[Sinkleberg]

Adds a filtering recipe for matching parsed CSV rows by header or position. The header example uses header_converters: :symbol, as suggested in #246.

The examples and both test suites passed on Ruby 3.3.13. I also checked the recipe in the generated docs.

[kou]

Could you update this?

• doc/csv/recipes/filtering.rdoc isn't a good place for this. "Filtering" in it means a Unix-style filter that reads CSV and writes CSV. Could you move this to doc/csv/recipes/parsing.rdoc and use the "Recipe: ..." heading style like other recipes?

• header_converters: :symbol doesn't just convert headers to symbols. It also downcases them and replaces spaces with _. For example, "First Name" is converted to :first_name. So Name: doesn't match even with header_converters: :symbol. Could you describe it? We can also mention that header_converters: ->(header) {header.to_sym} keeps the original case. The comment in lib/csv/row.rb has the same problem.

• Could you remove the tests? test_patterns_with_string_headers asserts that a symbol key doesn't match a string header but CSV::Row pattern matching Symbol assumption #246 is still open to discuss changing it. We don't want to fix the current behavior by a test. Other cases are already covered by existing tests. So this can be a document only change.

• "This example uses Ruby 3.0 or later, where +in+ returns +true+ or +false+." can be just "This example requires Ruby 3.0 or later."

• "Header conversion is opt-in: CSV::Row preserves the header key types supplied by the parser." is redundant. "Headers are strings by default. So a symbol key doesn't match:" is enough.

[Sinkleberg]

I’ll move the recipe to the parsing docs and drop the new tests. I’ll also fix both examples to show how the built-in converter turns First Name into :first_name.

[Sinkleberg]

Moved the recipe to the parsing docs and removed the added tests. The examples now show both how First Name becomes :first_name and how to keep the original case. The examples and the CSV test suite pass.