Demo: different source used in linting and typecheck for embedded frameworks

According to https://github.com/oxc-project/oxc/discussions/21936#discussioncomment-16754931, this repo is used to explore and verify the internal AST differences in embedded syntax frameworks

Vue and Svelte are used as primary examples.

We can use these following commands:

just vue: Show Vue's typecheck and linting result on the same file. just v-vue: Generate virtual files / AST which are actually used in vue-tsc and eslint-plugin-vue (vue-eslint-parser)

just svelte: Show Svelte's typecheck and linting result on the same file. just v-svelte: Generate virtual files / AST which are actually used in svelte-check and eslint-plugin-svelte (svelte-eslint-parser)

Vue side

Both tools report b is undefined, but vue-tsc treat as a field of an object, while eslint treat as a variable.

If we look into output/eslint.js, we can find vue directly use a and b (IdentifierReference).

But in the output/virtual.ts (Typechecker), we can find the virtual file use __VLS_ctx.a and __VLS_ctx.b.

Svelte side

Smaller in scope than Vue's, but the same class of divergence shows up around store auto-subscription ($store).

source.svelte declares a writable store user and references it two ways:

• {$user.age} — store-value property access (age doesn't exist on the value type)
• {missing} — undeclared bare identifier

Both reach the same position in the source, but each tool models them with a different AST shape:

• output/virtual.ts (svelte2tsx, what svelte-check feeds tsc) rewrites $user to __sveltets_2_store_get(user), so $user.age becomes a real MemberExpression on the store-value type. The typechecker reports:
  • Property 'age' does not exist on type '{ name: string; }'. — member-access diagnostic on $user.age
  • Cannot find name 'missing'. — identifier diagnostic on missing
• output/eslint.js (svelte-eslint-parser script view) keeps script identifiers bare; the parser's scope manager resolves $user against the user binding. ESLint reports:
  • nothing on $user.age — $user is bound, .age is just a property access ESLint can't type-check
  • 'missing' is not defined (no-undef) — same identifier the typechecker called "Cannot find name"

So at line 6, the typechecker emits a Property X does not exist on type Y diagnostic that ESLint cannot produce, because ESLint never sees the synthesized __sveltets_2_store_get(user) member access at all. This is the Svelte analog of Vue's __VLS_ctx.b vs raw b divergence.