Issue 10499: Modular interpolation in configparser

1 files changed, 309 insertions, 231 deletions

diff --git a/Lib/configparser.py b/Lib/configparser.py
index f9bb32c..56c02ba 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -4,23 +4,13 @@ A configuration file consists of sections, lead by a "[section]" header,
 and followed by "name: value" entries, with continuations and such in
 the style of RFC 822.
 
-The option values can contain format strings which refer to other values in
-the same section, or values in a special [DEFAULT] section.
-
-For example:
-
-    something: %(dir)s/whatever
-
-would resolve the "%(dir)s" to the value of dir.  All reference
-expansions are done late, on demand.
-
 Intrinsic defaults can be specified by passing them into the
-ConfigParser constructor as a dictionary.
+SafeConfigParser constructor as a dictionary.
 
 class:
 
-ConfigParser -- responsible for parsing a list of
-                configuration files, and managing the parsed database.
+SafeConfigParser -- responsible for parsing a list of
+                    configuration files, and managing the parsed database.
 
     methods:
 
@@ -316,7 +306,7 @@ class ParsingError(Error):
     def filename(self):
         """Deprecated, use `source'."""
         warnings.warn(
-            "This 'filename' attribute will be removed in future versions.  "
+            "The 'filename' attribute will be removed in future versions.  "
             "Use 'source' instead.",
             DeprecationWarning, stacklevel=2
         )
@@ -362,6 +352,204 @@ _COMPATIBLE = object()
 _UNSET = object()
 
