Multi Language Projects

[goto40]

I read #642 and https://github.com/langium/langium/pull/311in the context of multi language projects (langium 0.4.0). I wonder what a good starting point would be (an example project).

My thoughts so far: I have two DSLs.
(1) a DSL for requirements modeling requirements with a name and text:

req1: "the thing should do this" 
req2: "the thing should do that" 

(2) a DSL modeling test cases:

tst1: "tst1.py"
tst2: "tst2.py"

now I want the testcase DSL to reference elements from the requirement DSL:

tst1: "tst1.py" tests req1
tst2: "tst2.py" tests req2

How would I achieve this in langium?

• I want two languages (as separate as possible)
• I want cross-language references

what impact does this have on the DSL architecture? how do services from both DSL interact? How many language servers would I have? How to create an extension or extensions for vscode...

With a short introduction I could try to create the above example as langium example with some accompanying docs:

• I would create a single project with the two languages inside?
• I would create a single extension?

I was confused by the comment in #311 "The changes can be tested with the statemachine example package.": How is this meant?

[spoenemann]

If the two languages are totally separate, they can be handled by different language servers (and different vscode extensions). But if you want cross-language references, they need to be processed together (in the same langium-config.json) and run in the same language server. The language server disambiguates requests based on the file extension of incoming URIs.

What you mentioned about requirements and tests sounds like a good example that we could add to examples in this repo. Ideally with the same structure as the other examples, but with two .langium files in it (every language needs a dedicated entry grammar). The example might be overly simplistic though, maybe we can make the modeling of test cases more sophisticated than just delegating to Python files?

[goto40]

I will prepare something to review.

[goto40]

I setup an initial working demo (based on the tag 0.4.0). I still have questions and would like to to discuss this (in a PR). However, I have issues rebasing my branch on the current main: I get an error while generating code from my grammar using the current main:

Reading config from langium-config.json
TypeError: Cannot read properties of undefined (reading '$container')

This is possibly related to the fact that I import grammars into other grammars... Do you have any ideas?

My rebased branch is https://github.com/goto40/langium/tree/feature/multi-language-demo-current_main (I did not yet update my example to the newest version - because I got stuck while running langium:generate...)
(solved in #672 )

[goto40]

I created #671.