Only use `Sparkle` strategy if URL is specified explicitly.

Library/Homebrew/livecheck/livecheck.rb

@@ -435,9 +435,9 @@ module Homebrew
 
       has_livecheckable = formula_or_cask.livecheckable?
       livecheck = formula_or_cask.livecheck
+      livecheck_url = livecheck.url
       livecheck_regex = livecheck.regex
       livecheck_strategy = livecheck.strategy
-      livecheck_url = livecheck.url
 
       urls = [livecheck_url] if livecheck_url.present?
       urls ||= checkable_urls(formula_or_cask)
@@ -475,7 +475,9 @@ module Homebrew
         strategies = Strategy.from_url(
           url,
           livecheck_strategy: livecheck_strategy,
+          url_provided:       livecheck_url.present?,
           regex_provided:     livecheck_regex.present?,
+          block_provided: livecheck.strategy_block.present?,
         )
         strategy = Strategy.from_symbol(livecheck_strategy)
         strategy ||= strategies.first
@@ -490,8 +492,8 @@ module Homebrew
           puts "Regex:            #{livecheck_regex.inspect}" if livecheck_regex.present?
         end
 
-        if livecheck_strategy == :page_match && livecheck_regex.blank?
-          odebug "#{strategy_name} strategy requires a regex"
+        if livecheck_strategy == :page_match && (livecheck_regex.blank? && livecheck.strategy_block.blank?)
+          odebug "#{strategy_name} strategy requires a regex or block"
           next
         end
 

Library/Homebrew/livecheck/strategy.rb

@@ -57,12 +57,16 @@ module Homebrew
       # @param regex_provided [Boolean] whether a regex is provided in the
       #   `livecheck` block
       # @return [Array]
-      def from_url(url, livecheck_strategy: nil, regex_provided: nil)
+      def from_url(url, livecheck_strategy: nil, url_provided: nil, regex_provided: nil, block_provided: nil)
         usable_strategies = strategies.values.select do |strategy|
           if strategy == PageMatch
             # Only treat the `PageMatch` strategy as usable if a regex is
             # present in the `livecheck` block
-            next unless regex_provided
+            next unless (regex_provided || block_provided)
+          elsif strategy == Sparkle && (livecheck_strategy || !url_provided)
+            # Skip the `Sparkle` strategy if a strategy is specified explicitly
+            # or if the URL is not specified explicitly.
+            next
           elsif strategy.const_defined?(:PRIORITY) &&
                 !strategy::PRIORITY.positive? &&
                 from_symbol(livecheck_strategy) != strategy