 
+class Interpolation:
+    """Dummy interpolation that passes the value through with no changes."""
+
+    def before_get(self, parser, section, option, value, defaults):
+        return value
+
+    def before_set(self, parser, section, option, value):
+        return value
+
+    def before_read(self, parser, section, option, value):
+        return value
+
+    def before_write(self, parser, section, option, value):
+        return value
+
+
+class BasicInterpolation(Interpolation):
+    """Interpolation as implemented in the classic SafeConfigParser.
+
+    The option values can contain format strings which refer to other values in
+    the same section, or values in the special default section.
+
+    For example:
+
+        something: %(dir)s/whatever
+
+    would resolve the "%(dir)s" to the value of dir.  All reference
+    expansions are done late, on demand. If a user needs to use a bare % in
+    a configuration file, she can escape it by writing %%. Other other % usage
+    is considered a user error and raises `InterpolationSyntaxError'."""
+
+    _KEYCRE = re.compile(r"%\(([^)]+)\)s")
+
+    def before_get(self, parser, section, option, value, defaults):
+        L = []
+        self._interpolate_some(parser, option, L, value, section, defaults, 1)
+        return ''.join(L)
+
+    def before_set(self, parser, section, option, value):
+        tmp_value = value.replace('%%', '') # escaped percent signs
+        tmp_value = self._KEYCRE.sub('', tmp_value) # valid syntax
+        if '%' in tmp_value:
+            raise ValueError("invalid interpolation syntax in %r at "
+                             "position %d" % (value, tmp_value.find('%')))
+        return value
+
+    def _interpolate_some(self, parser, option, accum, rest, section, map,
+                          depth):
+        if depth > MAX_INTERPOLATION_DEPTH:
+            raise InterpolationDepthError(option, section, rest)
+        while rest:
+            p = rest.find("%")
+            if p < 0:
+                accum.append(rest)
+                return
+            if p > 0:
+                accum.append(rest[:p])
+                rest = rest[p:]
+            # p is no longer used
+            c = rest[1:2]
+            if c == "%":
+                accum.append("%")
+                rest = rest[2:]
+            elif c == "(":
+                m = self._KEYCRE.match(rest)
+                if m is None:
+                    raise InterpolationSyntaxError(option, section,
+                        "bad interpolation variable reference %r" % rest)
+                var = parser.optionxform(m.group(1))
+                rest = rest[m.end():]
+                try:
+                    v = map[var]
+                except KeyError:
+                    raise InterpolationMissingOptionError(
+                        option, section, rest, var)
+                if "%" in v:
+                    self._interpolate_some(parser, option, accum, v,
+                                           section, map, depth + 1)
+                else:
+                    accum.append(v)
+            else:
+                raise InterpolationSyntaxError(
+                    option, section,
+                    "'%%' must be followed by '%%' or '(', "
+                    "found: %r" % (rest,))
+
+
+class ExtendedInterpolation(Interpolation):
+    """Advanced variant of interpolation, supports the syntax used by
+    `zc.buildout'. Enables interpolation between sections."""
+
+    _KEYCRE = re.compile(r"\$\{([^}]+)\}")
+
+    def before_get(self, parser, section, option, value, defaults):
+        L = []
+        self._interpolate_some(parser, option, L, value, section, defaults, 1)
+        return ''.join(L)
+
+    def before_set(self, parser, section, option, value):
+        tmp_value = value.replace('$$', '') # escaped dollar signs
+        tmp_value = self._KEYCRE.sub('', tmp_value) # valid syntax
+        if '$' in tmp_value:
+            raise ValueError("invalid interpolation syntax in %r at "
+                             "position %d" % (value, tmp_value.find('%')))
+        return value
+
+    def _interpolate_some(self, parser, option, accum, rest, section, map,
+                          depth):
+        if depth > MAX_INTERPOLATION_DEPTH:
+            raise InterpolationDepthError(option, section, rest)
+        while rest:
+            p = rest.find("$")
+            if p < 0:
+                accum.append(rest)
+                return
+            if p > 0:
+                accum.append(rest[:p])
+                rest = rest[p:]
+            # p is no longer used
+            c = rest[1:2]
+            if c == "$":
+                accum.append("$")
+                rest = rest[2:]
+            elif c == "{":
+                m = self._KEYCRE.match(rest)
+                if m is None:
+                    raise InterpolationSyntaxError(option, section,
+                        "bad interpolation variable reference %r" % rest)
+                path = parser.optionxform(m.group(1)).split(':')
+                rest = rest[m.end():]
+                sect = section
+                opt = option
+                try:
+                    if len(path) == 1:
+                        opt = path[0]
+                        v = map[opt]
+                    elif len(path) == 2:
+                        sect = path[0]
+                        opt = path[1]
+                        v = parser.get(sect, opt, raw=True)
+                    else:
+                        raise InterpolationSyntaxError(
+                            option, section,
+                            "More than one ':' found: %r" % (rest,))
+                except KeyError:
+                    raise InterpolationMissingOptionError(
+                        option, section, rest, var)
+                if "$" in v:
+                    self._interpolate_some(parser, opt, accum, v, sect,
+                                           dict(parser.items(sect, raw=True)),
+                                           depth + 1)
+                else:
+                    accum.append(v)
+            else:
+                raise InterpolationSyntaxError(
+                    option, section,
+                    "'$' must be followed by '$' or '{', "
+                    "found: %r" % (rest,))
+
+
+class BrokenInterpolation(Interpolation):
+    """Deprecated interpolation as implemented in the classic ConfigParser.
+    Use BasicInterpolation or ExtendedInterpolation instead."""
+
+    _KEYCRE = re.compile(r"%\(([^)]*)\)s|.")
+
+    def before_get(self, parser, section, option, value, vars):
+        rawval = value
+        depth = MAX_INTERPOLATION_DEPTH
+        while depth:                    # Loop through this until it's done
+            depth -= 1
+            if value and "%(" in value:
+                replace = functools.partial(self._interpolation_replace,
+                                            parser=parser)
+                value = self._KEYCRE.sub(replace, value)
+                try:
+                    value = value % vars
+                except KeyError as e:
+                    raise InterpolationMissingOptionError(
+                        option, section, rawval, e.args[0])
+            else:
+                break
+        if value and "%(" in value:
+            raise InterpolationDepthError(option, section, rawval)
+        return value
+
+    def before_set(self, parser, section, option, value):
+        return value
+
+    @staticmethod
+    def _interpolation_replace(match, parser):
+        s = match.group(1)
+        if s is None:
+            return match.group()
+        else:
+            return "%%(%s)s" % parser.optionxform(s)
+
+
 class RawConfigParser(MutableMapping):
     """ConfigParser that does not do interpolation."""
 
