Issue #5412: extend configparser to support mapping access

1 files changed, 175 insertions, 66 deletions

diff --git a/Lib/configparser.py b/Lib/configparser.py
index 03d6713..80f6aed 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -85,7 +85,7 @@ ConfigParser -- responsible for parsing a list of
         and their keys will be added in order. Values are automatically
         converted to strings.
 
-    get(section, option, raw=False, vars=None, default=_UNSET)
+    get(section, option, raw=False, vars=None, fallback=_UNSET)
         Return a string value for the named option.  All % interpolations are
         expanded in the return values, based on the defaults passed into the
         constructor and the DEFAULT section.  Additional substitutions may be
@@ -93,13 +93,13 @@ ConfigParser -- responsible for parsing a list of
         contents override any pre-existing defaults. If `option' is a key in
         `vars', the value from `vars' is used.
 
-    getint(section, options, raw=False, vars=None, default=_UNSET)
+    getint(section, options, raw=False, vars=None, fallback=_UNSET)
         Like get(), but convert value to an integer.
 
-    getfloat(section, options, raw=False, vars=None, default=_UNSET)
+    getfloat(section, options, raw=False, vars=None, fallback=_UNSET)
         Like get(), but convert value to a float.
 
-    getboolean(section, options, raw=False, vars=None, default=_UNSET)
+    getboolean(section, options, raw=False, vars=None, fallback=_UNSET)
         Like get(), but convert value to a boolean (currently case
         insensitively defined as 0, false, no, off for False, and 1, true,
         yes, on for True).  Returns False or True.
@@ -123,13 +123,10 @@ ConfigParser -- responsible for parsing a list of
         between keys and values are surrounded by spaces.
 """
 
-try:
-    from collections import OrderedDict as _default_dict
-except ImportError:
-    # fallback for setup.py which hasn't yet built _collections
-    _default_dict = dict
-
+from collections import MutableMapping, OrderedDict as _default_dict
+import functools
 import io
+import itertools
 import re
 import sys
 import warnings
@@ -366,7 +363,7 @@ _COMPATIBLE = object()
 _UNSET = object()
 
 
-class RawConfigParser:
+class RawConfigParser(MutableMapping):
     """ConfigParser that does not do interpolation."""
 
     # Regular expressions for parsing section headers and options
@@ -413,6 +410,8 @@ class RawConfigParser:
         self._dict = dict_type
         self._sections = self._dict()
         self._defaults = self._dict()
+        self._views = self._dict()
+        self._views[DEFAULTSECT] = SectionProxy(self, DEFAULTSECT)
         if defaults:
             for key, value in defaults.items():
                 self._defaults[self.optionxform(key)] = value
@@ -434,6 +433,7 @@ class RawConfigParser:
             self._startonly_comment_prefixes = ()
             self._comment_prefixes = tuple(comment_prefixes or ())
         self._strict = strict
+        self._allow_no_value = allow_no_value
         self._empty_lines_in_values = empty_lines_in_values
 
     def defaults(self):
@@ -451,12 +451,13 @@ class RawConfigParser:
         already exists. Raise ValueError if name is DEFAULT or any of it's
         case-insensitive variants.
         """
-        if section.lower() == "default":
+        if section.upper() == DEFAULTSECT:
             raise ValueError('Invalid section name: %s' % section)
 
         if section in self._sections:
             raise DuplicateSectionError(section)
         self._sections[section] = self._dict()
+        self._views[section] = SectionProxy(self, section)
 
     def has_section(self, section):
         """Indicate whether the named section is present in the configuration.
@@ -534,7 +535,7 @@ class RawConfigParser:
         for section, keys in dictionary.items():
             try:
                 self.add_section(section)
-            except DuplicateSectionError:
+            except (DuplicateSectionError, ValueError):
                 if self._strict and section in elements_added:
                     raise
                 elements_added.add(section)
@@ -556,29 +557,31 @@ class RawConfigParser:
         )
         self.read_file(fp, source=filename)
 
-    def get(self, section, option, vars=None, default=_UNSET):
+    def get(self, section, option, *, vars=None, fallback=_UNSET):
         """Get an option value for a given section.
 
