When provided as a string to the importer the ] at the end of the JSON Array Format is optional. The Trace Viewer importer will automatically add a ] if needed to turn the string into valid JSON.. This is to support tracing systems that can not cleanly finish writing the trace. For example, when tracing the exit of a program.
Since there is no need to add a trailing ], it is possible to implement appending a json string without removing it from the file.
https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview
Since there is no need to add a trailing ], it is possible to implement appending a json string without removing it from the file.