phabricator: rework phabread to reduce memory usage and round-trips

This patch reworked phabread a bit so it fetches the lightweight
"Differential Revision" metadata for a stack first. Then read other data.

This allows the code to:

  a) send 1 request to get all `hg:meta` data instead of N requests
  b) patches are read in desired order, no need to buffer the output

"b)" reduces the memory usage from O(N^2) to O(N) since we no longer keep
old patch contents in memory.

The above `N` means the number of patches in the stack.

contrib/phabricator.py

@@ -1,378 +1,433 b''
 # phabricator.py - simple Phabricator integration
 #
 # Copyright 2017 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.
 """simple Phabricator integration
 
 This extension provides a ``phabsend`` command which sends a stack of
 changesets to Phabricator without amending commit messages, and a ``phabread``
 command which prints a stack of revisions in a format suitable
 for :hg:`import`.
 
 By default, Phabricator requires ``Test Plan`` which might prevent some
 changeset from being sent. The requirement could be disabled by changing
 ``differential.require-test-plan-field`` config server side.
 
 Config::
 
     [phabricator]
     # Phabricator URL
     url = https://phab.example.com/
 
     # API token. Get it from https://$HOST/conduit/login/
     token = cli-xxxxxxxxxxxxxxxxxxxxxxxxxxxx
 
     # Repo callsign. If a repo has a URL https://$HOST/diffusion/FOO, then its
     # callsign is "FOO".
     callsign = FOO
 
 """
 
 from __future__ import absolute_import
 
 import json
 import re
 
 from mercurial.i18n import _
 from mercurial import (
     encoding,
     error,
     mdiff,
     obsolete,
     patch,
     registrar,
     scmutil,
     tags,
     url as urlmod,
     util,
 )
 
 cmdtable = {}
 command = registrar.command(cmdtable)
 
 def urlencodenested(params):
     """like urlencode, but works with nested parameters.
 
     For example, if params is {'a': ['b', 'c'], 'd': {'e': 'f'}}, it will be
     flattened to {'a[0]': 'b', 'a[1]': 'c', 'd[e]': 'f'} and then passed to
     urlencode. Note: the encoding is consistent with PHP's http_build_query.
     """
     flatparams = util.sortdict()
     def process(prefix, obj):
         items = {list: enumerate, dict: lambda x: x.items()}.get(type(obj))
         if items is None:
             flatparams[prefix] = obj
         else:
             for k, v in items(obj):
                 if prefix:
                     process('%s[%s]' % (prefix, k), v)
                 else:
                     process(k, v)
     process('', params)
     return util.urlreq.urlencode(flatparams)
 
 def readurltoken(repo):
     """return conduit url, token and make sure they exist
 
     Currently read from [phabricator] config section. In the future, it might
     make sense to read from .arcconfig and .arcrc as well.
     """
     values = []
     section = 'phabricator'
     for name in ['url', 'token']:
         value = repo.ui.config(section, name)
         if not value:
             raise error.Abort(_('config %s.%s is required') % (section, name))
         values.append(value)
     return values
 
 def callconduit(repo, name, params):
     """call Conduit API, params is a dict. return json.loads result, or None"""
     host, token = readurltoken(repo)
     url, authinfo = util.url('/'.join([host, 'api', name])).authinfo()
     urlopener = urlmod.opener(repo.ui, authinfo)
     repo.ui.debug('Conduit Call: %s %s\n' % (url, params))
     params = params.copy()
     params['api.token'] = token
     request = util.urlreq.request(url, data=urlencodenested(params))
     body = urlopener.open(request).read()
     repo.ui.debug('Conduit Response: %s\n' % body)
     parsed = json.loads(body)
     if parsed.get(r'error_code'):
         msg = (_('Conduit Error (%s): %s')
                % (parsed[r'error_code'], parsed[r'error_info']))
         raise error.Abort(msg)
     return parsed[r'result']
 
 @command('debugcallconduit', [], _('METHOD'))
 def debugcallconduit(ui, repo, name):
     """call Conduit API
 
