phabricator: add a small language to query Differential Revisions

Previously, `phabread` can only be used to read a single patch, or a single
stack of patches. In the future, we want to have more complex queries like
filtering with status (open, accepted, closed, etc), or maybe more complex
like filtering by reviewers etc. The command line flag approach won't scale
with that.

Besides, we might want to have other commands to update Differential
Revision status in batch, like accepting a stack using a single command.

Therefore, this patch adds a small language. It has basic set operations:
`&`, `+`, `-` and an ancestor operator to support `--stack`.

Test Plan:
Try querying this Phabricator instance:

  hg phabread 1+2 # 1, 2
  hg phabread D2+D1 # 2, 1
  hg phabread ':118-115+:2-1' # 114, 116, 117, 118, 2
  hg phabread '((:118-(D115+117)))&:117' # 114, 116
  hg phabread ':2&:117' --debug # differential.query is called only once

Make sure the output is expected and prefetch works.

Differential Revision: https://phab.mercurial-scm.org/D125

contrib/phabricator.py

@@ -32,7 +32,9 b' Config::'
 
 from __future__ import absolute_import
 
+import itertools
 import json
+import operator
 import re
 
 from mercurial.node import bin, nullid
@@ -44,9 +46,11 b' from mercurial import ('
     error,
     mdiff,
     obsutil,
+    parser,
     patch,
     registrar,
     scmutil,
+    smartset,
     tags,
     url as urlmod,
     util,
@@ -484,11 +488,77 b' def _confirmbeforesend(repo, revs):'
 
     return True
 
-def querydrev(repo, params, stack=False):
+# Small language to specify differential revisions. Support symbols: (), :X,
+# +, and -.
+
+_elements = {
+    # token-type: binding-strength, primary, prefix, infix, suffix
+    '(':      (12, None, ('group', 1, ')'), None, None),
+    ':':      (8, None, ('ancestors', 8), None, None),
+    '&':      (5,  None, None, ('and_', 5), None),
+    '+':      (4,  None, None, ('add', 4), None),
+    '-':      (4,  None, None, ('sub', 4), None),
+    ')':      (0,  None, None, None, None),
+    'symbol': (0, 'symbol', None, None, None),
+    'end':    (0, None, None, None, None),
+}
+
+def _tokenize(text):
+    text = text.replace(' ', '') # remove space
+    view = memoryview(text) # zero-copy slice
+    special = '():+-&'
+    pos = 0
+    length = len(text)
+    while pos < length:
+        symbol = ''.join(itertools.takewhile(lambda ch: ch not in special,
+                                             view[pos:]))
+        if symbol:
+            yield ('symbol', symbol, pos)
+            pos += len(symbol)
+        else: # special char
+            yield (text[pos], None, pos)
+            pos += 1
+    yield ('end', None, pos)
+
+def _parse(text):
+    tree, pos = parser.parser(_elements).parse(_tokenize(text))
+    if pos != len(text):
+        raise error.ParseError('invalid token', pos)
+    return tree
+
+def _parsedrev(symbol):
+    """str -> int or None, ex. 'D45' -> 45; '12' -> 12; 'x' -> None"""
+    if symbol.startswith('D') and symbol[1:].isdigit():
+        return int(symbol[1:])
+    if symbol.isdigit():
+        return int(symbol)
+
+def _prefetchdrevs(tree):
+    """return ({single-drev-id}, {ancestor-drev-id}) to prefetch"""
+    drevs = set()
+    ancestordrevs = set()
+    op = tree[0]
+    if op == 'symbol':
+        r = _parsedrev(tree[1])
+        if r:
+            drevs.add(r)
+    elif op == 'ancestors':
+        r, a = _prefetchdrevs(tree[1])
+        drevs.update(r)
+        ancestordrevs.update(r)
+        ancestordrevs.update(a)
+    else:
+        for t in tree[1:]:
+            r, a = _prefetchdrevs(t)
+            drevs.update(r)
+            ancestordrevs.update(a)
+    return drevs, ancestordrevs
+
+def querydrev(repo, spec):
     """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.
+    spec is a string using a simple query language, see docstring in phabread
+    for details.
 
