small validator refactoring

_plugins/config_validator.rb

@@ -5,14 +5,17 @@
 # 1) Ensures required attributes are present in the config file.
 # 2) Ensures the baseurl is a consistent format based on the semester
 # 3) Uses a `course_department` config to implement some shared styling/language.
-# Future config validations might make sense, like footer/a11y/etc.
+# 4) Ensures the `color_scheme` is valid.
+# Future config validations might make sense, like footer/a11y/etc. configuration,
 
 # Implement additional validations by registering an entry in `KEY_VALIDATIONS`
 # This is a key_name => function_name map.
 # function_name should be defined in the ConfigValidator class, and is called with
-# the *value* of the config.
+# the key, value pair in the config.
 # Note that Jekyll parses the YAML file such that the config keys are *strings* not symbols.
 
+# See the inclusion_validator to add simple allow-list style validations
+
 # A simple class for nicer error message formatting.
 class ConfigValidationError < StandardError
   attr_reader :errors
@@ -55,11 +58,7 @@ def validate
       validate_keys!
 
       KEY_VALIDATIONS.each do |key, validator|
-        if validator == :inclusion_validator
-          send(validator, key, config[key.to_s], ConfigValidator.const_get("VALID_#{key.upcase}"))
-        elsif @config.key?(key.to_s)
-          send(validator, config[key.to_s])
-        end
+        send(validator, key, config[key.to_s]) if @config.key?(key.to_s)
       end
 
       raise ConfigValidationError, errors if errors.length.positive?
@@ -76,12 +75,12 @@ def validate_keys!
 
     private
 
-    def validate_clean_url(url)
+    def validate_clean_url(_key, url)
       errors << '`url` should not end with a `/`' if url.end_with?('/')
       errors << '`url` should contain a protocol' unless url.match?(%r{https?://})
     end
 
-    def validate_semester_format(baseurl)
+    def validate_semester_format(_key, baseurl)
       # This is just for consistency of URL presentation.
       errors << '`baseurl` must start with a `/`.' unless baseurl.match?(%r{^/})
       # skip, just for the template.
@@ -92,7 +91,8 @@ def validate_semester_format(baseurl)
       errors << "`baseurl` must be a valid semester (faXX, spXX, suXX or wiXX), not #{baseurl}"
     end
 
-    def inclusion_validator(key, value, allowed)
+    def inclusion_validator(key, value)
+      allowed = self.class.const_get("VALID_#{key.upcase}")
       errors << "`#{key}` must be one of #{allowed} (not '#{value}')" unless allowed.include?(value)
     end
   end