ngTagsInput: disabling the input for tags upon a condition

I am using ngTagsInput to create some tags for my app.

My problem is: tag input fields refuse to disable. Namely, I would like to disable the input field when the number of tags is equal to one.

I checked docs but nothing there. Since <tags-input> is a custom directive it ignores the disabled="disabled".

A demo of ngTagsInput.

The issue seems to be similar to this one. It does not have any reply so far.

Could it be that the only way to solve this issue is by adding disabled="disabled" attribute into the <input-tags> directive in the source code?