capybara/virtualenv/lib/python2.7/site-packages/pip/req/req_set.py
def add_requirement(self, install_req, parent_req_name=None):
        """Add install_req as a requirement to install.

        :param parent_req_name: The name of the requirement that needed this
            added. The name is used because when multiple unnamed requirements
            resolve to the same name, we could otherwise end up with dependency
            links that point outside the Requirements set. parent_req must
            already be added. Note that None implies that this is a user
            supplied requirement, vs an inferred one.
        :return: Additional requirements to scan. That is either [] if
            the requirement is not applicable, or [install_req] if the
            requirement is applicable and has just been added.
        """
        name = install_req.name
        if not install_req.match_markers():
            logger.warning("Ignoring %s: markers %r don't match your "
                           "environment", install_req.name,
                           install_req.markers)
            return []

        install_req.as_egg = self.as_egg
        install_req.use_user_site = self.use_user_site
        install_req.target_dir = self.target_dir
        install_req.pycompile = self.pycompile
        if not name:
            # url or path requirement w/o an egg fragment
            self.unnamed_requirements.append(install_req)
            return [install_req]
        else:
            if parent_req_name is None and self.has_requirement(name):
                raise InstallationError(
                    'Double requirement given: %s (already in %s, name=%r)'
                    % (install_req, self.get_requirement(name), name))
            if not self.has_requirement(name):
                # Add requirement
                self.requirements[name] = install_req
                # FIXME: what about other normalizations?  E.g., _ vs. -?
                if name.lower() != name:
                    self.requirement_aliases[name.lower()] = name
                result = [install_req]
            else:
                # Canonicalise to the already-added object
                install_req = self.get_requirement(name)
                # No need to scan, this is a duplicate requirement.
                result = []
            if parent_req_name:
                parent_req = self.get_requirement(parent_req_name)
                self._dependencies[parent_req].append(install_req)
            return result
def add_requirement(self, install_req, parent_req_name=None):
        """Add install_req as a requirement to install.

        :param parent_req_name: The name of the requirement that needed this
            added. The name is used because when multiple unnamed requirements
            resolve to the same name, we could otherwise end up with dependency
            links that point outside the Requirements set. parent_req must
            already be added. Note that None implies that this is a user
            supplied requirement, vs an inferred one.
        :return: Additional requirements to scan. That is either [] if
            the requirement is not applicable, or [install_req] if the
            requirement is applicable and has just been added.
        """
        name = install_req.name
        if not install_req.match_markers():
            logger.warning("Ignoring %s: markers %r don't match your "
                           "environment", install_req.name,
                           install_req.markers)
            return []

        install_req.as_egg = self.as_egg
        install_req.use_user_site = self.use_user_site
        install_req.target_dir = self.target_dir
        install_req.pycompile = self.pycompile
        if not name:
            # url or path requirement w/o an egg fragment
            self.unnamed_requirements.append(install_req)
            return [install_req]
        else:
            if parent_req_name is None and self.has_requirement(name):
                raise InstallationError(
                    'Double requirement given: %s (already in %s, name=%r)'
                    % (install_req, self.get_requirement(name), name))
            if not self.has_requirement(name):
                # Add requirement
                self.requirements[name] = install_req
                # FIXME: what about other normalizations?  E.g., _ vs. -?
                if name.lower() != name:
                    self.requirement_aliases[name.lower()] = name
                result = [install_req]
            else:
                # Canonicalise to the already-added object
                install_req = self.get_requirement(name)
                # No need to scan, this is a duplicate requirement.
                result = []
            if parent_req_name:
                parent_req = self.get_requirement(parent_req_name)
                self._dependencies[parent_req].append(install_req)
            return result
Add install_req as a requirement to install.

        :param parent_req_name: The name of the requirement that needed this
            added. The name is used because when multiple unnamed requirements
            resolve to the same name, we could otherwise end up with dependency
            links that point outside the Requirements set. parent_req must
            already be added. Note that None implies that this is a user
            supplied requirement, vs an inferred one.
        :return: Additional requirements to scan. That is either [] if
            the requirement is not applicable, or [install_req] if the
            requirement is applicable and has just been added.