     Call parameters are read from stdin as a JSON blob. Result will be written
     to stdout as a JSON blob.
     """
     params = json.loads(ui.fin.read())
     result = callconduit(repo, name, params)
     s = json.dumps(result, sort_keys=True, indent=2, separators=(',', ': '))
     ui.write('%s\n' % s)
 
 def getrepophid(repo):
     """given callsign, return repository PHID or None"""
     # developer config: phabricator.repophid
     repophid = repo.ui.config('phabricator', 'repophid')
     if repophid:
         return repophid
     callsign = repo.ui.config('phabricator', 'callsign')
     if not callsign:
         return None
     query = callconduit(repo, 'diffusion.repository.search',
                         {'constraints': {'callsigns': [callsign]}})
     if len(query[r'data']) == 0:
         return None
     repophid = encoding.strtolocal(query[r'data'][0][r'phid'])
     repo.ui.setconfig('phabricator', 'repophid', repophid)
     return repophid
 
 _differentialrevisiontagre = re.compile('\AD([1-9][0-9]*)\Z')
 _differentialrevisiondescre = re.compile(
     '^Differential Revision:.*D([1-9][0-9]*)$', re.M)
 
 def getmapping(ctx):
     """return (node, associated Differential Revision ID) or (None, None)
 
     Examines all precursors and their tags. Tags with format like "D1234" are
     considered a match and the node with that tag, and the number after "D"
     (ex. 1234) will be returned.
 
     If tags are not found, examine commit message. The "Differential Revision:"
     line could associate this changeset to a Differential Revision.
     """
     unfi = ctx.repo().unfiltered()
     nodemap = unfi.changelog.nodemap
 
     # Check tags like "D123"
     for n in obsolete.allprecursors(unfi.obsstore, [ctx.node()]):
         if n in nodemap:
             for tag in unfi.nodetags(n):
                 m = _differentialrevisiontagre.match(tag)
                 if m:
                     return n, int(m.group(1))
 
     # Check commit message
     m = _differentialrevisiondescre.search(ctx.description())
     if m:
         return None, int(m.group(1))
 
     return None, None
 
 def getdiff(ctx, diffopts):
     """plain-text diff without header (user, commit message, etc)"""
     output = util.stringio()
     for chunk, _label in patch.diffui(ctx.repo(), ctx.p1().node(), ctx.node(),
                                       None, opts=diffopts):
         output.write(chunk)
     return output.getvalue()
 
 def creatediff(ctx):
     """create a Differential Diff"""
     repo = ctx.repo()
     repophid = getrepophid(repo)
     # Create a "Differential Diff" via "differential.createrawdiff" API
     params = {'diff': getdiff(ctx, mdiff.diffopts(git=True, context=32767))}
     if repophid:
         params['repositoryPHID'] = repophid
     diff = callconduit(repo, 'differential.createrawdiff', params)
     if not diff:
         raise error.Abort(_('cannot create diff for %s') % ctx)
     return diff
 
 def writediffproperties(ctx, diff):
     """write metadata to diff so patches could be applied losslessly"""
     params = {
         'diff_id': diff[r'id'],
         'name': 'hg:meta',
         'data': json.dumps({
             'user': ctx.user(),
             'date': '%d %d' % ctx.date(),
             'node': ctx.hex(),
             'parent': ctx.p1().hex(),
         }),
     }
     callconduit(ctx.repo(), 'differential.setdiffproperty', params)
 
 def createdifferentialrevision(ctx, revid=None, parentrevid=None, oldnode=None):
     """create or update a Differential Revision
 
     If revid is None, create a new Differential Revision, otherwise update
     revid. If parentrevid is not None, set it as a dependency.
 
     If oldnode is not None, check if the patch content (without commit message
     and metadata) has changed before creating another diff.
     """
     repo = ctx.repo()
     if oldnode:
         diffopts = mdiff.diffopts(git=True, context=1)
         oldctx = repo.unfiltered()[oldnode]
         neednewdiff = (getdiff(ctx, diffopts) != getdiff(oldctx, diffopts))
     else:
         neednewdiff = True
 
     transactions = []
     if neednewdiff:
         diff = creatediff(ctx)
         writediffproperties(ctx, diff)
         transactions.append({'type': 'update', 'value': diff[r'phid']})
 
     # Use a temporary summary to set dependency. There might be better ways but
     # I cannot find them for now. But do not do that if we are updating an
     # existing revision (revid is not None) since that introduces visible
     # churns (someone edited "Summary" twice) on the web page.
     if parentrevid and revid is None:
         summary = 'Depends on D%s' % parentrevid
         transactions += [{'type': 'summary', 'value': summary},
                          {'type': 'summary', 'value': ' '}]
 
