check-code: catch Python 'is' comparing number or string literals

The Python 'is' operator compares object identity, so it should
definitely not be applied to string or number literals, which Python
implementations are free to represent with a temporary object.

This should catch the following kinds of bogus expressions (examples):

  x is 'foo'     x is not 'foo'
  x is "bar"     x is not "bar"
  x is 42        x is not 42
  x is -36       x is not -36

As originally proposed by Martin Geisler, amended with catching
negative numbers.

contrib/check-code.py

@@ -1,300 +1,301 b''
 #!/usr/bin/env python
 #
 # check-code - a style and portability checker for Mercurial
 #
 # Copyright 2010 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import re, glob, os, sys
 import optparse
 
 def repquote(m):
     t = re.sub(r"\w", "x", m.group('text'))
     t = re.sub(r"[^\sx]", "o", t)
     return m.group('quote') + t + m.group('quote')
 
 def reppython(m):
     comment = m.group('comment')
     if comment:
         return "#" * len(comment)
     return repquote(m)
 
 def repcomment(m):
     return m.group(1) + "#" * len(m.group(2))
 
 def repccomment(m):
     t = re.sub(r"((?<=\n) )|\S", "x", m.group(2))
     return m.group(1) + t + "*/"
 
 def repcallspaces(m):
     t = re.sub(r"\n\s+", "\n", m.group(2))
     return m.group(1) + t
 
 def repinclude(m):
     return m.group(1) + "<foo>"
 
 def rephere(m):
     t = re.sub(r"\S", "x", m.group(2))
     return m.group(1) + t
 
 
 testpats = [
     (r'(pushd|popd)', "don't use 'pushd' or 'popd', use 'cd'"),
     (r'\W\$?\(\([^\)]*\)\)', "don't use (()) or $(()), use 'expr'"),
     (r'^function', "don't use 'function', use old style"),
     (r'grep.*-q', "don't use 'grep -q', redirect to /dev/null"),
     (r'echo.*\\n', "don't use 'echo \\n', use printf"),
     (r'echo -n', "don't use 'echo -n', use printf"),
     (r'^diff.*-\w*N', "don't use 'diff -N'"),
     (r'(^| )wc[^|]*$', "filter wc output"),
     (r'head -c', "don't use 'head -c', use 'dd'"),
     (r'ls.*-\w*R', "don't use 'ls -R', use 'find'"),
     (r'printf.*\\\d\d\d', "don't use 'printf \NNN', use Python"),
     (r'printf.*\\x', "don't use printf \\x, use Python"),
     (r'\$\(.*\)', "don't use $(expr), use `expr`"),
     (r'rm -rf \*', "don't use naked rm -rf, target a directory"),
     (r'(^|\|\s*)grep (-\w\s+)*[^|]*[(|]\w',
      "use egrep for extended grep syntax"),
     (r'/bin/', "don't use explicit paths for tools"),
     (r'\$PWD', "don't use $PWD, use `pwd`"),
     (r'[^\n]\Z', "no trailing newline"),
     (r'export.*=', "don't export and assign at once"),
     ('^([^"\']|("[^"]*")|(\'[^\']*\'))*\\^', "^ must be quoted"),
     (r'^source\b', "don't use 'source', use '.'"),
     (r'touch -d', "don't use 'touch -d', use 'touch -t' instead"),
     (r'ls\s+[^-]+\s+-', "options to 'ls' must come before filenames"),
 ]
 
 testfilters = [
     (r"( *)(#([^\n]*\S)?)", repcomment),
     (r"<<(\S+)((.|\n)*?\n\1)", rephere),
 ]
 
 uprefix = r"^  \$ "
 uprefixc = r"^  > "
 utestpats = [
     (r'^(\S|  $ ).*(\S\s+|^\s+)\n', "trailing whitespace on non-output"),
     (uprefix + r'.*\|\s*sed', "use regex test output patterns instead of sed"),
     (uprefix + r'(true|exit 0)', "explicit zero exit unnecessary"),
     (uprefix + r'.*\$\?', "explicit exit code checks unnecessary"),
     (uprefix + r'.*\|\| echo.*(fail|error)',
      "explicit exit code checks unnecessary"),
     (uprefix + r'set -e', "don't use set -e"),
     (uprefixc + r'( *)\t', "don't use tabs to indent"),
 ]
 
