Trying Out Multi-language Projects

[ballcoach12]

Now that I have upgraded to 0.30, I am exploring a multi-language project. I generated a new 'hello-world' project and then added a second grammar. The second grammar was copied from another 0.3.0 project. I also updated my langium-config.json file to include the two languages.

When I run npm run langium:generate I get an error when the generator tries to validate my second grammar:

An exception occured executing a validation. TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)
    at StreamImpl.stream_1.StreamImpl.property [as startFn] (G:\PullmanGit\test-langium-030-generator\hello-world\node_modules\langium\lib\utils\ast-util.js:127:22)
    at StreamImpl.iterator (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\utils\stream.js:21:25)
    at StreamImpl.[Symbol.iterator] (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\utils\stream.js:28:21)
    at TreeStreamImpl.startFn (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\utils\stream.js:431:56)
    at TreeStreamImpl.iterator (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\utils\stream.js:454:25)
    at TreeStreamImpl.[Symbol.iterator] (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\utils\stream.js:28:21)
    at isDataTypeRuleInternal (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\grammar\grammar-util.js:59:57)
    at isDataTypeRule (G:\PullmanGit\test-langim-030-generator\hello-world\node_modules\langium\lib\grammar\grammar-util.js:51:12)
    at LangiumGrammarValidator.checkEntryGrammarRule (G:\PullmanGit\test-langium-030-generator\hello-world\node_modules\langium\lib\grammar\langium-grammar-validator.js:141:52)
src\language-server\flisr\flisr-feeder-dsl.langium:NaN:NaN - Expecting: expecting at least one iteration which starts with one of these possible Token sequences::
  <[entry:KW] ,[fragment:KW] ,[ID] ,[hidden:KW] ,[terminal:KW] ,[interface:KW] ,[type:KW]>
but found: ''

However, there are no errors in the original project for that grammar when I run `npm run langium:generate'.

Is there anything else that needs to be done in order to support a second language? I've also moved my module and validator for the second language into the project folder structure.

[ballcoach12]

You can disregard this question. I found that there was a file missing in my project.