Merge pull request #7832 from cool-RR/2020-06-11-raise-from

Fix exception causes all over the codebase

sphinx/builders/gettext.py

@@ -278,7 +278,7 @@ class MessageCatalogBuilder(I18nBuilder):
                     origin = MsgOrigin(template, line)
                     self.catalogs['sphinx'].add(msg, origin)
             except Exception as exc:
-                raise ThemeError('%s: %r' % (template, exc))
+                raise ThemeError('%s: %r' % (template, exc)) from exc
 
     def build(self, docnames: Iterable[str], summary: str = None, method: str = 'update') -> None:  # NOQA
         self._extract_from_template()

sphinx/builders/html/__init__.py

@@ -140,7 +140,7 @@ class BuildInfo:
             build_info.tags_hash = lines[3].split()[1].strip()
             return build_info
         except Exception as exc:
-            raise ValueError(__('build info file is broken: %r') % exc)
+            raise ValueError(__('build info file is broken: %r') % exc) from exc
 
     def __init__(self, config: Config = None, tags: Tags = None, config_categories: List[str] = []) -> None:  # NOQA
         self.config_hash = ''
@@ -1015,7 +1015,7 @@ class StandaloneHTMLBuilder(Builder):
             return
         except Exception as exc:
             raise ThemeError(__("An error happened in rendering the page %s.\nReason: %r") %
-                             (pagename, exc))
+                             (pagename, exc)) from exc
 
         if not outfilename:
             outfilename = self.get_outfilename(pagename)

sphinx/builders/latex/theming.py

@@ -87,10 +87,12 @@ class UserTheme(Theme):
             try:
                 value = self.config.get('theme', key)
                 setattr(self, key, value)
-            except configparser.NoSectionError:
+            except configparser.NoSectionError as exc:
-                raise ThemeError(__('%r doesn\'t have "theme" setting') % filename)
+                raise ThemeError(__('%r doesn\'t have "theme" setting') %
+                                 filename) from exc
             except configparser.NoOptionError as exc:
-                raise ThemeError(__('%r doesn\'t have "%s" setting') % (filename, exc.args[0]))
+                raise ThemeError(__('%r doesn\'t have "%s" setting') %
+                                 (filename, exc.args[0])) from exc
 
         for key in self.OPTIONAL_CONFIG_KEYS:
             try:

sphinx/config.py

@@ -196,9 +196,9 @@ class Config:
             elif isinstance(defvalue, int):
                 try:
                     return int(value)
-                except ValueError:
+                except ValueError as exc:
                     raise ValueError(__('invalid number %r for config value %r, ignoring') %
-                                     (value, name))
+                                     (value, name)) from exc
             elif hasattr(defvalue, '__call__'):
                 return value
             elif defvalue is not None and not isinstance(defvalue, str):
@@ -319,17 +319,17 @@ def eval_config_file(filename: str, tags: Tags) -> Dict[str, Any]:
             execfile_(filename, namespace)
         except SyntaxError as err:
             msg = __("There is a syntax error in your configuration file: %s\n")
-            raise ConfigError(msg % err)
+            raise ConfigError(msg % err) from err
-        except SystemExit:
+        except SystemExit as exc:
             msg = __("The configuration file (or one of the modules it imports) "
                      "called sys.exit()")
-            raise ConfigError(msg)
+            raise ConfigError(msg) from exc
         except ConfigError:
             # pass through ConfigError from conf.py as is.  It will be shown in console.
             raise
-        except Exception:
+        except Exception as exc:
             msg = __("There is a programmable error in your configuration file:\n\n%s")
-            raise ConfigError(msg % traceback.format_exc())
+            raise ConfigError(msg % traceback.format_exc()) from exc
 
     return namespace
 

sphinx/domains/c.py

@@ -2301,7 +2301,8 @@ class DefinitionParser(BaseParser):
                     errs = []
                     errs.append((exCast, "If type cast expression"))
                     errs.append((exUnary, "If unary expression"))
-                    raise self._make_multi_error(errs, "Error in cast expression.")
+                    raise self._make_multi_error(errs,
+                                                 "Error in cast expression.") from exUnary
         else:
             return self._parse_unary_expression()
 