 for p, m in testpats:
     if p.startswith('^'):
         p = uprefix + p[1:]
     else:
         p = uprefix + p
     utestpats.append((p, m))
 
 utestfilters = [
     (r"( *)(#([^\n]*\S)?)", repcomment),
 ]
 
 pypats = [
     (r'^\s*def\s*\w+\s*\(.*,\s*\(',
      "tuple parameter unpacking not available in Python 3+"),
     (r'lambda\s*\(.*,.*\)',
      "tuple parameter unpacking not available in Python 3+"),
     (r'(?<!def)\s+(cmp)\(', "cmp is not available in Python 3+"),
     (r'\breduce\s*\(.*', "reduce is not available in Python 3+"),
     (r'\.has_key\b', "dict.has_key is not available in Python 3+"),
     (r'^\s*\t', "don't use tabs"),
     (r'\S;\s*\n', "semicolon"),
     (r'\w,\w', "missing whitespace after ,"),
     (r'\w[+/*\-<>]\w', "missing whitespace in expression"),
     (r'^\s+\w+=\w+[^,)]$', "missing whitespace in assignment"),
     (r'.{85}', "line too long"),
     (r'.{81}', "warning: line over 80 characters"),
     (r'[^\n]\Z', "no trailing newline"),
     (r'(\S\s+|^\s+)\n', "trailing whitespace"),
 #    (r'^\s+[^_ ][^_. ]+_[^_]+\s*=', "don't use underbars in identifiers"),
 #    (r'\w*[a-z][A-Z]\w*\s*=', "don't use camelcase in identifiers"),
     (r'^\s*(if|while|def|class|except|try)\s[^[]*:\s*[^\]#\s]+',
      "linebreak after :"),
     (r'class\s[^(]:', "old-style class, use class foo(object)"),
     (r'^\s+del\(', "del isn't a function"),
     (r'\band\(', "and isn't a function"),
     (r'\bor\(', "or isn't a function"),
     (r'\bnot\(', "not isn't a function"),
     (r'^\s+except\(', "except isn't a function"),
     (r',]', "unneeded trailing ',' in list"),
 #    (r'class\s[A-Z][^\(]*\((?!Exception)',
 #     "don't capitalize non-exception classes"),
 #    (r'in range\(', "use xrange"),
 #    (r'^\s*print\s+', "avoid using print in core and extensions"),
     (r'[\x80-\xff]', "non-ASCII character literal"),
     (r'("\')\.format\(', "str.format() not available in Python 2.4"),
     (r'^\s*with\s+', "with not available in Python 2.4"),
     (r'(?<!def)\s+(any|all|format)\(',
      "any/all/format not available in Python 2.4"),
     (r'(?<!def)\s+(callable)\(',
      "callable not available in Python 3, use hasattr(f, '__call__')"),
     (r'if\s.*\selse', "if ... else form not available in Python 2.4"),
     (r'([\(\[]\s\S)|(\S\s[\)\]])', "gratuitous whitespace in () or []"),
 #    (r'\s\s=', "gratuitous whitespace before ="),
     (r'[^>< ](\+=|-=|!=|<>|<=|>=|<<=|>>=)\S',
      "missing whitespace around operator"),
     (r'[^>< ](\+=|-=|!=|<>|<=|>=|<<=|>>=)\s',
      "missing whitespace around operator"),
     (r'\s(\+=|-=|!=|<>|<=|>=|<<=|>>=)\S',
      "missing whitespace around operator"),
     (r'[^+=*!<>&| -](\s=|=\s)[^= ]',
      "wrong whitespace around ="),
     (r'raise Exception', "don't raise generic exceptions"),
     (r'ui\.(status|progress|write|note|warn)\([\'\"]x',
      "warning: unwrapped ui message"),
+    (r' is\s+(not\s+)?["\'0-9-]', "object comparison with literal"),
 ]
 
