fixdiv.py

#! /usr/bin/env python

"""fixdiv - tool to fix division operators.

To use this tool, first run `python -Qwarnall yourscript.py 2>warnings'.
This runs the script `yourscript.py' while writing warning messages
about all uses of the classic division operator to the file
`warnings'. The warnings look like this:

 <file>:<line>: DeprecationWarning: classic <type> division

The warnings are written to stderr, so you must use `2>' for the I/O
redirect. I know of no way to redirect stderr on Windows in a DOS
box, so you will have to modify the script to set sys.stderr to some
kind of log file if you want to do this on Windows.

The warnings are not limited to the script; modules imported by the
script may also trigger warnings. In fact a useful technique is to
write a test script specifically intended to exercise all code in a
particular module or set of modules.

Then run `python fixdiv.py warnings'. This first reads the warnings,
looking for classic division warnings, and sorts them by file name and
line number. Then, for each file that received at least one warning,
it parses the file and tries to match the warnings up to the division
operators found in the source code. If it is successful, it writes
its findings to stdout, preceded by a line of dashes and a line of the
form:

 Index: <file>

If the only findings found are suggestions to change a / operator into
a // operator, the output is acceptable input for the Unix 'patch'
program.

Here are the possible messages on stdout (N stands for a line number):

- A plain-diff-style change ('NcN', a line marked by '<', a line
 containing '---', and a line marked by '>'):

 A / operator was found that should be changed to //. This is the
 recommendation when only int and/or long arguments were seen.

- 'True division / operator at line N' and a line marked by '=':

 A / operator was found that can remain unchanged. This is the
 recommendation when only float and/or complex arguments were seen.

- 'Ambiguous / operator (..., ...) at line N', line marked by '?':

 A / operator was found for which int or long as well as float or
 complex arguments were seen. This is highly unlikely; if it occurs,
 you may have to restructure the code to keep the classic semantics,
 or maybe you don't care about the classic semantics.

- 'No conclusive evidence on line N', line marked by '*':

 A / operator was found for which no warnings were seen. This could
 be code that was never executed, or code that was only executed
 with user-defined objects as arguments. You will have to
 investigate further. Note that // can be overloaded separately from
 /, using __floordiv__. True division can also be separately
 overloaded, using __truediv__. Classic division should be the same
 as either of those. (XXX should I add a warning for division on
 user-defined objects, to disambiguate this case from code that was
 never executed?)

- 'Phantom ... warnings for line N', line marked by '*':

 A warning was seen for a line not containing a / operator. The most
 likely cause is a warning about code executed by 'exec' or eval()
 (see note below), or an indirect invocation of the / operator, for
 example via the div() function in the operator module. It could
 also be caused by a change to the file between the time the test
 script was run to collect warnings and the time fixdiv was run.

- 'More than one / operator in line N'; or
 'More than one / operator per statement in lines N-N':

 The scanner found more than one / operator on a single line, or in a
 statement split across multiple lines. Because the warnings
 framework doesn't (and can't) show the offset within the line, and
 the code generator doesn't always give the correct line number for
 operations in a multi-line statement, we can't be sure whether all
 operators in the statement were executed. To be on the safe side,
 by default a warning is issued about this case. In practice, these
 cases are usually safe, and the -m option suppresses these warning.

- 'Can't find the / operator in line N', line marked by '*':

 This really shouldn't happen. It means that the tokenize module
 reported a '/' operator but the line it returns didn't contain a '/'
 character at the indicated position.

- 'Bad warning for line N: XYZ', line marked by '*':

 This really shouldn't happen. It means that a 'classic XYZ
 division' warning was read with XYZ being something other than
 'int', 'long', 'float', or 'complex'.

Notes:

- The augmented assignment operator /= is handled the same way as the
 / operator.

- This tool never looks at the // operator; no warnings are ever
 generated for use of this operator.

- This tool never looks at the / operator when a future division
 statement is in effect; no warnings are generated in this case, and
 because the tool only looks at files for which at least one classic
 division warning was seen, it will never look at files containing a
 future division statement.

- Warnings may be issued for code not read from a file, but executed
 using an exec statement or the eval() function. These may have
 <string> in the filename position, in which case the fixdiv script
 will attempt and fail to open a file named '<string>' and issue a
 warning about this failure; or these may be reported as 'Phantom'
 warnings (see above). You're on your own to deal with these. You
 could make all recommended changes and add a future division
 statement to all affected files, and then re-run the test script; it
 should not issue any warnings. If there are any, and you have a
 hard time tracking down where they are generated, you can use the
 -Werror option to force an error instead of a first warning,
 generating a traceback.

- The tool should be run from the same directory as that from which
 the original script was run, otherwise it won't be able to open
 files given by relative pathnames.
"""

importsys
importgetopt
importre
importtokenize

multi_ok=0

defmain():
try:
opts, args=getopt.getopt(sys.argv[1:], "hm")
exceptgetopt.error, msg:
usage(msg)
return2
foro, ainopts:
ifo=="-h":
print__doc__
return
ifo=="-m":
globalmulti_ok
multi_ok=1
ifnotargs:
usage("at least one file argument is required")
return2
ifargs[1:]:
sys.stderr.write("%s: extra file arguments ignored\n", sys.argv[0])
warnings=readwarnings(args[0])
ifwarningsisNone:
return1
files=warnings.keys()
ifnotfiles:
print"No classic division warnings read from", args[0]
return
files.sort()
exit=None
forfilenameinfiles:
x=process(filename, warnings[filename])
exit=exitorx
returnexit

defusage(msg):
sys.stderr.write("%s: %s\n"% (sys.argv[0], msg))
sys.stderr.write("Usage: %s [-m] warnings\n"%sys.argv[0])
sys.stderr.write("Try `%s -h' for more information.\n"%sys.argv[0])

