100% test coverage, better mapping protocol compatibility, some minor bugfixes

Doc/library/configparser.rst

@@ -391,17 +391,20 @@ However, there are a few differences that should be taken into account:
 
 * Trying to delete the ``DEFAULTSECT`` raises ``ValueError``.
 
-* There are two parser-level methods in the legacy API that hide the dictionary
-  interface and are incompatible:
+* ``parser.get(section, option, **kwargs)`` - the second argument is **not**
+  a fallback value. Note however that the section-level ``get()`` methods are
+  compatible both with the mapping protocol and the classic configparser API.
 
-  * ``parser.get(section, option, **kwargs)`` - the second argument is **not** a
-    fallback value
-
-  * ``parser.items(section)`` - this returns a list of *option*, *value* pairs
-    for a specified ``section``
+* ``parser.items()`` is compatible with the mapping protocol (returns a list of
+  *section_name*, *section_proxy* pairs including the DEFAULTSECT).  However,
+  this method can also be invoked with arguments: ``parser.items(section, raw,
+  vars)``. The latter call returns a list of *option*, *value* pairs for
+  a specified ``section``, with all interpolations expanded (unless
+  ``raw=True`` is provided).
 
 The mapping protocol is implemented on top of the existing legacy API so that
-subclassing the original interface makes the mappings work as expected as well.
+subclasses overriding the original interface still should have mappings working
+as expected.
 
 
 Customizing Parser Behaviour
@@ -906,7 +909,8 @@ ConfigParser Objects
    .. method:: has_option(section, option)
 
       If the given *section* exists, and contains the given *option*, return
-      :const:`True`; otherwise return :const:`False`.
+      :const:`True`; otherwise return :const:`False`. If the specified
+      *section* is :const:`None` or an empty string, DEFAULT is assumed.
 
 
    .. method:: read(filenames, encoding=None)
@@ -964,14 +968,17 @@ ConfigParser Objects
 
    .. method:: read_dict(dictionary, source='<dict>')
 
-      Load configuration from a dictionary.  Keys are section names, values are
-      dictionaries with keys and values that should be present in the section.
-      If the used dictionary type preserves order, sections and their keys will
-      be added in order.  Values are automatically converted to strings.
+      Load configuration from any object that provides a dict-like ``items()``
+      method.  Keys are section names, values are dictionaries with keys and
+      values that should be present in the section.  If the used dictionary
+      type preserves order, sections and their keys will be added in order.
+      Values are automatically converted to strings.
 
       Optional argument *source* specifies a context-specific name of the
       dictionary passed.  If not given, ``<dict>`` is used.
 
+      This method can be used to copy state between parsers.
+
       .. versionadded:: 3.2
 
 
@@ -1019,10 +1026,13 @@ ConfigParser Objects
       *fallback*.
 
 
-   .. method:: items(section, raw=False, vars=None)
+   .. method:: items([section], raw=False, vars=None)
+
+      When *section* is not given, return a list of *section_name*,
+      *section_proxy* pairs, including DEFAULTSECT.
 
-      Return a list of *name*, *value* pairs for the options in the given
-      *section*.  Optional arguments have the same meaning as for the
+      Otherwise, return a list of *name*, *value* pairs for the options in the
+      given *section*.  Optional arguments have the same meaning as for the
       :meth:`get` method.
 
 

Lib/configparser.py

@@ -98,8 +98,10 @@ ConfigParser -- responsible for parsing a list of
         insensitively defined as 0, false, no, off for False, and 1, true,
         yes, on for True).  Returns False or True.
 
