Clash between two extensions using same language alias

[gjsjohnmurray]

Version: 1.30.2 (user setup)
OS: Windows_NT x64 10.0.16299

(also present in 1.31.0-insider)

I am developing a language extension (not yet published in Marketplace). It contributes three language IDs:

I have also installed a Marketplace extension intended for the same language, which contributes three different language IDs but assigns one of them the same name (ObjectScript) as one of mine:

When both extensions are enabled and I open the 'Select Language Mode' picker there is only one 'ObjectScript' entry despite every list entry also displaying the language ID in parentheses as a suffix, i.e.

Combined, the two extensions offer only five choices rather than six.

The documentation at https://code.visualstudio.com/docs/languages/identifiers didn't help me understand whether what I'm seeing is intentional. Nor does it say how the aliases array is supposed to function.

[alexdima]

Are these really different languages or the same programming language? If they are the same language, may I recommend to use the same language identifier.

Internally, we have maps and the maps will get overwritten/become conflicting. We have a map from file extension to language id (this will be conflicting in this case), another map for language name to language id (this is the one you notice in your screenshot), another map for language id to language name, etc... When picking the same language id, language name, or file extensions, these will be overwritten.

There are two possible solutions:

• aim at extension compatibility, i.e. both extensions should work at the same time. In this case, aim at reusing existing language ids if there exists an extension already and it is established.
• extension exclusivity. You can check via extensions.all if the other extension is installed and prompt users, explaining that they need to disable one or the other...

[gjsjohnmurray]

@alexandrudima - Thanks for your response. They are the same programming languages.

Is the 'language name' you mention always the first element of the aliases array in a member of the languages array in an extension's package.json?

Or do second and third aliases have equal significance with first aliases?

The doc at https://code.visualstudio.com/docs/languages/identifiers#_new-identifier-guidelines advises:

Search for other extensions in the Marketplace to find out if a language identifier has already been used.

Sounds like we also need to check language names as well as identifiers, right?

[alexdima]

Sounds like we also need to check language names as well as identifiers, right?

Yes, clashes in filename extension, language ids and language names will have funny effects, as you have found.

I recommend that you use the same language id and language names as already established. If you don't like to repeat the same definition, you can add an extension dependency from your extension to the other extension.

[gjsjohnmurray]

OK, thanks. Please can that doc section be improved? Either under this issue (which is why I haven't yet closed it), or on a fresh one. Ideally add info about aliases too.

[alexdima]

@gjsjohnmurray Would you be willing to create a PR at https://github.com/Microsoft/vscode-docs/blob/master/docs/languages/identifiers.md ?

[gregvanl]

Closing as no PR submitted.

[pecigonzalo]

I have a similar/related question. How are the users able to select between two extensions providing the same language?
I'm developing one that provides only syntax highlighting and grammar, but I would like to be compatible with the existing one, so I'm using the same language id but despite changing the aliases lists and other tricks.

I cant seem to get it to display both and let the user choose while keeping the same languages.id. Ideally, be able to set file associations to my extension so grammar and syntax are pulled from it but completion/etc uses the other extension.

It would be great to better describe what grammars.scopeName and grammars.language do along with lanaguages.id and languages.aliases

[alexdima]

@pecigonzalo What you desire is currently not possible.