Merge pull request #3042 from mroutis/refactor-exceptions

py3: refactor exceptions

dvc/api.py

@@ -104,9 +104,8 @@ def summon(name, repo=None, rev=None, summon_file="dvcsummon.yaml", args=None):
             info = obj["summon"]
         except SummonError as exc:
             raise SummonError(
-                str(exc) + " at '{}' in '{}'".format(summon_file, repo),
-                cause=exc.cause,
-            )
+                str(exc) + " at '{}' in '{}'".format(summon_file, repo)
+            ) from exc
 
         _pull_dependencies(_repo, info.get("deps", []))
 
@@ -138,7 +137,7 @@ def _get_object_from_summon_file(name, path):
     except FileMissingError:
         raise SummonError("Summon file not found")
     except ruamel.yaml.YAMLError as exc:
-        raise SummonError("Failed to parse summon file", exc)
+        raise SummonError("Failed to parse summon file") from exc
     except Invalid as exc:
         raise SummonError(str(exc))
 

dvc/config.py

@@ -17,19 +17,14 @@ logger = logging.getLogger(__name__)
 
 
 class ConfigError(DvcException):
-    """DVC config exception.
+    """DVC config exception."""
 
-    Args:
-        msg (str): error message.
-        cause (Exception): optional exception that has caused this error.
-    """
-
-    def __init__(self, msg, cause=None):
-        super().__init__("config file error: {}".format(msg), cause=cause)
+    def __init__(self, msg):
+        super().__init__("config file error: {}".format(msg))
 
 
 class NoRemoteError(ConfigError):
-    def __init__(self, command, cause=None):
+    def __init__(self, command):
         msg = (
             "no remote specified. Setup default remote with\n"
             "    dvc config core.remote <name>\n"
@@ -37,7 +32,7 @@ class NoRemoteError(ConfigError):
             "    dvc {} -r <name>\n".format(command)
         )
 
-        super().__init__(msg, cause=cause)
+        super().__init__(msg)
 
 
 def supported_cache_type(types):
@@ -392,7 +387,7 @@ class Config(object):  # pylint: disable=too-many-instance-attributes
         try:
             d = self.COMPILED_SCHEMA(d)
         except Invalid as exc:
-            raise ConfigError(str(exc), cause=exc)
+            raise ConfigError(str(exc)) from exc
         self.config = configobj.ConfigObj(d, write_empty_values=True)
 
     def save(self, config=None):

dvc/exceptions.py

@@ -1,29 +1,10 @@
 """Exceptions raised by the dvc."""
 
-import traceback
-
 from dvc.utils import relpath
 
 
 class DvcException(Exception):
-    """Base class for all dvc exceptions.
-
-    Args:
-        msg (unicode): message for this exception.
-        cause (Exception): optional cause exception.
-    """
-
-    def __init__(self, msg, cause=None):
-        # NOTE: unlike python 3, python 2 doesn't have built-in support
-        # for chained exceptions, so we are using our own implementation.
-        self.cause = cause
-        self.cause_tb = None
-        if cause:
-            try:
-                self.cause_tb = traceback.format_exc()
-            except AttributeError:  # pragma: no cover
-                pass
-        super().__init__(msg)
+    """Base class for all dvc exceptions."""
 
 
 class OutputDuplicationError(DvcException):
@@ -109,8 +90,7 @@ class ArgumentDuplicationError(DvcException):
 
     def __init__(self, path):
         assert isinstance(path, str)
-        msg = "file '{}' is specified more than once."
-        super().__init__(msg.format(path))
+        super().__init__("file '{}' is specified more than once.".format(path))
 
 
 class MoveNotDataSourceError(DvcException):
@@ -175,15 +155,13 @@ class ConfirmRemoveError(DvcException):
 
 
 class InitError(DvcException):
-    def __init__(self, msg):
-        super().__init__(msg)
+    pass
 
 
 class ReproductionError(DvcException):
-    def __init__(self, dvc_file_name, ex):
+    def __init__(self, dvc_file_name):
         self.path = dvc_file_name
-        msg = "failed to reproduce '{}'".format(dvc_file_name)
-        super().__init__(msg, cause=ex)
+        super().__init__("failed to reproduce '{}'".format(dvc_file_name))
 
