Simplify connection to sbt server?

[adpi2]

When the user wants to connect Metals to sbt server it can use two commands which are slightly different:

• BspSwitch: This command only works if the .bsp/sbt.json file is already available. The user can then select sbt and Metals will connect to it. If the .bsp/sbt.json is absent, Metals will not propose to connect to sbt, which is source of confusion or disapointment.
• GenerateBspConfig: This command forces the generation of a .bsp/sbt.json file by running sbt bspConfig. Then Metals read the generated .bsp/sbt.json file to connect to sbt server. This method is slower than the first one because sbt is loaded twice.

This situation is not ideal because:

• the first command can fail (not propose sbt) and the second is generally slower.
• 2 commands is more complex than 1: we assume that the user knows how connection to sbt via BSP works (generation of the .bsp/sbt.json file then read and run the argv command`).

Ideally the user should not need to understand that complexity and it should be able to use the same command in every situation.

I propose to make BspSwitch the default command to connect to sbt server:
If there is no .bsp/sbt.json file, Metals will check the version of sbt (it must be bigger than 1.4.1) and if it is it will suggest to connect to sbt. After the user chooses sbt and because .bsp/sbt.json is absent, it will run sbt bspConfig and connect to sbt server.

GenerateBspConfig will still be useful to force the generation of a new BSP config, but it would rarely be used.

[dos65]

Sounds good!
I agree that Metals should provide an option to select sbt-bsp from a start even if bsp-config wasn't generated.

[ckipp01]

👍🏼 I think this would be good to get rid of the extra step.

[ckipp01]

Hey @adpi2 just letting you know I started on this. I have working pretty much what you explained.

• The metals.generate-bsp-config command can still be used the same to generate and then connect.
• The metals.bsp-switch command now works a bit different in that it doesn't just search the .bsp/ but rather takes a look at whether the build tool can also be a build server and displays that option. You can see an example here:

Video on Imgur

Notice there is no .bsp/sbt.json entry, but you still see sbt as an option when you trigger the bsp switch.

[ckipp01]

Just tying this all together, this was now merged in #3304. It works for both sbt and mill.

[adpi2]

Amazing thanks!