Allow Configurable Converters on CSV

Lets the user specify which converters to pass to `CSV`, defaulting to `nil` if not present in config. This is specifically so that numeric values in a CSV file can be parsed as something other than strings.

docs/_docs/datafiles.md

@@ -148,3 +148,30 @@ author: dave
 {% endraw %}
 
 For information on how to build robust navigation for your site (especially if you have a documentation website or another type of Jekyll site with a lot of pages to organize), see [Navigation]({{ '/tutorials/navigation/' | relative_url }}).
+
+## CSV/TSV Parse Options
+
+The way that Ruby parses CSV and TSV files can be customized with the `csv_reader` and `tsv_reader`
+configuration options. Each configuration key exposes the same options:
+
+`converters`: What [CSV converters](https://ruby-doc.org/stdlib-2.6.1/libdoc/csv/rdoc/CSV.html#Converters) should be
+              used when parsing the file. This will need to be set with `numeric` if you want number fields in the
+              CSV to be parsed into numeric types rather than into strings. By default, this list is empty.
+`encoding`:   What encoding the files are in. Defaults to the site `encoding` configuration option.
+`headers`:    Boolean field for whether to parse the first line of the file as headers. When `false`, it treats the
+              first row as data. Defaults to `true`.
+
+Examples:
+
+```yaml
+csv_reader:
+    converters:
+      - numeric
+      - datetime
+    headers: true
+    encoding: utf-8
+tsv_reader:
+    converters:
+      - all
+    headers: false
+```

lib/jekyll/readers/data_reader.rb

@@ -59,14 +59,9 @@ def read_data_file(path)
 
       case File.extname(path).downcase
       when ".csv"
-        CSV.read(path,
-                 :headers  => true,
-                 :encoding => site.config["encoding"]).map(&:to_hash)
+        CSV.read(path, **csv_config).map { |row| convert_row(row) }
       when ".tsv"
-        CSV.read(path,
-                 :col_sep  => "\t",
-                 :headers  => true,
-                 :encoding => site.config["encoding"]).map(&:to_hash)
+        CSV.read(path, **tsv_config).map { |row| convert_row(row) }
       else
         SafeYAML.load_file(path)
       end
@@ -76,5 +71,43 @@ def sanitize_filename(name)
       name.gsub(%r![^\w\s-]+|(?<=^|\b\s)\s+(?=$|\s?\b)!, "")
         .gsub(%r!\s+!, "_")
     end
+
+    private
+
+    # @return [Hash]
+    def csv_config
+      @csv_config ||= read_config("csv_reader")
+    end
+
+    # @return [Hash]
+    def tsv_config
+      @tsv_config ||= read_config("tsv_reader", { :col_sep => "\t" })
+    end
+
+    # @param config_key [String]
+    # @param overrides [Hash]
+    # @return [Hash]
+    # @see https://ruby-doc.org/stdlib-2.5.0/libdoc/csv/rdoc/CSV.html#Converters
+    def read_config(config_key, overrides = {})
+      reader_config = config[config_key] || {}
+
+      defaults = {
+        :converters => reader_config.fetch("csv_converters", []).map(&:to_sym),
+        :headers    => reader_config.fetch("headers", true),
+        :encoding   => reader_config.fetch("encoding", config["encoding"]),
+      }
+
+      defaults.merge(overrides)
+    end
+
+    def config
+      @config ||= site.config
+    end
+
+    # @param row [Array, CSV::Row]
+    # @return [Array, Hash]
+    def convert_row(row)
+      row.instance_of?(CSV::Row) ? row.to_hash : row
+    end
   end
 end

test/fixtures/sample.csv

@@ -0,0 +1,3 @@
+id,field_a
+1,"foo"
+2,"bar"

test/fixtures/sample.tsv

@@ -0,0 +1,3 @@
+id	field_a
+1	"foo"
+2	"bar"

test/test_data_reader.rb

@@ -14,4 +14,47 @@ class TestDataReader < JekyllUnitTest
       )
     end
   end
+
+  context "with no csv options set" do
+    setup do
+      @reader = DataReader.new(fixture_site)
+      @parsed = [{ "id" => "1", "field_a" => "foo" }, { "id" => "2", "field_a" => "bar" }]
+    end
+
+    should "parse CSV normally" do
+      assert_equal @parsed, @reader.read_data_file(File.expand_path("fixtures/sample.csv", __dir__))
+    end
+
+    should "parse TSV normally" do
+      assert_equal @parsed, @reader.read_data_file(File.expand_path("fixtures/sample.tsv", __dir__))
+    end
+  end
+
+  context "with csv options set" do
+    setup do
+      reader_config = {
+        "csv_converters" => [:numeric],
+        "headers"        => false,
+      }
+
+      @reader = DataReader.new(
+        fixture_site(
+          {
+            "csv_reader" => reader_config,
+            "tsv_reader" => reader_config,
+          }
+        )
+      )
+
+      @parsed = [%w(id field_a), [1, "foo"], [2, "bar"]]
+    end
+
+    should "parse CSV with options" do
+      assert_equal @parsed, @reader.read_data_file(File.expand_path("fixtures/sample.csv", __dir__))
+    end
+
+    should "parse TSV with options" do
+      assert_equal @parsed, @reader.read_data_file(File.expand_path("fixtures/sample.tsv", __dir__))
+    end
+  end
 end