proposal: consider a `unnecessary_library_names` lint

[pq]

Current guidance discourages named libraries (dart-lang/site-www@dbac48c) and we should consider a lint to support the advice.

Related lints:

• library_names
• unnecessary_library_directive

/fyi @MaryaBelanger @munificent @srawlins

[MaryaBelanger]

My take:

1. library_names shouldn't be a lint anymore
   (it conflicts or at least confuses "no named libraries" if we also promote a "right" way to name libraries)
2. Add a new lint called unnecessary_library_name

Something like this:

const _name = 'unnecessary_library_name';

const _desc =
    'Avoid library names.';

const _details = r'''
From the [style guide](https://dart.dev/guides/language/effective-dart/style#dont-explicitly-name-libraries):

**DON'T** explicitly name libraries by attaching a name to a library directive.

**BAD:**
library my_library;

**GOOD:**
library;

''';
// ....

class UnnecessaryLibraryName extends LintRule {
  static const LintCode code = LintCode(
    _name,
    'Library directives should not have names.',
    correctionMessage: 'Try deleting the library name.',
  );

(not set on From the [style guide]... but that's a different conversation)

[pq]

I think we're in agreement so I'm bumping this to "accepted". Chime in if you have reservations!

[bwilkerson]

I also prefer the name unnecessary_library_name.

But I have a question: will the lint still fire if the library has parts and at least one of the parts uses the name of the library?

I'd kind of prefer that the answer be "yes", and we can easily automate converting the part-of directive to use a URL, but it is harder for users to update manually and there are code generators that might still be using names.

I'd like to see a more complete specification before we mark this as accepted.