     A "Differential Revision dict" looks like:
 
@@ -525,26 +595,13 b' def querydrev(repo, params, stack=False)'
             "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".
     """
-    prefetched = {} # {id or phid: drev}
     def fetch(params):
         """params -> single drev or None"""
         key = (params.get(r'ids') or params.get(r'phids') or [None])[0]
         if key in prefetched:
             return prefetched[key]
-        # Otherwise, send the request. If we're fetching a stack, be smarter
-        # and fetch more ids in one batch, even if it could be unnecessary.
-        batchparams = params
-        if stack and len(params.get(r'ids', [])) == 1:
-            i = int(params[r'ids'][0])
-            # developer config: phabricator.batchsize
-            batchsize = repo.ui.configint('phabricator', 'batchsize', 12)
-            batchparams = {'ids': range(max(1, i - batchsize), i + 1)}
-        drevs = callconduit(repo, 'differential.query', batchparams)
+        drevs = callconduit(repo, 'differential.query', params)
         # Fill prefetched with the result
         for drev in drevs:
             prefetched[drev[r'phid']] = drev
@@ -553,23 +610,62 b' def querydrev(repo, params, stack=False)'
             raise error.Abort(_('cannot get Differential Revision %r') % params)
         return prefetched[key]
 
-    visited = set()
-    result = []
-    queue = [params]
-    while queue:
-        params = queue.pop()
-        drev = fetch(params)
-        if drev[r'id'] in visited:
-            continue
-        visited.add(drev[r'id'])
-        result.append(drev)
-        if stack:
+    def getstack(topdrevids):
+        """given a top, get a stack from the bottom, [id] -> [id]"""
+        visited = set()
+        result = []
+        queue = [{r'ids': [i]} for i in topdrevids]
+        while queue:
+            params = queue.pop()
+            drev = fetch(params)
+            if drev[r'id'] in visited:
+                continue
+            visited.add(drev[r'id'])
+            result.append(int(drev[r'id']))
             auxiliary = drev.get(r'auxiliary', {})
             depends = auxiliary.get(r'phabricator:depends-on', [])
             for phid in depends:
                 queue.append({'phids': [phid]})
-    result.reverse()
-    return result
+        result.reverse()
+        return smartset.baseset(result)
+
+    # Initialize prefetch cache
+    prefetched = {} # {id or phid: drev}
+
+    tree = _parse(spec)
+    drevs, ancestordrevs = _prefetchdrevs(tree)
+
+    # developer config: phabricator.batchsize
+    batchsize = repo.ui.configint('phabricator', 'batchsize', 12)
+
+    # Prefetch Differential Revisions in batch
+    tofetch = set(drevs)
+    for r in ancestordrevs:
+        tofetch.update(range(max(1, r - batchsize), r + 1))
+    if drevs:
+        fetch({r'ids': list(tofetch)})
+    getstack(list(ancestordrevs))
+
+    # Walk through the tree, return smartsets
+    def walk(tree):
+        op = tree[0]
+        if op == 'symbol':
+            drev = _parsedrev(tree[1])
+            if drev:
+                return smartset.baseset([drev])
+            else:
+                raise error.Abort(_('unknown symbol: %s') % tree[1])
+        elif op in {'and_', 'add', 'sub'}:
+            assert len(tree) == 3
+            return getattr(operator, op)(walk(tree[1]), walk(tree[2]))
+        elif op == 'group':
+            return walk(tree[1])
+        elif op == 'ancestors':
+            return getstack(walk(tree[1]))
+        else:
+            raise error.ProgrammingError('illegal tree: %r' % tree)
+
+    return [prefetched[r] for r in walk(tree)]
 
 def getdescfromdrev(drev):
     """get description (commit message) from "Differential Revision"
@@ -667,18 +763,22 b' def readpatch(repo, drevs, write):'
 
 @command('phabread',
          [('', 'stack', False, _('read dependencies'))],
-         _('REVID [OPTIONS]'))
-def phabread(ui, repo, revid, **opts):
+         _('DREVSPEC [OPTIONS]'))
+def phabread(ui, repo, spec, **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``.
+    DREVSPEC could be a Differential Revision identity, like ``D123``, or just
+    the number ``123``. It could also have common operators like ``+``, ``-``,
+    ``&``, ``(``, ``)`` for complex queries. Prefix ``:`` could be used to
+    select a stack.
+
+    For example, ``:D6+8-(2+D4)`` selects a stack up to D6, plus D8 and exclude
+    D2 and D4.
 
     If --stack is given, follow dependencies information and read all patches.
+    It is equivalent to the ``:`` operator.
     """
-    try:
-        revid = int(revid.split('/')[-1].replace('D', ''))
-    except ValueError:
-        raise error.Abort(_('invalid Revision ID: %s') % revid)
-    drevs = querydrev(repo, {'ids': [revid]}, opts.get('stack'))
+    if opts.get('stack'):
+        spec = ':(%s)' % spec
+    drevs = querydrev(repo, spec)
     readpatch(repo, drevs, ui.write)