[ruby/csv] Enhanced Rdoc for CSV (#122)

https://github.com/ruby/csv/commit/cd670595d5

21 files changed, 640 insertions, 0 deletions

diff --git a/doc/csv/col_sep.rdoc b/doc/csv/col_sep.rdoc
new file mode 100644
index 0000000000..bb4d3ce389
--- /dev/null
+++ b/doc/csv/col_sep.rdoc
@@ -0,0 +1,45 @@
+====== Option +col_sep+
+
+Specifies the \String field separator to be used
+for both parsing and generating.
+The \String will be transcoded into the data's \Encoding before use.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:col_sep) # => "," (comma)
+
+For examples in this section:
+  ary = ['a', 'b', 'c']
+
+Using the default:
+  str = CSV.generate_line(line)
+  str # => "a,b,c\n"
+  ary = CSV.parse_line(str)
+  ary # => ["a", "b", "c"]
+
+Using +:+ (colon):
+  col_sep = ':'
+  str = CSV.generate_line(ary, col_sep: col_sep)
+  str # => "a:b:c\n"
+  ary = CSV.parse_line(str, col_sep: col_sep)
+  ary # => [["a", "b", "c"]]
+
+Using +::+ (two colons):
+  col_sep = '::'
+  str = CSV.generate_line(ary, col_sep: col_sep)
+  str # => "a::b::c\n"
+  ary = CSV.parse_line(str, col_sep: col_sep)
+  ary # => [["a", "b", "c"]]
+
+---
+
+Raises an exception if given the empty \String:
+  col_sep = ''
+  # Raises ArgumentError (:col_sep must be 1 or more characters: "")
+  CSV.parse_line("a:b:c\n", col_sep: col_sep)
+
+Raises an exception if the given value is not String-convertible:
+  col_sep = BasicObject.new
+  # Raises NoMethodError (undefined method `to_s' for #<BasicObject:>)
+  CSV.generate_line(line, col_sep: col_sep)
+  # Raises NoMethodError (undefined method `to_s' for #<BasicObject:>)
+  CSV.parse(str, col_sep: col_sep)
diff --git a/doc/csv/converters.rdoc b/doc/csv/converters.rdoc
new file mode 100644
index 0000000000..993803c5d0
--- /dev/null
+++ b/doc/csv/converters.rdoc
@@ -0,0 +1,45 @@
+====== Option +converters+
+
+Specifies a single field converter name or \Proc,
+or an \Array of field converter names and Procs.
+
+See {Field Converters}[#class-CSV-label-Field+Converters]
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:converters) # => nil
+
+The value may be a single field converter name:
+  str = '1,2,3'
+  # Without a converter
+  ary = CSV.parse_line(str)
+  ary # => ["1", "2", "3"]
+  # With built-in converter :integer
+  ary = CSV.parse_line(str, converters: :integer)
+  ary # => [1, 2, 3]
+
+The value may be an \Array of field converter names:
+  str = '1,3.14159'
+  # Without converters
+  ary = CSV.parse_line(str)
+  ary # => ["1", "3.14159"]
+  # With built-in converters
+  ary = CSV.parse_line(str, converters: [:integer, :float])
+  ary # => [1, 3.14159]
+
+The value may be a \Proc custom converter:
+  str = ' foo  ,  bar  ,  baz  '
+  # Without a converter
+  ary = CSV.parse_line(str)
+  ary # => [" foo  ", "  bar  ", "  baz  "]
+  # With a custom converter
+  ary = CSV.parse_line(str, converters: proc {|field| field.strip })
+  ary # => ["foo", "bar", "baz"]
+
+See also {Custom Converters}[#class-CSV-label-Custom+Converters]
+
+---
+
+Raises an exception if the converter is not a converter name or a \Proc:
+  str = 'foo,0'
+  # Raises NoMethodError (undefined method `arity' for nil:NilClass)
+  CSV.parse(str, converters: :foo)