 pyfilters = [
     (r"""(?msx)(?P<comment>\#.*?$)|
          ((?P<quote>('''|\"\"\"|(?<!')'(?!')|(?<!")"(?!")))
           (?P<text>(([^\\]|\\.)*?))
           (?P=quote))""", reppython),
 ]
 
 cpats = [
     (r'//', "don't use //-style comments"),
     (r'^  ', "don't use spaces to indent"),
     (r'\S\t', "don't use tabs except for indent"),
     (r'(\S\s+|^\s+)\n', "trailing whitespace"),
     (r'.{85}', "line too long"),
     (r'(while|if|do|for)\(', "use space after while/if/do/for"),
     (r'return\(', "return is not a function"),
     (r' ;', "no space before ;"),
     (r'\w+\* \w+', "use int *foo, not int* foo"),
     (r'\([^\)]+\) \w+', "use (int)foo, not (int) foo"),
     (r'\S+ (\+\+|--)', "use foo++, not foo ++"),
     (r'\w,\w', "missing whitespace after ,"),
     (r'\w[+/*]\w', "missing whitespace in expression"),
     (r'^#\s+\w', "use #foo, not # foo"),
     (r'[^\n]\Z', "no trailing newline"),
 ]
 
 cfilters = [
     (r'(/\*)(((\*(?!/))|[^*])*)\*/', repccomment),
     (r'''(?P<quote>(?<!")")(?P<text>([^"]|\\")+)"(?!")''', repquote),
     (r'''(#\s*include\s+<)([^>]+)>''', repinclude),
     (r'(\()([^)]+\))', repcallspaces),
 ]
 
 checks = [
     ('python', r'.*\.(py|cgi)$', pyfilters, pypats),
     ('test script', r'(.*/)?test-[^.~]*$', testfilters, testpats),
     ('c', r'.*\.c$', cfilters, cpats),
     ('unified test', r'.*\.t$', utestfilters, utestpats),
 ]
 
 class norepeatlogger(object):
     def __init__(self):
         self._lastseen = None
 
     def log(self, fname, lineno, line, msg, blame):
         """print error related a to given line of a given file.
 
         The faulty line will also be printed but only once in the case
         of multiple errors.
 
         :fname: filename
         :lineno: line number
         :line: actual content of the line
         :msg: error message
         """
         msgid = fname, lineno, line
         if msgid != self._lastseen:
             if blame:
                 print "%s:%d (%s):" % (fname, lineno, blame)
             else:
                 print "%s:%d:" % (fname, lineno)
             print " > %s" % line
             self._lastseen = msgid
         print " " + msg
 
 _defaultlogger = norepeatlogger()
 
 def getblame(f):
     lines = []
     for l in os.popen('hg annotate -un %s' % f):
         start, line = l.split(':', 1)
         user, rev = start.split()
         lines.append((line[1:-1], user, rev))
     return lines
 
 def checkfile(f, logfunc=_defaultlogger.log, maxerr=None, warnings=False,
               blame=False):
     """checks style and portability of a given file
 
     :f: filepath
     :logfunc: function used to report error
               logfunc(filename, linenumber, linecontent, errormessage)
     :maxerr: number of error to display before arborting.
              Set to None (default) to report all errors
 
     return True if no error is found, False otherwise.
     """
     blamecache = None
     result = True
     for name, match, filters, pats in checks:
         fc = 0
         if not re.match(match, f):
             continue
         pre = post = open(f).read()
         if "no-" + "check-code" in pre:
             break
         for p, r in filters:
             post = re.sub(p, r, post)
         # print post # uncomment to show filtered version
         z = enumerate(zip(pre.splitlines(), post.splitlines(True)))
         for n, l in z:
             if "check-code" + "-ignore" in l[0]:
                 continue
             for p, msg in pats:
                 if not warnings and msg.startswith("warning"):
                     continue
                 if re.search(p, l[1]):
                     bd = ""
                     if blame:
                         bd = 'working directory'
                         if not blamecache:
                             blamecache = getblame(f)
                         if n < len(blamecache):
                             bl, bu, br = blamecache[n]
                             if bl == l[0]:
                                 bd = '%s@%s' % (bu, br)
                     logfunc(f, n + 1, l[0], msg, bd)
                     fc += 1
                     result = False
             if maxerr is not None and fc >= maxerr:
                 print " (too many errors, giving up)"
                 break
         break
     return result
 
