config parsers as context mangers can now be reentered for locks

Author: boidolr

git/config.py

@@ -133,10 +133,11 @@ def release(self):
         return self._config.release()
 
     def __enter__(self):
+        self._config.__enter__()
         return self
 
     def __exit__(self, exception_type, exception_value, traceback):
-        self.release()
+        self._config.__exit__(exception_type, exception_value, traceback)
 
 
 class GitConfigParser(with_metaclass(MetaParserBuilder, cp.RawConfigParser, object)):
@@ -155,8 +156,7 @@ class GitConfigParser(with_metaclass(MetaParserBuilder, cp.RawConfigParser, obje
     :note:
         The config is case-sensitive even when queried, hence section and option names
         must match perfectly.
-        If used as a context manager, will release the locked file. This parser cannot
-        be used afterwards."""
+        If used as a context manager, will release the locked file."""
 
     #{ Configuration
     # The lock type determines the type of lock to use in new configuration readers.
@@ -206,18 +206,23 @@ def __init__(self, file_or_files, read_only=True, merge_includes=True):
         self._is_initialized = False
         self._merge_includes = merge_includes
         self._lock = None
-
-        if not read_only:
-            if isinstance(file_or_files, (tuple, list)):
-                raise ValueError(
-                    "Write-ConfigParsers can operate on a single file only, multiple files have been passed")
-            # END single file check
-
-            if not isinstance(file_or_files, string_types):
-                file_or_files = file_or_files.name
-            # END get filename from handle/stream
-            # initialize lock base - we want to write
-            self._lock = self.t_lock(file_or_files)
+        self._aquire_lock()
+
+    def _aquire_lock(self):
+        if not self._read_only:
+            if not self._lock:
+                if isinstance(self._file_or_files, (tuple, list)):
+                    raise ValueError(
+                        "Write-ConfigParsers can operate on a single file only, multiple files have been passed")
+                # END single file check
+
+                file_or_files = self._file_or_files
+                if not isinstance(self._file_or_files, string_types):
+                    file_or_files = self._file_or_files.name
+                # END get filename from handle/stream
+                # initialize lock base - we want to write
+                self._lock = self.t_lock(file_or_files)
+            # END lock check
 
             self._lock._obtain_lock()
         # END read-only check
@@ -228,6 +233,7 @@ def __del__(self):
         self.release()
 
     def __enter__(self):
+        self._aquire_lock()
         return self
 
     def __exit__(self, exception_type, exception_value, traceback):

git/test/test_config.py

@@ -72,6 +72,23 @@ def test_read_write(self):
             w_config.release()
         # END for each filename
 
+    @with_rw_directory
+    def test_lock_reentry(self, rw_dir):
+        fpl = os.path.join(rw_dir, 'l')
+        gcp = GitConfigParser(fpl, read_only=False)
+        with gcp as cw:
+            cw.set_value('include', 'some_value', 'a')
+        # entering again locks the file again...
+        with gcp as cw:
+            cw.set_value('include', 'some_other_value', 'b')
+            # ...so creating an additional config writer must fail due to exclusive access
+            self.failUnlessRaises(IOError, GitConfigParser, fpl, read_only=False)
+        # but work when the lock is removed
+        with GitConfigParser(fpl, read_only=False):
+            assert os.path.exists(fpl)
+            # reentering with an existing lock must fail due to exclusive access
+            self.failUnlessRaises(IOError, gcp.__enter__)
+
     def test_multi_line_config(self):
         file_obj = self._to_memcache(fixture_path("git_config_with_comments"))
         config = GitConfigParser(file_obj, read_only=False)