 
 class BadMetricError(DvcException):
@@ -205,12 +183,11 @@ class NoMetricsError(DvcException):
 
 
 class StageFileCorruptedError(DvcException):
-    def __init__(self, path, cause=None):
+    def __init__(self, path):
         path = relpath(path)
         super().__init__(
             "unable to read DVC-file: {} "
-            "YAML file structure is corrupted".format(path),
-            cause=cause,
+            "YAML file structure is corrupted".format(path)
         )
 
 
@@ -236,10 +213,8 @@ class OverlappingOutputPathsError(DvcException):
 
 
 class CheckoutErrorSuggestGit(DvcException):
-    def __init__(self, target, cause):
-        super().__init__(
-            "Did you mean `git checkout {}`?".format(target), cause=cause
-        )
+    def __init__(self, target):
+        super().__init__("Did you mean `git checkout {}`?".format(target))
 
 
 class ETagMismatchError(DvcException):
@@ -251,10 +226,9 @@ class ETagMismatchError(DvcException):
 
 
 class FileMissingError(DvcException):
-    def __init__(self, path, cause=None):
+    def __init__(self, path):
         super().__init__(
-            "Can't find '{}' neither locally nor on remote".format(path),
-            cause=cause,
+            "Can't find '{}' neither locally nor on remote".format(path)
         )
 
 

dvc/logger.py

@@ -114,11 +114,11 @@ class ColorFormatter(logging.Formatter):
         tb_list = [tb]
 
         # NOTE: parsing chained exceptions. See dvc/exceptions.py for more info
-        while hasattr(exc, "cause") and exc.cause:
-            exc_list.append(str(exc.cause))
+        while hasattr(exc, "__cause__") and exc.__cause__:
+            exc_list.append(str(exc.__cause__))
             if hasattr(exc, "cause_tb") and exc.cause_tb:
                 tb_list.insert(0, str(exc.cause_tb))
-            exc = exc.cause
+            exc = exc.__cause__
 
         return exc_list, tb_list
 

dvc/remote/base.py

@@ -63,10 +63,9 @@ class RemoteMissingDepsError(DvcException):
 
 
 class DirCacheError(DvcException):
-    def __init__(self, checksum, cause=None):
+    def __init__(self, checksum):
         super().__init__(
-            "Failed to load dir cache for checksum: '{}'.".format(checksum),
-            cause=cause,
+            "Failed to load dir cache for checksum: '{}'.".format(checksum)
         )
 
 
@@ -264,7 +263,7 @@ class RemoteBASE(object):
             with self.cache.open(path_info, "r") as fobj:
                 d = json.load(fobj)
         except (ValueError, FileNotFoundError) as exc:
-            raise DirCacheError(checksum, cause=exc)
+            raise DirCacheError(checksum) from exc
 
         if not isinstance(d, list):
             msg = "dir cache file format error '{}' [skipping the file]"

dvc/remote/gdrive.py

@@ -19,18 +19,15 @@ FOLDER_MIME_TYPE = "application/vnd.google-apps.folder"
 
 
 class GDriveRetriableError(DvcException):
-    def __init__(self, msg, cause=None):
-        super().__init__(msg, cause=cause)
+    pass
 
 
 class GDriveAccessTokenRefreshError(DvcException):
-    def __init__(self, msg, cause=None):
-        super().__init__(msg, cause=cause)
+    pass
 
 
 class GDriveMissedCredentialKeyError(DvcException):
-    def __init__(self, msg, cause=None):
-        super().__init__(msg, cause=cause)
+    pass
 
