Fix config precedence with popular_enabled

The original approach cannot be used to properly handle the precedence
of `popular_enabled` in relations to the new `pages_enabled` since it
is impossible to determine whether they are unset due to the presence
of default values.

In addition the original precedence handling wasn't actually doing
anything since PagesEnabled.has_key? will always return true if the key
is valid and thus use page_enabled and its default values regardless of
whether popular_enabled was set or not (which again is also impossible
to know)

To fix this two new instance variables are introduced in order to track
whether these two attributes were present in the YAML config and the
logic for handling them is instead reduced to only using `page_enabled`
and copying `popular_enabled` to page_enabled["popular"] when
`page_enabled` field is unset.

src/invidious/config.cr

@@ -72,34 +72,26 @@ struct HTTPProxyConfig
 end
 
 # Structure used for global per-page feature toggles
-struct PagesEnabled
+record PagesEnabled,
+  trending : Bool = true,
+  popular : Bool = true,
+  search : Bool = true do
   include YAML::Serializable
 
-  property trending : Bool = true
-  property popular : Bool = true
-  property search : Bool = true
-
-  def initialize(@trending, @popular, @search); end
-
-  def has_key?(key : String) : Bool
-    %w(trending popular search).includes?(key)
+  def [](key : String) : Bool
+    fetch(key) { raise KeyError.new("Unknown page '#{key}'") }
   end
 
-  def [](key : String) : Bool
+  def []?(key : String) : Bool
+    fetch(key) { nil }
+  end
+
+  private def fetch(key : String, &)
     case key
     when "trending" then @trending
     when "popular"  then @popular
     when "search"   then @search
-    else                 raise KeyError.new("Unknown page '#{key}'")
-    end
-  end
-
-  def []=(key : String, value : Bool)
-    case key
-    when "trending" then @trending = value
-    when "popular"  then @popular = value
-    when "search"   then @search = value
-    else                 raise KeyError.new("Unknown page '#{key}'")
+    else                 yield
     end
   end
 end
@@ -153,14 +145,26 @@ class Config
   property use_pubsub_feeds : Bool | Int32 = false
 
   # —————————————————————————————————————————————————————————————————————————————————————
+
+  # A @{{key}}_present variable is required for both fields in order to handle the precedence for
+  # the deprecated `popular_enabled` in relations to `pages_enabled`
+
   # DEPRECATED: use `pages_enabled["popular"]` instead.
   @[Deprecated("`popular_enabled` will be removed in a future release; use pages_enabled[\"popular\"] instead")]
+  @[YAML::Field(presence: true)]
   property popular_enabled : Bool = true
 
+  @[YAML::Field(ignore: true)]
+  property popular_enabled_present : Bool
+
   # Global per-page feature toggles.
   # Valid keys: "trending", "popular", "search"
   # If someone sets both `popular_enabled` and `pages_enabled["popular"]`, the latter takes precedence.
+  @[YAML::Field(presence: true)]
   property pages_enabled : PagesEnabled = PagesEnabled.from_yaml("")
+
+  @[YAML::Field(ignore: true)]
+  property pages_enabled_present : Bool
   # —————————————————————————————————————————————————————————————————————————————————————
 
   property captcha_enabled : Bool = true
@@ -241,13 +245,7 @@ class Config
 
   # Centralized page toggle with legacy fallback for `popular_enabled`
   def page_enabled?(page : String) : Bool
-    if @pages_enabled.has_key?(page)
-      @pages_enabled[page]
-    elsif page == "popular"
-      @popular_enabled
-    else
-      true
-    end
+    return @pages_enabled[page]
   end
 
   def self.load
@@ -336,6 +334,8 @@ class Config
       exit(1)
     end
 
+    config.process_deprecation
+
     # Build database_url from db.* if it's not set directly
     if config.database_url.to_s.empty?
       if db = config.db
@@ -373,4 +373,24 @@ class Config
 
     return config
   end
+
+  # Processes deprecated values
+  #
+  # Warns when they are set and handles any precedence issue that may arise when present alongside a successor attribute
+  #
+  # This method is public as to allow specs to test the behavior without going through #load
+  #
+  # :nodoc:
+  def process_deprecation(log_io : IO = STDOUT)
+    # Handle deprecated popular_enabled config and warn if it is set
+    if self.popular_enabled_present
+      log_io.puts "Warning: `popular_enabled` has been deprecated and replaced by the `pages_enabled` config"
+      log_io.puts "If both are set `pages_enabled` will take precedence over `popular_enabled`"
+
+      # Only use popular_enabled value when pages_enabled is unset
+      if !self.pages_enabled_present
+        self.pages_enabled = self.pages_enabled.copy_with(popular: self.popular_enabled)
+      end
+    end
+  end
 end