diff --git a/doc/csv/empty_value.rdoc b/doc/csv/empty_value.rdoc
new file mode 100644
index 0000000000..7d3bcc078c
--- /dev/null
+++ b/doc/csv/empty_value.rdoc
@@ -0,0 +1,13 @@
+====== Option +empty_value+
+
+Specifies the object that is to be substituted
+for each field that has an empty \String.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:empty_value) # => "" (empty string)
+
+With the default, <tt>""</tt>:
+  CSV.parse_line('a,"",b,"",c') # => ["a", "", "b", "", "c"]
+
+With a different object:
+  CSV.parse_line('a,"",b,"",c', empty_value: 'x') # => ["a", "x", "b", "x", "c"]
diff --git a/doc/csv/field_size_limit.rdoc b/doc/csv/field_size_limit.rdoc
new file mode 100644
index 0000000000..797c5776fc
--- /dev/null
+++ b/doc/csv/field_size_limit.rdoc
@@ -0,0 +1,39 @@
+====== Option +field_size_limit+
+
+Specifies the \Integer field size limit.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:field_size_limit) # => nil
+
+This is a maximum size CSV will read ahead looking for the closing quote for a field.
+(In truth, it reads to the first line ending beyond this size.)
+If a quote cannot be found within the limit CSV will raise a MalformedCSVError,
+assuming the data is faulty.
+You can use this limit to prevent what are effectively DoS attacks on the parser.
+However, this limit can cause a legitimate parse to fail;
+therefore the default value is +nil+ (no limit).
+
+For the examples in this section:
+  str = <<~EOT
+    "a","b"
+    "
+    2345
+    ",""
+  EOT
+  str # => "\"a\",\"b\"\n\"\n2345\n\",\"\"\n"
+
+Using the default +nil+:
+  ary = CSV.parse(str)
+  ary # => [["a", "b"], ["\n2345\n", ""]]
+
+Using <tt>50</tt>:
+  field_size_limit = 50
+  ary = CSV.parse(str, field_size_limit: field_size_limit)
+  ary # => [["a", "b"], ["\n2345\n", ""]]
+
+---
+
+Raises an exception if a field is too long:
+  big_str = "123456789\n" * 1024
+  # Raises CSV::MalformedCSVError (Field size exceeded in line 1.)
+  CSV.parse('valid,fields,"' + big_str + '"', field_size_limit: 2048)
diff --git a/doc/csv/force_quotes.rdoc b/doc/csv/force_quotes.rdoc
new file mode 100644
index 0000000000..11afd1a16c
--- /dev/null
+++ b/doc/csv/force_quotes.rdoc
@@ -0,0 +1,17 @@
+====== Option +force_quotes+
+
+Specifies the boolean that determines whether each output field is to be double-quoted.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:force_quotes) # => false
+
+For examples in this section:
+  ary = ['foo', 0, nil]
+
+Using the default, +false+:
+  str = CSV.generate_line(ary)
+  str # => "foo,0,\n"
+
+Using +true+:
+  str = CSV.generate_line(ary, force_quotes: true)
+  str # => "\"foo\",\"0\",\"\"\n"
diff --git a/doc/csv/header_converters.rdoc b/doc/csv/header_converters.rdoc
new file mode 100644
index 0000000000..329d96a897
--- /dev/null
+++ b/doc/csv/header_converters.rdoc
@@ -0,0 +1,31 @@
+====== Option +header_converters+
+
+Specifies a \String converter name or an \Array of converter names.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:header_converters) # => nil
+
+Identical in functionality to option {converters}[#class-CSV-label-Option+converters]
+except that:
+- The converters apply only to the header row.
+- The built-in header converters are +:downcase+ and +:symbol+.
