Initial implementation of tag filtering

src/spectator/config/cli_arguments_applicator.cr

@@ -5,6 +5,7 @@ require "../line_node_filter"
 require "../location"
 require "../location_node_filter"
 require "../name_node_filter"
+require "../tag_node_filter"
 
 module Spectator
   class Config
@@ -105,6 +106,7 @@ module Spectator
         example_option(parser, builder)
         line_option(parser, builder)
         location_option(parser, builder)
+        tag_option(parser, builder)
       end
 
       # Adds the example filter option to the parser.
@@ -135,6 +137,17 @@ module Spectator
         end
       end
 
+      # Adds the tag filter option to the parser.
+      private def tag_option(parser, builder)
+        parser.on("--tag TAG", "run examples with the specified TAG, or exclude examples by adding ~ before the TAG.") do |tag|
+          negated = tag.starts_with?('~')
+          tag = tag.lchop('~')
+          Log.debug { "Filtering for example with tag #{tag}" }
+          filter = TagNodeFilter.new(tag)
+          builder.add_node_filter(filter)
+        end
+      end
+
       # Adds options to the parser for changing output.
       private def output_parser_options(parser, builder)
         verbose_option(parser, builder)

src/spectator/includes.cr

@@ -51,6 +51,7 @@ require "./runner_events"
 require "./runner"
 require "./spec_builder"
 require "./spec"
+require "./tag_node_filter"
 require "./test_context"
 require "./value"
 require "./wrapper"

src/spectator/tag_node_filter.cr

@@ -0,0 +1,16 @@
+require "./node_filter"
+
+module Spectator
+  # Filter that matches nodes with a given tag.
+  class TagNodeFilter < NodeFilter
+    # Creates the filter.
+    # The *tag* indicates which tag the node must have in its metadata.
+    def initialize(@tag : String)
+    end
+
+    # Checks whether the node satisfies the filter.
+    def includes?(node) : Bool
+      node.metadata.each_key.any? { |key| key.to_s == @tag }
+    end
+  end
+end