@@ -2768,7 +2769,7 @@ class DefinitionParser(BaseParser):
                         msg += " (e.g., 'void (*f(int arg))(double)')"
                     prevErrors.append((exNoPtrParen, msg))
                     header = "Error in declarator"
-                    raise self._make_multi_error(prevErrors, header)
+                    raise self._make_multi_error(prevErrors, header) from exNoPtrParen
         pos = self.pos
         try:
             return self._parse_declarator_name_suffix(named, paramMode, typed)
@@ -2776,7 +2777,7 @@ class DefinitionParser(BaseParser):
             self.pos = pos
             prevErrors.append((e, "If declarator-id"))
             header = "Error in declarator or parameters"
-            raise self._make_multi_error(prevErrors, header)
+            raise self._make_multi_error(prevErrors, header) from e
 
     def _parse_initializer(self, outer: str = None, allowFallback: bool = True
                            ) -> ASTInitializer:
@@ -2844,7 +2845,7 @@ class DefinitionParser(BaseParser):
                     if True:
                         header = "Type must be either just a name or a "
                         header += "typedef-like declaration."
-                        raise self._make_multi_error(prevErrors, header)
+                        raise self._make_multi_error(prevErrors, header) from exTyped
                     else:
                         # For testing purposes.
                         # do it again to get the proper traceback (how do you
@@ -2995,7 +2996,7 @@ class DefinitionParser(BaseParser):
                 errs = []
                 errs.append((exExpr, "If expression"))
                 errs.append((exType, "If type"))
-                raise self._make_multi_error(errs, header)
+                raise self._make_multi_error(errs, header) from exType
         return res
 
 
@@ -3133,7 +3134,7 @@ class CObject(ObjectDescription):
             name = _make_phony_error_name()
             symbol = parentSymbol.add_name(name)
             self.env.temp_data['c:last_symbol'] = symbol
-            raise ValueError
+            raise ValueError from e
 
         try:
             symbol = parentSymbol.add_declaration(ast, docname=self.env.docname)

sphinx/domains/cpp.py

@@ -4883,7 +4883,7 @@ class DefinitionParser(BaseParser):
                 raise self._make_multi_error([
                     (eFold, "If fold expression"),
                     (eExpr, "If parenthesized expression")
-                ], "Error in fold expression or parenthesized expression.")
+                ], "Error in fold expression or parenthesized expression.") from eExpr
             return ASTParenExpr(res)
         # now it definitely is a fold expression
         if self.skip_string(')'):
@@ -5067,7 +5067,7 @@ class DefinitionParser(BaseParser):
                     errors = []
                     errors.append((eType, "If type"))
                     errors.append((eExpr, "If expression"))
-                    raise self._make_multi_error(errors, header)
+                    raise self._make_multi_error(errors, header) from eExpr
         else:  # a primary expression or a type
             pos = self.pos
             try:
@@ -5094,7 +5094,7 @@ class DefinitionParser(BaseParser):
                     errors = []
                     errors.append((eOuter, "If primary expression"))
                     errors.append((eInner, "If type"))
-                    raise self._make_multi_error(errors, header)
+                    raise self._make_multi_error(errors, header) from eInner
 
         # and now parse postfixes
         postFixes = []  # type: List[ASTPostfixOp]
@@ -5254,7 +5254,8 @@ class DefinitionParser(BaseParser):
                     errs = []
                     errs.append((exCast, "If type cast expression"))
                     errs.append((exUnary, "If unary expression"))
-                    raise self._make_multi_error(errs, "Error in cast expression.")
+                    raise self._make_multi_error(errs,
+                                                 "Error in cast expression.") from exUnary
         else:
             return self._parse_unary_expression()
 
@@ -5505,7 +5506,7 @@ class DefinitionParser(BaseParser):
                     self.pos = pos
                     prevErrors.append((e, "If non-type argument"))
                     header = "Error in parsing template argument list."
-                    raise self._make_multi_error(prevErrors, header)
+                    raise self._make_multi_error(prevErrors, header) from e
             if parsedEnd:
                 assert not parsedComma
                 break
@@ -5950,7 +5951,7 @@ class DefinitionParser(BaseParser):
                     self.pos = pos
                     prevErrors.append((exNoPtrParen, "If parenthesis in noptr-declarator"))
                     header = "Error in declarator"
-                    raise self._make_multi_error(prevErrors, header)
+                    raise self._make_multi_error(prevErrors, header) from exNoPtrParen
         if typed:  # pointer to member
             pos = self.pos
             try:
@@ -5989,7 +5990,7 @@ class DefinitionParser(BaseParser):
             self.pos = pos
             prevErrors.append((e, "If declarator-id"))
             header = "Error in declarator or parameters-and-qualifiers"
-            raise self._make_multi_error(prevErrors, header)
+            raise self._make_multi_error(prevErrors, header) from e
 