+
+Examples:
+  str = <<-EOT
+  foo,0
+  bar,1
+  baz,2
+  EOT
+  headers = ['Name', 'Value']
+  # With no header converter
+  csv = CSV.parse(str, headers: headers)
+  csv.headers # => ["Name", "Value"]
+  # With header converter :downcase
+  csv = CSV.parse(str, headers: headers, header_converters: :downcase)
+  csv.headers # => ["name", "value"]
+  # With header converter :symbol
+  csv = CSV.parse(str, headers: headers, header_converters: :symbol)
+  csv.headers # => [:name, :value]
+  # With both
+  csv = CSV.parse(str, headers: headers, header_converters: [:downcase, :symbol])
+  csv.headers # => [:name, :value]
diff --git a/doc/csv/headers.rdoc b/doc/csv/headers.rdoc
new file mode 100644
index 0000000000..0ea151f24b
--- /dev/null
+++ b/doc/csv/headers.rdoc
@@ -0,0 +1,63 @@
+====== Option +headers+
+
+Specifies a boolean, \Symbol, \Array, or \String to be used
+to define column headers.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:headers) # => false
+
+---
+
+Without +headers+:
+  str = <<-EOT
+  Name,Count
+  foo,0
+  bar,1
+  bax,2
+  EOT
+  csv = CSV.new(str)
+  csv # => #<CSV io_type:StringIO encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
+  csv.headers # => nil
+  csv.shift # => ["Name", "Count"]
+
+---
+
+If set to +true+ or the \Symbol +:first_row+,
+the first row of the data is treated as a row of headers:
+  str = <<-EOT
+  Name,Count
+  foo,0
+  bar,1
+  bax,2
+  EOT
+  csv = CSV.new(str, headers: true)
+  csv # => #<CSV io_type:StringIO encoding:UTF-8 lineno:2 col_sep:"," row_sep:"\n" quote_char:"\"" headers:["Name", "Count"]>
+  csv.headers # => ["Name", "Count"]
+  csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
+
+---
+
+If set to an \Array, the \Array elements are treated as headers:
+  str = <<-EOT
+  foo,0
+  bar,1
+  bax,2
+  EOT
+  csv = CSV.new(str, headers: ['Name', 'Count'])
+  csv
+  csv.headers # => ["Name", "Count"]
+  csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
+
+---
+
+If set to a \String +str+, method <tt>CSV::parse_line(str, options)</tt> is called
+with the current +options+, and the returned \Array is treated as headers:
+  str = <<-EOT
+  foo,0
+  bar,1
+  bax,2
+  EOT
+  csv = CSV.new(str, headers: 'Name,Count')
+  csv
+  csv.headers # => ["Name", "Count"]
+  csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
diff --git a/doc/csv/liberal_parsing.rdoc b/doc/csv/liberal_parsing.rdoc
new file mode 100644
index 0000000000..b8b9b00c98
--- /dev/null
+++ b/doc/csv/liberal_parsing.rdoc
@@ -0,0 +1,19 @@
+====== Option +liberal_parsing+
+
+Specifies the boolean value that determines whether
+CSV will attempt to parse input not conformant with RFC 4180,
+such as double quotes in unquoted fields.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:liberal_parsing) # => false
+
+For examples in this section:
+  str = 'is,this "three, or four",fields'
+
+Without +liberal_parsing+:
+  # Raises CSV::MalformedCSVError (Illegal quoting in str 1.)
+  CSV.parse_line(str)
+
+With +liberal_parsing+:
+  ary = CSV.parse_line(str, liberal_parsing: true)
+  ary # => ["is", "this \"three", " or four\"", "fields"]
diff --git a/doc/csv/nil_value.rdoc b/doc/csv/nil_value.rdoc
new file mode 100644
index 0000000000..412e8795e8
--- /dev/null
+++ b/doc/csv/nil_value.rdoc
@@ -0,0 +1,12 @@
+====== Option +nil_value+
+
+Specifies the object that is to be substituted for each null (no-text) field.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:nil_value) # => nil
+
+With the default, +nil+:
+  CSV.parse_line('a,,b,,c') # => ["a", nil, "b", nil, "c"]
+
+With a different object:
+  CSV.parse_line('a,,b,,c', nil_value: 0) # => ["a", 0, "b", 0, "c"]
diff --git a/doc/csv/quote_char.rdoc b/doc/csv/quote_char.rdoc
new file mode 100644
index 0000000000..eb2ad9c0c8
--- /dev/null
+++ b/doc/csv/quote_char.rdoc
@@ -0,0 +1,32 @@
+====== Option +quote_char+
+
+Specifies the character (\String of length 1) used used to quote fields
+in both parsing and generating.
