Document new parenthesized with statements (GH-24281)

pablogsal · web-flow · commit 7c8e0b03366e · 2021-01-25T23:15:51.000Z
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst
@@ -411,7 +411,8 @@ This allows common :keyword:`try`...\ :keyword:`except`...\ :keyword:`finally`
 usage patterns to be encapsulated for convenient reuse.
 
 .. productionlist:: python-grammar
-   with_stmt: "with" `with_item` ("," `with_item`)* ":" `suite`
+   with_stmt: "with" ( "(" `with_stmt_contents` ","? ")" | `with_stmt_contents` ) ":" `suite`
+   with_stmt_contents: `with_item` ("," `with_item`)*
    with_item: `expression` ["as" `target`]
 
 The execution of the :keyword:`with` statement with one "item" proceeds as follows:
@@ -488,9 +489,21 @@ is semantically equivalent to::
        with B() as b:
            SUITE
 
+You can also write multi-item context managers in multiple lines if
+the items are surrounded by parentheses. For example::
+
+   with (
+       A() as a,
+       B() as b,
+   ):
+       SUITE
+
 .. versionchanged:: 3.1
    Support for multiple context expressions.
 
+.. versionchanged:: 3.10
+   Support for using grouping parentheses to break the statement in multiple lines.
+
 .. seealso::
 
    :pep:`343` - The "with" statement
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
@@ -72,6 +72,59 @@ New Features
 
 .. _whatsnew310-pep563:
 
+Parenthesized context managers
+------------------------------
+
+Using enclosing parentheses for continuation across multiple lines
+in context managers is now supported. This allows formatting a long
+collection of context managers in multiple lines in a similar way
+as it was previously possible with import statements. For instance,
+all these examples are now valid:
+
+.. code-block:: python
+
+    with (CtxManager() as example):
+        ...
+
+    with (
+        CtxManager1(),
+        CtxManager2()
+    ):
+        ...
+
+    with (CtxManager1() as example,
+          CtxManager2()):
+        ...
+
+    with (CtxManager1(),
+          CtxManager2() as example):
+        ...
+
+    with (
+        CtxManager1() as example1,
+        CtxManager2() as example2
+    ):
+        ...
+
+it is also possible to use a trailing comma at the end of the
+enclosed group:
+
+.. code-block:: python
+
+    with (
+        CtxManager1() as example1,
+        CtxManager2() as example2,
+        CtxManager3() as example3,
+    ):
+        ...
+
+This new syntax uses the non LL(1) capacities of the new parser.
+Check :pep:`617` for more details.
+
+(Contributed by Guido van Rossum, Pablo Galindo and Lysandros Nikolaou
+in :issue:`12782` and :issue:`40334`.)
+
+
 PEP 563: Postponed Evaluation of Annotations Becomes Default
 ------------------------------------------------------------
 
