Add handling for ambiguous parsing options

lib/csv.rb

@@ -341,14 +341,14 @@
 #     liberal_parsing:    false,
 #     nil_value:          nil,
 #     empty_value:        "",
+#     strip:              false,
 #     # For generating.
 #     write_headers:      nil,
 #     quote_empty:        true,
 #     force_quotes:       false,
 #     write_converters:   nil,
 #     write_nil_value:    nil,
 #     write_empty_value:  "",
-#     strip:              false,
 #   }
 #
 # ==== Options for Parsing
@@ -366,8 +366,9 @@
 # - +header_converters+: Specifies the header converters to be used.
 # - +skip_blanks+: Specifies whether blanks lines are to be ignored.
 # - +skip_lines+: Specifies how comments lines are to be recognized.
-# - +strip+: Specifies whether leading and trailing whitespace are
-#   to be stripped from fields..
+# - +strip+: Specifies whether leading and trailing whitespace are to be
+#   stripped from fields. This must be compatible with +col_sep+; if it is not,
+#   then an +ArgumentError+ exception will be raised.
 # - +liberal_parsing+: Specifies whether \CSV should attempt to parse
 #   non-compliant data.
 # - +nil_value+: Specifies the object that is to be substituted for each null (no-text) field.
@@ -946,14 +947,14 @@ def initialize(message, line_number)
     liberal_parsing:    false,
     nil_value:          nil,
     empty_value:        "",
+    strip:              false,
     # For generating.
     write_headers:      nil,
     quote_empty:        true,
     force_quotes:       false,
     write_converters:   nil,
     write_nil_value:    nil,
     write_empty_value:  "",
-    strip:              false,
   }.freeze
 
   class << self
@@ -1879,11 +1880,11 @@ def initialize(data,
                  encoding: nil,
                  nil_value: nil,
                  empty_value: "",
+                 strip: false,
                  quote_empty: true,
                  write_converters: nil,
                  write_nil_value: nil,
-                 write_empty_value: "",
-                 strip: false)
+                 write_empty_value: "")
     raise ArgumentError.new("Cannot parse nil as CSV") if data.nil?
 
     if data.is_a?(String)

lib/csv/parser.rb

@@ -361,6 +361,7 @@ def prepare
       prepare_skip_lines
       prepare_strip
       prepare_separators
+      validate_strip_and_col_sep_options
       prepare_quoted
       prepare_unquoted
       prepare_line
@@ -531,6 +532,28 @@ def prepare_separators
       @not_line_end = Regexp.new("[^\r\n]+".encode(@encoding))
     end
 
+    # This method verifies that there are no (obvious) ambiguities with the
+    # provided +col_sep+ and +strip+ parsing options. For example, if +col_sep+
+    # and +strip+ were both equal to +\t+, then there would be no clear way to
+    # parse the input.
+    def validate_strip_and_col_sep_options
+      return unless @strip
+
+      if @strip.is_a?(String)
+        if @column_separator.start_with?(@strip) || @column_separator.end_with?(@strip)
+          raise ArgumentError,
+                "The provided strip (#{@escaped_strip}) and " \
+                "col_sep (#{@escaped_column_separator}) options are incompatible."
+        end
+      else
+        if Regexp.new("\\A[#{@escaped_strip}]|[#{@escaped_strip}]\\z").match?(@column_separator)
+          raise ArgumentError,
+                "The provided strip (true) and " \
+                "col_sep (#{@escaped_column_separator}) options are incompatible."
+        end
+      end
+    end
+
     def prepare_quoted
       if @quote_character
         @quotes = Regexp.new(@escaped_quote_character +

test/csv/parse/test_strip.rb

@@ -80,4 +80,33 @@ def test_do_not_strip_crlf
                            %Q{"a" ,"b " \r\n},
                            strip: true))
   end
+
+  def test_col_sep_incompatible_true
+    message = "The provided strip (true) and " \
+              "col_sep (\\t) options are incompatible."
+    assert_raise_with_message(ArgumentError, message) do
+      CSV.parse_line(%Q{"a"\t"b"\n},
+                     col_sep: "\t",
+                     strip: true)
+    end
+  end
+
+  def test_col_sep_incompatible_string
+    message = "The provided strip (\\t) and " \
+              "col_sep (\\t) options are incompatible."
+    assert_raise_with_message(ArgumentError, message) do
+      CSV.parse_line(%Q{"a"\t"b"\n},
+                     col_sep: "\t",
+                     strip: "\t")
+    end
+  end
+
+  def test_col_sep_compatible_string
+    assert_equal(
+      ["a", "b"],
+      CSV.parse_line(%Q{\va\tb\v\n},
+                     col_sep: "\t",
+                     strip: "\v")
+    )
+  end
 end