annotate tests/drawdag.py @ 33289:abd7dedbaa36

sparse: vendor Facebook-developed extension

Facebook has developed an extension to enable "sparse" checkouts -
a working directory with a subset of files. This feature is a critical
component in enabling repositories to scale to infinite number of
files while retaining reasonable performance. It's worth noting
that sparse checkout is only one possible solution to this problem:
another is virtual filesystems that realize files on first access.
But given that virtual filesystems may not be accessible to all
users, sparse checkout is necessary as a fallback.

Per mailing list discussion at
https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-March/095868.html
we want to add sparse checkout to the Mercurial distribution via
roughly the following mechanism:

1. Vendor extension as-is with minimal modifications (this patch)
2. Refactor extension so it is more clearly experimental and inline
   with Mercurial practices
3. Move code from extension into core where possible
4. Drop experimental labeling and/or move feature into core
   after sign-off from narrow clone feature owners

This commit essentially copies the sparse extension and tests
from revision 71e0a2aeca92a4078fe1b8c76e32c88ff1929737 of the
https://bitbucket.org/facebook/hg-experimental repository.

A list of modifications made as part of vendoring is as follows:

* "EXPERIMENTAL" added to module docstring
* Imports were changed to match Mercurial style conventions
* "testedwith" value was updated to core Mercurial special value and
  comment boilerplate was inserted
* A "clone_sparse" function was renamed to "clonesparse" to appease
  the style checker
* Paths to the sparse extension in tests reflect built-in location
* test-sparse-extensions.t was renamed to test-sparse-fsmonitor.t
  and references to "simplecache" were removed. The test always skips
  because it isn't trivial to run it given the way we currently run
  fsmonitor tests
* A double empty line was removed from test-sparse-profiles.t

There are aspects of the added code that are obviously not ideal.
The goal is to make a minimal number of modifications as part of
the vendoring to make it easier to track changes from the original
implementation. Refactoring will occur in subsequent patches.

# drawdag.py - convert ASCII revision DAG to actual changesets
#
# Copyright 2016 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""
create changesets from an ASCII graph for testing purpose.

For example, given the following input::

    c d
    |/
    b
    |
    a

4 changesets and 4 local tags will be created.
`hg log -G -T "{rev} {desc} (tag: {tags})"` will output::

    o  3 d (tag: d tip)
    |
    | o  2 c (tag: c)
    |/
    o  1 b (tag: b)
    |
    o  0 a (tag: a)

For root nodes (nodes without parents) in the graph, they can be revsets
pointing to existing nodes.  The ASCII graph could also have disconnected
components with same names referring to the same changeset.

Therefore, given the repo having the 4 changesets (and tags) above, with the
following ASCII graph as input::

    foo    bar       bar  foo
     |     /          |    |
    ancestor(c,d)     a   baz

The result (`hg log -G -T "{desc}"`) will look like::

    o    foo
    |\
    +---o  bar
    | | |
    | o |  baz
    |  /
    +---o  d
    | |
    +---o  c
    | |
    o |  b
    |/
    o  a

Note that if you take the above `hg log` output directly as input. It will work
as expected - the result would be an isomorphic graph::

    o    foo
    |\
    | | o  d
    | |/
    | | o  c
    | |/
    | | o  bar
    | |/|
    | o |  b
    | |/
    o /  baz
     /
    o  a

This is because 'o' is specially handled in the input: instead of using 'o' as
the node name, the word to the right will be used.

