Dev mode server deletes application.log on startup

Play Version (2.5.x / etc)

All Play 2.x

API (Scala / Java / Neither / Both)

Both

Expected Behavior

Play project developers should have an option not to delete application.log on every restart.

Actual Behavior

logs/application.log is deleted on each start, without the ability to disable this behavior or configure the filename.

Details

This was reported in Lagom (https://github.com/lagom/lagom/issues/533) and @jroper traced it back to code that was taken from Play's DevServerStart, originally introduced many years ago in https://github.com/playframework/playframework/commit/cdd8a71f2559bbbfa4c7d4cb93933a57399d3405#diff-5d88ec4ba69d14c245bd0ec3c50607ccR10

In Lagom, we're choosing to delete this code, and instead change the default dev mode Logback configuration to set append to false. This will preserve the behavior of deleting the file on start by default, while allowing users to turn this off or change the filename.

Start in framework/src/play-server/src/main/scala/play/core/server/DevServerStart.scala around lines 78-83, where the startup behavior was introduced. Trace how the dev server removes logs and how the Logback configuration is applied. Done means the default behavior is preserved while developers can disable deletion or configure the filename.