feat: automatically updating tsconfig.json's paths mapping for core workspaces.

[rui-rayqiu]

What does this PR do?

Impact: this PR only has impact on core workspaces for Salesforce internal users working on core. For external users working on SFDX workspaces, this PR should have no impact.

This PR adds a new feature for automatically updating tsconfig.json's paths mapping for core workspaces.

LWC team is working on supporting TypeScript for authoring LWCs on core. In order for TypeScript compiler to work with LWC’s folder structure, we need to add a series of paths entries in tsconfig.json that re-map imports of LWC components to relative file paths of the imported components. For example, if component one/cmpA imports force/wireUtils, the import statement in one/cmpA will be like import { someUtil } from ‘force/wireUtils’; and for TypeScript to know where to look for force/wireUtils we need to add a path entry in tsconfig.json as the following.

    "compilerOptions": {
        "paths": {
            "force/wireUtils": ["../ui-force-components/modules/force/wireUtils/wireUtils"],
        }
    }

Maintaining this mapping in tsconfig.json manually is not convenient and a less ideal DX for developers on core. This PR adds a new indexer in the lwc-language-server that maintains a mapping between LWCs and their paths in tsconfig.json, automatically updating the tsconfig.json file when language server is initialized and whenever a LWC TypeScript file is changed. Thus developers won't need to create entries for paths manually when creating new LWCs in TypeScript.

This new feature will update tsconfig.json file for the paths attribute for all the core modules in the workspace when language server is initialized. Then whenever a LWC TS file is changed, all the imports are analyzed and any necessary LWC imports will be added to tsconfig.json automatically.

Here is a short demo video link on this feature. In the video, the test workspace lightning-language-server/test-workspace/core-like-workspace/coreTS/core (created in this PR) is opened in VSCode, there are two modules ui-force-components and ui-global-components in the workspace. Both tsconfig.json files for them don't have a paths entries. After the indexer's init function is executed, both tsconfig.json files are updated with the paths mappings. After that, if I add an import statement in a ts file, the tsconfig.json file is also updated to have the mapping for the new import.

Testing this locally will require this PR for adding TS files to file watcher.

What issues does this PR fix or reference?

@W-14958700@

[ravijayaramappa]

Not sure I understand why this is outside of the namespace root.

[rui-rayqiu]

This is to test that if a ts file that is outside of the VSCode workspace is modified, we do not update tsconfig.json. Here the context workspace root is CORE_PROJECT_ROOT which is ui-global-components so if a file in ui-force-components is modified the return value of isLWCTypeScript should be false. I'll add an inline comment to explain this.

[ravijayaramappa]

Is "lightning/confirm" excluded because it is an off-core component? Saw your comment below about special cases.

[ravijayaramappa]

Assuming a folder layout like this

/ui-force-components
-->/modules
---->/force
------>/one
-------->/one.ts
-------->/util/util.ts

/*/modules/*/*/*.ts would not include any nested folders(util.ts) underneath a component folder. I think that is fine because the importer only can import the main entry file of a module.

[rui-rayqiu]

Yes, that's correct. We only want to include the main component entry ts file and ignore all other utility files.

[ravijayaramappa]

LGTM, I would defer to the language-server team to approve since there are aspects here that I am not familiar with.

[nwcm]

Related but slightly off topic. This issue is also prevalent in SFDX workspaces and makes the DX painful. Would love to see similar ported to SFDX workspaces especially with the move to TS