@@ -388,7 +576,8 @@ class RawConfigParser(MutableMapping):
                                            # space/tab
         (?P<value>.*))?$                   # everything up to eol
         """
-
+    # Interpolation algorithm to be used if the user does not specify another
+    _DEFAULT_INTERPOLATION = Interpolation()
     # Compiled regular expression for matching sections
     SECTCRE = re.compile(_SECT_TMPL, re.VERBOSE)
     # Compiled regular expression for matching options with typical separators
@@ -406,7 +595,15 @@ class RawConfigParser(MutableMapping):
                  allow_no_value=False, *, delimiters=('=', ':'),
                  comment_prefixes=_COMPATIBLE, strict=False,
                  empty_lines_in_values=True,
-                 default_section=DEFAULTSECT):
+                 default_section=DEFAULTSECT,
+                 interpolation=_UNSET):
+
+        if self.__class__ is RawConfigParser:
+            warnings.warn(
+                "The RawConfigParser class will be removed in future versions."
+                " Use 'SafeConfigParser(interpolation=None)' instead.",
+                DeprecationWarning, stacklevel=2
+            )
         self._dict = dict_type
         self._sections = self._dict()
         self._defaults = self._dict()
@@ -435,7 +632,11 @@ class RawConfigParser(MutableMapping):
         self._strict = strict
         self._allow_no_value = allow_no_value
         self._empty_lines_in_values = empty_lines_in_values
-        self._default_section=default_section
+        if interpolation is _UNSET:
+            self._interpolation = self._DEFAULT_INTERPOLATION
+        else:
+            self._interpolation = interpolation
+        self.default_section=default_section
 
     def defaults(self):
         return self._defaults
@@ -451,7 +652,7 @@ class RawConfigParser(MutableMapping):
         Raise DuplicateSectionError if a section by the specified name
         already exists. Raise ValueError if name is DEFAULT.
         """
-        if section == self._default_section:
+        if section == self.default_section:
             raise ValueError('Invalid section name: %s' % section)
 
         if section in self._sections:
@@ -555,7 +756,7 @@ class RawConfigParser(MutableMapping):
         )
         self.read_file(fp, source=filename)
 
-    def get(self, section, option, *, vars=None, fallback=_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
@@ -563,7 +764,12 @@ class RawConfigParser(MutableMapping):
         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.
+        If interpolation is enabled and the optional argument `raw' is False,
+        all interpolations are expanded in the return values.
+
+        Arguments `raw', `vars', and `fallback' are keyword only.
+
+        The section DEFAULT is special.
         """
         try:
             d = self._unify_values(section, vars)
@@ -574,61 +780,90 @@ class RawConfigParser(MutableMapping):
                 return fallback
         option = self.optionxform(option)
         try:
-            return d[option]
+            value = d[option]
         except KeyError:
             if fallback is _UNSET:
                 raise NoOptionError(option, section)
             else:
                 return fallback
 
-    def items(self, section):
-        try:
-            d2 = self._sections[section]
-        except KeyError:
-            if section != self._default_section:
-                raise NoSectionError(section)
-            d2 = self._dict()
-        d = self._defaults.copy()
-        d.update(d2)
-        return d.items()
+        if raw or value is None:
+            return value
+        else:
+            return self._interpolation.before_get(self, section, option, value,
+                                                  d)
 
     def _get(self, section, conv, option, **kwargs):
         return conv(self.get(section, option, **kwargs))
 
-    def getint(self, section, option, *, vars=None, fallback=_UNSET):
+    def getint(self, section, option, *, raw=False, vars=None,
+               fallback=_UNSET):
         try:
-            return self._get(section, int, option, vars=vars)
+            return self._get(section, int, option, raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
             if fallback is _UNSET:
                 raise
             else:
                 return fallback
 
