Fix exception causes all over the codebase

10 files changed, 51 insertions, 41 deletions

diff --git a/changelog.d/2199.misc.rst b/changelog.d/2199.misc.rst
new file mode 100644
index 00000000..f795256b
--- /dev/null
+++ b/changelog.d/2199.misc.rst
@@ -0,0 +1 @@
+Fix exception causes all over the codebase by using ``raise new_exception from old_exception``
\ No newline at end of file
diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index 2c589d55..c40f184a 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -1378,7 +1378,7 @@ def evaluate_marker(text, extra=None):
         marker = packaging.markers.Marker(text)
         return marker.evaluate()
     except packaging.markers.InvalidMarker as e:
-        raise SyntaxError(e)
+        raise SyntaxError(e) from e
 
 
 class NullProvider:
@@ -2287,8 +2287,8 @@ def declare_namespace(packageName):
                 __import__(parent)
             try:
                 path = sys.modules[parent].__path__
-            except AttributeError:
-                raise TypeError("Not a package:", parent)
+            except AttributeError as e:
+                raise TypeError("Not a package:", parent) from e
 
         # Track what packages are namespaces, so when new path items are added,
         # they can be updated
@@ -2468,7 +2468,7 @@ class EntryPoint:
         try:
             return functools.reduce(getattr, self.attrs, module)
         except AttributeError as exc:
-            raise ImportError(str(exc))
+            raise ImportError(str(exc)) from exc
 
     def require(self, env=None, installer=None):
         if self.extras and not self.dist:
@@ -2688,14 +2688,14 @@ class Distribution:
     def version(self):
         try:
             return self._version
-        except AttributeError:
+        except AttributeError as e:
             version = self._get_version()
             if version is None:
                 path = self._get_metadata_path_for_display(self.PKG_INFO)
                 msg = (
                     "Missing 'Version:' header and/or {} file at path: {}"
                 ).format(self.PKG_INFO, path)
-                raise ValueError(msg, self)
+                raise ValueError(msg, self) from e
 
             return version
 
@@ -2748,10 +2748,10 @@ class Distribution:
         for ext in extras:
             try:
                 deps.extend(dm[safe_extra(ext)])
-            except KeyError:
+            except KeyError as e:
                 raise UnknownExtra(
                     "%s has no such extra feature %r" % (self, ext)
-                )
+                ) from e
         return deps
 
     def _get_metadata_path_for_display(self, name):
@@ -3109,7 +3109,7 @@ class Requirement(packaging.requirements.Requirement):
         try:
             super(Requirement, self).__init__(requirement_string)
         except packaging.requirements.InvalidRequirement as e:
-            raise RequirementParseError(str(e))
+            raise RequirementParseError(str(e)) from e
         self.unsafe_name = self.name
         project_name = safe_name(self.name)
         self.project_name, self.key = project_name, project_name.lower()
diff --git a/setuptools/archive_util.py b/setuptools/archive_util.py
index 64528ca7..0ce190b8 100644
--- a/setuptools/archive_util.py
+++ b/setuptools/archive_util.py
@@ -134,10 +134,10 @@ def unpack_tarfile(filename, extract_dir, progress_filter=default_filter):
     """
     try:
         tarobj = tarfile.open(filename)
-    except tarfile.TarError:
+    except tarfile.TarError as e:
         raise UnrecognizedFormat(
             "%s is not a compressed or uncompressed tar file" % (filename,)
-        )
+        ) from e
     with contextlib.closing(tarobj):
         # don't do any chowning!
         tarobj.chown = lambda *args: None
diff --git a/setuptools/command/easy_install.py b/setuptools/command/easy_install.py
index 27b4558b..8890ec88 100644
--- a/setuptools/command/easy_install.py
+++ b/setuptools/command/easy_install.py
@@ -356,8 +356,10 @@ class easy_install(Command):
                 self.optimize = int(self.optimize)
                 if not (0 <= self.optimize <= 2):
                     raise ValueError
-            except ValueError:
-                raise DistutilsOptionError("--optimize must be 0, 1, or 2")
+            except ValueError as e:
+                raise DistutilsOptionError(
+                    "--optimize must be 0, 1, or 2"
+                ) from e
 