     def _parse_initializer(self, outer: str = None, allowFallback: bool = True
                            ) -> ASTInitializer:
@@ -6097,7 +6098,7 @@ class DefinitionParser(BaseParser):
                             header = "Error when parsing function declaration."
                         else:
                             assert False
-                        raise self._make_multi_error(prevErrors, header)
+                        raise self._make_multi_error(prevErrors, header) from exTyped
                     else:
                         # For testing purposes.
                         # do it again to get the proper traceback (how do you
@@ -6164,7 +6165,7 @@ class DefinitionParser(BaseParser):
             errs.append((eType, "If default template argument is a type"))
             msg = "Error in non-type template parameter"
             msg += " or constrained template parameter."
-            raise self._make_multi_error(errs, msg)
+            raise self._make_multi_error(errs, msg) from eType
 
     def _parse_type_using(self) -> ASTTypeUsing:
         name = self._parse_nested_name()
@@ -6511,7 +6512,7 @@ class DefinitionParser(BaseParser):
                 self.pos = pos
                 prevErrors.append((e, "If type alias or template alias"))
                 header = "Error in type declaration."
-                raise self._make_multi_error(prevErrors, header)
+                raise self._make_multi_error(prevErrors, header) from e
         elif objectType == 'concept':
             declaration = self._parse_concept()
         elif objectType == 'member':
@@ -6577,7 +6578,7 @@ class DefinitionParser(BaseParser):
                 errs.append((e1, "If shorthand ref"))
                 errs.append((e2, "If full function ref"))
                 msg = "Error in cross-reference."
-                raise self._make_multi_error(errs, msg)
+                raise self._make_multi_error(errs, msg) from e2
 
     def parse_expression(self) -> Union[ASTExpression, ASTType]:
         pos = self.pos
@@ -6598,7 +6599,7 @@ class DefinitionParser(BaseParser):
                 errs = []
                 errs.append((exExpr, "If expression"))
                 errs.append((exType, "If type"))
-                raise self._make_multi_error(errs, header)
+                raise self._make_multi_error(errs, header) from exType
 
 
 def _make_phony_error_name() -> ASTNestedName:
@@ -6791,7 +6792,7 @@ class CPPObject(ObjectDescription):
             name = _make_phony_error_name()
             symbol = parentSymbol.add_name(name)
             self.env.temp_data['cpp:last_symbol'] = symbol
-            raise ValueError
+            raise ValueError from e
 
         try:
             symbol = parentSymbol.add_declaration(ast, docname=self.env.docname)

sphinx/domains/std.py

@@ -1061,10 +1061,10 @@ class StandardDomain(Domain):
             try:
                 figure_id = target_node['ids'][0]
                 return env.toc_fignumbers[docname][figtype][figure_id]
-            except (KeyError, IndexError):
+            except (KeyError, IndexError) as exc:
                 # target_node is found, but fignumber is not assigned.
                 # Maybe it is defined in orphaned document.
-                raise ValueError
+                raise ValueError from exc
 
     def get_full_qualified_name(self, node: Element) -> str:
         if node.get('reftype') == 'option':

sphinx/environment/__init__.py

@@ -393,7 +393,8 @@ class BuildEnvironment:
                         if catalog.domain == domain:
                             self.dependencies[docname].add(catalog.mo_path)
         except OSError as exc:
-            raise DocumentError(__('Failed to scan documents in %s: %r') % (self.srcdir, exc))
+            raise DocumentError(__('Failed to scan documents in %s: %r') %
+                                (self.srcdir, exc)) from exc
 
     def get_outdated_files(self, config_changed: bool) -> Tuple[Set[str], Set[str], Set[str]]:
         """Return (added, changed, removed) sets."""
@@ -511,8 +512,8 @@ class BuildEnvironment:
         """
         try:
             return self.domains[domainname]
-        except KeyError:
+        except KeyError as exc:
-            raise ExtensionError(__('Domain %r is not registered') % domainname)
+            raise ExtensionError(__('Domain %r is not registered') % domainname) from exc
 
