reported by user: https://www.mediawiki.org/wiki/Topic:Tv01r0b9t13e0zti
Expected behavior
file name should be "Hubble's_law)
Observed behavior
file name saves as "'s law"
Note: also reproduced with:
https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion
https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion
Checking https://en.wikipedia.org/api/rest_v1/page/pdf/Hubble's_law, the returned content-disposition header shows attachment; filename=Hubble's_law.pdf; filename*=Hubble's_law.pdf. At least the second half of this looks broken, and causes Chrome to suggest the file name "Hubble's_law.pdf; filename-=Hubble's_law.pdf" when saving. Firefox however suggests s_law.pdf, which matches the task description.
https://tools.ietf.org/html/rfc5987#section-3.2.2 shows an example for a correct extended attribute encoding: foo: bar; title*=UTF-8''%c2%a3%20and%20%e2%82%ac%20rates. The encoding parameter is mandatory, and the delimiter is an apostrophe ('). This explains why Firefox cuts off the name.
At least for the regular filename parameter, we should also use the quoted string syntax described in https://tools.ietf.org/html/rfc2616#section-2.2.