drawdag: inline transaction() function

I suspect Jun wrote the method before he learnt that Python 2.7 allows
multiple context managers in a single with-clause.

tests/drawdag.py

@@ -1,362 +1,354
 # 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 contextlib
 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)
 
[e-mail]
-def transaction(repo):
-    with repo.wlock():
-        with repo.lock():
-            with repo.transaction('drawdag'):
-                yield
-
 @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 transaction(repo):
+    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)