     # --------- RESOLVING REFERENCES AND TOCTREES ------------------------------
 

sphinx/ext/autodoc/importer.py

@@ -33,7 +33,7 @@ def import_module(modname: str, warningiserror: bool = False) -> Any:
     except BaseException as exc:
         # Importing modules may cause any side effects, including
         # SystemExit, so we need to catch all errors.
-        raise ImportError(exc, traceback.format_exc())
+        raise ImportError(exc, traceback.format_exc()) from exc
 
 
 def import_object(modname: str, objpath: List[str], objtype: str = '',
@@ -98,7 +98,7 @@ def import_object(modname: str, objpath: List[str], objtype: str = '',
             errmsg += '; the following exception was raised:\n%s' % traceback.format_exc()
 
         logger.debug(errmsg)
-        raise ImportError(errmsg)
+        raise ImportError(errmsg) from exc
 
 
 def get_module_members(module: Any) -> List[Tuple[str, Any]]:

sphinx/ext/autosummary/__init__.py

@@ -654,7 +654,7 @@ def _import_by_name(name: str) -> Tuple[Any, Any, str]:
         else:
             return sys.modules[modname], None, modname
     except (ValueError, ImportError, AttributeError, KeyError) as e:
-        raise ImportError(*e.args)
+        raise ImportError(*e.args) from e
 
 
 # -- :autolink: (smart default role) -------------------------------------------

sphinx/ext/graphviz.py

@@ -256,7 +256,7 @@ def render_dot(self: SphinxTranslator, code: str, options: Dict,
         return None, None
     except CalledProcessError as exc:
         raise GraphvizError(__('dot exited with error:\n[stderr]\n%r\n'
-                               '[stdout]\n%r') % (exc.stderr, exc.stdout))
+                               '[stdout]\n%r') % (exc.stderr, exc.stdout)) from exc
 
 
 def render_dot_html(self: HTMLTranslator, node: graphviz, code: str, options: Dict,
@@ -270,7 +270,7 @@ def render_dot_html(self: HTMLTranslator, node: graphviz, code: str, options: Di
         fname, outfn = render_dot(self, code, options, format, prefix)
     except GraphvizError as exc:
         logger.warning(__('dot code %r: %s'), code, exc)
-        raise nodes.SkipNode
+        raise nodes.SkipNode from exc
 
     classes = [imgcls, 'graphviz'] + node.get('classes', [])
     imgcls = ' '.join(filter(None, classes))
@@ -321,7 +321,7 @@ def render_dot_latex(self: LaTeXTranslator, node: graphviz, code: str,
         fname, outfn = render_dot(self, code, options, 'pdf', prefix)
     except GraphvizError as exc:
         logger.warning(__('dot code %r: %s'), code, exc)
-        raise nodes.SkipNode
+        raise nodes.SkipNode from exc
 
     is_inline = self.is_inline(node)
 
@@ -358,7 +358,7 @@ def render_dot_texinfo(self: TexinfoTranslator, node: graphviz, code: str,
         fname, outfn = render_dot(self, code, options, 'png', prefix)
     except GraphvizError as exc:
         logger.warning(__('dot code %r: %s'), code, exc)
-        raise nodes.SkipNode
+        raise nodes.SkipNode from exc
     if fname is not None:
         self.body.append('@image{%s,,,[graphviz],png}\n' % fname[:-4])
     raise nodes.SkipNode

sphinx/ext/imgconverter.py

@@ -70,7 +70,7 @@ class ImagemagickConverter(ImageConverter):
         except CalledProcessError as exc:
             raise ExtensionError(__('convert exited with error:\n'
                                     '[stderr]\n%r\n[stdout]\n%r') %
-                                 (exc.stderr, exc.stdout))
+                                 (exc.stderr, exc.stdout)) from exc
 
 
 def setup(app: Sphinx) -> Dict[str, Any]:

sphinx/ext/imgmath.py

@@ -165,13 +165,13 @@ def compile_math(latex: str, builder: Builder) -> str:
     try:
         subprocess.run(command, stdout=PIPE, stderr=PIPE, cwd=tempdir, check=True)
         return path.join(tempdir, 'math.dvi')
-    except OSError:
+    except OSError as exc:
         logger.warning(__('LaTeX command %r cannot be run (needed for math '
                           'display), check the imgmath_latex setting'),
                        builder.config.imgmath_latex)
-        raise InvokeError
+        raise InvokeError from exc
     except CalledProcessError as exc:
-        raise MathExtError('latex exited with error', exc.stderr, exc.stdout)
+        raise MathExtError('latex exited with error', exc.stderr, exc.stdout) from exc
 