     # Parse commit message and update related fields.
     desc = ctx.description()
     info = callconduit(repo, 'differential.parsecommitmessage',
                        {'corpus': desc})
     for k, v in info[r'fields'].items():
         if k in ['title', 'summary', 'testPlan']:
             transactions.append({'type': k, 'value': v})
 
     params = {'transactions': transactions}
     if revid is not None:
         # Update an existing Differential Revision
         params['objectIdentifier'] = revid
 
     revision = callconduit(repo, 'differential.revision.edit', params)
     if not revision:
         raise error.Abort(_('cannot create revision for %s') % ctx)
 
     return revision
 
 @command('phabsend',
          [('r', 'rev', [], _('revisions to send'), _('REV'))],
          _('REV [OPTIONS]'))
 def phabsend(ui, repo, *revs, **opts):
     """upload changesets to Phabricator
 
     If there are multiple revisions specified, they will be send as a stack
     with a linear dependencies relationship using the order specified by the
     revset.
 
     For the first time uploading changesets, local tags will be created to
     maintain the association. After the first time, phabsend will check
     obsstore and tags information so it can figure out whether to update an
     existing Differential Revision, or create a new one.
     """
     revs = list(revs) + opts.get('rev', [])
     revs = scmutil.revrange(repo, revs)
 
     if not revs:
         raise error.Abort(_('phabsend requires at least one changeset'))
 
     # Send patches one by one so we know their Differential Revision IDs and
     # can provide dependency relationship
     lastrevid = None
     for rev in revs:
         ui.debug('sending rev %d\n' % rev)
         ctx = repo[rev]
 
         # Get Differential Revision ID
         oldnode, revid = getmapping(ctx)
         if oldnode != ctx.node():
             # Create or update Differential Revision
             revision = createdifferentialrevision(ctx, revid, lastrevid,
                                                   oldnode)
             newrevid = int(revision[r'object'][r'id'])
             if revid:
                 action = _('updated')
             else:
                 action = _('created')
 
             # Create a local tag to note the association
             tagname = 'D%d' % newrevid
             tags.tag(repo, tagname, ctx.node(), message=None, user=None,
                      date=None, local=True)
         else:
             # Nothing changed. But still set "newrevid" so the next revision
             # could depend on this one.
             newrevid = revid
             action = _('skipped')
 
         ui.write(_('D%s: %s - %s: %s\n') % (newrevid, action, ctx,
                                             ctx.description().split('\n')[0]))
         lastrevid = newrevid
 
 _summaryre = re.compile('^Summary:\s*', re.M)
 
 # Map from "hg:meta" keys to header understood by "hg import". The order is
 # consistent with "hg export" output.
 _metanamemap = util.sortdict([(r'user', 'User'), (r'date', 'Date'),
                               (r'node', 'Node ID'), (r'parent', 'Parent ')])
 
-def readpatch(repo, params, recursive=False):
+def querydrev(repo, params, stack=False):
+    """return a list of "Differential Revision" dicts
+
+    params is the input of "differential.query" API, and is expected to match
+    just a single Differential Revision.
+
+    A "Differential Revision dict" looks like:
+
+        {
+            "id": "2",
+            "phid": "PHID-DREV-672qvysjcczopag46qty",
+            "title": "example",
+            "uri": "https://phab.example.com/D2",
+            "dateCreated": "1499181406",
+            "dateModified": "1499182103",
+            "authorPHID": "PHID-USER-tv3ohwc4v4jeu34otlye",
+            "status": "0",
+            "statusName": "Needs Review",
+            "properties": [],
+            "branch": null,
+            "summary": "",
+            "testPlan": "",
+            "lineCount": "2",
+            "activeDiffPHID": "PHID-DIFF-xoqnjkobbm6k4dk6hi72",
+            "diffs": [
+              "3",
+              "4",
+            ],
+            "commits": [],
+            "reviewers": [],
+            "ccs": [],
+            "hashes": [],
+            "auxiliary": {
+              "phabricator:projects": [],
+              "phabricator:depends-on": [
+                "PHID-DREV-gbapp366kutjebt7agcd"
+              ]
+            },
+            "repositoryPHID": "PHID-REPO-hub2hx62ieuqeheznasv",
+            "sourcePath": null
+        }
+
+    If stack is True, return a list of "Differential Revision dict"s in an
+    order that the latter ones depend on the former ones. Otherwise, return a
+    list of a unique "Differential Revision dict".
+    """
+    result = []
+    queue = [params]
+    while queue:
+        params = queue.pop()
+        drevs = callconduit(repo, 'differential.query', params)
+        if len(drevs) != 1:
+            raise error.Abort(_('cannot get Differential Revision %r') % params)
+        drev = drevs[0]
+        result.append(drev)
+        if stack:
+            auxiliary = drev.get(r'auxiliary', {})
+            depends = auxiliary.get(r'phabricator:depends-on', [])
+            for phid in depends:
+                queue.append({'phids': [phid]})
+    result.reverse()
+    return result
+
+def readpatch(repo, params, write, stack=False):
     """generate plain-text patch readable by 'hg import'
 
