[7.1] MIME parsing raising errors on valid parameters

[glennsarti]

Steps to reproduce

It's very easy to demonstrate in the test files:

in actionpack/test/dispatch/mime_type_test.rb add the following tests;

test "works1" do
    accept = "*/*;q=0.2"
    expect = ["*/*"]
    assert_equal expect.map(&:to_s), Mime::Type.parse(accept).map(&:to_s)
  end

  test "works2" do
    accept = "foo/*;q=0.2 abc=123"
    expect = ["foo/*"]
    assert_equal expect.map(&:to_s), Mime::Type.parse(accept).map(&:to_s)
  end

  test "works3" do
    accept = "*/*;q=1.0 abc=123"
    expect = ["*/*"]
    assert_equal expect.map(&:to_s), Mime::Type.parse(accept).map(&:to_s)
  end

 # The test below should pass but it does not ------------

  test "doesnt_work2" do
    accept = "*/*;abc=123"
    expect = ["*/*;abc=123"]
    assert_equal expect.map(&:to_s), Mime::Type.parse(accept).map(&:to_s)
  end

Expected behavior

The test cases should all pass because */*;abc=123 is a valid accept header value

Relevant RFC section

The RFC doesn't make any distinction between */* and a full type / subtype, the parameter should be allowed.

Each media-range might be followed by zero or more applicable media
type parameters (e.g., charset), an optional "q" parameter for
indicating a relative weight (Section 5.3.1), and then zero or more
extension parameters.

Actual behavior

The test case fails.

System configuration

Rails version:
Rails 7.2.0.alpha

However I've noticed the behaviour from Rails 7.1.0 onwards. (Rails 7.0.8.1 does not have the same problem)

Ruby version:
ruby 3.1.4p223 (2023-03-30 revision 957bb7cb81) [arm64-darwin22]

[glennsarti]

We currently have a monkey patch for this line;

rails/actionpack/lib/action_dispatch/http/mime_type.rb

Line 160 in a3f3c3e

PARAMETER_SEPARATOR_REGEXP = /;\s*q="?/

From

PARAMETER_SEPARATOR_REGEXP = /;\s*q="?/

To

PARAMETER_SEPARATOR_REGEXP = /(?>\s*#{Mime::Type::MIME_PARAMETER}\s*)*\z/

This may not be a preferred solution but it works for the moment.