D10290: refactor: prefer checks against nullrev over nullid

[joerg.sonnenberger (Joerg Sonnenberger)]

joerg.sonnenberger created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REVISION SUMMARY
  A common pattern is using a changeset context and obtaining the node to
  compare against nullid. Change this to obtain the nullrev instead. In
  the future, the nullid becomes a property of the repository and is no
  longer a global constant, so using nullrev is much easier to reason
  about. Python function call overhead makes the difference moot, but
  future changes will result in more dictionary lookups otherwise, so
  prefer the simpler pattern.

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D10290

AFFECTED FILES
  hgext/extdiff.py
  hgext/split.py
  mercurial/context.py
  mercurial/copies.py
  mercurial/logcmdutil.py
  mercurial/mergestate.py
  mercurial/shelve.py
  mercurial/simplemerge.py

CHANGE DETAILS

diff --git a/mercurial/simplemerge.py b/mercurial/simplemerge.py
--- a/mercurial/simplemerge.py
+++ b/mercurial/simplemerge.py
@@ -19,7 +19,7 @@
 from __future__ import absolute_import
 
 from .i18n import _
-from .node import nullid
+from .node import nullrev
 from . import (
     error,
     mdiff,
@@ -427,7 +427,7 @@
 def is_not_null(ctx):
     if not util.safehasattr(ctx, "node"):
         return False
-    return ctx.node() != nullid
+    return ctx.rev() != nullrev
 
 
 def _mergediff(m3, name_a, name_b, name_base):
diff --git a/mercurial/shelve.py b/mercurial/shelve.py
--- a/mercurial/shelve.py
+++ b/mercurial/shelve.py
@@ -534,7 +534,7 @@
     parent = parents[0]
     origbranch = wctx.branch()
 
-    if parent.node() != nullid:
+    if parent.rev() != nullrev:
         desc = b"changes to: %s" % parent.description().split(b'\n', 1)[0]
     else:
         desc = b'(changes in empty repository)'
diff --git a/mercurial/mergestate.py b/mercurial/mergestate.py
--- a/mercurial/mergestate.py
+++ b/mercurial/mergestate.py
@@ -11,6 +11,7 @@
     hex,
     nullhex,
     nullid,
+    nullrev,
 )
 from . import (
     error,
@@ -341,7 +342,7 @@
         flo = fco.flags()
         fla = fca.flags()
         if b'x' in flags + flo + fla and b'l' not in flags + flo + fla:
-            if fca.node() == nullid and flags != flo:
+            if fca.rev() == nullrev and flags != flo:
                 if preresolve:
                     self._repo.ui.warn(
                         _(
diff --git a/mercurial/logcmdutil.py b/mercurial/logcmdutil.py
--- a/mercurial/logcmdutil.py
+++ b/mercurial/logcmdutil.py
@@ -14,6 +14,7 @@
 from .i18n import _
 from .node import (
     nullid,
+    nullrev,
     wdirid,
     wdirrev,
 )
@@ -82,7 +83,7 @@
     If diff.merge is enabled, an overlayworkingctx of the auto-merged parents will be returned.
     """
     repo = ctx.repo()
-    if repo.ui.configbool(b"diff", b"merge") and ctx.p2().node() != nullid:
+    if repo.ui.configbool(b"diff", b"merge") and ctx.p2().rev() != nullrev:
         # avoid cycle context -> subrepo -> cmdutil -> logcmdutil
         from . import context
 
diff --git a/mercurial/copies.py b/mercurial/copies.py
--- a/mercurial/copies.py
+++ b/mercurial/copies.py
@@ -149,7 +149,7 @@
     # optimization, since the ctx.files() for a merge commit is not correct for
     # this comparison.
     forwardmissingmatch = match
-    if b.p1() == a and b.p2().node() == nullid:
+    if b.p1() == a and b.p2().rev() == nullrev:
         filesmatcher = matchmod.exact(b.files())
         forwardmissingmatch = matchmod.intersectmatchers(match, filesmatcher)
     if repo.ui.configbool(b'devel', b'copy-tracing.trace-all-files'):
diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -2885,7 +2885,7 @@
         # "1 < len(self._parents)" can't be used for checking
         # existence of the 2nd parent, because "memctx._parents" is
         # explicitly initialized by the list, of which length is 2.
-        if p2.node() != nullid:
+        if p2.rev() != nullrev:
             man2 = p2.manifest()
             managing = lambda f: f in man1 or f in man2
         else:
@@ -2903,7 +2903,7 @@
         return scmutil.status(modified, added, removed, [], [], [], [])
 
     def parents(self):
-        if self._parents[1].node() == nullid:
+        if self._parents[1].rev() == nullrev:
             return [self._parents[0]]
         return self._parents
 
@@ -3052,7 +3052,7 @@
         # "1 < len(self._parents)" can't be used for checking
         # existence of the 2nd parent, because "metadataonlyctx._parents" is
         # explicitly initialized by the list, of which length is 2.
-        if p2.node() != nullid:
+        if p2.rev() != nullrev:
             man2 = p2.manifest()
             managing = lambda f: f in man1 or f in man2
         else:
diff --git a/hgext/split.py b/hgext/split.py
--- a/hgext/split.py
+++ b/hgext/split.py
@@ -12,7 +12,7 @@
 from mercurial.i18n import _
 
 from mercurial.node import (
-    nullid,
+    nullrev,
     short,
 )
 
@@ -80,12 +80,12 @@
                 raise error.InputError(_(b'cannot split multiple revisions'))
 
             rev = revs.first()
-            ctx = repo[rev]
-            # Handle nullid specially here (instead of leaving for precheck()
+            # Handle nullrev specially here (instead of leaving for precheck()
             # below) so we get a nicer message and error code.
-            if rev is None or ctx.node() == nullid:
+            if rev is None or rev == nullrev:
                 ui.status(_(b'nothing to split\n'))
                 return 1
+            ctx = repo[rev]
             if ctx.node() is None:
                 raise error.InputError(_(b'cannot split working directory'))
 
diff --git a/hgext/extdiff.py b/hgext/extdiff.py
--- a/hgext/extdiff.py
+++ b/hgext/extdiff.py
@@ -91,7 +91,7 @@
 
 from mercurial.i18n import _
 from mercurial.node import (
-    nullid,
+    nullrev,
     short,
 )
 from mercurial import (
@@ -565,18 +565,18 @@
             repo, [from_rev] + [to_rev], b'nowarn'
         )
         ctx1a = scmutil.revsingle(repo, from_rev, None)
-        ctx1b = repo[nullid]
+        ctx1b = repo[nullrev]
         ctx2 = scmutil.revsingle(repo, to_rev, None)
     else:
         ctx1a, ctx2 = scmutil.revpair(repo, revs)
         if not revs:
             ctx1b = repo[None].p2()
         else:
-            ctx1b = repo[nullid]
+            ctx1b = repo[nullrev]
 
     # Disable 3-way merge if there is only one parent
     if do3way:
-        if ctx1b.node() == nullid:
+        if ctx1b.rev() == nullrev:
             do3way = False
 
     matcher = scmutil.match(ctx2, pats, opts)



To: joerg.sonnenberger, #hg-reviewers
Cc: mercurial-patches, mercurial-devel