Some special comments could have side effects:

    - Create obsmarkers
      # replace: A -> B -> C -> D  # chained 1 to 1 replacements
      # split: A -> B, C           # 1 to many
      # prune: A, B, C             # many to nothing
"""
from __future__ import absolute_import, print_function

import collections
import itertools

from mercurial.i18n import _
from mercurial import (
    context,
    error,
    node,
    obsolete,
    registrar,
    scmutil,
    tags as tagsmod,
)

cmdtable = {}
command = registrar.command(cmdtable)

_pipechars = '\\/+-|'
_nonpipechars = ''.join(chr(i) for i in xrange(33, 127)
                        if chr(i) not in _pipechars)

def _isname(ch):
    """char -> bool. return True if ch looks like part of a name, False
    otherwise"""
    return ch in _nonpipechars

def _parseasciigraph(text):
    """str -> {str : [str]}. convert the ASCII graph to edges"""
    lines = text.splitlines()
    edges = collections.defaultdict(list)  # {node: []}

    def get(y, x):
        """(int, int) -> char. give a coordinate, return the char. return a
        space for anything out of range"""
        if x < 0 or y < 0:
            return ' '
        try:
            return lines[y][x]
        except IndexError:
            return ' '

    def getname(y, x):
        """(int, int) -> str. like get(y, x) but concatenate left and right
        parts. if name is an 'o', try to replace it to the right"""
        result = ''
        for i in itertools.count(0):
            ch = get(y, x - i)
            if not _isname(ch):
                break
            result = ch + result
        for i in itertools.count(1):
            ch = get(y, x + i)
            if not _isname(ch):
                break
            result += ch
        if result == 'o':
            # special handling, find the name to the right
            result = ''
            for i in itertools.count(2):
                ch = get(y, x + i)
                if ch == ' ' or ch in _pipechars:
                    if result or x + i >= len(lines[y]):
                        break
                else:
                    result += ch
            return result or 'o'
        return result

    def parents(y, x):
        """(int, int) -> [str]. follow the ASCII edges at given position,
        return a list of parents"""
        visited = {(y, x)}
        visit = []
        result = []

        def follow(y, x, expected):
            """conditionally append (y, x) to visit array, if it's a char
            in excepted. 'o' in expected means an '_isname' test.
            if '-' (or '+') is not in excepted, and get(y, x) is '-' (or '+'),
            the next line (y + 1, x) will be checked instead."""
            ch = get(y, x)
            if any(ch == c and c not in expected for c in '-+'):
                y += 1
                return follow(y + 1, x, expected)
            if ch in expected or ('o' in expected and _isname(ch)):
                visit.append((y, x))

        #  -o-  # starting point:
        #  /|\ # follow '-' (horizontally), and '/|\' (to the bottom)
        follow(y + 1, x, '|')
        follow(y + 1, x - 1, '/')
        follow(y + 1, x + 1, '\\')
        follow(y, x - 1, '-')
        follow(y, x + 1, '-')

        while visit:
            y, x = visit.pop()
            if (y, x) in visited:
                continue
            visited.add((y, x))
            ch = get(y, x)
            if _isname(ch):
                result.append(getname(y, x))
                continue
            elif ch == '|':
                follow(y + 1, x, '/|o')
                follow(y + 1, x - 1, '/')
                follow(y + 1, x + 1, '\\')
            elif ch == '+':
                follow(y, x - 1, '-')
                follow(y, x + 1, '-')
                follow(y + 1, x - 1, '/')
                follow(y + 1, x + 1, '\\')
                follow(y + 1, x, '|')
            elif ch == '\\':
                follow(y + 1, x + 1, '\\|o')
            elif ch == '/':
                follow(y + 1, x - 1, '/|o')
            elif ch == '-':
                follow(y, x - 1, '-+o')
                follow(y, x + 1, '-+o')
        return result

    for y, line in enumerate(lines):
        for x, ch in enumerate(line):
            if ch == '#':  # comment
                break
            if _isname(ch):
                edges[getname(y, x)] += parents(y, x)

    return dict(edges)

class simplefilectx(object):
    def __init__(self, path, data):
        self._data = data
        self._path = path

    def data(self):
        return self._data

    def filenode(self):
        return None

    def path(self):
        return self._path

    def renamed(self):
        return None

    def flags(self):
        return ''