 if __name__ == "__main__":
     parser = optparse.OptionParser("%prog [options] [files]")
     parser.add_option("-w", "--warnings", action="store_true",
                       help="include warning-level checks")
     parser.add_option("-p", "--per-file", type="int",
                       help="max warnings per file")
     parser.add_option("-b", "--blame", action="store_true",
                       help="use annotate to generate blame info")
 
     parser.set_defaults(per_file=15, warnings=False, blame=False)
     (options, args) = parser.parse_args()
 
     if len(args) == 0:
         check = glob.glob("*")
     else:
         check = args
 
     for f in check:
         ret = 0
         if not checkfile(f, maxerr=options.per_file, warnings=options.warnings,
                          blame=options.blame):
             ret = 1
     sys.exit(ret)

tests/test-check-code.t

@@ -1,54 +1,95 b''
   $ cat > correct.py <<EOF
   > def toto(arg1, arg2):
   >     del arg2
   >     return (5 + 6, 9)
   > EOF
   $ cat > wrong.py <<EOF
   > def toto( arg1, arg2):
   >     del(arg2)
   >     return ( 5+6, 9)
   > EOF
   $ cat > quote.py <<EOF
   > # let's use quote in comments
   > (''' ( 4x5 )
   > but """\\''' and finally''',
   > """let's fool checkpatch""", '1+2',
   > '"""', 42+1, """and
   > ( 4-1 ) """, "( 1+1 )\" and ")
   > a, '\\\\\\\\', "\\\\\\" x-2", "c-1"
   > EOF
   $ cat > non-py24.py <<EOF
   > # Using builtins that does not exist in Python 2.4
   > if any():
   >     x = all()
   >     y = format(x)
   > 
   > # Do not complain about our own definition
   > def any(x):
   >     pass
   > EOF
   $ check_code="$TESTDIR"/../contrib/check-code.py
   $ "$check_code" ./wrong.py ./correct.py ./quote.py ./non-py24.py
   ./wrong.py:1:
    > def toto( arg1, arg2):
    gratuitous whitespace in () or []
   ./wrong.py:2:
    >     del(arg2)
    del isn't a function
   ./wrong.py:3:
    >     return ( 5+6, 9)
    missing whitespace in expression
    gratuitous whitespace in () or []
   ./quote.py:5:
    > '"""', 42+1, """and
    missing whitespace in expression
   ./non-py24.py:2:
    > if any():
    any/all/format not available in Python 2.4
   ./non-py24.py:3:
    >     x = all()
    any/all/format not available in Python 2.4
   ./non-py24.py:4:
    >     y = format(x)
    any/all/format not available in Python 2.4
   [1]
+
+  $ cat > is-op.py <<EOF
+  > # is-operator comparing number or string literal
+  > x = None
+  > y = x is 'foo'
+  > y = x is "foo"
+  > y = x is 5346
+  > y = x is -6
+  > y = x is not 'foo'
+  > y = x is not "foo"
+  > y = x is not 5346
+  > y = x is not -6
+  > EOF
+
+  $ "$check_code" ./is-op.py
+  ./is-op.py:3:
+   > y = x is 'foo'
+   object comparison with literal
+  ./is-op.py:4:
+   > y = x is "foo"
+   object comparison with literal
+  ./is-op.py:5:
+   > y = x is 5346
+   object comparison with literal
+  ./is-op.py:6:
+   > y = x is -6
+   object comparison with literal
+  ./is-op.py:7:
+   > y = x is not 'foo'
+   object comparison with literal
+  ./is-op.py:8:
+   > y = x is not "foo"
+   object comparison with literal
+  ./is-op.py:9:
+   > y = x is not 5346
+   object comparison with literal
+  ./is-op.py:10:
+   > y = x is not -6
+   object comparison with literal
+  [1]
+