i18n: add the tool to check Mercurial specific translation problems in *.po

Existing tool like "msgfmt --check" can check typical translation
problems (missing "%s" in msgstr, for example), but can't check
Mercurial specific ones.

For example, "msgfmt --check" can't check whether the translated
string given to "ui.promptchoice()" is correct or not, even though
problems like below cause run-time error or unexpected behavior:

  - less or more choices than msgid,
  - choices without '&', or
  - choices with '&' followed by none

This patch adds the tool to check Mercurial specific translation
problems in *.po files.

i18n/check-translation.py

@@ -0,0 +1,148 @@
+#!/usr/bin/env python
+#
+# check-translation.py - check Mercurial specific translation problems
+
+import polib
+import re
+
+checkers = []
+
+def checker(level, msgidpat):
+    def decorator(func):
+        if msgidpat:
+            match = re.compile(msgidpat).search
+        else:
+            match = lambda msgid: True
+        checkers.append((func, level))
+        func.match = match
+        return func
+    return decorator
+
+def match(checker, pe):
+    """Examine whether POEntry "pe" is target of specified checker or not
+    """
+    if not checker.match(pe.msgid):
+        return
+    # examine suppression by translator comment
+    nochecker = 'no-%s-check' % checker.__name__
+    for tc in pe.tcomment.split():
+        if nochecker == tc:
+            return
+    return True
+
+####################
+
+def fatalchecker(msgidpat=None):
+    return checker('fatal', msgidpat)
+
+@fatalchecker(r'\$\$')
+def promptchoice(pe):
+    """Check translation of the string given to "ui.promptchoice()"
+
+    >>> pe = polib.POEntry(
+    ...     msgid ='prompt$$missing &sep$$missing &amp$$followed by &none',
+    ...     msgstr='prompt  missing &sep$$missing  amp$$followed by none&')
+    >>> match(promptchoice, pe)
+    True
+    >>> for e in promptchoice(pe): print e
+    number of choices differs between msgid and msgstr
+    msgstr has invalid choice missing '&'
+    msgstr has invalid '&' followed by none
+    """
+    idchoices = [c.rstrip(' ') for c in pe.msgid.split('$$')[1:]]
+    strchoices = [c.rstrip(' ') for c in pe.msgstr.split('$$')[1:]]
+
+    if len(idchoices) != len(strchoices):
+        yield "number of choices differs between msgid and msgstr"
+
+    indices = [(c, c.find('&')) for c in strchoices]
+    if [c for c, i in indices if i == -1]:
+        yield "msgstr has invalid choice missing '&'"
+    if [c for c, i in indices if len(c) == i + 1]:
+        yield "msgstr has invalid '&' followed by none"
+
+####################
+
+def warningchecker(msgidpat=None):
+    return checker('warning', msgidpat)
+
+####################
+
+def check(pofile, fatal=True, warning=False):
+    targetlevel = { 'fatal': fatal, 'warning': warning }
+    targetcheckers = [(checker, level)
+                      for checker, level in checkers
+                      if targetlevel[level]]
+    if not targetcheckers:
+        return []
+
+    detected = []
+    for pe in pofile.translated_entries():
+        errors = []
+        for checker, level in targetcheckers:
+            if match(checker, pe):
+                errors.extend((level, checker.__name__, error)
+                              for error in checker(pe))
+        if errors:
+            detected.append((pe, errors))
+    return detected
+
+########################################
+
+if __name__ == "__main__":
+    import sys
+    import optparse
+
+    optparser = optparse.OptionParser("""%prog [options] pofile ...
+
+This checks Mercurial specific translation problems in specified
+'*.po' files.
+
+Each detected problems are shown in the format below::
+
+    filename:linenum:type(checker): problem detail .....
+
+"type" is "fatal" or "warning". "checker" is the name of the function
+detecting corresponded error.
+
+Checking by checker "foo" on the specific msgstr can be suppressed by
+the "translator comment" like below. Multiple "no-xxxx-check" should
+be separated by whitespaces::
+
+    # no-foo-check
+    msgid = "....."
+    msgstr = "....."
+""")
+    optparser.add_option("", "--warning",
+                         help="show also warning level problems",
+                         action="store_true")
+    optparser.add_option("", "--doctest",
+                         help="run doctest of this tool, instead of check",
+                         action="store_true")
+    (options, args) = optparser.parse_args()
+
+    if options.doctest:
+        import doctest
+        failures, tests = doctest.testmod()
+        sys.exit(failures and 1 or 0)
+
+    # replace polib._POFileParser to show linenum of problematic msgstr
+    class ExtPOFileParser(polib._POFileParser):
+        def process(self, symbol, linenum):
+            super(ExtPOFileParser, self).process(symbol, linenum)
+            if symbol == 'MS': # msgstr
+                self.current_entry.linenum = linenum
+    polib._POFileParser = ExtPOFileParser
+
+    detected = []
+    warning = options.warning
+    for f in args:
+        detected.extend((f, pe, errors)
+                        for pe, errors in check(polib.pofile(f),
+                                                warning=warning))
+    if detected:
+        for f, pe, errors in detected:
+            for level, checker, error in errors:
+                sys.stderr.write('%s:%d:%s(%s): %s\n'
+                                 % (f, pe.linenum, level, checker, error))
+        sys.exit(1)

tests/test-i18n.t

@@ -38,3 +38,10 @@ Test keyword search in translated help text:
   
    pager Verwendet einen externen Pager zum Bl\xc3\xa4ttern in der Ausgabe von Befehlen (esc)
 
+Check Mercurial specific translation problems in each *.po files, and
+tool itself by doctest
+
+  $ cd "$TESTDIR"/../i18n
+  $ python check-translation.py *.po
+  $ python check-translation.py --doctest
+  $ cd $TESTTMP