-    def getfloat(self, section, option, *, vars=None, fallback=_UNSET):
+    def getfloat(self, section, option, *, raw=False, vars=None,
+                 fallback=_UNSET):
         try:
-            return self._get(section, float, option, vars=vars)
+            return self._get(section, float, option, raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
             if fallback is _UNSET:
                 raise
             else:
                 return fallback
 
-    def getboolean(self, section, option, *, vars=None, fallback=_UNSET):
+    def getboolean(self, section, option, *, raw=False, vars=None,
+                   fallback=_UNSET):
         try:
             return self._get(section, self._convert_to_boolean, option,
-                             vars=vars)
+                             raw=raw, vars=vars)
         except (NoSectionError, NoOptionError):
             if fallback is _UNSET:
                 raise
             else:
                 return fallback
 
+    def items(self, section, 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
+        defaults passed into the constructor, unless the optional argument
+        `raw' is true.  Additional substitutions may be provided using the
+        `vars' argument, which must be a dictionary whose contents overrides
+        any pre-existing defaults.
+
+        The section DEFAULT is special.
+        """
+        d = self._defaults.copy()
+        try:
+            d.update(self._sections[section])
+        except KeyError:
+            if section != self.default_section:
+                raise NoSectionError(section)
+        # Update with the entry specific variables
+        if vars:
+            for key, value in vars.items():
+                d[self.optionxform(key)] = value
+        options = list(d.keys())
+        if raw:
+            return [(option, d[option])
+                    for option in options]
+        else:
+            return [(option, self._interpolation.before_get(self, section,
+                                                            option, d[option],
+                                                            d))
+                    for option in options]
+
     def optionxform(self, optionstr):
         return optionstr.lower()
 
     def has_option(self, section, option):
         """Check for the existence of a given option in a given section."""
-        if not section or section == self._default_section:
+        if not section or section == self.default_section:
             option = self.optionxform(option)
             return option in self._defaults
         elif section not in self._sections:
@@ -640,7 +875,10 @@ class RawConfigParser(MutableMapping):
 
     def set(self, section, option, value=None):
         """Set an option."""
-        if not section or section == self._default_section:
+        if value:
+            value = self._interpolation.before_set(self, section, option,
+                                                   value)
+        if not section or section == self.default_section:
             sectdict = self._defaults
         else:
             try:
@@ -660,7 +898,7 @@ class RawConfigParser(MutableMapping):
         else:
             d = self._delimiters[0]
         if self._defaults:
-            self._write_section(fp, self._default_section,
+            self._write_section(fp, self.default_section,
                                     self._defaults.items(), d)
         for section in self._sections:
             self._write_section(fp, section,
@@ -670,6 +908,8 @@ class RawConfigParser(MutableMapping):
         """Write a single section to the specified `fp'."""
         fp.write("[{}]\n".format(section_name))
         for key, value in section_items:
+            value = self._interpolation.before_write(self, section_name, key,
+                                                     value)
             if value is not None or not self._allow_no_value:
                 value = delimiter + str(value).replace('\n', '\n\t')
             else:
@@ -679,7 +919,7 @@ class RawConfigParser(MutableMapping):
 
     def remove_option(self, section, option):
         """Remove an option."""
-        if not section or section == self._default_section:
+        if not section or section == self.default_section:
             sectdict = self._defaults
         else:
             try:
@@ -701,7 +941,7 @@ class RawConfigParser(MutableMapping):
         return existed
 
     def __getitem__(self, key):
-        if key != self._default_section and not self.has_section(key):
+        if key != self.default_section and not self.has_section(key):
             raise KeyError(key)
         return self._proxies[key]
 
