/arpy.py

The result is: (with the end of verbose output)

...
ClassDef class_name[ArchiveFileData] base_classes: ['io.IOBase'] base_rclasses: ['io.IOBase']
ClassDef class_name[ArchiveFileData] bases: ['Io.IOBase']
self._self_functions : ['__init__', 'read', 'tell', 'seek', 'seekable', '__enter__', '__exit__']
self._classes_self_functions : {'ArchiveFormatError': [], 'ArchiveAccessError': [], 'ArchiveFileHeader': ['__init__', '__repr__']}
Traceback (most recent call last):
  File "/home/viraptor/Projects/py2cr/py2cr.py", line 5, in <module>
    py2cr.main()
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 3189, in main
    rtn = convert_py2rb_write(py_path, options.base_path_count, subfilenames,
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 2966, in convert_py2rb_write
    rtn, header, data = convert_py2rb(s, dir_path, name_path, base_path_count, mods, mod_paths, no_stop=no_stop, verbose=verbose)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 2912, in convert_py2rb
    v.visit(t)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 425, in visit
    return visitor(node)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 451, in visit_Module
    self.visit(stmt)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 425, in visit
    return visitor(node)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 795, in visit_ClassDef
    self.visit(stmt)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 425, in visit
    return visitor(node)
  File "/home/viraptor/Projects/py2cr/py2cr/__init__.py", line 532, in visit_FunctionDef
    argxlist.append(anno.visit())
  File "/home/viraptor/Projects/py2cr/py2cr/types.py", line 87, in visit
    raise Exception("Unknown klass %s in CrystalTypes" % type(node))
Exception: Unknown klass <class 'ast.Constant'> in CrystalTypes

[nanobowers]

Hi @viraptor I've been working on some feature branches with improved types support, num.cr support and more tests. Per your report I've made updates just now that should allow you to translate the arpy.py code you provided (thanks for the testcase), though the post-translated Crystal code has features that prevent it from compiling cleanly. The changes have all been merged into the main branch of py2cr. Let me know if you still have crashes or suggestions for better output.

[viraptor]

That's awesome, thanks. I just did a driveby check out of curiosity.

I haven't looked into this deeply, but some obvious things that seem to be needed for this file to compile are:

• struct implementation/renaming
• io.seekable - from python doesn't seem to have a match in crystal (apart from checking if seek(0, Seek::Current) raises?)

Also I noticed that foo is None is translated into foo.nil?, but:

while self.read_next_header() is not None:

became

while !read_next_header().equal?(nil)

instead of

while !read_next_header().nil?

[nanobowers]

@viraptor, I updated handing of is None and is not None with some added tests just a moment ago, which should take care of the last concern.

As for the other two concerns: struct renaming and io.seekable - It's not clear to me at this point how that may be workable in py2cr, as the differences between Python/Crystal here may not be 1:1, and i'm not sure how what the appropriate mapping is.
I only briefly glanced at your arpy code (and haven't used struct in python) but if it involves packing/unpacking binary, maybe something in here could be of use? https://therubyist.org/2020/05/07/rewriting-rubys-pack-and-unpack-methods-in-crystal/

Please feel free to submit a PR for these if you wish.