Custom case insensitive index fails to validate

[stephendolan]

Using Shoulda Matchers 4.0.1 with Rails 6.0.0.rc1.

Rails allows you to create case-insensitive unique indices like this:
add_index :api_tokens, "lower(token)", unique: true

In PostgreSQL, this would generate:
"index_api_tokens_on_lower_token" UNIQUE, btree (lower(token::text))

In my model spec, I've tried validating:
it { should have_db_index(:token).unique }
it { should have_db_index("lower(token::text)").unique }
it { should have_db_index("lower(token)").unique }

I get some variation of the following failure no matter what form the validation takes:
Expected ApiToken to have a unique index on columns lower(token::text) ()

Is there some way to accommodate for this type of index in the existing gem functionality?

[mcmire]

There is not, but this has been reported already: #945. I don't have any bandwidth at the moment unfortunately to implement this but I would gladly take a PR!