Python 3.x is patched in a way that integrates `.hy` source files into
Pythons default `importlib` machinery. In Python 2.7, a PEP-302 "importer"
and "loader" is implemented according to the standard `import` logic (via
`pkgutil` and later pure-Python `imp` package code).
In both cases, the entry-point for the loaders is through `sys.path_hooks` only.
As well, the import semantics have been updated all throughout to utilize
`importlib` and follow aspects of PEP-420. This, along with some light
patches, should allow for basic use of `runpy`, `py_compile` and `reload`.
In all cases, if a `.hy` file is shadowed by a `.py`, Hy will silently use
`.hy`.
Importing or executing a Hy file now loads the byte-compiled version if it exists and is up to date, and if not, the source is byte-compiled after it's parsed.
This change can speed up Hy a lot. Here are some examples comparing run times of the current master (491b474e) to this commit, on my laptop with Python 3.6:
- `nosetests --exclude='test_bin'` goes from 3.8 s to 0.7 s (a 5-fold speedup)
- `hy -c '(print "hello world")` goes from 0.47 s to 0.20 s (a 2-fold speedup)
- Rogue TV's startup goes from 3.6 s to 0.4 s (a 9-fold speedup)
Accompanying changes include:
- `setup.py` now creates and installs bytecode for `hy.core`, `hy.contrib`, and `hy.extra`.
- The `hyc` command under Python 3 now creates bytecode in `__pycache__`, as usual for Python 3, instead of putting the `.pyc` right next to the source file like Python 2 does.
I've removed a test of `hy.extra.anaphoric.a-if` that triggers #1268 when the test file is byte-compiled and then hits some weird `macroexpand` bug or something when I try to work around that—Nose crashes when trying to produce an error message, and I can't seem to replicate the bug without Nose.
