In which package file is a default programmer selected?

Question

After a clean IDE install, the programmer submenu already has a default option selected as shown below: post of default selection

I am working on creating a core package and would like a default programmer to be selected after choosing a board, though I'm not sure which file sets the default. For example, here is a different 3rd party package that does not select a default programmer when a board is chosen.

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Answer 1

The default preferences.txt file in IDE installation has this setting. It is not read from the boards package configuration files.

The programmer key in preferences.txt contains the last selected programmer. The default preferences.txt in lib folder in IDE installation has programmer = arduino:avrispmkii. It is used if preferences.txt in Arduino15 folder doesn't exist or doesn't have the specific key.

With the recent change in Arduino IDE only programmers from boards package of the selected board are displayed, so it happens that no programmer is selected.