 
 @decorator
@@ -208,21 +205,22 @@ class RemoteGDrive(RemoteBASE):
 
             try:
                 gauth.CommandLineAuth()
-            except RefreshError as e:
+            except RefreshError as exc:
                 raise GDriveAccessTokenRefreshError(
-                    "Google Drive's access token refreshment is failed", e
-                )
-            except KeyError as e:
+                    "Google Drive's access token refreshment is failed"
+                ) from exc
+            except KeyError as exc:
                 raise GDriveMissedCredentialKeyError(
                     "Google Drive's user credentials file '{}' "
                     "misses value for key '{}'".format(
-                        self.gdrive_user_credentials_path, str(e)
-                    ),
-                    e,
+                        self.gdrive_user_credentials_path, str(exc)
+                    )
                 )
             # Handle pydrive.auth.AuthenticationError and others auth failures
-            except Exception as e:
-                raise DvcException("Google Drive authentication failed", e)
+            except Exception as exc:
+                raise DvcException(
+                    "Google Drive authentication failed"
+                ) from exc
             finally:
                 if os.getenv(RemoteGDrive.GDRIVE_USER_CREDENTIALS_DATA):
                     os.remove(self.gdrive_user_credentials_path)

dvc/remote/s3.py

@@ -87,8 +87,8 @@ class RemoteS3(RemoteBASE):
             obj = s3.head_object(Bucket=bucket, Key=path, *args, **kwargs)
         except Exception as exc:
             raise DvcException(
-                "s3://{}/{} does not exist".format(bucket, path), exc
-            )
+                "s3://{}/{} does not exist".format(bucket, path)
+            ) from exc
         return obj
 
     @classmethod

dvc/remote/ssh/connection.py

@@ -103,14 +103,13 @@ class SSHConnection:
         if tail:
             try:
                 self.sftp.mkdir(path)
-            except IOError as e:
+            except IOError as exc:
                 # Since paramiko errors are very vague we need to recheck
                 # whether it's because path already exists or something else
-                if e.errno == errno.EACCES or not self.exists(path):
+                if exc.errno == errno.EACCES or not self.exists(path):
                     raise DvcException(
-                        "unable to create remote directory '{}'".format(path),
-                        cause=e,
-                    )
+                        "unable to create remote directory '{}'".format(path)
+                    ) from exc
 
     def walk(self, directory, topdown=True):
         # NOTE: original os.walk() implementation [1] with default options was
@@ -123,9 +122,8 @@ class SSHConnection:
             raise DvcException(
                 "couldn't get the '{}' remote directory files list".format(
                     directory
-                ),
-                cause=exc,
-            )
+                )
+            ) from exc
 
         dirs = []
         nondirs = []

dvc/repo/__init__.py

@@ -444,24 +444,24 @@ class Repo(object):
         cause = None
         try:
             out, = self.find_outs_by_path(path)
-        except OutputNotFoundError as e:
+        except OutputNotFoundError as exc:
             out = None
-            cause = e
+            cause = exc
 
         if out and out.use_cache:
             try:
                 with self._open_cached(out, remote, mode, encoding) as fd:
                     yield fd
                 return
-            except FileNotFoundError as e:
-                raise FileMissingError(relpath(path, self.root_dir), cause=e)
+            except FileNotFoundError as exc:
+                raise FileMissingError(relpath(path, self.root_dir)) from exc
 
         if self.tree.exists(path):
             with self.tree.open(path, mode, encoding) as fd:
                 yield fd
             return
 
-        raise FileMissingError(relpath(path, self.root_dir), cause=cause)
+        raise FileMissingError(relpath(path, self.root_dir)) from cause
 
     def _open_cached(self, out, remote=None, mode="r", encoding=None):
         if out.isdir():

dvc/repo/checkout.py

@@ -49,7 +49,7 @@ def _checkout(
         except (StageFileDoesNotExistError, StageFileBadNameError) as exc:
             if not target:
                 raise
-            raise CheckoutErrorSuggestGit(target, exc)
+            raise CheckoutErrorSuggestGit(target) from exc
 
     total = get_all_files_numbers(pairs)
     if total == 0:

dvc/repo/reproduce.py

@@ -162,6 +162,6 @@ def _reproduce_stages(
                 kwargs["force"] = True
 
             result.extend(ret)
-        except Exception as ex:
-            raise ReproductionError(st.relpath, ex)
+        except Exception as exc:
+            raise ReproductionError(st.relpath) from exc
     return result