         if self.editable and not self.build_directory:
             raise DistutilsArgError(
@@ -765,9 +767,9 @@ class easy_install(Command):
                 [requirement], self.local_index, self.easy_install
             )
         except DistributionNotFound as e:
-            raise DistutilsError(str(e))
+            raise DistutilsError(str(e)) from e
         except VersionConflict as e:
-            raise DistutilsError(e.report())
+            raise DistutilsError(e.report()) from e
         if self.always_copy or self.always_copy_from:
             # Force all the relevant distros to be copied or activated
             for dist in distros:
@@ -1156,7 +1158,9 @@ class easy_install(Command):
         try:
             run_setup(setup_script, args)
         except SystemExit as v:
-            raise DistutilsError("Setup script exited with %s" % (v.args[0],))
+            raise DistutilsError(
+                "Setup script exited with %s" % (v.args[0],)
+            ) from v
 
     def build_and_install(self, setup_script, setup_base):
         args = ['bdist_egg', '--dist-dir']
diff --git a/setuptools/command/egg_info.py b/setuptools/command/egg_info.py
index 7fa89541..0855207c 100644
--- a/setuptools/command/egg_info.py
+++ b/setuptools/command/egg_info.py
@@ -208,11 +208,11 @@ class egg_info(InfoCommon, Command):
             list(
                 parse_requirements(spec % (self.egg_name, self.egg_version))
             )
-        except ValueError:
+        except ValueError as e:
             raise distutils.errors.DistutilsOptionError(
                 "Invalid distribution name or version syntax: %s-%s" %
                 (self.egg_name, self.egg_version)
-            )
+            ) from e
 
         if self.egg_base is None:
             dirs = self.distribution.package_dir
diff --git a/setuptools/command/rotate.py b/setuptools/command/rotate.py
index b89353f5..e398834f 100644
--- a/setuptools/command/rotate.py
+++ b/setuptools/command/rotate.py
@@ -36,8 +36,8 @@ class rotate(Command):
             raise DistutilsOptionError("Must specify number of files to keep")
         try:
             self.keep = int(self.keep)
-        except ValueError:
-            raise DistutilsOptionError("--keep must be an integer")
+        except ValueError as e:
+            raise DistutilsOptionError("--keep must be an integer") from e
         if isinstance(self.match, six.string_types):
             self.match = [
                 convert_path(p.strip()) for p in self.match.split(',')
diff --git a/setuptools/config.py b/setuptools/config.py
index 45df2e3f..a8f8b6b0 100644
--- a/setuptools/config.py
+++ b/setuptools/config.py
@@ -42,9 +42,10 @@ class StaticModule:
                 for target in statement.targets
                 if isinstance(target, ast.Name) and target.id == attr
             )
-        except Exception:
+        except Exception as e:
             raise AttributeError(
-                "{self.name} has no attribute {attr}".format(**locals()))
+                "{self.name} has no attribute {attr}".format(**locals())
+            ) from e
 
 
 @contextlib.contextmanager
diff --git a/setuptools/dist.py b/setuptools/dist.py
index fe64afa9..e813b11c 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -204,11 +204,11 @@ def check_importable(dist, attr, value):
     try:
         ep = pkg_resources.EntryPoint.parse('x=' + value)
         assert not ep.extras
-    except (TypeError, ValueError, AttributeError, AssertionError):
+    except (TypeError, ValueError, AttributeError, AssertionError) as e:
         raise DistutilsSetupError(
             "%r must be importable 'module:attrs' string (got %r)"
             % (attr, value)
-        )
+        ) from e
 
 
 def assert_string_list(dist, attr, value):
@@ -219,10 +219,10 @@ def assert_string_list(dist, attr, value):
         assert isinstance(value, (list, tuple))
         # verify that elements of value are strings
         assert ''.join(value) != value
-    except (TypeError, ValueError, AttributeError, AssertionError):
+    except (TypeError, ValueError, AttributeError, AssertionError) as e:
         raise DistutilsSetupError(
             "%r must be a list of strings (got %r)" % (attr, value)
-        )
+        ) from e
 
 
 def check_nsp(dist, attr, value):
@@ -247,12 +247,12 @@ def check_extras(dist, attr, value):
     """Verify that extras_require mapping is valid"""
     try:
         list(itertools.starmap(_check_extra, value.items()))
-    except (TypeError, ValueError, AttributeError):
+    except (TypeError, ValueError, AttributeError) as e:
         raise DistutilsSetupError(
             "'extras_require' must be a dictionary whose values are "
             "strings or lists of strings containing valid project/version "
             "requirement specifiers."
-        )
+        ) from e
 
