Merge pull request #1503 from pallets/except-chain

use exception chaining

src/jinja2/filters.py

@@ -1350,8 +1350,8 @@ def do_reverse(value: t.Union[str, t.Iterable[V]]) -> t.Union[str, t.Iterable[V]
             rv = list(value)
             rv.reverse()
             return rv
-        except TypeError:
-            raise FilterArgumentError("argument must be iterable")
+        except TypeError as e:
+            raise FilterArgumentError("argument must be iterable") from e
 
 
 @pass_environment
@@ -1691,7 +1691,7 @@ def prepare_map(
             name = args[0]
             args = args[1:]
         except LookupError:
-            raise FilterArgumentError("map requires a filter argument")
+            raise FilterArgumentError("map requires a filter argument") from None
 
         def func(item: t.Any) -> t.Any:
             return context.environment.call_filter(
@@ -1712,7 +1712,7 @@ def prepare_select_or_reject(
         try:
             attr = args[0]
         except LookupError:
-            raise FilterArgumentError("Missing parameter for attribute name")
+            raise FilterArgumentError("Missing parameter for attribute name") from None
 
         transfunc = make_attrgetter(context.environment, attr)
         off = 1

src/jinja2/lexer.py

@@ -655,7 +655,7 @@ def wrap(
                     )
                 except Exception as e:
                     msg = str(e).split(":")[-1].strip()
-                    raise TemplateSyntaxError(msg, lineno, name, filename)
+                    raise TemplateSyntaxError(msg, lineno, name, filename) from e
             elif token == TOKEN_INTEGER:
                 value = int(value_str.replace("_", ""), 0)
             elif token == TOKEN_FLOAT:

src/jinja2/loaders.py

@@ -336,8 +336,8 @@ def up_to_date() -> bool:
             # Package is a zip file.
             try:
                 source = self._loader.get_data(p)  # type: ignore
-            except OSError:
-                raise TemplateNotFound(template)
+            except OSError as e:
+                raise TemplateNotFound(template) from e
 
             # Could use the zip's mtime for all template mtimes, but
             # would need to safely reload the module if it's out of
@@ -476,8 +476,8 @@ def get_loader(self, template: str) -> t.Tuple[BaseLoader, str]:
         try:
             prefix, name = template.split(self.delimiter, 1)
             loader = self.mapping[prefix]
-        except (ValueError, KeyError):
-            raise TemplateNotFound(template)
+        except (ValueError, KeyError) as e:
+            raise TemplateNotFound(template) from e
         return loader, name
 
     def get_source(
@@ -486,10 +486,10 @@ def get_source(
         loader, name = self.get_loader(template)
         try:
             return loader.get_source(environment, name)
-        except TemplateNotFound:
+        except TemplateNotFound as e:
             # re-raise the exception with the correct filename here.
             # (the one that includes the prefix)
-            raise TemplateNotFound(template)
+            raise TemplateNotFound(template) from e
 
     @internalcode
     def load(
@@ -501,10 +501,10 @@ def load(
         loader, local_name = self.get_loader(name)
         try:
             return loader.load(environment, local_name, globals)
-        except TemplateNotFound:
+        except TemplateNotFound as e:
             # re-raise the exception with the correct filename here.
             # (the one that includes the prefix)
-            raise TemplateNotFound(name)
+            raise TemplateNotFound(name) from e
 
     def list_templates(self) -> t.List[str]:
         result = []
@@ -627,8 +627,8 @@ def load(
         if mod is None:
             try:
                 mod = __import__(module, None, None, ["root"])
-            except ImportError:
-                raise TemplateNotFound(name)
+            except ImportError as e:
+                raise TemplateNotFound(name) from e
 
             # remove the entry from sys.modules, we only want the attribute
             # on the module object we have stored on the loader.

src/jinja2/nodes.py

@@ -507,8 +507,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
         f = _binop_to_func[self.operator]
         try:
             return f(self.left.as_const(eval_ctx), self.right.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
 
 class UnaryExpr(Expr):
@@ -531,8 +531,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
         f = _uaop_to_func[self.operator]
         try:
             return f(self.node.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
 
 class Name(Expr):
@@ -723,14 +723,14 @@ def args_as_const(
     if node.dyn_args is not None:
         try:
             args.extend(node.dyn_args.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
     if node.dyn_kwargs is not None:
         try:
             kwargs.update(node.dyn_kwargs.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
     return args, kwargs
 
@@ -779,8 +779,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
 
         try:
             return func(*args, **kwargs)
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
 
 class Filter(_FilterTestCommon):
@@ -847,8 +847,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
             return eval_ctx.environment.getitem(
                 self.node.as_const(eval_ctx), self.arg.as_const(eval_ctx)
             )
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
 
 class Getattr(Expr):
@@ -869,8 +869,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
 
         try:
             return eval_ctx.environment.getattr(self.node.as_const(eval_ctx), self.attr)
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
 
 class Slice(Expr):
@@ -929,8 +929,8 @@ def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any:
                     return False
 
                 value = new_value
-        except Exception:
-            raise Impossible()
+        except Exception as e:
+            raise Impossible() from e
 
         return result
 

src/jinja2/utils.py

@@ -824,7 +824,7 @@ def __getattribute__(self, name: str) -> t.Any:
         try:
             return self.__attrs[name]
         except KeyError:
-            raise AttributeError(name)
+            raise AttributeError(name) from None
 
     def __setitem__(self, name: str, value: t.Any) -> None:
         self.__attrs[name] = value