patch: make extract() a context manager (API)

Previously, this function was creating a temporary file and relying
on callers to unlink it. Yuck.

We convert the function to a context manager and tie the lifetime of
the temporary file to that of the context manager. This changed
indentation not only from the context manager, but also from the
elination of try blocks. It was just easier to split the heart of
extract() into its own function.

The single consumer of this function has been refactored to use it as
a context manager. Code for cleaning up the file in tryimportone()
has also been removed.

.. api::

   ``patch.extract()`` is now a context manager. Callers no longer have
   to worry about deleting the temporary file it creates, as the file is
   tied to the lifetime of the context manager.

Differential Revision: https://phab.mercurial-scm.org/D3306

mercurial/cmdutil.py

@@ -1379,12 +1379,12 b' def tryimportone(ui, repo, patchdata, pa'
     strip = opts["strip"]
     prefix = opts["prefix"]
     sim = float(opts.get('similarity') or 0)
+
     if not tmpname:
-        return (None, None, False)
+        return None, None, False
 
     rejects = False
 
-    try:
         cmdline_message = logmessage(ui, opts)
         if cmdline_message:
             # pickup the cmdline msg
@@ -1511,9 +1511,7 b' def tryimportone(ui, repo, patchdata, pa'
         if n:
             # i18n: refers to a short changeset id
             msg = _('created %s') % short(n)
-        return (msg, n, rejects)
-    finally:
-        os.unlink(tmpname)
+    return msg, n, rejects
 
 # facility to let extensions include additional data in an exported patch
 # list of identifiers to be executed in order

mercurial/commands.py

@@ -3089,8 +3089,7 b' def import_(ui, repo, patch1=None, *patc'
 
             haspatch = False
             for hunk in patch.split(patchfile):
-                patchdata = patch.extract(ui, hunk)
-
+                with patch.extract(ui, hunk) as patchdata:
                 msg, node, rej = cmdutil.tryimportone(ui, repo, patchdata,
                                                       parents, opts,
                                                       msgs, hg.clean)

mercurial/patch.py

@@ -9,6 +9,7 b''
 from __future__ import absolute_import, print_function
 
 import collections
+import contextlib
 import copy
 import difflib
 import email
@@ -192,6 +193,7 b" patchheadermap = [('Date', 'date'),"
                   ('Node ID', 'nodeid'),
                  ]
 
[e-mail]
 def extract(ui, fileobj):
     '''extract patch from data read from fileobj.
 
@@ -209,6 +211,16 b' def extract(ui, fileobj):'
     Any item can be missing from the dictionary. If filename is missing,
     fileobj did not contain a patch. Caller must unlink filename when done.'''
 
+    fd, tmpname = tempfile.mkstemp(prefix='hg-patch-')
+    tmpfp = os.fdopen(fd, r'wb')
+    try:
+        yield _extract(ui, fileobj, tmpname, tmpfp)
+    finally:
+        tmpfp.close()
+        os.unlink(tmpname)
+
+def _extract(ui, fileobj, tmpname, tmpfp):
+
     # attempt to detect the start of a patch
     # (this heuristic is borrowed from quilt)
     diffre = re.compile(br'^(?:Index:[ \t]|diff[ \t]-|RCS file: |'
@@ -218,9 +230,7 b' def extract(ui, fileobj):'
                         re.MULTILINE | re.DOTALL)
 
     data = {}
-    fd, tmpname = tempfile.mkstemp(prefix='hg-patch-')
-    tmpfp = os.fdopen(fd, r'wb')
-    try:
+
         msg = pycompat.emailparser().parse(fileobj)
 
         subject = msg[r'Subject'] and mail.headdecode(msg[r'Subject'])
@@ -294,10 +304,6 b' def extract(ui, fileobj):'
                         tmpfp.write('\n')
             elif not diffs_seen and message and content_type == 'text/plain':
                 message += '\n' + payload
-    except: # re-raises
-        tmpfp.close()
-        os.unlink(tmpname)
-        raise
 
     if subject and not message.startswith(subject):
         message = '%s\n%s' % (subject, message)
@@ -310,8 +316,7 b' def extract(ui, fileobj):'
 
     if diffs_seen:
         data['filename'] = tmpname
-    else:
-        os.unlink(tmpname)
+
     return data
 
 class patchmeta(object):