         If `vars' is provided, it must be a dictionary. The option is looked up
         in `vars' (if provided), `section', and in `DEFAULTSECT' in that order.
-        If the key is not found and `default' is provided, it is used as
-        a fallback value. `None' can be provided as a `default' value.
+        If the key is not found and `fallback' is provided, it is used as
+        a fallback value. `None' can be provided as a `fallback' value.
+
+        Arguments `vars' and `fallback' are keyword only.
         """
         try:
             d = self._unify_values(section, vars)
         except NoSectionError:
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
         option = self.optionxform(option)
         try:
             return d[option]
         except KeyError:
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise NoOptionError(option, section)
             else:
-                return default
+                return fallback
 
     def items(self, section):
         try:
@@ -593,35 +596,36 @@ class RawConfigParser:
             del d["__name__"]
         return d.items()
 
-    def _get(self, section, conv, option, *args, **kwargs):
-        return conv(self.get(section, option, *args, **kwargs))
+    def _get(self, section, conv, option, **kwargs):
+        return conv(self.get(section, option, **kwargs))
 
-    def getint(self, section, option, vars=None, default=_UNSET):
+    def getint(self, section, option, *, vars=None, fallback=_UNSET):
         try:
-            return self._get(section, int, option, vars)
+            return self._get(section, int, option, vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
-    def getfloat(self, section, option, vars=None, default=_UNSET):
+    def getfloat(self, section, option, *, vars=None, fallback=_UNSET):
         try:
-            return self._get(section, float, option, vars)
+            return self._get(section, float, option, vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
-    def getboolean(self, section, option, vars=None, default=_UNSET):
+    def getboolean(self, section, option, *, vars=None, fallback=_UNSET):
         try:
-            return self._get(section, self._convert_to_boolean, option, vars)
+            return self._get(section, self._convert_to_boolean, option,
+                             vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
     def optionxform(self, optionstr):
         return optionstr.lower()
@@ -671,7 +675,7 @@ class RawConfigParser:
         for key, value in section_items:
             if key == "__name__":
                 continue
-            if (value is not None) or (self._optcre == self.OPTCRE):
+            if value is not None or not self._allow_no_value:
                 value = delimiter + str(value).replace('\n', '\n\t')
             else:
                 value = ""
@@ -698,8 +702,40 @@ class RawConfigParser:
         existed = section in self._sections
         if existed:
             del self._sections[section]
+            del self._views[section]
         return existed
 
+    def __getitem__(self, key):
+        if key != DEFAULTSECT and not self.has_section(key):
+            raise KeyError(key)
+        return self._views[key]
+
+    def __setitem__(self, key, value):
+        # To conform with the mapping protocol, overwrites existing values in
+        # the section.
+
+        # XXX this is not atomic if read_dict fails at any point. Then again,
+        # no update method in configparser is atomic in this implementation.
+        self.remove_section(key)
+        self.read_dict({key: value})
+
+    def __delitem__(self, key):
+        if key == DEFAULTSECT:
+            raise ValueError("Cannot remove the default section.")
+        if not self.has_section(key):
+            raise KeyError(key)
+        self.remove_section(key)
+
+    def __contains__(self, key):
+        return key == DEFAULTSECT or self.has_section(key)
+
+    def __len__(self):
+        return len(self._sections) + 1 # the default section
+
+    def __iter__(self):
+        # XXX does it break when underlying container state changed?
+        return itertools.chain((DEFAULTSECT,), self._sections.keys())
+
     def _read(self, fp, fpname):
         """Parse a sectioned configuration file.
 
@@ -776,6 +812,7 @@ class RawConfigParser:
                         cursect = self._dict()
                         cursect['__name__'] = sectname
                         self._sections[sectname] = cursect
+                        self._views[sectname] = SectionProxy(self, sectname)
                         elements_added.add(sectname)
                     # So sections can't start with a continuation line
                     optname = None
@@ -818,8 +855,8 @@ class RawConfigParser:
         self._join_multiline_values()
 
     def _join_multiline_values(self):
-        all_sections = [self._defaults]
-        all_sections.extend(self._sections.values())
+        all_sections = itertools.chain((self._defaults,),
+                                       self._sections.values())
         for options in all_sections:
             for name, val in options.items():
                 if isinstance(val, list):
@@ -857,73 +894,95 @@ class RawConfigParser:
             raise ValueError('Not a boolean: %s' % value)
         return self.BOOLEAN_STATES[value.lower()]
 
+    def _validate_value_type(self, value):
+        """Raises a TypeError for non-string values.
+
+        The only legal non-string value if we allow valueless
+        options is None, so we need to check if the value is a
+        string if:
+        - we do not allow valueless options, or
+        - we allow valueless options but the value is not None
+
+        For compatibility reasons this method is not used in classic set()
+        for RawConfigParsers and ConfigParsers. It is invoked in every
+        case for mapping protocol access and in SafeConfigParser.set().
+        """
+        if not self._allow_no_value or value:
+            if not isinstance(value, str):
+                raise TypeError("option values must be strings")
+
+
 
 class ConfigParser(RawConfigParser):
     """ConfigParser implementing interpolation."""
 
-    def get(self, section, option, raw=False, vars=None, default=_UNSET):
+    def get(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
         """Get an option value for a given section.
 