 
 def _check_extra(extra, reqs):
@@ -280,7 +280,9 @@ def check_requirements(dist, attr, value):
             "{attr!r} must be a string or list of strings "
             "containing valid project/version requirement specifiers; {error}"
         )
-        raise DistutilsSetupError(tmpl.format(attr=attr, error=error))
+        raise DistutilsSetupError(
+            tmpl.format(attr=attr, error=error)
+        ) from error
 
 
 def check_specifier(dist, attr, value):
@@ -292,7 +294,9 @@ def check_specifier(dist, attr, value):
             "{attr!r} must be a string "
             "containing valid version specifiers; {error}"
         )
-        raise DistutilsSetupError(tmpl.format(attr=attr, error=error))
+        raise DistutilsSetupError(
+            tmpl.format(attr=attr, error=error)
+        ) from error
 
 
 def check_entry_points(dist, attr, value):
@@ -300,7 +304,7 @@ def check_entry_points(dist, attr, value):
     try:
         pkg_resources.EntryPoint.parse_map(value)
     except ValueError as e:
-        raise DistutilsSetupError(e)
+        raise DistutilsSetupError(e) from e
 
 
 def check_test_suite(dist, attr, value):
@@ -609,8 +613,8 @@ class Distribution(_Distribution):
                         setattr(self, opt, strtobool(val))
                     else:
                         setattr(self, opt, val)
-                except ValueError as msg:
-                    raise DistutilsOptionError(msg)
+                except ValueError as e:
+                    raise DistutilsOptionError(e) from e
 
     @staticmethod
     def _try_str(val):
@@ -676,8 +680,8 @@ class Distribution(_Distribution):
                     raise DistutilsOptionError(
                         "error in %s: command '%s' has no such option '%s'"
                         % (source, command_name, option))
-            except ValueError as msg:
-                raise DistutilsOptionError(msg)
+            except ValueError as e:
+                raise DistutilsOptionError(e) from e
 
     def parse_config_files(self, filenames=None, ignore_option_errors=False):
         """Parses configuration files from various levels
@@ -843,10 +847,10 @@ class Distribution(_Distribution):
             )
         try:
             old = getattr(self, name)
-        except AttributeError:
+        except AttributeError as e:
             raise DistutilsSetupError(
                 "%s: No such distribution setting" % name
-            )
+            ) from e
         if old is not None and not isinstance(old, sequence):
             raise DistutilsSetupError(
                 name + ": this setting cannot be changed via include/exclude"
@@ -863,10 +867,10 @@ class Distribution(_Distribution):
             )
         try:
             old = getattr(self, name)
-        except AttributeError:
+        except AttributeError as e:
             raise DistutilsSetupError(
                 "%s: No such distribution setting" % name
-            )
+            ) from e
         if old is None:
             setattr(self, name, value)
         elif not isinstance(old, sequence):
diff --git a/setuptools/installer.py b/setuptools/installer.py
index 1f183bd9..e5acec27 100644
--- a/setuptools/installer.py
+++ b/setuptools/installer.py
@@ -127,7 +127,7 @@ def fetch_build_egg(dist, req):
         try:
             subprocess.check_call(cmd)
         except subprocess.CalledProcessError as e:
-            raise DistutilsError(str(e))
+            raise DistutilsError(str(e)) from e
         wheel = Wheel(glob.glob(os.path.join(tmpdir, '*.whl'))[0])
         dist_location = os.path.join(eggs_dir, wheel.egg_name())
         wheel.install_as_egg(dist_location)
diff --git a/setuptools/msvc.py b/setuptools/msvc.py
index 213e39c9..72ba0d0c 100644
--- a/setuptools/msvc.py
+++ b/setuptools/msvc.py
@@ -277,7 +277,7 @@ def _msvc14_get_vc_env(plat_spec):
     except subprocess.CalledProcessError as exc:
         raise distutils.errors.DistutilsPlatformError(
             "Error executing {}".format(exc.cmd)
-        )
+        ) from exc
 
     env = {
         key.lower(): value