[che-dev] Mounting of project sources - recap

[Lukas Krejci <lkrejci@xxxxxxxxxx>]

Hi all,

thanks for all the input on the issue of mounting the project sources. I 
am very glad some important issues were raised that maybe change the 
scope of the change but are very important to solve right.

Let me recap the problems we identified during the discussion:

1) LS requires a file to be represented using the same URI across all 
plugin containers - that's because it can require changes to files that 
are identified using an URI containing the path of the file.

2) Go's peculiar conventions require checking out code of the projects 
into a sub-directory structure, not directly under some root (e.g. 
/projects).

I've briefly looked at Gitpod and their solution seems quite simple:

a) they allow "checkoutLocation" - a relative path to /projects as a 
target dir of the checkout

b) they are able to figure out the checkoutLocation automagically if not 
explicitly configured in their .gitpod.yml file (an equivalent of our 
devfile).

https://docs.gitpod.io/45_Config_Go.html

Given all the information above, I'd like to split the task of "Use of 
the property mountProjectSources" to a couple of steps:

1) Be able to use "mountSources" bool attribute in che-plugin.yaml file 
and disallow mounting projects using the volumes approach.

2) Define the "sourceRoot" (i.e. /projects) in devfile and propagate its 
value to the tool containers as an env variable (CHE_SOURCE_ROOT) if 
they have mountSources=true. Note that this is actually not needed but 
is "nice" for the user. Things would also work with for example 
autogenerated name stored in DB or something.

3) Define "checkoutPath" in the devfile to specify a subdir of 
CHE_SOURCE_ROOT where the sources should be actually checked out (maybe 
also forward this as an env var to the tool containers).

4) Implement auto-detection of "checkoutPath" based on the contents of 
the project.

Steps 1) to 3) are fairly easy to do in my largely uninformed humble 
opinion, although step 3 probably requires changes in GWT IDE and Theia 
factory extension, while step 4) will require more work.

WDYT?

Lukas