PATTERN= ("^(.+?):(\d+): DeprecationWarning: "
"classic (int|long|float|complex) division$")

defreadwarnings(warningsfile):
prog=re.compile(PATTERN)
try:
f=open(warningsfile)
exceptIOError, msg:
sys.stderr.write("can't open: %s\n"%msg)
return
warnings= {}
while1:
line=f.readline()
ifnotline:
break
m=prog.match(line)
ifnotm:
ifline.find("division") >=0:
sys.stderr.write("Warning: ignored input "+line)
continue
filename, lineno, what=m.groups()
list=warnings.get(filename)
iflistisNone:
warnings[filename] =list= []
list.append((int(lineno), intern(what)))
f.close()
returnwarnings

defprocess(filename, list):
print"-"*70
assertlist# if this fails, readwarnings() is broken
try:
fp=open(filename)
exceptIOError, msg:
sys.stderr.write("can't open: %s\n"%msg)
return1
print"Index:", filename
f=FileContext(fp)
list.sort()
index=0# list[:index] has been processed, list[index:] is still to do
g=tokenize.generate_tokens(f.readline)
while1:
startlineno, endlineno, slashes=lineinfo=scanline(g)
ifstartlinenoisNone:
break
assertstartlineno<=endlinenoisnotNone
orphans= []
whileindex<len(list) andlist[index][0] <startlineno:
orphans.append(list[index])
index+=1
iforphans:
reportphantomwarnings(orphans, f)
warnings= []
whileindex<len(list) andlist[index][0] <=endlineno:
warnings.append(list[index])
index+=1
ifnotslashesandnotwarnings:
pass
elifslashesandnotwarnings:
report(slashes, "No conclusive evidence")
elifwarningsandnotslashes:
reportphantomwarnings(warnings, f)
else:
iflen(slashes) >1:
ifnotmulti_ok:
rows= []
lastrow=None
for (row, col), lineinslashes:
ifrow==lastrow:
continue
rows.append(row)
lastrow=row
assertrows
iflen(rows) ==1:
print"*** More than one / operator in line", rows[0]
else:
print"*** More than one / operator per statement",
print"in lines %d-%d"% (rows[0], rows[-1])
intlong= []
floatcomplex= []
bad= []
forlineno, whatinwarnings:
ifwhatin ("int", "long"):
intlong.append(what)
elifwhatin ("float", "complex"):
floatcomplex.append(what)
else:
bad.append(what)
lastrow=None
for (row, col), lineinslashes:
ifrow==lastrow:
continue
lastrow=row
line=chop(line)
ifline[col:col+1] !="/":
print"*** Can't find the / operator in line %d:"%row
print"*", line
continue
ifbad:
print"*** Bad warning for line %d:"%row, bad
print"*", line
elifintlongandnotfloatcomplex:
print"%dc%d"% (row, row)
print"<", line
print"---"
print">", line[:col] +"/"+line[col:]
eliffloatcomplexandnotintlong:
print"True division / operator at line %d:"%row
print"=", line
elifintlongandfloatcomplex:
print"*** Ambiguous / operator (%s, %s) at line %d:"% (
"|".join(intlong), "|".join(floatcomplex), row)
print"?", line
fp.close()

defreportphantomwarnings(warnings, f):
blocks= []
lastrow=None
lastblock=None
forrow, whatinwarnings:
ifrow!=lastrow:
lastblock= [row]
blocks.append(lastblock)
lastblock.append(what)
forblockinblocks:
row=block[0]
whats="/".join(block[1:])
print"*** Phantom %s warnings for line %d:"% (whats, row)
f.report(row, mark="*")

defreport(slashes, message):
lastrow=None
for (row, col), lineinslashes:
ifrow!=lastrow:
print"*** %s on line %d:"% (message, row)
print"*", chop(line)
lastrow=row

classFileContext:
def__init__(self, fp, window=5, lineno=1):
self.fp=fp
self.window=5
self.lineno=1
self.eoflookahead=0
self.lookahead= []
self.buffer= []
deffill(self):
whilelen(self.lookahead) <self.windowandnotself.eoflookahead:
line=self.fp.readline()
ifnotline:
self.eoflookahead=1
break
self.lookahead.append(line)
defreadline(self):
self.fill()
ifnotself.lookahead:
return""
line=self.lookahead.pop(0)
self.buffer.append(line)
self.lineno+=1
returnline
def__getitem__(self, index):
self.fill()
bufstart=self.lineno-len(self.buffer)
lookend=self.lineno+len(self.lookahead)
ifbufstart<=index<self.lineno:
returnself.buffer[index-bufstart]
ifself.lineno<=index<lookend:
returnself.lookahead[index-self.lineno]
raiseKeyError
defreport(self, first, last=None, mark="*"):
iflastisNone:
last=first
foriinrange(first, last+1):
try:
line=self[first]
exceptKeyError:
line="<missing line>"
printmark, chop(line)

defscanline(g):
slashes= []
startlineno=None
endlineno=None
fortype, token, start, end, lineing:
endlineno=end[0]
ifstartlinenoisNone:
startlineno=endlineno
iftokenin ("/", "/="):
slashes.append((start, line))
iftype==tokenize.NEWLINE:
break
returnstartlineno, endlineno, slashes

defchop(line):
ifline.endswith("\n"):
returnline[:-1]
else:
returnline

if__name__=="__main__":
sys.exit(main())