 
 def convert_dvi_to_image(command: List[str], name: str) -> Tuple[bytes, bytes]:
@@ -179,13 +179,13 @@ def convert_dvi_to_image(command: List[str], name: str) -> Tuple[bytes, bytes]:
     try:
         ret = subprocess.run(command, stdout=PIPE, stderr=PIPE, check=True)
         return ret.stdout, ret.stderr
-    except OSError:
+    except OSError as exc:
         logger.warning(__('%s command %r cannot be run (needed for math '
                           'display), check the imgmath_%s setting'),
                        name, command[0], name)
-        raise InvokeError
+        raise InvokeError from exc
     except CalledProcessError as exc:
-        raise MathExtError('%s exited with error' % name, exc.stderr, exc.stdout)
+        raise MathExtError('%s exited with error' % name, exc.stderr, exc.stdout) from exc
 
 
 def convert_dvi_to_png(dvipath: str, builder: Builder) -> Tuple[str, int]:
@@ -326,7 +326,7 @@ def html_visit_math(self: HTMLTranslator, node: nodes.math) -> None:
                                   backrefs=[], source=node.astext())
         sm.walkabout(self)
         logger.warning(__('display latex %r: %s'), node.astext(), msg)
-        raise nodes.SkipNode
+        raise nodes.SkipNode from exc
     if fname is None:
         # something failed -- use text-only as a bad substitute
         self.body.append('<span class="math">%s</span>' %
@@ -352,7 +352,7 @@ def html_visit_displaymath(self: HTMLTranslator, node: nodes.math_block) -> None
                                   backrefs=[], source=node.astext())
         sm.walkabout(self)
         logger.warning(__('inline latex %r: %s'), node.astext(), msg)
-        raise nodes.SkipNode
+        raise nodes.SkipNode from exc
     self.body.append(self.starttag(node, 'div', CLASS='math'))
     self.body.append('<p>')
     if node['number']:

sphinx/ext/intersphinx.py

@@ -179,7 +179,7 @@ def fetch_inventory(app: Sphinx, uri: str, inv: Any) -> Any:
                 join = path.join if localuri else posixpath.join
                 invdata = InventoryFile.load(f, uri, join)
             except ValueError as exc:
-                raise ValueError('unknown or unsupported inventory version: %r' % exc)
+                raise ValueError('unknown or unsupported inventory version: %r' % exc) from exc
     except Exception as err:
         err.args = ('intersphinx inventory %r not readable due to %s: %s',
                     inv, err.__class__.__name__, str(err))

sphinx/pycode/__init__.py

@@ -37,7 +37,7 @@ class ModuleAnalyzer:
         try:
             mod = import_module(modname)
         except Exception as err:
-            raise PycodeError('error importing %r' % modname, err)
+            raise PycodeError('error importing %r' % modname, err) from err
         loader = getattr(mod, '__loader__', None)
         filename = getattr(mod, '__file__', None)
         if loader and getattr(loader, 'get_source', None):
@@ -54,7 +54,7 @@ class ModuleAnalyzer:
             try:
                 filename = loader.get_filename(modname)
             except ImportError as err:
-                raise PycodeError('error getting filename for %r' % modname, err)
+                raise PycodeError('error getting filename for %r' % modname, err) from err
         if filename is None:
             # all methods for getting filename failed, so raise...
             raise PycodeError('no source found for module %r' % modname)
@@ -92,7 +92,7 @@ class ModuleAnalyzer:
             if '.egg' + path.sep in filename:
                 obj = cls.cache['file', filename] = cls.for_egg(filename, modname)
             else:
-                raise PycodeError('error opening %r' % filename, err)
+                raise PycodeError('error opening %r' % filename, err) from err
         return obj
 
     @classmethod
@@ -104,7 +104,7 @@ class ModuleAnalyzer:
                 code = egg.read(relpath).decode()
                 return cls.for_string(code, modname, filename)
         except Exception as exc:
-            raise PycodeError('error opening %r' % filename, exc)
+            raise PycodeError('error opening %r' % filename, exc) from exc
 
