JSON::Ext::Generator::State#allow_nan=

allow_nan=(enable)

ext/json/generator/generator.c View on GitHub ↗

static VALUE cState_allow_nan_set(VALUE self, VALUE enable)
{
    GET_STATE(self);
    state->allow_nan = RTEST(enable);
    return Qnil;
}

This sets whether or not to serialize NaN, Infinity, and -Infinity

See also #allow_nan? #[]= #[] #array_nl also in 4.1 · 4.0