Fix exception causes in 7 modules

git/refs/symbolic.py

@@ -219,8 +219,8 @@ def set_commit(self, commit, logmsg=None):
         else:
             try:
                 invalid_type = self.repo.rev_parse(commit).type != Commit.type
-            except (BadObject, BadName):
-                raise ValueError("Invalid object: %s" % commit)
+            except (BadObject, BadName) as e:
+                raise ValueError("Invalid object: %s" % commit) from e
             # END handle exception
         # END verify type
 
@@ -301,8 +301,8 @@ def set_reference(self, ref, logmsg=None):
             try:
                 obj = self.repo.rev_parse(ref + "^{}")    # optionally deref tags
                 write_value = obj.hexsha
-            except (BadObject, BadName):
-                raise ValueError("Could not extract object from %s" % ref)
+            except (BadObject, BadName) as e:
+                raise ValueError("Could not extract object from %s" % ref) from e
             # END end try string
         else:
             raise ValueError("Unrecognized Value: %r" % ref)

git/remote.py

@@ -146,8 +146,8 @@ def _from_line(cls, remote, line):
         # control character handling
         try:
             flags |= cls._flag_map[control_character]
-        except KeyError:
-            raise ValueError("Control character %r unknown as parsed from line %r" % (control_character, line))
+        except KeyError as e:
+            raise ValueError("Control character %r unknown as parsed from line %r" % (control_character, line)) from e
         # END handle control character
 
         # from_to handling
@@ -296,15 +296,15 @@ def _from_line(cls, repo, line, fetch_line):
         try:
             _new_hex_sha, _fetch_operation, fetch_note = fetch_line.split("\t")
             ref_type_name, fetch_note = fetch_note.split(' ', 1)
-        except ValueError:  # unpack error
-            raise ValueError("Failed to parse FETCH_HEAD line: %r" % fetch_line)
+        except ValueError as e:  # unpack error
+            raise ValueError("Failed to parse FETCH_HEAD line: %r" % fetch_line) from e
 
         # parse flags from control_character
         flags = 0
         try:
             flags |= cls._flag_map[control_character]
-        except KeyError:
-            raise ValueError("Control character %r unknown as parsed from line %r" % (control_character, line))
+        except KeyError as e:
+            raise ValueError("Control character %r unknown as parsed from line %r" % (control_character, line)) from e
         # END control char exception handling
 
         # parse operation string for more info - makes no sense for symbolic refs, but we parse it anyway

git/repo/base.py

@@ -341,8 +341,8 @@ def submodule(self, name):
         :raise ValueError: If no such submodule exists"""
         try:
             return self.submodules[name]
-        except IndexError:
-            raise ValueError("Didn't find submodule named %r" % name)
+        except IndexError as e:
+            raise ValueError("Didn't find submodule named %r" % name) from e
         # END exception handling
 
     def create_submodule(self, *args, **kwargs):

git/repo/fun.py

@@ -251,16 +251,16 @@ def rev_parse(repo, rev):
                 try:
                     # transform reversed index into the format of our revlog
                     revlog_index = -(int(output_type) + 1)
-                except ValueError:
+                except ValueError as e:
                     # TODO: Try to parse the other date options, using parse_date
                     # maybe
-                    raise NotImplementedError("Support for additional @{...} modes not implemented")
+                    raise NotImplementedError("Support for additional @{...} modes not implemented") from e
                 # END handle revlog index
 
                 try:
                     entry = ref.log_entry(revlog_index)
-                except IndexError:
-                    raise IndexError("Invalid revlog index: %i" % revlog_index)
+                except IndexError as e:
+                    raise IndexError("Invalid revlog index: %i" % revlog_index) from e
                 # END handle index out of bound
 
                 obj = Object.new_from_sha(repo, hex_to_bin(entry.newhexsha))
@@ -324,8 +324,10 @@ def rev_parse(repo, rev):
             else:
                 raise ValueError("Invalid token: %r" % token)
             # END end handle tag
-        except (IndexError, AttributeError):
-            raise BadName("Invalid revision spec '%s' - not enough parent commits to reach '%s%i'" % (rev, token, num))
+        except (IndexError, AttributeError) as e:
+            raise BadName(
+                "Invalid revision spec '%s' - not enough "
+                "parent commits to reach '%s%i'" % (rev, token, num)) from e
         # END exception handling
     # END parse loop
 

git/test/test_base.py

@@ -129,8 +129,8 @@ def test_add_unicode(self, rw_repo):
         # verify first that we could encode file name in this environment
         try:
             file_path.encode(sys.getfilesystemencoding())
-        except UnicodeEncodeError:
-            raise SkipTest("Environment doesn't support unicode filenames")
+        except UnicodeEncodeError as e:
+            raise SkipTest("Environment doesn't support unicode filenames") from e
 
         with open(file_path, "wb") as fp:
             fp.write(b'something')

git/test/test_config.py

@@ -98,10 +98,10 @@ def test_includes_order(self):
             assert r_config.get_value('diff', 'tool') == "meld"
             try:
                 assert r_config.get_value('sec', 'var1') == "value1_main"
-            except AssertionError:
+            except AssertionError as e:
                 raise SkipTest(
                     'Known failure -- included values are not in effect right away'
-                )
+                ) from e
 
     @with_rw_directory
     def test_lock_reentry(self, rw_dir):

git/util.py

@@ -94,7 +94,7 @@ def onerror(func, path, exc_info):
             func(path)  # Will scream if still not possible to delete.
         except Exception as ex:
             if HIDE_WINDOWS_KNOWN_ERRORS:
-                raise SkipTest("FIXME: fails with: PermissionError\n  {}".format(ex))
+                raise SkipTest("FIXME: fails with: PermissionError\n  {}".format(ex)) from ex
             raise
 
     return shutil.rmtree(path, False, onerror)
@@ -746,7 +746,7 @@ def _obtain_lock_or_raise(self):
             fd = os.open(lock_file, flags, 0)
             os.close(fd)
         except OSError as e:
-            raise IOError(str(e))
+            raise IOError(str(e)) from e
 
         self._owns_lock = True
 
@@ -801,19 +801,19 @@ def _obtain_lock(self):
         while True:
             try:
                 super(BlockingLockFile, self)._obtain_lock()
-            except IOError:
+            except IOError as e:
                 # synity check: if the directory leading to the lockfile is not
                 # readable anymore, raise an exception
                 curtime = time.time()
                 if not osp.isdir(osp.dirname(self._lock_file_path())):
                     msg = "Directory containing the lockfile %r was not readable anymore after waiting %g seconds" % (
                         self._lock_file_path(), curtime - starttime)
-                    raise IOError(msg)
+                    raise IOError(msg) from e
                 # END handle missing directory
 
                 if curtime >= maxtime:
                     msg = "Waited %g seconds for lock at %r" % (maxtime - starttime, self._lock_file_path())
-                    raise IOError(msg)
+                    raise IOError(msg) from e
                 # END abort if we wait too long
                 time.sleep(self._check_interval)
             else:
@@ -878,8 +878,8 @@ def __getitem__(self, index):
 
         try:
             return getattr(self, index)
-        except AttributeError:
-            raise IndexError("No item found with id %r" % (self._prefix + index))
+        except AttributeError as e:
+            raise IndexError("No item found with id %r" % (self._prefix + index)) from e
         # END handle getattr
 
     def __delitem__(self, index):