+This String will be transcoded into the data's \Encoding before use.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:quote_char) # => "\"" (backslash)
+
+This is useful for an application that incorrectly uses <tt>'</tt> (single-quote)
+to quote fields, instead of the correct <tt>"</tt> (double-quote).
+
+Using the default:
+  ary = ['a', 'b', '"c"', 'd']
+  str = CSV.generate_line(ary)
+  str # => "a,b,\"\"\"c\"\"\",d\n"
+  ary = CSV.parse_line(str)
+  ary # => ["a", "b", "\"c\"", "d"]
+
+Using <tt>'</tt> (single-quote):
+  quote_char = "'"
+  ary = ['a', 'b', '\'c\'', 'd']
+  str = CSV.generate_line(ary, quote_char: quote_char)
+  str # => "a,b,'''c''',d\n"
+  ary = CSV.parse_line(str, quote_char: quote_char)
+  ary # => [["a", "b", "'c'", "d"]]
+
+---
+
+Raises an exception if the \String length is greater than 1:
+  # Raises ArgumentError (:quote_char has to be nil or a single character String)
+  CSV.new('', quote_char: 'xx')
diff --git a/doc/csv/quote_empty.rdoc b/doc/csv/quote_empty.rdoc
new file mode 100644
index 0000000000..4c5645c662
--- /dev/null
+++ b/doc/csv/quote_empty.rdoc
@@ -0,0 +1,12 @@
+====== Option +quote_empty+
+
+Specifies the boolean that determines whether an empty value is to be double-quoted.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:quote_empty) # => true
+
+With the default +true+:
+  CSV.generate_line(['"', ""]) # => "\"\"\"\",\"\"\n"
+
+With +false+:
+    CSV.generate_line(['"', ""], quote_empty: false) # => "\"\"\"\",\n"
diff --git a/doc/csv/return_headers.rdoc b/doc/csv/return_headers.rdoc
new file mode 100644
index 0000000000..45d2e3f3de
--- /dev/null
+++ b/doc/csv/return_headers.rdoc
@@ -0,0 +1,22 @@
+====== Option +return_headers+
+
+Specifies the boolean that determines whether method #shift
+returns or ignores the header row.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:return_headers) # => false
+
+Examples:
+  str = <<-EOT
+  Name,Count
+  foo,0
+  bar,1
+  bax,2
+  EOT
+  # Without return_headers first row is str.
+  csv = CSV.new(str, headers: true)
+  csv.shift # => #<CSV::Row "Name":"foo" "Count":"0">
+  # With return_headers first row is headers.
+  csv = CSV.new(str, headers: true, return_headers: true)
+  csv.shift # => #<CSV::Row "Name":"Name" "Count":"Count">
+
diff --git a/doc/csv/row_sep.rdoc b/doc/csv/row_sep.rdoc
new file mode 100644
index 0000000000..a9e2c5b2fb
--- /dev/null
+++ b/doc/csv/row_sep.rdoc
@@ -0,0 +1,91 @@
+====== Option +row_sep+
+
+Specifies the row separator, a \String or the \Symbol <tt>:auto</tt> (see below),
+to be used for both parsing and generating.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:row_sep) # => :auto
+
+---
+
+When +row_sep+ is a \String, that \String becomes the row separator.
+The String will be transcoded into the data's Encoding before use.
