: fix GH-225 With Ruby 3.0.2 and csv 3.2.1, the file ```ruby require "csv" File.open("example.tsv", "w") { |f| f.puts("foo\t\tbar") } CSV.read("example.tsv", col_sep: "\t", strip: true) ``` produces the error ``` lib/csv/parser.rb:935:in `parse_quotable_robust': TODO: Meaningful message in line 1. (CSV::MalformedCSVError) ``` However, the CSV in this example is not malformed; instead, ambiguous options were provided to the parser. It is not obvious (to me) whether the string should be parsed as - `["foo\t\tbar"]`, - `["foo", "bar"]`, - `["foo", "", "bar"]`, or - `["foo", nil, "bar"]`. This commit adds code that raises an exception when this situation is encountered. Specifically, it checks if the column separator either ends with or starts with the characters that would be stripped away. This commit also adds unit tests and updates the documentation. https://.com/ruby/csv/commit/cc317dd42d