     @classmethod
     def for_module(cls, modname: str) -> "ModuleAnalyzer":
@@ -169,7 +169,7 @@ class ModuleAnalyzer:
             self.tags = parser.definitions
             self.tagorder = parser.deforders
         except Exception as exc:
-            raise PycodeError('parsing %r failed: %r' % (self.srcname, exc))
+            raise PycodeError('parsing %r failed: %r' % (self.srcname, exc)) from exc
 
     def find_attr_docs(self) -> Dict[Tuple[str, str], List[str]]:
         """Find class and module-level attributes and their documentation."""

sphinx/registry.py

@@ -139,9 +139,9 @@ class SphinxComponentRegistry:
             entry_points = iter_entry_points('sphinx.builders', name)
             try:
                 entry_point = next(entry_points)
-            except StopIteration:
+            except StopIteration as exc:
                 raise SphinxError(__('Builder name %s not registered or available'
-                                     ' through entry point') % name)
+                                     ' through entry point') % name) from exc
 
             self.load_extension(app, entry_point.module_name)
 
@@ -273,8 +273,8 @@ class SphinxComponentRegistry:
     def get_source_parser(self, filetype: str) -> "Type[Parser]":
         try:
             return self.source_parsers[filetype]
-        except KeyError:
+        except KeyError as exc:
-            raise SphinxError(__('Source parser for %s not registered') % filetype)
+            raise SphinxError(__('Source parser for %s not registered') % filetype) from exc
 
     def get_source_parsers(self) -> Dict[str, "Type[Parser]"]:
         return self.source_parsers
@@ -311,9 +311,11 @@ class SphinxComponentRegistry:
             try:
                 visit, depart = handlers  # unpack once for assertion
                 translation_handlers[node.__name__] = (visit, depart)
-            except ValueError:
+            except ValueError as exc:
-                raise ExtensionError(__('kwargs for add_node() must be a (visit, depart) '
+                raise ExtensionError(
-                                        'function tuple: %r=%r') % (builder_name, handlers))
+                    __('kwargs for add_node() must be a (visit, depart) '
+                       'function tuple: %r=%r') % (builder_name, handlers)
+                ) from exc
 
     def get_translator_class(self, builder: Builder) -> "Type[nodes.NodeVisitor]":
         return self.translators.get(builder.name,
@@ -407,7 +409,8 @@ class SphinxComponentRegistry:
                 mod = import_module(extname)
             except ImportError as err:
                 logger.verbose(__('Original exception:\n') + traceback.format_exc())
-                raise ExtensionError(__('Could not import extension %s') % extname, err)
+                raise ExtensionError(__('Could not import extension %s') % extname,
+                                     err) from err
 
             setup = getattr(mod, 'setup', None)
             if setup is None:
@@ -423,7 +426,7 @@ class SphinxComponentRegistry:
                         __('The %s extension used by this project needs at least '
                            'Sphinx v%s; it therefore cannot be built with this '
                            'version.') % (extname, err)
-                    )
+                    ) from err
 
             if metadata is None:
                 metadata = {}

sphinx/search/ja.py

@@ -528,9 +528,9 @@ class SearchJapanese(SearchLanguage):
         dotted_path = options.get('type', 'sphinx.search.ja.DefaultSplitter')
         try:
             self.splitter = import_object(dotted_path)(options)
-        except ExtensionError:
+        except ExtensionError as exc:
             raise ExtensionError("Splitter module %r can't be imported" %
-                                 dotted_path)
+                                 dotted_path) from exc
 
     def split(self, input: str) -> List[str]:
         return self.splitter.split(input)

sphinx/setup_command.py

@@ -198,7 +198,7 @@ class BuildDoc(Command):
             except Exception as exc:
                 handle_exception(app, self, exc, sys.stderr)
                 if not self.pdb:
-                    raise SystemExit(1)
+                    raise SystemExit(1) from exc
 
             if not self.link_index:
                 continue

sphinx/theming.py

@@ -74,17 +74,17 @@ class Theme:
 
         try:
             inherit = self.config.get('theme', 'inherit')
-        except configparser.NoSectionError:
+        except configparser.NoSectionError as exc:
-            raise ThemeError(__('theme %r doesn\'t have "theme" setting') % name)
+            raise ThemeError(__('theme %r doesn\'t have "theme" setting') % name) from exc
-        except configparser.NoOptionError:
+        except configparser.NoOptionError as exc:
-            raise ThemeError(__('theme %r doesn\'t have "inherit" setting') % name)
+            raise ThemeError(__('theme %r doesn\'t have "inherit" setting') % name) from exc
 