+
+Using <tt>"\n"</tt>:
+  str = CSV.generate do |csv|
+    csv << [:foo, 0]
+    csv << [:bar, 1]
+    csv << [:baz, 2]
+  end
+  str # => "foo,0\nbar,1\nbaz,2\n"
+  ary = CSV.parse(str)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+Using <tt>|</tt> (pipe):
+  row_sep = '|'
+  str = CSV.generate(row_sep: row_sep) do |csv|
+    csv << [:foo, 0]
+    csv << [:bar, 1]
+    csv << [:baz, 2]
+  end
+  str # => "foo,0|bar,1|baz,2|"
+  ary = CSV.parse(str, row_sep: row_sep)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+Using <tt>--</tt> (two hyphens):
+  row_sep = '--'
+  str = CSV.generate(row_sep: row_sep) do |csv|
+    csv << [:foo, 0]
+    csv << [:bar, 1]
+    csv << [:baz, 2]
+  end
+  str # => "foo,0--bar,1--baz,2--"
+  ary = CSV.parse(str, row_sep: row_sep)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+Using <tt>''</tt> (empty string):
+  row_sep = ''
+  str = CSV.generate(row_sep: row_sep) do |csv|
+    csv << [:foo, 0]
+    csv << [:bar, 1]
+    csv << [:baz, 2]
+  end
+  str # => "foo,0bar,1baz,2"
+  ary = CSV.parse(str, row_sep: row_sep)
+  ary # => [["foo", "0bar", "1baz", "2"]]
+
+---
+
+When +row_sep+ is the \Symbol +:auto+ (the default),
+invokes auto-discovery of the row separator.
+
+Auto-discovery reads ahead in the data looking for the next <tt>\r\n</tt>, +\n+, or +\r+ sequence.
+The sequence will be selected even if it occurs in a quoted field,
+assuming that you would have the same line endings there.
+
+  row_sep = :auto
+  str = CSV.generate(row_sep: row_sep) do |csv|
+    csv << [:foo, 0]
+    csv << [:bar, 1]
+    csv << [:baz, 2]
+  end
+  str # => "foo,0\nbar,1\nbaz,2\n"
+  ary = CSV.parse(str, row_sep: row_sep)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+The default <tt>$INPUT_RECORD_SEPARATOR</tt> (<tt>$/</tt>) is used
+if any of the following is true:
+* None of those sequences is found.
+* Data is +ARGF+, +STDIN+, +STDOUT+, or +STDERR+.
+* The stream is only available for output.
+
+Obviously, discovery takes a little time. Set manually if speed is important. Also note that IO objects should be opened in binary mode on Windows if this feature will be used as the line-ending translation can cause problems with resetting the document position to where it was before the read ahead.
+
+---
+
+Raises an exception if the given value is not String-convertible:
+  row_sep = BasicObject.new
+  # Raises NoMethodError (undefined method `to_s' for #<BasicObject:>)
+  CSV.generate_line(ary, row_sep: row_sep)
+  # Raises NoMethodError (undefined method `to_s' for #<BasicObject:>)
+  CSV.parse(str, row_sep: row_sep)
diff --git a/doc/csv/skip_blanks.rdoc b/doc/csv/skip_blanks.rdoc
new file mode 100644
index 0000000000..2c8f7b7bb8
--- /dev/null
+++ b/doc/csv/skip_blanks.rdoc
@@ -0,0 +1,31 @@
+====== Option +skip_blanks+
+
+Specifies a boolean that determines whether blank lines in the input will be ignored;
+a line that contains a column separator is not considered to be blank.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:skip_blanks) # => false
+
+See also option {skiplines}[#class-CSV-label-Option+skip_lines].
