Add bare bones console application for filtering CSV (#321)

This is the bare bones (no input/output options yet). Options to be
added piecemeal.

The help text is a little misleading; it mentions input and output
options, but there are none (yet).

---------

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

Author: BurdetteLamar

bin/csv-filter

@@ -0,0 +1,28 @@
+#!/usr/bin/env ruby
+
+require 'optparse'
+require 'csv'
+
+options = {}
+
+parser = OptionParser.new
+
+parser.version = CSV::VERSION
+parser.banner = <<-BANNER
+Usage: #{parser.program_name} [options]
+
+  Reads and parses the CSV text content of the standard input per the given input options.
+  From that content, generates CSV text per the given output options
+  and writes that text to the standard output.
+BANNER
+
+begin
+  parser.parse!
+rescue OptionParser::InvalidOption
+  $stderr.puts($!.message)
+  $stderr.puts(parser)
+  exit(false)
+end
+
+CSV.filter(**options) do |row|
+end

csv.gemspec

@@ -38,6 +38,7 @@ Gem::Specification.new do |spec|
     end
   end
   spec.files = files
+  spec.executables = ["csv-filter"]
   spec.rdoc_options.concat(["--main", "README.md"])
   rdoc_files = [
     "LICENSE.txt",

test/csv/test_csv_filter.rb

@@ -0,0 +1,74 @@
+# frozen_string_literal: false
+
+require_relative "helper"
+
+class TestCSVFilter < Test::Unit::TestCase
+  def setup
+    @csv = <<-CSV
+aaa,bbb,ccc
+ddd,eee,fff
+    CSV
+  end
+
+  # Return stdout and stderr from CLI execution.
+  def run_csv_filter(csv, *options)
+    top_dir = File.join(__dir__, "..", "..")
+    csv_filter = File.join(top_dir, "bin", "csv-filter")
+    if File.exist?(csv_filter)
+      # In-place test
+      command_line = [
+        Gem.ruby,
+        "-I",
+        File.join(top_dir, "lib"),
+        csv_filter,
+        *options,
+      ]
+    else
+      # Gem test
+      command_line = [
+        Gem.ruby,
+        "-S",
+        "csv-filter",
+        *options,
+      ]
+    end
+    Tempfile.create("stdout", mode: File::RDWR) do |stdout|
+      Tempfile.create("stderr", mode: File::RDWR) do |stderr|
+        Tempfile.create(["csv-filter", ".csv"]) do |input|
+          input.write(csv)
+          input.close
+          system(*command_line, in: input.path, out: stdout, err: stderr)
+          stdout.rewind
+          stderr.rewind
+          [stdout.read, stderr.read]
+        end
+      end
+    end
+  end
+
+  # Test for invalid option.
+  def test_invalid_option
+    output, error = run_csv_filter("", "-Z")
+    assert_equal(["", "invalid option: -Z\n"],
+                 [output, error.lines.first])
+  end
+
+  # Test for no options.
+  def test_no_options
+    assert_equal([@csv, ""],
+                 run_csv_filter(@csv))
+  end
+
+  # Tests for general options.
+
+  def test_option_h
+    output, error = run_csv_filter("", "-h")
+    assert_equal(["Usage: csv-filter [options]\n", ""],
+                 [output.lines.first, error])
+  end
+
+  def test_option_v
+    assert_equal(["csv-filter #{CSV::VERSION}\n", ""],
+                 run_csv_filter("", "-v"))
+  end
+end