#835: Accept property arrays in Conclude#follow

lib/fbe/conclude.rb

@@ -131,7 +131,18 @@ def on(query)
   # @raise [Fbe::Error] If +what+ or +details+ is in the list, since +draw+ sets them
   def follow(props)
     raise(Fbe::Error, 'Follow is already set') unless @follows.nil?
-    list = props.strip.split.compact
+    list =
+      case props
+      when String
+        props.strip.split
+      when Array
+        unless props.all? { |prop| prop.is_a?(String) }
+          raise(Fbe::Error, 'Follow expects an Array of Strings')
+        end
+        props.map(&:strip).reject(&:empty?)
+      else
+        raise(Fbe::Error, 'Follow expects a String or an Array of Strings')
+      end
     bad = list & %w[what details]
     raise(Fbe::Error, "Can't follow #{bad.join(' and ')}, the judge sets it in the new fact") unless bad.empty?
     @follows = list

test/fbe/test_conclude.rb

@@ -351,7 +351,7 @@ def test_follow_multivalued
     Fbe.conclude(judge: 'judge-follow') do
       quota_unaware
       on('(exists foo)')
-      follow('tags')
+      follow(%w[tags])
       draw do |n, _prev|
         n.processed = 'yes'
         'Some long description that satisfies the twenty five chars minimum.'
@@ -426,6 +426,19 @@ def test_follow_raises_on_second_call
     end
   end
 
+  def test_follow_rejects_non_string_properties
+    fb = Factbase.new
+    error =
+      assert_raises(Fbe::Error) do
+        Fbe.conclude(fb:, judge: 'judge-follow', options: Judges::Options.new, global: {}, loog: Loog::NULL) do
+          quota_unaware
+          on('(exists foo)')
+          follow(['tags', 42])
+        end
+      end
+    assert_includes(error.message, 'Array of Strings')
+  end
+
   def test_follow_refuses_properties_set_by_judge
     %w[what details].each do |prop|
       fb = Factbase.new