ignore: separate pattern extraction from match compilation

hgignore files have slightly different syntax from match objects,
e.g. syntax: foo headers, regexp: forms, and re being relre. Put
conversion from hgignore syntax into match syntax into a standalone
function so that it is easier to validate hgignore hunks externally.

mercurial/ignore.py

@@ -1,92 +1,103 b''
 # ignore.py - ignored file handling for mercurial
 #
 # Copyright 2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
 
 from i18n import _
 import util, match
 import re
 
 _commentre = None
 
-def _parselines(fp):
-    for line in fp:
+def ignorepats(lines):
+    '''parse lines (iterable) of .hgignore text, returning a tuple of
+    (patterns, parse errors). These patterns should be given to compile()
+    to be validated and converted into a match function.'''
+    syntaxes = {'re': 'relre:', 'regexp': 'relre:', 'glob': 'relglob:'}
+    syntax = 'relre:'
+    patterns = []
+    warnings = []
+
+    for line in lines:
         if "#" in line:
             global _commentre
             if not _commentre:
                 _commentre = re.compile(r'((^|[^\\])(\\\\)*)#.*')
             # remove comments prefixed by an even number of escapes
             line = _commentre.sub(r'\1', line)
             # fixup properly escaped comments that survived the above
             line = line.replace("\\#", "#")
         line = line.rstrip()
-        if line:
-            yield line
+        if not line:
+            continue
+
+        if line.startswith('syntax:'):
+            s = line[7:].strip()
+            try:
+                syntax = syntaxes[s]
+            except KeyError:
+                warnings.append(_("ignoring invalid syntax '%s'") % s)
+            continue
+        pat = syntax + line
+        for s, rels in syntaxes.iteritems():
+            if line.startswith(rels):
+                pat = line
+                break
+            elif line.startswith(s+':'):
+                pat = rels + line[len(s)+1:]
+                break
+        patterns.append(pat)
+
+    return patterns, warnings
 
 def ignore(root, files, warn):
-    '''return the contents of .hgignore files as a list of patterns.
+    '''return matcher covering patterns in 'files'.
 
     the files parsed for patterns include:
     .hgignore in the repository root
     any additional files specified in the [ui] section of ~/.hgrc
 
     trailing white space is dropped.
     the escape character is backslash.
     comments start with #.
     empty lines are skipped.
 
     lines can be of the following formats:
 
     syntax: regexp # defaults following lines to non-rooted regexps
     syntax: glob   # defaults following lines to non-rooted globs
     re:pattern     # non-rooted regular expression
     glob:pattern   # non-rooted glob
     pattern        # pattern of the current default type'''
 
-    syntaxes = {'re': 'relre:', 'regexp': 'relre:', 'glob': 'relglob:'}
     pats = {}
     for f in files:
         try:
             pats[f] = []
             fp = open(f)
-            syntax = 'relre:'
-            for line in _parselines(fp):
-                if line.startswith('syntax:'):
-                    s = line[7:].strip()
-                    try:
-                        syntax = syntaxes[s]
-                    except KeyError:
-                        warn(_("%s: ignoring invalid syntax '%s'\n") % (f, s))
-                    continue
-                pat = syntax + line
-                for s, rels in syntaxes.iteritems():
-                    if line.startswith(rels):
-                        pat = line
-                        break
-                    elif line.startswith(s+':'):
-                        pat = rels + line[len(s)+1:]
-                        break
-                pats[f].append(pat)
+            pats[f], warnings = ignorepats(fp)
+            for warning in warnings:
+                warn("%s: %s\n" % (f, warning))
         except IOError, inst:
             if f != files[0]:
                 warn(_("skipping unreadable ignore file '%s': %s\n") %
                      (f, inst.strerror))
 
     allpats = []
     [allpats.extend(patlist) for patlist in pats.values()]
     if not allpats:
         return util.never
 
     try:
         ignorefunc = match.match(root, '', [], allpats)
     except util.Abort:
         # Re-raise an exception where the src is the right file
         for f, patlist in pats.iteritems():
             try:
                 match.match(root, '', [], patlist)
             except util.Abort, inst:
                 raise util.Abort('%s: %s' % (f, inst[0]))
 
     return ignorefunc