tests/test-hashutil.py

dirstate-tree: Fold "tracked descendants" counter update in main walk

For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.

Before this changeset, mutating or inserting a node at a given path would
involve:

* Walking the tree from root through ancestors to find the node or the spot
  where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes

When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.

It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).

---

Profiling was done by compiling with this `.cargo/config`:

    [profile.release]
    debug = true

then running with:

    py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
    ./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1

then visualizing the recorded JSON file in https://www.speedscope.app/

Differential Revision: https://phab.mercurial-scm.org/D10554

# Tests to ensure that sha1dc.sha1 is exactly a drop-in for
# hashlib.sha1 for our needs.
from __future__ import absolute_import

import hashlib
import unittest

import silenttestrunner

try:
    from mercurial.thirdparty import sha1dc
except ImportError:
    sha1dc = None


class hashertestsbase(object):
    def test_basic_hash(self):
        h = self.hasher()
        h.update(b'foo')
        self.assertEqual(
            '0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33', h.hexdigest()
        )
        h.update(b'bar')
        self.assertEqual(
            '8843d7f92416211de9ebb963ff4ce28125932878', h.hexdigest()
        )

    def test_copy_hasher(self):
        h = self.hasher()
        h.update(b'foo')
        h2 = h.copy()
        h.update(b'baz')
        h2.update(b'bar')
        self.assertEqual(
            '21eb6533733a5e4763acacd1d45a60c2e0e404e1', h.hexdigest()
        )
        self.assertEqual(
            '8843d7f92416211de9ebb963ff4ce28125932878', h2.hexdigest()
        )

    def test_init_hasher(self):
        h = self.hasher(b'initial string')
        self.assertEqual(
            b'\xc9y|n\x1f3S\xa4:\xbaJ\xca,\xc1\x1a\x9e\xb8\xd8\xdd\x86',
            h.digest(),
        )

    def test_bytes_like_types(self):
        h = self.hasher()
        h.update(bytearray(b'foo'))
        h.update(memoryview(b'baz'))
        self.assertEqual(
            '21eb6533733a5e4763acacd1d45a60c2e0e404e1', h.hexdigest()
        )

        h = self.hasher(bytearray(b'foo'))
        h.update(b'baz')
        self.assertEqual(
            '21eb6533733a5e4763acacd1d45a60c2e0e404e1', h.hexdigest()
        )

        h = self.hasher(memoryview(b'foo'))
        h.update(b'baz')
        self.assertEqual(
            '21eb6533733a5e4763acacd1d45a60c2e0e404e1', h.hexdigest()
        )


class hashlibtests(unittest.TestCase, hashertestsbase):
    hasher = hashlib.sha1


if sha1dc:

    class sha1dctests(unittest.TestCase, hashertestsbase):
        hasher = sha1dc.sha1


if __name__ == '__main__':
    silenttestrunner.main(__name__)