New answers tagged conventions
We have the same situation on a project i am working on currently. We have a script (velocity - ie backend) that checks the size of the list and if it is only one item it puts the text onto the page because it has to be chosen. If the list is more than one but less than 10 we show a dropdown but if it is more than 10 we show a combo box
The other answers touch on why/why not, but there are other options available to you. The appropriate control may depend on how many options there will be and how they are generated. Use a radio instead If your options are going to be a fairly short list (1~5), radios will be clear to users who only have one option available and users who have many ...
The only time you should use a dropdown where there is only one available option is: to stay consistent with pages that have many options for the same selection. For example: You are shopping for a new pair of shoes and are currently looking at a style that has sizes 5-14 available. These sizes are displayed in a dropdown. You click on a different style ...
In this situation, I would not use a drop down until you need to. Using a drop down with one option will be annoying to some degree because people will click on it and expect more choices but not find any. Also, people will be trained to not click on that drop down because its 'useless'. You'll have to somehow retrain them to look for the new options ...
Here is recent article about choosing shortcuts for Web applications, may be it will be useful to someone: https://medium.com/design-ux/a7c3b7b408ee
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