Check copyright headers for consistency

[kevmoo]

May be tricky to do without convention.

An idea: look for a starting commend (double-slash) block of one or more line. If one exists anywhere, make sure the same text exists everywhere

Be careful about https://en.wikipedia.org/wiki/Shebang_(Unix) though...

[bwilkerson]

We need to be able to run lints on a single file without reference to other files (except those needed in order to analyze the file being linted). That precludes us from comparing the headers of multiple files.

Besides, for most projects what matters is not whether two arbitrary files have the same header, but whether every file has the appropriate header. I suspect what you really want is the ability to configure a lint rule such that it knows the header that ought to be used and compares that to each file. Unfortunately, we don't have configurable lint rules yet either.

[kevmoo]

Understood...just brainstorming 😄

[pq]

FWIW, we check for copyright headers in the linter code base like this:

https://github.com/dart-lang/linter/blob/1f6011389d52eb1086e80f5f9d987330f2046973/test/validate_headers_test.dart#L25-L32

Not elegant but it works.

We could do something similar in a lint if we made them configurable ¹.

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¹ Looking at #57673, I see @a14n used file headers as a motivation for configurable lints.