Rails Unable to convert unpermitted parameters to hash

In Rails 5, ActionController::Parameters no longer inherits from Hash, in an attempt to discourage people from using Hash-related methods on the request parameters without explicitly filtering them.

As part of this pull request, which was backported into Rails 5.1 and partially into Rails 5.0, an exception is raised if you try to call to_h on the parameters object without calling permit.

Calling merge on the original params object (params.merge(:sort => column, :direction => direction, :page => nil)) returns a new ActionController::Parameters object with the same permitted status (that is, permit has not been called on it). The link_to method then ends up calling to_h on that object, which raises the exception.

If you know which parameters should be allowed in the link, you can call permit with those listed.

params.permit(:param_1, :param_2).merge(:sort => column, :direction => direction, :page => nil)
# OR
params.merge(:sort => column, :direction => direction, :page => nil).permit(:param_1, :param_2, :sort, :direction, :page)

If you don't know which parameters could be included in the link, then it's possible to call request.parameters.merge(...) (as mentioned in this answer) or params.to_unsafe_h.merge(...). However, as pointed out in comments, this is a security risk when the result is passed to link_to, as a parameter like host would be interpreted as the actual host for the link instead of a query parameter. There are several other keys that also have special meaning in link_to (everything accepted by url_for, plus :method), so it's generally a risky approach.

You can use this hack:

params.to_enum.to_h

I think rails developers will restrict it when they know it's the way to use unpermitted parameters. :)