+
+For examples in this section:
+  str = <<-EOT
+  foo,0
+
+  bar,1
+  baz,2
+
+  ,
+  EOT
+
+Using the default, +false+:
+  ary = CSV.parse(str)
+  ary # => [["foo", "0"], [], ["bar", "1"], ["baz", "2"], [], [nil, nil]]
+
+Using +true+:
+  ary = CSV.parse(str, skip_blanks: true)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"], [nil, nil]]
+
+Using a truthy value:
+  ary = CSV.parse(str, skip_blanks: :foo)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"], [nil, nil]]
diff --git a/doc/csv/skip_lines.rdoc b/doc/csv/skip_lines.rdoc
new file mode 100644
index 0000000000..1481c40a5f
--- /dev/null
+++ b/doc/csv/skip_lines.rdoc
@@ -0,0 +1,37 @@
+====== Option +skip_lines+
+
+Specifies an object to use in identifying comment lines in the input that are to be ignored:
+* If a \Regexp, ignores lines that match it.
+* If a \String, converts it to a \Regexp, ignores lines that match it.
+* If +nil+, no lines are considered to be comments.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:skip_lines) # => nil
+
+For examples in this section:
+  str = <<-EOT
+  # Comment
+  foo,0
+  bar,1
+  baz,2
+  # Another comment
+  EOT
+  str # => "# Comment\nfoo,0\nbar,1\nbaz,2\n# Another comment\n"
+
+Using the default, +nil+:
+  ary = CSV.parse(str)
+  ary # => [["# Comment"], ["foo", "0"], ["bar", "1"], ["baz", "2"], ["# Another comment"]]
+
+Using a \Regexp:
+  ary = CSV.parse(str, skip_lines: /^#/)
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+Using a \String:
+  ary = CSV.parse(str, skip_lines: '#')
+  ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
+
+---
+
+Raises an exception if given an object that is not a \Regexp, a \String, or +nil+:
+  # Raises ArgumentError (:skip_lines has to respond to #match: 0)
+  CSV.parse(str, skip_lines: 0)
diff --git a/doc/csv/strip.rdoc b/doc/csv/strip.rdoc
new file mode 100644
index 0000000000..56ae4310c3
--- /dev/null
+++ b/doc/csv/strip.rdoc
@@ -0,0 +1,15 @@
+====== Option +strip+
+
+Specifies the boolean value that determines whether
+whitespace is stripped from each input field.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:strip) # => false
+
+With default value +false+:
+  ary = CSV.parse_line(' a , b ')
+  ary # => [" a ", " b "]
+
+With value +true+:
+  ary = CSV.parse_line(' a , b ', strip: true)
+  ary # => ["a", "b"]
diff --git a/doc/csv/unconverted_fields.rdoc b/doc/csv/unconverted_fields.rdoc
new file mode 100644
index 0000000000..3e7f839d49
--- /dev/null
+++ b/doc/csv/unconverted_fields.rdoc
@@ -0,0 +1,27 @@
+====== Option +unconverted_fields+
+
+Specifies the boolean that determines whether unconverted field values are to be available.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:unconverted_fields) # => nil
+
+The unconverted field values are those found in the source data,
+prior to any conversions performed via option +converters+.