dvc/rwlock.py

@@ -17,18 +17,17 @@ SCHEMA = Schema({"write": {str: INFO_SCHEMA}, "read": {str: [INFO_SCHEMA]}})
 
 
 class RWLockFileCorruptedError(DvcException):
-    def __init__(self, path, cause):
+    def __init__(self, path):
         super().__init__(
             "Unable to read RWLock-file '{}'. JSON structure is "
-            "corrupted".format(relpath(path)),
-            cause=cause,
+            "corrupted".format(relpath(path))
         )
 
 
 class RWLockFileFormatError(DvcException):
-    def __init__(self, path, cause):
+    def __init__(self, path):
         super().__init__(
-            "RWLock-file '{}' format error.".format(relpath(path)), cause=cause
+            "RWLock-file '{}' format error.".format(relpath(path))
         )
 
 
@@ -42,9 +41,9 @@ def _edit_rwlock(lock_dir):
     except FileNotFoundError:
         lock = SCHEMA({})
     except json.JSONDecodeError as exc:
-        raise RWLockFileCorruptedError(path, cause=exc)
+        raise RWLockFileCorruptedError(path) from exc
     except Invalid as exc:
-        raise RWLockFileFormatError(path, cause=exc)
+        raise RWLockFileFormatError(path) from exc
     lock = defaultdict(dict, lock)
     lock["read"] = defaultdict(list, lock["read"])
     lock["write"] = defaultdict(dict, lock["write"])

dvc/scm/base.py

@@ -22,17 +22,14 @@ class FileNotInCommitError(SCMError):
 
 
 class CloneError(SCMError):
-    def __init__(self, url, path, cause):
-        super().__init__(
-            "Failed to clone repo '{}' to '{}'".format(url, path), cause=cause
-        )
+    def __init__(self, url, path):
+        super().__init__("Failed to clone repo '{}' to '{}'".format(url, path))
 
 
 class RevError(SCMError):
-    def __init__(self, url, rev, cause):
+    def __init__(self, url, rev):
         super().__init__(
-            "Failed to access revision '{}' for repo '{}'".format(rev, url),
-            cause=cause,
+            "Failed to access revision '{}' for repo '{}'".format(rev, url)
         )
 
 

dvc/scm/git/__init__.py

@@ -85,7 +85,7 @@ class Git(Base):
             )
             tmp_repo.close()
         except git.exc.GitCommandError as exc:
-            raise CloneError(url, to_path, exc)
+            raise CloneError(url, to_path) from exc
 
         # NOTE: using our wrapper to make sure that env is fixed in __init__
         repo = Git(to_path)
@@ -94,7 +94,7 @@ class Git(Base):
             try:
                 repo.checkout(rev)
             except git.exc.GitCommandError as exc:
-                raise RevError(url, rev, exc)
+                raise RevError(url, rev) from exc
 
         return repo
 
@@ -331,8 +331,8 @@ class Git(Base):
             commits.append(b_commit)
             trees[DIFF_A_TREE] = self.get_tree(commits[0])
             trees[DIFF_B_TREE] = self.get_tree(commits[1])
-        except (BadName, BadObject) as e:
-            raise SCMError("git problem", cause=e)
+        except (BadName, BadObject) as exc:
+            raise SCMError("git problem") from exc
         return trees, commits
 
     def get_diff_trees(self, a_ref, b_ref=None):

dvc/scm/git/tree.py

@@ -104,9 +104,8 @@ class GitTree(BaseTree):
             raise DvcException(
                 "revision '{}' not found in git '{}'".format(
                     self.rev, os.path.relpath(self.git.working_dir)
-                ),
-                cause=exc,
-            )
+                )
+            ) from exc
 
         if not path or path == ".":
             return tree

dvc/stage.py

@@ -71,8 +71,7 @@ class StageFileIsNotDvcFileError(DvcException):
 
 
 class StageFileBadNameError(DvcException):
-    def __init__(self, msg):
-        super().__init__(msg)
+    pass
 
 
 class StagePathOutsideError(DvcException):

dvc/system.py

@@ -31,7 +31,7 @@ class System(object):
                 os.link(source, link_name)
                 return
             except Exception as exc:
-                raise DvcException("link", cause=exc)
+                raise DvcException("link") from exc
 