         if inherit != 'none':
             try:
                 self.base = factory.create(inherit)
-            except ThemeError:
+            except ThemeError as exc:
                 raise ThemeError(__('no theme named %r found, inherited by %r') %
-                                 (inherit, name))
+                                 (inherit, name)) from exc
 
     def get_theme_dirs(self) -> List[str]:
         """Return a list of theme directories, beginning with this theme's,
@@ -101,13 +101,13 @@ class Theme:
         """
         try:
             return self.config.get(section, name)
-        except (configparser.NoOptionError, configparser.NoSectionError):
+        except (configparser.NoOptionError, configparser.NoSectionError) as exc:
             if self.base:
                 return self.base.get_config(section, name, default)
 
             if default is NODEFAULT:
                 raise ThemeError(__('setting %s.%s occurs in none of the '
-                                    'searched theme configs') % (section, name))
+                                    'searched theme configs') % (section, name)) from exc
             else:
                 return default
 

sphinx/transforms/post_transforms/__init__.py

@@ -82,8 +82,8 @@ class ReferencesResolver(SphinxPostTransform):
                     # let the domain try to resolve the reference
                     try:
                         domain = self.env.domains[node['refdomain']]
-                    except KeyError:
+                    except KeyError as exc:
-                        raise NoUri(target, typ)
+                        raise NoUri(target, typ) from exc
                     newnode = domain.resolve_xref(self.env, refdoc, self.app.builder,
                                                   typ, target, node, contnode)
                 # really hardwired reference types

sphinx/util/__init__.py

@@ -285,21 +285,21 @@ def get_module_source(modname: str) -> Tuple[str, str]:
     try:
         mod = import_module(modname)
     except Exception as err:
-        raise PycodeError('error importing %r' % modname, err)
+        raise PycodeError('error importing %r' % modname, err) from err
     filename = getattr(mod, '__file__', None)
     loader = getattr(mod, '__loader__', None)
     if loader and getattr(loader, 'get_filename', None):
         try:
             filename = loader.get_filename(modname)
         except Exception as err:
-            raise PycodeError('error getting filename for %r' % filename, err)
+            raise PycodeError('error getting filename for %r' % filename, err) from err
     if filename is None and loader:
         try:
             filename = loader.get_source(modname)
             if filename:
                 return 'string', filename
         except Exception as err:
-            raise PycodeError('error getting source for %r' % modname, err)
+            raise PycodeError('error getting source for %r' % modname, err) from err
     if filename is None:
         raise PycodeError('no source found for module %r' % modname)
     filename = path.normpath(path.abspath(filename))
@@ -456,8 +456,8 @@ def parselinenos(spec: str, total: int) -> List[int]:
                 items.extend(range(start - 1, end))
             else:
                 raise ValueError
-        except Exception:
+        except Exception as exc:
-            raise ValueError('invalid line number spec: %r' % spec)
+            raise ValueError('invalid line number spec: %r' % spec) from exc
 
     return items
 
@@ -596,9 +596,9 @@ def import_object(objname: str, source: str = None) -> Any:
     except (AttributeError, ImportError) as exc:
         if source:
             raise ExtensionError('Could not import %s (needed for %s)' %
-                                 (objname, source), exc)
+                                 (objname, source), exc) from exc
         else:
-            raise ExtensionError('Could not import %s' % objname, exc)
+            raise ExtensionError('Could not import %s' % objname, exc) from exc
 
 
 def split_full_qualified_name(name: str) -> Tuple[str, str]:

sphinx/util/i18n.py

@@ -312,7 +312,7 @@ def get_image_filename_for_language(filename: str, env: "BuildEnvironment") -> s
     try:
         return filename_format.format(**d)
     except KeyError as exc:
-        raise SphinxError('Invalid figure_language_filename: %r' % exc)
+        raise SphinxError('Invalid figure_language_filename: %r' % exc) from exc
 
 
 def search_image_for_language(filename: str, env: "BuildEnvironment") -> str:

sphinx/util/inspect.py

@@ -322,7 +322,7 @@ def safe_getattr(obj: Any, name: str, *defargs: Any) -> Any:
     """A getattr() that turns all exceptions into AttributeErrors."""
     try:
         return getattr(obj, name, *defargs)
-    except Exception:
+    except Exception as exc:
         # sometimes accessing a property raises an exception (e.g.
         # NotImplementedError), so let's try to read the attribute directly
         try:
@@ -337,7 +337,7 @@ def safe_getattr(obj: Any, name: str, *defargs: Any) -> Any:
         if defargs:
             return defargs[0]
 
