Issue #25179: Preparatory cleanup of existing docs on string formatting

* Various sections were pointing to the section on the string.Formatter
  class, when the section on the common format string syntax is probably more
  appropriate
* Fix references to various format() functions and methods
* Nested replacement fields may contain conversions and format specifiers,
  and this is tested; see Issue #19729 for instance

6 files changed, 27 insertions, 24 deletions

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 976cd49..980dfcf 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -604,7 +604,7 @@ Instance methods:
 
 .. method:: date.__format__(format)
 
-   Same as :meth:`.date.strftime`. This makes it possible to specify format
+   Same as :meth:`.date.strftime`. This makes it possible to specify a format
    string for a :class:`.date` object when using :meth:`str.format`. For a
    complete list of formatting directives, see
    :ref:`strftime-strptime-behavior`.
@@ -1179,7 +1179,7 @@ Instance methods:
 
 .. method:: datetime.__format__(format)
 
-   Same as :meth:`.datetime.strftime`.  This makes it possible to specify format
+   Same as :meth:`.datetime.strftime`.  This makes it possible to specify a format
    string for a :class:`.datetime` object when using :meth:`str.format`.  For a
    complete list of formatting directives, see
    :ref:`strftime-strptime-behavior`.
@@ -1424,7 +1424,7 @@ Instance methods:
 
 .. method:: time.__format__(format)
 
-   Same as :meth:`.time.strftime`. This makes it possible to specify format string
+   Same as :meth:`.time.strftime`. This makes it possible to specify a format string
    for a :class:`.time` object when using :meth:`str.format`.  For a
    complete list of formatting directives, see
    :ref:`strftime-strptime-behavior`.
diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst
index 81f97b3..8a02a55 100644
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -555,12 +555,12 @@ Some rules:
 3. When another data type is mixed in, the :attr:`value` attribute is *not the
    same* as the enum member itself, although it is equivalent and will compare
    equal.
-4. %-style formatting:  `%s` and `%r` call :class:`Enum`'s :meth:`__str__` and
-   :meth:`__repr__` respectively; other codes (such as `%i` or `%h` for
-   IntEnum) treat the enum member as its mixed-in type.
-5. :meth:`str.__format__` (or :func:`format`) will use the mixed-in
-   type's :meth:`__format__`.  If the :class:`Enum`'s :func:`str` or
-   :func:`repr` is desired use the `!s` or `!r` :class:`str` format codes.
+4. %-style formatting:  `%s` and `%r` call the :class:`Enum` class's
+   :meth:`__str__` and :meth:`__repr__` respectively; other codes (such as
+   `%i` or `%h` for IntEnum) treat the enum member as its mixed-in type.
+5. :meth:`str.format` (or :func:`format`) will use the mixed-in
+   type's :meth:`__format__`.  If the :class:`Enum` class's :func:`str` or
+   :func:`repr` is desired, use the `!s` or `!r` format codes.
 
 
 Interesting examples
diff --git a/Doc/library/pprint.rst b/Doc/library/pprint.rst
index 0b44dc8..b109efe 100644
--- a/Doc/library/pprint.rst
+++ b/Doc/library/pprint.rst
@@ -197,7 +197,7 @@ are converted to strings.  The default implementation uses the internals of the
    the current presentation context (direct and indirect containers for *object*
    that are affecting the presentation) as the keys; if an object needs to be
    presented which is already represented in *context*, the third return value
-   should be ``True``.  Recursive calls to the :meth:`format` method should add
+   should be ``True``.  Recursive calls to the :meth:`.format` method should add
    additional entries for containers to this dictionary.  The third argument,
    *maxlevels*, gives the requested limit to recursion; this will be ``0`` if there
    is no requested limit.  This argument should be passed unmodified to recursive
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index 8bcc4a0..774b0c6 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -1450,7 +1450,7 @@ multiple fragments.
 
    For more information on the ``str`` class and its methods, see
    :ref:`textseq` and the :ref:`string-methods` section below.  To output
-   formatted strings, see the :ref:`string-formatting` section.  In addition,
+   formatted strings, see the :ref:`formatstrings` section.  In addition,
    see the :ref:`stringservices` section.
 
 
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 2bd8dfd..5b917d9 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -75,14 +75,14 @@ The constants defined in this module are:
 
 .. _string-formatting:
 
-String Formatting
------------------
+Custom String Formatting
+------------------------
 
 The built-in string class provides the ability to do complex variable
-substitutions and value formatting via the :func:`format` method described in
+substitutions and value formatting via the :meth:`~str.format` method described in
 :pep:`3101`.  The :class:`Formatter` class in the :mod:`string` module allows
 you to create and customize your own string formatting behaviors using the same
-implementation as the built-in :meth:`format` method.
+implementation as the built-in :meth:`~str.format` method.
 
 
 .. class:: Formatter
@@ -91,9 +91,9 @@ implementation as the built-in :meth:`format` method.
 
    .. method:: format(format_string, *args, **kwargs)
 
-      :meth:`format` is the primary API method.  It takes a format string and
+      The primary API method.  It takes a format string and
       an arbitrary set of positional and keyword arguments.
-      :meth:`format` is just a wrapper that calls :meth:`vformat`.
+      It is just a wrapper that calls :meth:`vformat`.
 
       .. deprecated:: 3.5
          Passing a format string as keyword argument *format_string* has been
@@ -267,8 +267,9 @@ Most built-in types support a common formatting mini-language, which is
 described in the next section.
 
 A *format_spec* field can also include nested replacement fields within it.
-These nested replacement fields can contain only a field name; conversion flags
-and format specifications are not allowed.  The replacement fields within the
+These nested replacement fields may contain a field name, conversion flag
+and format specification, but deeper nesting is
+not allowed.  The replacement fields within the
 format_spec are substituted before the *format_spec* string is interpreted.
 This allows the formatting of a value to be dynamically specified.
 
@@ -306,8 +307,10 @@ The general form of a *standard format specifier* is:
 
 If a valid *align* value is specified, it can be preceded by a *fill*
 character that can be any character and defaults to a space if omitted.
-Note that it is not possible to use ``{`` and ``}`` as *fill* char while
-using the :meth:`str.format` method; this limitation however doesn't
+It is not possible to use a literal curly brace ("``{``" or "``}``") as
+the *fill* character when using the :meth:`str.format`
+method.  However, it is possible to insert a curly brace
+with a nested replacement field.  This limitation doesn't
 affect the :func:`format` function.
 
 The meaning of the various alignment options is as follows:
@@ -496,8 +499,8 @@ The available presentation types for floating point and decimal values are:
 Format examples
 ^^^^^^^^^^^^^^^
 
-This section contains examples of the new format syntax and comparison with
-the old ``%``-formatting.
+This section contains examples of the :meth:`str.format` syntax and
+comparison with the old ``%``-formatting.
 
 In most of the cases the syntax is similar to the old ``%``-formatting, with the
 addition of the ``{}`` and with ``:`` used instead of ``%``.
diff --git a/Doc/library/tracemalloc.rst b/Doc/library/tracemalloc.rst
index 861be37..5feb2d9 100644
--- a/Doc/library/tracemalloc.rst
+++ b/Doc/library/tracemalloc.rst
@@ -620,7 +620,7 @@ Traceback
       *limit* is set, only format the *limit* most recent frames.
 
       Similar to the :func:`traceback.format_tb` function, except that
-      :meth:`format` does not include newlines.
+      :meth:`.format` does not include newlines.
 
       Example::