proposal: `file_import_inside_lib_references_file_outside`

`file_import_inside_lib_references_file_outside`

Description

This rule was originally proposed (and implemented?) as an analyzer Hint, but the implementation is either gone or never existed, and this is more a style recommendation so should be a Lint rule.

Details

The YAML definition of the Hint was the following:

  FILE_IMPORT_INSIDE_LIB_REFERENCES_FILE_OUTSIDE:
    problemMessage: "A file in the 'lib' directory shouldn't import a file outside the 'lib' directory."
    correctionMessage: "Try removing the import, or moving the imported file inside the 'lib' directory."
    comment: |-
      It is a bad practice for a source file in a package "lib" directory
      hierarchy to traverse outside that directory hierarchy. For example, a
      source file in the "lib" directory should not contain a directive such as
      `import '../web/some.dart'` which references a file outside the lib
      directory.

Kind

Style

Bad Examples

Relative imports from lib/ that go outside lib/.

// in lib/foo.dart:

import '../bin/bar.dart';

Good Examples

Relative imports from lib/ that don't go outside lib/.

// in lib/foo.dart:

import 'bar.dart';

Relative imports from outside lib/.

// in test/foo.dart:

import '../tool/bar.dart';

Discussion

Discussion checklist

[x] List any existing rules this proposal modifies, complements, overlaps or conflicts with.
[ ] List any relevant issues (reported here, the SDK Tracker, or elsewhere).
[ ] If there's any prior art (e.g., in other linters), please add references here.
[ ] If this proposal corresponds to Effective Dart or Flutter Style Guide advice, please call it out. (If there isn't any corresponding advice, should there be?)
[ ] If this proposal is motivated by real-world examples, please provide as many details as you can. Demonstrating potential impact is especially valuable.

dart-lang / linter

proposal: `file_import_inside_lib_references_file_outside` #4103