-    items(section, raw=False, vars=None)
-        Return a list of tuples with (name, value) for each option
+    items(section=_UNSET, raw=False, vars=None)
+        If section is given, return a list of tuples with (section_name,
+        section_proxy) for each section, including DEFAULTSECT. Otherwise,
+        return a list of tuples with (name, value) for each option
         in the section.
 
     remove_section(section)
@@ -495,9 +497,9 @@ class ExtendedInterpolation(Interpolation):
                         raise InterpolationSyntaxError(
                             option, section,
                             "More than one ':' found: %r" % (rest,))
-                except KeyError:
+                except (KeyError, NoSectionError, NoOptionError):
                     raise InterpolationMissingOptionError(
-                        option, section, rest, var)
+                        option, section, rest, ":".join(path))
                 if "$" in v:
                     self._interpolate_some(parser, opt, accum, v, sect,
                                            dict(parser.items(sect, raw=True)),
@@ -730,7 +732,7 @@ class RawConfigParser(MutableMapping):
             except (DuplicateSectionError, ValueError):
                 if self._strict and section in elements_added:
                     raise
-                elements_added.add(section)
+            elements_added.add(section)
             for key, value in keys.items():
                 key = self.optionxform(str(key))
                 if value is not None:
@@ -820,7 +822,7 @@ class RawConfigParser(MutableMapping):
             else:
                 return fallback
 
-    def items(self, section, raw=False, vars=None):
+    def items(self, section=_UNSET, raw=False, vars=None):
         """Return a list of (name, value) tuples for each option in a section.
 
         All % interpolations are expanded in the return values, based on the
@@ -831,6 +833,8 @@ class RawConfigParser(MutableMapping):
 
         The section DEFAULT is special.
         """
+        if section is _UNSET:
+            return super().items()
         d = self._defaults.copy()
         try:
             d.update(self._sections[section])
@@ -851,7 +855,9 @@ class RawConfigParser(MutableMapping):
         return optionstr.lower()
 
     def has_option(self, section, option):
-        """Check for the existence of a given option in a given section."""
+        """Check for the existence of a given option in a given section.
+        If the specified `section' is None or an empty string, DEFAULT is
+        assumed. If the specified `section' does not exist, returns False."""
         if not section or section == self.default_section:
             option = self.optionxform(option)
             return option in self._defaults
@@ -1059,9 +1065,6 @@ class RawConfigParser(MutableMapping):
                         # match if it would set optval to None
                         if optval is not None:
                             optval = optval.strip()
-                            # allow empty values
-                            if optval == '""':
-                                optval = ''
                             cursect[optname] = [optval]
                         else:
                             # valueless option handling
@@ -1196,21 +1199,24 @@ class SectionProxy(MutableMapping):
         return self._parser.set(self._name, key, value)
 
     def __delitem__(self, key):
-        if not self._parser.has_option(self._name, key):
+        if not (self._parser.has_option(self._name, key) and
+                self._parser.remove_option(self._name, key)):
             raise KeyError(key)
-        return self._parser.remove_option(self._name, key)
 
     def __contains__(self, key):
         return self._parser.has_option(self._name, key)
 
     def __len__(self):
-        # XXX weak performance
-        return len(self._parser.options(self._name))
+        return len(self._options())
 
     def __iter__(self):
-        # XXX weak performance
-        # XXX does not break when underlying container state changed
-        return self._parser.options(self._name).__iter__()
+        return self._options().__iter__()
+
+    def _options(self):
+        if self._name != self._parser.default_section:
+            return self._parser.options(self._name)
+        else:
+            return self._parser.defaults()
 
     def get(self, option, fallback=None, *, raw=False, vars=None):
         return self._parser.get(self._name, option, raw=raw, vars=vars,

Misc/NEWS

@@ -293,6 +293,8 @@ Library
 - Issue #10467: Fix BytesIO.readinto() after seeking into a position after the
   end of the file.
 
+- configparser: 100% test coverage.
+
 - Issue #10499: configparser supports pluggable interpolation handlers. The
   default classic interpolation handler is called BasicInterpolation. Another
   interpolation handler added (ExtendedInterpolation) which supports the syntax
@@ -314,7 +316,9 @@ Library
 - Issue #9421: configparser's getint(), getfloat() and getboolean() methods
   accept vars and default arguments just like get() does.
 
-- Issue #9452: configparser supports reading from strings and dictionaries.
+- Issue #9452: configparser supports reading from strings and dictionaries
+  (thanks to the mapping protocol API, the latter can be used to copy data
+  between parsers).
 
 - configparser: accepted INI file structure is now customizable, including
   comment prefixes, name of the DEFAULT section, empty lines in multiline