App not redeployed by dev mode after pasting code in Java editor in IntelliJ

[turkeylurkey]

This issue is caused by a peculiar behaviour of the Java editor in IntelliJ and the way dev mode rebuilds and redeploys the app.

Dev mode redeploys when it detects a write to the Java file. However, the IntelliJ editor does not always write the file even if you type Ctrl-S or Cmd-S.

If you type something incorrect into a Java file and type Ctrl-S then IntelliJ will save to disk.
If you erase the incorrect input IntelliJ will write the file as soon as the Java file compiles.
If you paste from the clipboard some valid code like int i = 1; into a Java file that already compiles then IntelliJ will not (or may not necessarily) write the file to disk even if you type Ctrl-S. In this case the file transitions from a valid compiled state to another valid compiled state.

This affects dev mode because you may paste valid code into your app but IntelliJ will not write the file and dev mode will not detect the change. Then the user will not be able to test the code on the server because dev mode has not deployed it.