+
+When option +unconverted_fields+ is +true+,
+each returned row (\Array or \CSV::Row) has an added method,
++unconverted_fields+, that returns the unconverted field values:
+  str = <<-EOT
+  foo,0
+  bar,1
+  baz,2
+  EOT
+  # Without unconverted_fields
+  csv = CSV.parse(str, converters: :integer)
+  csv # => [["foo", 0], ["bar", 1], ["baz", 2]]
+  csv.first.respond_to?(:unconverted_fields) # => false
+  # With unconverted_fields
+  csv = CSV.parse(str, converters: :integer, unconverted_fields: true)
+  csv # => [["foo", 0], ["bar", 1], ["baz", 2]]
+  csv.first.respond_to?(:unconverted_fields) # => true
+  csv.first.unconverted_fields # => ["foo", "0"]
diff --git a/doc/csv/write_converters.rdoc b/doc/csv/write_converters.rdoc
new file mode 100644
index 0000000000..c7367b96fd
--- /dev/null
+++ b/doc/csv/write_converters.rdoc
@@ -0,0 +1,31 @@
+====== Option +write_converters+
+
+Specifies the \Proc or \Array of Procs that are to be called
+for converting each output field.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:write_converters) # => nil
+
+With no write converter:
+  str = CSV.generate_line(["\na\n", "\tb\t", " c "])
+  str # => "\"\na\n\",\tb\t, c \n"
+
+With a write converter:
+  strip_converter = lambda {|field| field.strip }
+  str = CSV.generate_line(["\na\n", "\tb\t", " c "], write_converters: strip_converter)
+  str # => "a,b,c\n"
+
+With two write converters (called in order):
+  upcase_converter = lambda {|field| field.upcase }
+  downcase_converter = lambda {|field| field.downcase }
+  write_converters = [upcase_converter, downcase_converter]
+  str = CSV.generate_line(['a', 'b', 'c'], write_converters: write_converters)
+  str # => "a,b,c\n"
+
+---
+
+Raises an exception if the converter returns a value that is neither +nil+
+nor \String-convertible:
+  bad_converter = lambda {|field| BasicObject.new }
+  # Raises NoMethodError (undefined method `is_a?' for #<BasicObject:>)
+  CSV.generate_line(['a', 'b', 'c'], write_converters: bad_converter)
\ No newline at end of file
diff --git a/doc/csv/write_empty_value.rdoc b/doc/csv/write_empty_value.rdoc
new file mode 100644
index 0000000000..67be5662cb
--- /dev/null
+++ b/doc/csv/write_empty_value.rdoc
@@ -0,0 +1,15 @@
+====== Option +write_empty_value+
+
+Specifies the object that is to be substituted for each field
+that has an empty \String.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:write_empty_value) # => ""
+
+Without the option:
+  str = CSV.generate_line(['a', '', 'c', ''])
+  str # => "a,\"\",c,\"\"\n"
+
+With the option:
+  str = CSV.generate_line(['a', '', 'c', ''], write_empty_value: "x")
+  str # => "a,x,c,x\n"
diff --git a/doc/csv/write_headers.rdoc b/doc/csv/write_headers.rdoc
new file mode 100644
index 0000000000..f9faa9d438
--- /dev/null
+++ b/doc/csv/write_headers.rdoc
@@ -0,0 +1,29 @@
+====== Option +write_headers+
+
+Specifies the boolean that determines whether a header row is included in the output;
+ignored if there are no headers.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:write_headers) # => nil
+
+Without +write_headers+:
+  file_path = 't.csv'
+  CSV.open(file_path,'w',
+      :headers => ['Name','Value']
+    ) do |csv|
+      csv << ['foo', '0']
+  end
+  CSV.open(file_path) do |csv|
+    csv.shift
+  end # => ["foo", "0"]
+
+With +write_headers+":
+  CSV.open(file_path,'w',
+      :write_headers=> true,
+      :headers => ['Name','Value']
+    ) do |csv|
+      csv << ['foo', '0']
+  end
+  CSV.open(file_path) do |csv|
+    csv.shift
+  end # => ["Name", "Value"]
diff --git a/doc/csv/write_nil_value.rdoc b/doc/csv/write_nil_value.rdoc
new file mode 100644
index 0000000000..8560f644b3
--- /dev/null
+++ b/doc/csv/write_nil_value.rdoc
@@ -0,0 +1,14 @@
+====== Option +write_nil_value+
+
+Specifies the object that is to be substituted for each +nil+ field.
+
+Default value:
+  CSV::DEFAULT_OPTIONS.fetch(:write_nil_value) # => nil
+
+Without the option:
+  str = CSV.generate_line(['a', nil, 'c', nil])
+  str # => "a,,c,\n"
+
+With the option:
+  str = CSV.generate_line(['a', nil, 'c', nil], write_nil_value: "x")
+  str # => "a,x,c,x\n"