`package_identifier` is missing in some cases

[2nishantg]

For the following snippet

package main

import "context"

func foo(ctx context.Context) {
	ctx := context.WithCancel(ctx)
}

the tree-sitter AST is

  package_clause:
    package_identifier:
  import_declaration:
    import_spec:
      interpreted_string_literal:
  function_declaration:
    identifier:
    parameter_list:
      parameter_declaration:
        identifier:
        qualified_type:
          package_identifier:
          type_identifier:
    block:
      short_var_declaration:
        expression_list:
          identifier:
        expression_list:
          call_expression:
            selector_expression:
              identifier:
              field_identifier:
            argument_list:
              identifier:

For the function call context.WithCancel, package_identifier is not emitted but its emitted for parameter.

I am using tree-sitter via https://github.com/emacs-tree-sitter, please let me know if you want me to test this in some other way or if you require some other info.

[maxbrunsfeld]

Yeah, context.Context is intentionally treated differently than context.WithCancel, because one is a type and one is an expression. We parse context.WithCancel as a selector_expression, because there's no way to know whether context is a package name or the name of a local variable (without maintaining a symbol table).

[adonovan]

I don't think this is a bug.

There's a question as to whether it's worth Tree Sitter trying to distinguish ambiguous terms like identifier.identifier based on context (for example, if you know it's a parameter or field type then it must be a qualified reference to a type imported from another package) even though in the general case you can't tell. For example, context.WithCancel could refer to a func/var/const/type imported by import "context", but it's possible that that package has a different name, and context actually refers to a top-level var in an adjacent file in this package. Attempting this disambiguation gives better results with partial information, but it may require clients to handle more cases.

[ameddin73]

Any progress on this? I'm using nvim-treesitter and I'd like to see package names highlighted like in Goland.