Support main module configuration in package.json

[hendrikvanantwerpen]

Similar to tree-sitter-stack-graphs-javascript, this PR add support for the main attribute in package.json files.

If a main module is specified, the exports of that module are accessible directly from the package name. If it is unspecified, we default to index as Node does.

[BekaValentine]

What are the TSG-side components that make this work?

[hendrikvanantwerpen]

What are the TSG-side components that make this work?

Good question! It works because of the following pre-existing behavior:

• In TSG we introduce module definitions prefixed by %M guards. For example a module src/api.ts becomes %M -> src -> api.

• In npm_package.rs the package name becomes a definition prefixed by a %NonRelM guard (because non-relative imports can resolve to it). For example, package @acme/foo becomes %NonRelM -> @acme -> foo`.

What is added is the following:

• The main property introduces a reference from the package definition to the main module. If main is ./src/api.ts, it becomes a reference api -> src -> %M.

The whole chain that works like a rewrite: a reference to @acme/foo becomes src/api via:

%NonRelM` -> @acme -> foo -> api -> src -> %M

I'd add a picture, but the graphs for these examples are already quite large. Does this clarify things?

[BekaValentine]

It does not clarify things. In package.json, the programmer can specify different choices for main files. They can say that the main file, say, index.ts or that its foo.ts or whatever.

How does this information make it's way into the TSG file such that the graphs can be built differently depending on what that value is?