Dynamically changing appearance of UI widgets in Shiny

[William.Rinauto]

I am curious if anyone has any ideas for a solution to this. I have a shiny app that has a large number of input widgets.

The values of these widgets can be set manually by the user each session, or the user has the option of choosing a set of saved input values.

For example, say I have the following inputs in my UI:

input1 (numericInput)
input2 (textInput)
input3 (radioButtons)

The user can set these manually. Or, they can choose from sets of saved inputs from a dropdown (more common workflow). When they press 'Submit', the input values populate throughout the application based on their selection.

For example, imagine a user can choose "Set 1", "Set 2", or "Set 3" from a dropdown, where

Set 1:
input1 = 3
input2 = apple
input3 = Yes

Set 2:
input1 = 55
input2 = orange
input3 = Yes

Set 3:
input1 = 100

input3 = No

Notice that in set 3, I left out input2. That was intentional, and it gets to the point of my question. Sometimes when the user is selecting inputs from a saved set, the set that they choose might not have a corresponding value for each possible UI input (based on the nature of an external system that generates these saved inputs). So in this case, if the user chooses set 3, they are stuck with either the default value for input2, or they are responsible for manually setting input2 (the more likely situation).

If the user selects "Set 3" from the dropdown, then this would be the ideal outcome that I want to achieve:

1. User presses 'Submit'
2. input1 and input3 in the UI are populated with 100 and No
3. input2 (the actual UI element) is highlighted to draw the user's attention to the fact that "Set 3" did not provide a value here
4. Either when the user clicks input2, or when they click/click off of input2, it becomes un-highlighted.

It is 3 and 4 that I am hoping to get help on.

I am also open to any ideas that functionally solve this problem, where the ultimate goal is: Draw the user's attention directly to any input elements that were not populated with a value from the saved set.

I hope I was able to explain that clearly enough. Thanks in advance for your input.