Add more functions and properties to VirtualPath that directly
correspond to functions and properties of pathlib.PurePath, except that
types are adapted of course, and that for API consistency, VirtualPath
methods use mixedCaseStyle whereas those of pathlib.PurePath use
underscore_style.
Add classes VirtualPath and MutableVirtualPath (the latter derived from
the former) to manipulate slash-separated paths where the root '/'
represents the TerraScenery root. This makes it clear what a function
expects when you see that one of its arguments is a VirtualPath
instance: you don't have to ask yourself whether it can start or end
with a slash, how to interpret it, etc. Operating on these paths is also
easy[1], be it to assemble URLs in order to retrieve files or to join
their relative part with a local directory path in order to obtain a
real (deeper) local path.
VirtualPath and MutableVirtualPath are essentially the same; the former
is hashable and therefore has to be immutable, whereas the latter can be
modified in-place with the /= operator (used to append path components),
and therefore can't be hashable. As a consequence, MutableVirtualPath
instances can't be used as dictionary keys, elements of a set or
frozenset, etc.
VirtualPath and MutableVirtualPath use the pathlib.PurePath API where
applicable (part of this API has been implemented in
[Mutable]VirtualPath; more can be added, of course). These classes have
no assumptions related to TerraSync and thus should be fit for use in
other projects.
To convert a [Mutable]VirtualPath instance to a string, just use str()
on it. The result is guaranteed to start with a '/' and not to end with
a '/', except for the virtual root '/'. Upon construction, the given
string is interpreted relatively to the virtual root, i.e.:
VirtualPath("") == VirtualPath("/")
VirtualPath("abc/def/ghi") == VirtualPath("/abc/def/ghi")
etc.
VirtualPath and MutableVirtualPath instances sort like the respective
strings str() converts them too. The __hash__() method of VirtualPath is
based on the type and this string representation, too. Such objects can
only compare equal (using ==) if they have the same type. If you want to
compare the underlying virtual paths inside a VirtualPath and a
MutableVirtualPath, use the samePath() method of either class.
For more info, see scripts/python/TerraSync/terrasync/virtual_path.py
and unit tests in scripts/python/TerraSync/tests/test_virtual_path.py.
[1] Most useful is the / operator, which works as for SGPath:
VirtualPath("/abc/def/ghi") == VirtualPath("/abc") / "def" / "ghi"
VirtualPath("/abc/def/ghi") == VirtualPath("/abc") / "def/ghi"
