Create output dir if it doesn't exist

[bengterik]

Some generators do not automatically create the output directory which results in this cryptic error when running mavgen for JavaScript, Python and TypeScript.

remoteaero% python3 -m pymavlink.tools.mavgen --lang=Python --wire-protocol=2.0 --output=include/v2.0 message_definitions/v1.0/common.xml
Validating message_definitions/v1.0/common.xml
Traceback (most recent call last):
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/remote/Documents/git/pymavlink/tools/mavgen.py", line 30, in <module>
    ok = mavgen.mavgen(args, args.definitions)
  File "/Users/remote/Documents/git/pymavlink/generator/mavgen.py", line 229, in mavgen
    if not mavgen_validate(fname):
  File "/Users/remote/Documents/git/pymavlink/generator/mavgen.py", line 198, in mavgen_validate
    with open(xmlfile, 'r') as f:
FileNotFoundError: [Errno 2] No such file or directory: 'message_definitions/v1.0/common.xml'

[peterbarker]

Please remove the merge commit

[peterbarker]

LGTM

[peterbarker]

@bengterik well, CI isn't happy. Is it possible some of the generators are creating the output directory without saying, "exists is OK"?

[bengterik]

Hm, seems like some generators create a file with the same name as the output directory.

Thought I'd solve it for the general case in mavgen.py but I guess I'll add it to the individual JS, TS and Python generators.

@peterbarker do I create a new PR or just commit here on this branch?

[shancock884]

For a number of generators (including Python, JS and WLua), the last bit of the output argument is the base part of a filename, rather than a folder name.
In which case, your code could do this instead:

dirname = os.path.dirname(opts.output)
if dirname != '':
    os.makedirs(dirname, exist_ok=True)

That way, the parent folder is sure to exist before writing.

For any generators that are genuinely want the output to be a folder, they should check/create it themselves (C, C++ and Java already seem to do this).