         CreateHardLink = ctypes.windll.kernel32.CreateHardLinkW
         CreateHardLink.argtypes = [
@@ -43,7 +43,7 @@ class System(object):
 
         res = CreateHardLink(link_name, source, None)
         if res == 0:
-            raise DvcException("CreateHardLinkW", cause=ctypes.WinError())
+            raise DvcException("CreateHardLinkW") from ctypes.WinError()
 
     @staticmethod
     def symlink(source, link_name):
@@ -69,7 +69,7 @@ class System(object):
         func.restype = ctypes.c_ubyte
 
         if func(link_name, source, flags) == 0:
-            raise DvcException("CreateSymbolicLinkW", cause=ctypes.WinError())
+            raise DvcException("CreateSymbolicLinkW") from ctypes.WinError()
 
     @staticmethod
     def _reflink_darwin(src, dst):

dvc/utils/stage.py

@@ -19,7 +19,7 @@ def parse_stage(text, path):
     try:
         return yaml.load(text, Loader=SafeLoader) or {}
     except yaml.error.YAMLError as exc:
-        raise StageFileCorruptedError(path, cause=exc)
+        raise StageFileCorruptedError(path) from exc
 
 
 def parse_stage_for_update(text, path):
@@ -35,7 +35,7 @@ def parse_stage_for_update(text, path):
         yaml = YAML()
         return yaml.load(text) or {}
     except YAMLError as exc:
-        raise StageFileCorruptedError(path, cause=exc)
+        raise StageFileCorruptedError(path) from exc
 
 
 def dump_stage_file(path, data):

tests/func/test_checkout.py

@@ -392,15 +392,15 @@ class TestCheckoutSuggestGit(TestRepro):
             self.dvc.checkout(targets=["gitbranch"])
         except DvcException as exc:
             self.assertIsInstance(exc, CheckoutErrorSuggestGit)
-            self.assertIsInstance(exc.cause, StageFileDoesNotExistError)
-            self.assertIsNone(exc.cause.cause)
+            self.assertIsInstance(exc.__cause__, StageFileDoesNotExistError)
+            self.assertIsNone(exc.__cause__.__cause__)
 
         try:
             self.dvc.checkout(targets=[self.FOO])
         except DvcException as exc:
             self.assertIsInstance(exc, CheckoutErrorSuggestGit)
-            self.assertIsInstance(exc.cause, StageFileBadNameError)
-            self.assertIsNone(exc.cause.cause)
+            self.assertIsInstance(exc.__cause__, StageFileBadNameError)
+            self.assertIsNone(exc.__cause__.__cause__)
 
 
 class TestCheckoutTargetRecursiveShouldNotRemoveOtherUsedFiles(TestDvc):

tests/unit/test_logger.py

@@ -107,11 +107,10 @@ class TestColorFormatter:
             try:
                 raise Exception("first")
             except Exception as exc:
-                first_traceback = traceback.format_exc()
                 try:
-                    raise DvcException("second", cause=exc)
+                    raise DvcException("second") from exc
                 except DvcException:
-                    second_traceback = traceback.format_exc()
+                    stack_trace = traceback.format_exc()
                     logger.exception("message")
 
             expected = (
@@ -119,13 +118,12 @@ class TestColorFormatter:
                 "{red}{line}{nc}\n"
                 "{stack_trace}"
                 "{red}{line}{nc}\n".format(
-                    line="-" * 60,
-                    stack_trace="\n".join([first_traceback, second_traceback]),
-                    **colors
+                    line="-" * 60, stack_trace=stack_trace, **colors
                 )
             )
-
             assert expected == formatter.format(caplog.records[0])
+            assert "Exception: first" in stack_trace
+            assert "dvc.exceptions.DvcException: second" in stack_trace
 
     def test_progress_awareness(self, mocker, capsys, caplog):
         from dvc.progress import Tqdm