@@ -715,21 +955,21 @@ class RawConfigParser(MutableMapping):
         self.read_dict({key: value})
 
     def __delitem__(self, key):
-        if key == self._default_section:
+        if key == self.default_section:
             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 == self._default_section or self.has_section(key)
+        return key == self.default_section 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((self._default_section,), self._sections.keys())
+        return itertools.chain((self.default_section,), self._sections.keys())
 
     def _read(self, fp, fpname):
         """Parse a sectioned configuration file.
@@ -801,7 +1041,7 @@ class RawConfigParser(MutableMapping):
                                                         lineno)
                         cursect = self._sections[sectname]
                         elements_added.add(sectname)
-                    elif sectname == self._default_section:
+                    elif sectname == self.default_section:
                         cursect = self._defaults
                     else:
                         cursect = self._dict()
@@ -836,7 +1076,7 @@ class RawConfigParser(MutableMapping):
                             cursect[optname] = [optval]
                         else:
                             # valueless option handling
-                            cursect[optname] = optval
+                            cursect[optname] = None
                     else:
                         # a non-fatal parsing error occurred. set up the
                         # exception but keep going. the exception will be
@@ -849,12 +1089,16 @@ class RawConfigParser(MutableMapping):
         self._join_multiline_values()
 
     def _join_multiline_values(self):
-        all_sections = itertools.chain((self._defaults,),
-                                       self._sections.values())
-        for options in all_sections:
+        defaults = self.default_section, self._defaults
+        all_sections = itertools.chain((defaults,),
+                                       self._sections.items())
+        for section, options in all_sections:
             for name, val in options.items():
                 if isinstance(val, list):
-                    options[name] = '\n'.join(val).rstrip()
+                    val = '\n'.join(val).rstrip()
+                options[name] = self._interpolation.before_read(self,
+                                                                section,
+                                                                name, val)
 
     def _handle_error(self, exc, fpname, lineno, line):
         if not exc:
@@ -871,7 +1115,7 @@ class RawConfigParser(MutableMapping):
         try:
             d.update(self._sections[section])
         except KeyError:
-            if section != self._default_section:
+            if section != self.default_section:
                 raise NoSectionError(section)
         # Update with the entry specific variables
         if vars:
@@ -906,197 +1150,31 @@ class RawConfigParser(MutableMapping):
                 raise TypeError("option values must be strings")
 
 
-
 class ConfigParser(RawConfigParser):
     """ConfigParser implementing interpolation."""
 
-    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 `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 fallback is _UNSET:
-                raise
-            else:
-                return fallback
-        option = self.optionxform(option)
-        try:
-            value = d[option]
-        except KeyError:
-            if fallback is _UNSET:
-                raise NoOptionError(option, section)
-            else:
-                return fallback
-
-        if raw or value is None:
-            return value
-        else:
-            return self._interpolate(section, option, value, d)
+    _DEFAULT_INTERPOLATION = BrokenInterpolation()
 
