Stop the generator reading commented-out code

[VSN2015]

A bug, not a new feature. Found by sweeping the generator's parser against source it will actually meet.

The bug

A controller keeping a line for reference:

def create
  # Legacy: params.require(:admin).permit(:superuser)
  params.require(:user).permit(:name)
end

drafted:

permit_params :create, :update, root: :admin, mode: :monitor do
  optional :superuser, :string, virtual: true # TODO: not a database column
  optional :name, :string # TODO: confirm the type
end

Both :admin and :superuser came from a line that does not execute. The wrong root is annoying; drafting superuser as a permitted parameter is the kind of wrong suggestion that shouldn't survive a review, and shouldn't have been offered in the first place. =begin/=end blocks and trailing comments on live lines had the same effect.

before: {root: :admin, scalars: [:superuser, :name], calls: 2}
after:  {root: :user,  scalars: [:name],             calls: 1}

Why Ripper and not a regexp

# is only sometimes a comment. Two cases a regexp gets wrong, both now pinned by specs:

• A permit call inside #{...} interpolation is live code and is still read.
• String content is deliberately kept. permit("name") is a supported spelling and its keys live in string tokens — so dropping string bodies, which is the obvious next step after dropping comments, would silently lose them. That one nearly caught me: the first version of this fix dropped on_tstring_content too.

Ripper is stdlib, so no dependency is added (the gem's one-runtime-dependency claim is untouched, and #14's runtime-deps job would catch it if it weren't).

The fallback

A file Ripper cannot lex falls back to the raw source, so a syntactically odd controller scans exactly as it did before rather than not at all. There's a spec for that too.

Verification

• 205 examples, 0 failures (6 new, written before the fix): line comments, trailing comments, =begin/=end, a # inside a string, quoted permit keys, and the unlexable fallback
• RuboCop clean

[VSN2015]

Review of PR #28: Using Ripper lexing to strip comments prevents commented-out parameter code from accidentally drafting root envelopes or fields, while preserving live string literals and interpolations.

[VSN2015]

Targeting on_comment, on_embdoc, on_embdoc_beg, and on_embdoc_end handles both standard # comments and =begin/=end documentation blocks.

[VSN2015]

Rescuing StandardError and falling back to raw source ensures that files with unusual syntax errors still draft as best as possible rather than failing outright.