This is just a stub for future extension. I could add a version constant to
CFFI modules by putting it to both ffi.set_source() and ffi.cdef(), but that
doesn't seem right. So for now, cffi modules will be explicitly unversioned
(i.e. version constant must be undefined or set to None.) We can revisit it
later when we need to consider CFFI support more seriously.
These functions are sysstr API since __import__() and getattr() hate byte
strings on Python 3.
There's a minor BC, which is ImportError will be raised if invalid
HGMODULEPOLICY is specified. I think this is more desired behavior.
We're planning to add strict checking for C API compatibility. This patch
includes the stub for it.
We're going to make the 'c' policy more strict, where no missing attribute
will be allowed. Since we want to run 'hg bisect' without rebuilding the C
extension modules, we'll need a looser policy for development environment.
The default for system installation isn't changed.
Note that the current 'c' policy is practically 'allow'-ish as we have lots
of adhoc fallbacks to pure functions.
String literals without explicit prefix in __init__.py and policy.py
are treated as unicode object on Python3, because these modules are
loaded before setup of our specific code transformation (the later
module is imported at the beginning of __init__.py).
BTW, "modulepolicy" in __init__.py is initialized by "policy.policy".
This causes issues below;
- checking "policy" value in other modules causes unintentional result
For example, "b'py' not in (u'c', u'py')" returns True
unintentionally on Python3.
- writing "policy" out fails at conversion from unicode to bytes
db1ebf457295 fixed this issue for default code path, but "policy"
can be overridden by HGMODULEPOLICY environment variable (it should
be rare case for developer using Python3, though).
This patch does:
- add "b" prefix to all string literals, which are related to module
policy, in modules above.
- check existence of HGMODULEPOLICY, and overwrite "policy" only if
it exists
For simplicity, this patch omits checking "supports_bytes_environ",
switching os.environ/os.environb, and so on (Yuya agreed this in
personal talking)
