Fix: Allow \r in unquoted fields when row separator doesn't contain \r (#346)

Fixes #60

This has been bugging me for a while - the CSV parser was rejecting `\r`
characters in unquoted fields even when the row separator was something
completely different like `\n` or a custom separator.

For example, this would fail unnecessarily:
```ruby
CSV.parse("field1,field\rwith\rcr,field3\n", row_sep: "\n")
```

The problem was in `prepare_unquoted` where we were hardcoding `"\r\n"`
instead of checking what the actual row separator was.

**What changed:**
- Now we only exclude characters that are actually part of the row
separator
- If your row separator is `\n`, then `\r` is allowed in unquoted fields
- If your row separator is `\r\n`, then both `\r` and `\n` are still
properly excluded
- Quoted fields work exactly the same as before

**Testing:**
- Updated the tests that were expecting the old behavior
- Added comprehensive tests for different row separator scenarios
- All existing tests still pass

This makes the parser more flexible while keeping it safe for the cases
where `\r` should actually be restricted.

---------

Co-authored-by: Sutou Kouhei <kou@cozmixng.org>

Author: jsxs0

lib/csv/parser.rb

@@ -675,7 +675,7 @@ def prepare_quoted
     def prepare_unquoted
       return if @quote_character.nil?
 
-      no_unquoted_values = "\r\n".encode(@encoding)
+      no_unquoted_values = Regexp.escape(@row_separator).encode(@encoding)
       no_unquoted_values << @escaped_first_column_separator
       unless @liberal_parsing
         no_unquoted_values << @escaped_quote_character

test/csv/parse/test_general.rb

@@ -138,28 +138,57 @@ def test_non_regex_edge_cases
     end
   end
 
-  def test_malformed_csv_cr_first_line
+  def test_unquoted_cr_with_lf_row_separator
+    data = "field1,field\rwith\rcr,field3\nrow2,data,here\n"
+    expected = [
+      ["field1", "field\rwith\rcr", "field3"],
+      ["row2", "data", "here"]
+    ]
+    assert_equal(expected, CSV.parse(data, row_sep: "\n"))
+  end
+
+  def test_unquoted_cr_with_custom_row_separator
+    data = "field1,field\rwith\rcr,field3|row2,data,here|"
+    expected = [
+      ["field1", "field\rwith\rcr", "field3"],
+      ["row2", "data", "here"]
+    ]
+    assert_equal(expected, CSV.parse(data, row_sep: "|"))
+  end
+
+  def test_unquoted_cr_with_crlf_row_separator
+    data = "field1,field\r2,field3\r\nrow2,data,here\r\n"
     error = assert_raise(CSV::MalformedCSVError) do
-      CSV.parse_line("1,2\r,3", row_sep: "\n")
+      CSV.parse(data, row_sep: "\r\n")
     end
     assert_equal("Unquoted fields do not allow new line <\"\\r\"> in line 1.",
                  error.message)
   end
 
-  def test_malformed_csv_cr_middle_line
-    csv = <<-CSV
-line,1,abc
-line,2,"def\nghi"
+  def test_quoted_cr_with_custom_row_separator
+    data = "field1,\"field\rwith\rcr\",field3|row2,data,here|"
+    expected = [
+      ["field1", "field\rwith\rcr", "field3"],
+      ["row2", "data", "here"]
+    ]
+    assert_equal(expected, CSV.parse(data, row_sep: "|"))
+  end
 
-line,4,some\rjunk
-line,5,jkl
-    CSV
+  def test_unquoted_cr_in_middle_line
+    csv = "line,1,abc\nline,2,\"def\nghi\"\nline,4,some\rjunk\nline,5,jkl\n"
+    result = CSV.parse(csv)
+    expected = [
+      ["line", "1", "abc"],
+      ["line", "2", "def\nghi"],
+      ["line", "4", "some\rjunk"],
+      ["line", "5", "jkl"]
+    ]
+    assert_equal(expected, result)
+  end
 
-    error = assert_raise(CSV::MalformedCSVError) do
-      CSV.parse(csv)
-    end
-    assert_equal("Unquoted fields do not allow new line <\"\\r\"> in line 4.",
-                 error.message)
+  def test_empty_rows_with_cr
+    result = CSV.parse("\n" + "\r")
+    assert_equal([[], ["\r"]], result)
   end
 
   def test_malformed_csv_unclosed_quote

test/csv/parse/test_invalid.rb

@@ -1,18 +1,8 @@
-# -*- coding: utf-8 -*-
 # frozen_string_literal: false
 
 require_relative "../helper"
 
 class TestCSVParseInvalid < Test::Unit::TestCase
-  def test_no_column_mixed_new_lines
-    error = assert_raise(CSV::MalformedCSVError) do
-      CSV.parse("\n" +
-                "\r")
-    end
-    assert_equal("New line must be <\"\\n\"> not <\"\\r\"> in line 2.",
-                 error.message)
-  end
-
   def test_ignore_invalid_line
     csv = CSV.new(<<-CSV, headers: true, return_headers: true)
 head1,head2,head3

test/csv/parse/test_liberal_parsing.rb

@@ -80,6 +80,15 @@ def test_space_quote
                  CSV.parse(input, liberal_parsing: true))
   end
 
+  def test_unquoted_cr_with_custom_row_separator
+    data = "field1,field\rwith\rcr,field3|row2,data,here|"
+    expected = [
+      ["field1", "field\rwith\rcr", "field3"],
+      ["row2", "data", "here"]
+    ]
+    assert_equal(expected, CSV.parse(data, row_sep: "|", liberal_parsing: true))
+  end
+
   def test_double_quote_outside_quote
     data = %Q{a,""b""}
     error = assert_raise(CSV::MalformedCSVError) do