         If `vars' is provided, it must be a dictionary. The option is looked up
         in `vars' (if provided), `section', and in `DEFAULTSECT' in that order.
-        If the key is not found and `default' is provided, it is used as
-        a fallback value. `None' can be provided as a `default' value.
+        If the key is not found and `fallback' is provided, it is used as
+        a fallback value. `None' can be provided as a `fallback' value.
 
         All % interpolations are expanded in the return values, unless the
         optional argument `raw' is true.  Values for interpolation keys are
         looked up in the same manner as the option.
 
+        Arguments `raw', `vars', and `fallback' are keyword only.
+
         The section DEFAULT is special.
         """
         try:
             d = self._unify_values(section, vars)
         except NoSectionError:
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
         option = self.optionxform(option)
         try:
             value = d[option]
         except KeyError:
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise NoOptionError(option, section)
             else:
-                return default
+                return fallback
 
         if raw or value is None:
             return value
         else:
             return self._interpolate(section, option, value, d)
 
-    def getint(self, section, option, raw=False, vars=None, default=_UNSET):
+    def getint(self, section, option, *, raw=False, vars=None,
+               fallback=_UNSET):
         try:
-            return self._get(section, int, option, raw, vars)
+            return self._get(section, int, option, raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
-    def getfloat(self, section, option, raw=False, vars=None, default=_UNSET):
+    def getfloat(self, section, option, *, raw=False, vars=None,
+                 fallback=_UNSET):
         try:
-            return self._get(section, float, option, raw, vars)
+            return self._get(section, float, option, raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
-    def getboolean(self, section, option, raw=False, vars=None,
-                   default=_UNSET):
+    def getboolean(self, section, option, *, raw=False, vars=None,
+                   fallback=_UNSET):
         try:
-            return self._get(section, self._convert_to_boolean, option, raw,
-                             vars)
+            return self._get(section, self._convert_to_boolean, option,
+                             raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
-            if default is _UNSET:
+            if fallback is _UNSET:
                 raise
             else:
-                return default
+                return fallback
 
     def items(self, section, raw=False, vars=None):
         """Return a list of (name, value) tuples for each option in a section.
@@ -1037,14 +1096,7 @@ class SafeConfigParser(ConfigParser):
 
     def set(self, section, option, value=None):
         """Set an option.  Extend ConfigParser.set: check for string values."""
-        # The only legal non-string value if we allow valueless
-        # options is None, so we need to check if the value is a
-        # string if:
-        # - we do not allow valueless options, or
-        # - we allow valueless options but the value is not None
-        if self._optcre is self.OPTCRE or value:
-            if not isinstance(value, str):
-                raise TypeError("option values must be strings")
+        self._validate_value_type(value)
         # check for bad percent signs
         if value:
             tmp_value = value.replace('%%', '') # escaped percent signs
@@ -1053,3 +1105,60 @@ class SafeConfigParser(ConfigParser):
                 raise ValueError("invalid interpolation syntax in %r at "
                                 "position %d" % (value, tmp_value.find('%')))
         ConfigParser.set(self, section, option, value)
+
+
+class SectionProxy(MutableMapping):
+    """A proxy for a single section from a parser."""
+
+    _noname = ("__name__ special key access and modification "
+               "not supported through the mapping interface.")
+
+    def __init__(self, parser, section_name):
+        """Creates a view on a section named `section_name` in `parser`."""
+        self._parser = parser
+        self._section = section_name
+        self.getint = functools.partial(self._parser.getint,
+                                        self._section)
+        self.getfloat = functools.partial(self._parser.getfloat,
+                                          self._section)
+        self.getboolean = functools.partial(self._parser.getboolean,
+                                            self._section)
+
+    def __repr__(self):
+        return '<Section: {}>'.format(self._section)
+
+    def __getitem__(self, key):
+        if key == '__name__':
+            raise ValueError(self._noname)
+        if not self._parser.has_option(self._section, key):
+            raise KeyError(key)
+        return self._parser.get(self._section, key)
+
+    def __setitem__(self, key, value):
+        if key == '__name__':
+            raise ValueError(self._noname)
+        self._parser._validate_value_type(value)
+        return self._parser.set(self._section, key, value)
+
+    def __delitem__(self, key):
+        if key == '__name__':
+            raise ValueError(self._noname)
+        if not self._parser.has_option(self._section, key):
+            raise KeyError(key)
+        return self._parser.remove_option(self._section, key)
+
+    def __contains__(self, key):
+        if key == '__name__':
+            return False
+        return self._parser.has_option(self._section, key)
+
+    def __len__(self):
+        # __name__ is properly hidden by .options()
+        # XXX weak performance
+        return len(self._parser.options(self._section))
+
+    def __iter__(self):
+        # __name__ is properly hidden by .options()
+        # XXX weak performance
+        # XXX does not break when underlying container state changed
+        return self._parser.options(self._section).__iter__()