view tests/test-walkrepo.py @ 46667:93e9f448273c

rhg: Add support for automatic fallback to Python

`rhg` is a command-line application that can do a small subset of what
`hg` can. It is written entirely in Rust, which avoids the cost of starting
a Python interpreter and importing many Python modules.
In a script that runs many `hg` commands, this cost can add up.

However making users decide when to use `rhg` instead of `hg` is
not practical as we want the subset of supported functionality
to grow over time.

Instead we introduce "fallback" behavior where, when `rhg` encounters
something (a sub-command, a repository format, …) that is not implemented
in Rust-only, it does nothing but silently start a subprocess of
Python-based `hg` running the same command.
That way `rhg` becomes a drop-in replacement for `hg` that sometimes
goes faster. Whether Python is used should be an implementation detail
not apparent to users (other than through speed).

A new `fallback` value is added to the previously introduced
`rhg.on-unsupported` configuration key. When in this mode, the new
`rhg.fallback-executable` config is determine what command to use
to run a Python-based `hg`.

The previous `rhg.on-unsupported = abort-silent` configuration was designed
to let a wrapper script call `rhg` and then fall back to `hg` based on the
exit code. This is still available, but having fallback behavior built-in
in rhg might be easier for users instead of leaving that script "as an
exercise for the reader".

Using a subprocess like this is not idea, especially when `rhg` is to be
installed in `$PATH` as `hg`, since the other `hg.py` executable needs
to still be available… somewhere. Eventually this could be replaced
by using PyOxidizer to a have a single executable that embeds a Python
interpreter, but only starts it when needed.

Differential Revision: https://phab.mercurial-scm.org/D10093

from __future__ import absolute_import, print_function

import os

from mercurial import (
    hg,
    scmutil,
    ui as uimod,
    util,
)

chdir = os.chdir
mkdir = os.mkdir
pjoin = os.path.join

walkrepos = scmutil.walkrepos
checklink = util.checklink

u = uimod.ui.load()
sym = checklink(b'.')

hg.repository(u, b'top1', create=1)
mkdir(b'subdir')
chdir(b'subdir')
hg.repository(u, b'sub1', create=1)
mkdir(b'subsubdir')
chdir(b'subsubdir')
hg.repository(u, b'subsub1', create=1)
chdir(os.path.pardir)
if sym:
    os.symlink(os.path.pardir, b'circle')
    os.symlink(pjoin(b'subsubdir', b'subsub1'), b'subsub1')


def runtest():
    reposet = frozenset(walkrepos(b'.', followsym=True))
    if sym and (len(reposet) != 3):
        print("reposet = %r" % (reposet,))
        print(
            (
                "Found %d repositories when I should have found 3"
                % (len(reposet),)
            )
        )
    if (not sym) and (len(reposet) != 2):
        print("reposet = %r" % (reposet,))
        print(
            (
                "Found %d repositories when I should have found 2"
                % (len(reposet),)
            )
        )
    sub1set = frozenset(
        (pjoin(b'.', b'sub1'), pjoin(b'.', b'circle', b'subdir', b'sub1'))
    )
    if len(sub1set & reposet) != 1:
        print("sub1set = %r" % (sub1set,))
        print("reposet = %r" % (reposet,))
        print("sub1set and reposet should have exactly one path in common.")
    sub2set = frozenset(
        (pjoin(b'.', b'subsub1'), pjoin(b'.', b'subsubdir', b'subsub1'))
    )
    if len(sub2set & reposet) != 1:
        print("sub2set = %r" % (sub2set,))
        print("reposet = %r" % (reposet,))
        print("sub2set and reposet should have exactly one path in common.")
    sub3 = pjoin(b'.', b'circle', b'top1')
    if sym and sub3 not in reposet:
        print("reposet = %r" % (reposet,))
        print("Symbolic links are supported and %s is not in reposet" % (sub3,))


runtest()
if sym:
    # Simulate not having symlinks.
    del os.path.samestat
    sym = False
    runtest()