class simplecommitctx(context.committablectx):
    def __init__(self, repo, name, parentctxs, added=None):
        opts = {
            'changes': scmutil.status([], added or [], [], [], [], [], []),
            'date': '0 0',
            'extra': {'branch': 'default'},
        }
        super(simplecommitctx, self).__init__(self, name, **opts)
        self._repo = repo
        self._name = name
        self._parents = parentctxs
        self._parents.sort(key=lambda c: c.node())
        while len(self._parents) < 2:
            self._parents.append(repo[node.nullid])

    def filectx(self, key):
        return simplefilectx(key, self._name)

    def commit(self):
        return self._repo.commitctx(self)

def _walkgraph(edges):
    """yield node, parents in topologically order"""
    visible = set(edges.keys())
    remaining = {}  # {str: [str]}
    for k, vs in edges.iteritems():
        for v in vs:
            if v not in remaining:
                remaining[v] = []
        remaining[k] = vs[:]
    while remaining:
        leafs = [k for k, v in remaining.items() if not v]
        if not leafs:
            raise error.Abort(_('the graph has cycles'))
        for leaf in sorted(leafs):
            if leaf in visible:
                yield leaf, edges[leaf]
            del remaining[leaf]
            for k, v in remaining.iteritems():
                if leaf in v:
                    v.remove(leaf)

@command('debugdrawdag', [])
def debugdrawdag(ui, repo, **opts):
    """read an ASCII graph from stdin and create changesets

    The ASCII graph is like what :hg:`log -G` outputs, with each `o` replaced
    to the name of the node. The command will create dummy changesets and local
    tags with those names to make the dummy changesets easier to be referred
    to.

    If the name of a node is a single character 'o', It will be replaced by the
    word to the right. This makes it easier to reuse
    :hg:`log -G -T '{desc}'` outputs.

    For root (no parents) nodes, revset can be used to query existing repo.
    Note that the revset cannot have confusing characters which can be seen as
    the part of the graph edges, like `|/+-\`.
    """
    text = ui.fin.read()

    # parse the graph and make sure len(parents) <= 2 for each node
    edges = _parseasciigraph(text)
    for k, v in edges.iteritems():
        if len(v) > 2:
            raise error.Abort(_('%s: too many parents: %s')
                              % (k, ' '.join(v)))

    committed = {None: node.nullid}  # {name: node}

    # for leaf nodes, try to find existing nodes in repo
    for name, parents in edges.iteritems():
        if len(parents) == 0:
            try:
                committed[name] = scmutil.revsingle(repo, name)
            except error.RepoLookupError:
                pass

    # commit in topological order
    for name, parents in _walkgraph(edges):
        if name in committed:
            continue
        pctxs = [repo[committed[n]] for n in parents]
        ctx = simplecommitctx(repo, name, pctxs, [name])
        n = ctx.commit()
        committed[name] = n
        tagsmod.tag(repo, name, n, message=None, user=None, date=None,
                    local=True)

    # handle special comments
    with repo.wlock(), repo.lock(), repo.transaction('drawdag'):
        getctx = lambda x: repo.unfiltered()[committed[x.strip()]]
        for line in text.splitlines():
            if ' # ' not in line:
                continue

            rels = [] # obsolete relationships
            comment = line.split(' # ', 1)[1].split(' # ')[0].strip()
            args = comment.split(':', 1)
            if len(args) <= 1:
                continue

            cmd = args[0].strip()
            arg = args[1].strip()

            if cmd in ('replace', 'rebase', 'amend'):
                nodes = [getctx(m) for m in arg.split('->')]
                for i in range(len(nodes) - 1):
                    rels.append((nodes[i], (nodes[i + 1],)))
            elif cmd in ('split',):
                pre, succs = arg.split('->')
                succs = succs.split(',')
                rels.append((getctx(pre), (getctx(s) for s in succs)))
            elif cmd in ('prune',):
                for n in arg.split(','):
                    rels.append((getctx(n), ()))
            if rels:
                obsolete.createmarkers(repo, rels, date=(0, 0), operation=cmd)