Feature suggestion: Code round-tripping

The blockly interface is amazing. However, one thing that makes it feel very different from the existing PXT experience is the absence of round-tripping.

I found a paper on round-tripping by one of the blockpy contributors here, in case it is of any use to you for future developments:

https://groups.google.com/forum/#!topic/blockly/kzq_g-jF98c

Start by reading the issue and its linked paper on round-tripping, then compare the Blockly interface with the existing PXT experience. Done would require a defined round-tripping design and an agreed implementation scope; no files or tests are named.

Written by the indexing model from the issue text.