-        raise AttributeError(name)
+        raise AttributeError(name) from exc
 
 
 def safe_getmembers(object: Any, predicate: Callable[[str], bool] = None,
@@ -386,8 +386,8 @@ def object_description(object: Any) -> str:
                                                  for x in sorted_values)
     try:
         s = repr(object)
-    except Exception:
+    except Exception as exc:
-        raise ValueError
+        raise ValueError from exc
     # Strip non-deterministic memory addresses such as
     # ``<__main__.A at 0x7f68cb685710>``
     s = memory_address_re.sub('', s)

sphinx/util/osutil.py

@@ -168,10 +168,10 @@ def abspath(pathdir: str) -> str:
         if isinstance(pathdir, bytes):
             try:
                 pathdir = pathdir.decode(fs_encoding)
-            except UnicodeDecodeError:
+            except UnicodeDecodeError as exc:
                 raise UnicodeDecodeError('multibyte filename not supported on '
                                          'this filesystem encoding '
-                                         '(%r)' % fs_encoding)
+                                         '(%r)' % fs_encoding) from exc
         return pathdir
 
 

sphinx/util/pycompat.py

@@ -34,11 +34,11 @@ def convert_with_2to3(filepath: str) -> str:
     try:
         from lib2to3.refactor import RefactoringTool, get_fixers_from_package
         from lib2to3.pgen2.parse import ParseError
-    except ImportError:
+    except ImportError as exc:
         # python 3.9.0a6+ emits PendingDeprecationWarning for lib2to3.
         # Additionally, removal of the module is still discussed at PEP-594.
         # To support future python, this catches ImportError for lib2to3.
-        raise SyntaxError
+        raise SyntaxError from exc
 
     fixers = get_fixers_from_package('lib2to3.fixes')
     refactoring_tool = RefactoringTool(fixers)
@@ -49,7 +49,8 @@ def convert_with_2to3(filepath: str) -> str:
         # do not propagate lib2to3 exceptions
         lineno, offset = err.context[1]
         # try to match ParseError details with SyntaxError details
-        raise SyntaxError(err.msg, (filepath, lineno, offset, err.value))
+
+        raise SyntaxError(err.msg, (filepath, lineno, offset, err.value)) from err
     return str(tree)
 
 

sphinx/writers/texinfo.py

@@ -853,8 +853,8 @@ class TexinfoTranslator(SphinxTranslator):
         num = node.astext().strip()
         try:
             footnode, used = self.footnotestack[-1][num]
-        except (KeyError, IndexError):
+        except (KeyError, IndexError) as exc:
-            raise nodes.SkipNode
+            raise nodes.SkipNode from exc
         # footnotes are repeated for each reference
         footnode.walkabout(self)  # type: ignore
         raise nodes.SkipChildren

tests/test_build_latex.py

@@ -64,8 +64,8 @@ def compile_latex_document(app, filename='python.tex'):
                     '-output-directory=%s' % app.config.latex_engine,
                     filename]
             subprocess.run(args, stdout=PIPE, stderr=PIPE, check=True)
-    except OSError:  # most likely the latex executable was not found
+    except OSError as exc:  # most likely the latex executable was not found
-        raise pytest.skip.Exception
+        raise pytest.skip.Exception from exc
     except CalledProcessError as exc:
         print(exc.stdout)
         print(exc.stderr)

tests/test_build_texinfo.py

@@ -58,8 +58,8 @@ def test_texinfo(app, status, warning):
     try:
         args = ['makeinfo', '--no-split', 'sphinxtests.texi']
         subprocess.run(args, stdout=PIPE, stderr=PIPE, cwd=app.outdir, check=True)
-    except OSError:
+    except OSError as exc:
-        raise pytest.skip.Exception  # most likely makeinfo was not found
+        raise pytest.skip.Exception from exc  # most likely makeinfo was not found
     except CalledProcessError as exc:
         print(exc.stdout)
         print(exc.stderr)