-    params is passed to "differential.query". If recursive is True, also return
-    dependent patches.
+    write is usually ui.write. params is passed to "differential.query". If
+    stack is True, also write dependent patches.
     """
     # Differential Revisions
-    drevs = callconduit(repo, 'differential.query', params)
-    if len(drevs) == 1:
-        drev = drevs[0]
-    else:
-        raise error.Abort(_('cannot get Differential Revision %r') % params)
-
-    repo.ui.note(_('reading D%s\n') % drev[r'id'])
+    drevs = querydrev(repo, params, stack)
 
-    diffid = max(int(v) for v in drev[r'diffs'])
-    body = callconduit(repo, 'differential.getrawdiff', {'diffID': diffid})
-    desc = callconduit(repo, 'differential.getcommitmessage',
-                       {'revision_id': drev[r'id']})
-    header = '# HG changeset patch\n'
+    # Prefetch hg:meta property for all diffs
+    diffids = sorted(set(max(int(v) for v in drev[r'diffs']) for drev in drevs))
+    diffs = callconduit(repo, 'differential.querydiffs', {'ids': diffids})
 
-    # Remove potential empty "Summary:"
-    desc = _summaryre.sub('', desc)
+    # Generate patch for each drev
+    for drev in drevs:
+        repo.ui.note(_('reading D%s\n') % drev[r'id'])
 
-    # Try to preserve metadata from hg:meta property. Write hg patch headers
-    # that can be read by the "import" command. See patchheadermap and extract
-    # in mercurial/patch.py for supported headers.
-    diffs = callconduit(repo, 'differential.querydiffs', {'ids': [diffid]})
-    props = diffs[str(diffid)][r'properties'] # could be empty list or dict
-    if props and r'hg:meta' in props:
-        meta = props[r'hg:meta']
-        for k in _metanamemap.keys():
-            if k in meta:
-                header += '# %s %s\n' % (_metanamemap[k], meta[k])
+        diffid = max(int(v) for v in drev[r'diffs'])
+        body = callconduit(repo, 'differential.getrawdiff', {'diffID': diffid})
+        desc = callconduit(repo, 'differential.getcommitmessage',
+                           {'revision_id': drev[r'id']})
+        header = '# HG changeset patch\n'
+
+        # Remove potential empty "Summary:"
+        desc = _summaryre.sub('', desc)
 
-    patch = ('%s%s\n%s') % (header, desc, body)
+        # Try to preserve metadata from hg:meta property. Write hg patch
+        # headers that can be read by the "import" command. See patchheadermap
+        # and extract in mercurial/patch.py for supported headers.
+        props = diffs[str(diffid)][r'properties'] # could be empty list or dict
+        if props and r'hg:meta' in props:
+            meta = props[r'hg:meta']
+            for k in _metanamemap.keys():
+                if k in meta:
+                    header += '# %s %s\n' % (_metanamemap[k], meta[k])
 
-    # Check dependencies
-    if recursive:
-        auxiliary = drev.get(r'auxiliary', {})
-        depends = auxiliary.get(r'phabricator:depends-on', [])
-        for phid in depends:
-            patch = readpatch(repo, {'phids': [phid]}, recursive=True) + patch
-    return patch
+        write(('%s%s\n%s') % (header, desc, body))
 
 @command('phabread',
          [('', 'stack', False, _('read dependencies'))],
          _('REVID [OPTIONS]'))
 def phabread(ui, repo, revid, **opts):
     """print patches from Phabricator suitable for importing
 
     REVID could be a Differential Revision identity, like ``D123``, or just the
     number ``123``, or a full URL like ``https://phab.example.com/D123``.
 
     If --stack is given, follow dependencies information and read all patches.
     """
     try:
         revid = int(revid.split('/')[-1].replace('D', ''))
     except ValueError:
         raise error.Abort(_('invalid Revision ID: %s') % revid)
-    patch = readpatch(repo, {'ids': [revid]}, recursive=opts.get('stack'))
-    ui.write(patch)
+    readpatch(repo, {'ids': [revid]}, ui.write, opts.get('stack'))