Send schema associations to JSON language server

[kaloyan-raev]

The VS Code language server expects a custom (not part of the protocol) notification json/schemaAssociations to associate JSON files to JSON schemas. This activates capabilities like code completion, validation and hover without the need to add a $schema key.

Here is an example object passed with the json/schemaAssociations notification:

{
    "/bower.json": [
        "http://json.schemastore.org/bower"
    ],
    "/composer.json": [
        "https://getcomposer.org/schema.json"
    ],
}

Currently, Che does not send the json/schemaAssociations notification, which significantly limits the capabilities of the JSON language server integration. It is not realistic to expect that users will manually add the $schema key to each JSON file they work with.

Reproduction Steps:

1. Open a bower.json file
2. Try code completion

Expected behavior:

Code completion, validation and hover work without specifying a proper $schema key.

Observed behavior:

Code completion, validation and hover do not work without specifying a proper $schema key.

Che version: 5.0.0-M2-SNAPSHOT (latest master)
OS and version: Fedora 24
Docker version: 1.10.3
Che install: local build, run with the bin/che.sh script

Additional information:

• Problem started happening recently, didn't happen in an older version of Che: [No]
• Problem can be reliably reproduced, doesn't happen randomly: [Yes]

[kaloyan-raev]

I submitted PR #2474 with the fix.

Note that it contains a hardcoded list of associations. It's enough as a first step, but in future we should think about an extensible way to contribute to this list by plugins.

For example:

• The JavaScript plugin should contribute the associations for bower.json
• The Node plugin - for package.json
• The PHP plugin - for composer.json
• The TypeScript plugin - for tsconfig.json
• etc.

For reference here is how the PHP plugin in VS Code contributes the schema association for composer.json: https://github.com/Microsoft/vscode/blob/master/extensions/php/package.json#L51-L56

[bmicklea]

@kaloyan-raev I'm moving this to M6 milestone because we're pushing to get M5 out ASAP.

[tolusha]

@kaloyan-raev
Nice work.

Concerning implementation to have code cleaner I would change a bit your approach. I would add a new entity SchemeAssociator as observer of the ServerInitializer and wouldn't mix it with LanguageServer itself.

[kaloyan-raev]

@tolusha OK. I am curious to see how this new approach looks like.