-    def getint(self, section, option, *, raw=False, vars=None,
-               fallback=_UNSET):
-        try:
-            return self._get(section, int, option, raw=raw, vars=vars)
-        except (NoSectionError, NoOptionError):
-            if fallback is _UNSET:
-                raise
-            else:
-                return fallback
-
-    def getfloat(self, section, option, *, raw=False, vars=None,
-                 fallback=_UNSET):
-        try:
-            return self._get(section, float, option, raw=raw, vars=vars)
-        except (NoSectionError, NoOptionError):
-            if fallback is _UNSET:
-                raise
-            else:
-                return fallback
-
-    def getboolean(self, section, option, *, raw=False, vars=None,
-                   fallback=_UNSET):
-        try:
-            return self._get(section, self._convert_to_boolean, option,
-                             raw=raw, vars=vars)
-        except (NoSectionError, NoOptionError):
-            if fallback is _UNSET:
-                raise
-            else:
-                return fallback
-
-    def items(self, section, 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
-        defaults passed into the constructor, unless the optional argument
-        `raw' is true.  Additional substitutions may be provided using the
-        `vars' argument, which must be a dictionary whose contents overrides
-        any pre-existing defaults.
-
-        The section DEFAULT is special.
-        """
-        d = self._defaults.copy()
-        try:
-            d.update(self._sections[section])
-        except KeyError:
-            if section != self._default_section:
-                raise NoSectionError(section)
-        # Update with the entry specific variables
-        if vars:
-            for key, value in vars.items():
-                d[self.optionxform(key)] = value
-        options = list(d.keys())
-        if raw:
-            return [(option, d[option])
-                    for option in options]
-        else:
-            return [(option, self._interpolate(section, option, d[option], d))
-                    for option in options]
-
-    def _interpolate(self, section, option, rawval, vars):
-        # do the string interpolation
-        value = rawval
-        depth = MAX_INTERPOLATION_DEPTH
-        while depth:                    # Loop through this until it's done
-            depth -= 1
-            if value and "%(" in value:
-                value = self._KEYCRE.sub(self._interpolation_replace, value)
-                try:
-                    value = value % vars
-                except KeyError as e:
-                    raise InterpolationMissingOptionError(
-                        option, section, rawval, e.args[0])
-            else:
-                break
-        if value and "%(" in value:
-            raise InterpolationDepthError(option, section, rawval)
-        return value
-
-    _KEYCRE = re.compile(r"%\(([^)]*)\)s|.")
-
-    def _interpolation_replace(self, match):
-        s = match.group(1)
-        if s is None:
-            return match.group()
-        else:
-            return "%%(%s)s" % self.optionxform(s)
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        if self.__class__ is ConfigParser:
+            warnings.warn(
+                "The ConfigParser class will be removed in future versions."
+                " Use SafeConfigParser instead.",
+                DeprecationWarning, stacklevel=2
+            )
 
 
 class SafeConfigParser(ConfigParser):
     """ConfigParser implementing sane interpolation."""
 
-    def _interpolate(self, section, option, rawval, vars):
-        # do the string interpolation
-        L = []
-        self._interpolate_some(option, L, rawval, section, vars, 1)
-        return ''.join(L)
-
-    _interpvar_re = re.compile(r"%\(([^)]+)\)s")
-
-    def _interpolate_some(self, option, accum, rest, section, map, depth):
-        if depth > MAX_INTERPOLATION_DEPTH:
-            raise InterpolationDepthError(option, section, rest)
-        while rest:
-            p = rest.find("%")
-            if p < 0:
-                accum.append(rest)
-                return
-            if p > 0:
-                accum.append(rest[:p])
-                rest = rest[p:]
-            # p is no longer used
-            c = rest[1:2]
-            if c == "%":
-                accum.append("%")
-                rest = rest[2:]
-            elif c == "(":
-                m = self._interpvar_re.match(rest)
-                if m is None:
-                    raise InterpolationSyntaxError(option, section,
-                        "bad interpolation variable reference %r" % rest)
-                var = self.optionxform(m.group(1))
-                rest = rest[m.end():]
-                try:
-                    v = map[var]
-                except KeyError:
-                    raise InterpolationMissingOptionError(
-                        option, section, rest, var)
-                if "%" in v:
-                    self._interpolate_some(option, accum, v,
-                                           section, map, depth + 1)
-                else:
-                    accum.append(v)
-            else:
-                raise InterpolationSyntaxError(
-                    option, section,
-                    "'%%' must be followed by '%%' or '(', "
-                    "found: %r" % (rest,))
+    _DEFAULT_INTERPOLATION = BasicInterpolation()
 
     def set(self, section, option, value=None):
-        """Set an option.  Extend ConfigParser.set: check for string values."""
+        """Set an option.  Extends RawConfigParser.set by validating type and
+        interpolation syntax on the value."""
         self._validate_value_type(value)
-        # check for bad percent signs
-        if value:
-            tmp_value = value.replace('%%', '') # escaped percent signs
-            tmp_value = self._interpvar_re.sub('', tmp_value) # valid syntax
-            if '%' in tmp_value:
-                raise ValueError("invalid interpolation syntax in %r at "
-                                "position %d" % (value, tmp_value.find('%')))
-        ConfigParser.set(self, section, option, value)
+        super().set(section, option, value)
 
 
 class SectionProxy(MutableMapping):