code style: prefer 'is' and 'is not' tests with singletons

contrib/check-code.py

@@ -150,6 +150,8 b' pypats = ['
     (r'ui\.(status|progress|write|note|warn)\([\'\"]x',
      "warning: unwrapped ui message"),
     (r' is\s+(not\s+)?["\'0-9-]', "object comparison with literal"),
+    (r' [=!]=\s+(True|False|None)',
+     "comparison with singleton, use 'is' or 'is not' instead"),
 ]
 
 pyfilters = [

hgext/bookmarks.py

@@ -137,7 +137,7 b' def bookmark(ui, repo, mark=None, rev=No'
         write(repo)
         return
 
-    if mark != None:
+    if mark is not None:
         if "\n" in mark:
             raise util.Abort(_("bookmark name cannot contain newlines"))
         mark = mark.strip()

hgext/hgk.py

@@ -181,14 +181,14 b' def revtree(ui, args, repo, full="tree",'
                 if i + x >= count:
                     l[chunk - x:] = [0] * (chunk - x)
                     break
-                if full != None:
+                if full is not None:
                     l[x] = repo[i + x]
                     l[x].changeset() # force reading
                 else:
                     l[x] = 1
             for x in xrange(chunk - 1, -1, -1):
                 if l[x] != 0:
-                    yield (i + x, full != None and l[x] or None)
+                    yield (i + x, full is not None and l[x] or None)
             if i == 0:
                 break
 

hgext/mq.py

@@ -1523,7 +1523,7 b' class queue(object):'
                 l = line.rstrip()
                 l = l[10:].split(' ')
                 qpp = [bin(x) for x in l]
-            elif datastart != None:
+            elif datastart is not None:
                 l = line.rstrip()
                 n, name = l.split(':', 1)
                 if n:

hgext/transplant.py

@@ -401,7 +401,7 b' class transplanter(object):'
 
 def hasnode(repo, node):
     try:
-        return repo.changelog.rev(node) != None
+        return repo.changelog.rev(node) is not None
     except error.RevlogError:
         return False
 

mercurial/config.py

@@ -130,7 +130,7 b' class config(object):'
                 name = m.group(1)
                 if sections and section not in sections:
                     continue
-                if self.get(section, name) != None:
+                if self.get(section, name) is not None:
                     del self._data[section][name]
                 continue
 

mercurial/context.py

@@ -179,7 +179,7 b' class changectx(object):'
         """
         # deal with workingctxs
         n2 = c2._node
-        if n2 == None:
+        if n2 is None:
             n2 = c2._parents[0]._node
         n = self._repo.changelog.ancestor(self._node, n2)
         return changectx(self._repo, n)

mercurial/manifest.py

@@ -171,19 +171,19 b' class manifest(revlog.revlog):'
                         raise AssertionError(
                                 _("failed to remove %s from manifest") % f)
                     l = ""
-                if dstart != None and dstart <= start and dend >= start:
+                if dstart is not None and dstart <= start and dend >= start:
                     if dend < end:
                         dend = end
                     if l:
                         dline.append(l)
                 else:
-                    if dstart != None:
+                    if dstart is not None:
                         delta.append([dstart, dend, "".join(dline)])
                     dstart = start
                     dend = end
                     dline = [l]
 
-            if dstart != None:
+            if dstart is not None:
                 delta.append([dstart, dend, "".join(dline)])
             # apply the delta to the addlist, and get a delta for addrevision
             cachedelta = (self.rev(p1), addlistdelta(addlist, delta))

mercurial/revlog.py

@@ -212,7 +212,7 b' class lazyparser(object):'
             return None
         self.mapfind_count += 1
         last = self.l - 1
-        while self.index[last] != None:
+        while self.index[last] is not None:
             if last == 0:
                 self.all = 1
                 self.allmap = 1

mercurial/revset.py

@@ -715,7 +715,7 b' methods = {'
 }
 
 def optimize(x, small):
-    if x == None:
+    if x is None:
         return 0, x
 
     smallbonus = 1

mercurial/ui.py

@@ -589,7 +589,7 b' class ui(object):'
         termination.
         '''
 
-        if pos == None or not self.debugflag:
+        if pos is None or not self.debugflag:
             return
 
         if unit:

mercurial/util.py

@@ -1054,7 +1054,7 b' def strdate(string, format, defaults=[])'
 
     # NOTE: unixtime = localunixtime + offset
     offset, date = timezone(string), string
-    if offset != None:
+    if offset is not None:
         date = " ".join(string.split()[:-1])
 
     # add missing elements from defaults

mercurial/verify.py

@@ -34,7 +34,7 b' def _verify(repo):'
         raise util.Abort(_("cannot verify bundle or remote repos"))
 
     def err(linkrev, msg, filename=None):
-        if linkrev != None:
+        if linkrev is not None:
             badrevs.add(linkrev)
         else:
             linkrev = '?'

tests/run-tests.py

@@ -594,7 +594,7 b' def run(cmd, options, replacements):'
         tochild.close()
         output = fromchild.read()
         ret = fromchild.close()
-        if ret == None:
+        if ret is None:
             ret = 0
     else:
         proc = Popen4(cmd)
@@ -714,7 +714,7 b' def runone(options, test, skips, fails):'
     # If we're not in --debug mode and reference output file exists,
     # check test output against it.
     if options.debug:
-        refout = None                   # to match out == None
+        refout = None                   # to match "out is None"
     elif os.path.exists(ref):
         f = open(ref, "r")
         refout = splitnewlines(f.read())