Error relating to BTR during watch mode

[JamesLMilner]

Bug

Package Version: 5.0.1-pre

Expected behavior:

Watch mode does not crash

Actual behavior:

Watch mode will crash with the error above

[agubler]

This seems to be because the manifest plugin that is used, keeps a counter that is incremented when webpack runs and decremented when webpack emits. Before adding the manifest.json to the compilation.assets the plugin checks that the counter is equal to 0, i.e. webpack has been run and emitted an equal number of times.

In serve mode the NoEmitOnErrorsPlugin is used which during an error build stops webpack from running the emit phase, this leaves the counter at a non zero number - meaning that every subsequent build will skip adding the manifest.json to the assets as the counter is greater 0.