The ReferenceInfo.index is always missing from the completion provider.

[raylras]

Some cross-reference syntaxes rely on the index of refInfo when calculating scope.

langium/packages/langium/src/syntax-tree.ts

Lines 137 to 146 in 38d5f16

	/**
	* Information about a cross-reference. This is used when traversing references in an AST or to describe
	* unresolved references.
	*/
	export interface ReferenceInfo {
	reference: Reference | MultiReference
	container: AstNode
	property: string
	index?: number
	}

For example:

ImportDeclaration:
    'import' path+=[Entity:ID] ('.' path+=[Entity:ID])*
;

NamedType:
    path+=[Entity:ID] ('.' path+=[Entity:ID])*
;

During normal parsing, the index property is set correctly. However, in the case of a completion provider, the index is always undefined.

langium/packages/langium/src/lsp/completion/completion-provider.ts

Lines 444 to 448 in 38d5f16

	const refInfo: ReferenceInfo = {
	reference,
	container: node,
	property: assignment.feature
	};

We can see that the index property is missing here in any case.

If we want to complete cross-refs like the ones below, providing the index is necessary.

import foo|
import foo.|
import foo.bar|

Any thoughts?

[msujew]

Hey @raylras,

we probably never noticed that because we usually build our grammar in a way that it does not depend on the ordering of specific array elements. You can rewrite those kinds of imports using a different syntax that does not depend on array indices:

ImportDeclaration:
    'import' item=ImportItem;

ImportItem:
  entity=[Entity:ID] ({infer ImportItem.previous=current} entity=[Entity:ID])*;

This also makes scoping much easier. However, it definitely makes sense to add the array indices to the completion context. Do you mind creating an issue for that?

[raylras]

This also makes scoping much easier.

I agree. The scoping and completion now works as expected. It is much easier 👍

Here's the new syntax:

ImportDeclaration:
    'import' item=ImportItem
;

ImportItem:
  entity=[Entity:ID] ({infer ImportItem.previous=current} '.' entity=[Entity:ID])*
;

it definitely makes sense to add the array indices to the completion context. Do you mind creating an issue for that?

Sure.

[raylras]

Related issue: #2026