download_strategy: fix bad unescaping in basename parsing

Library/Homebrew/download_strategy.rb

@@ -328,8 +328,11 @@ class AbstractFileDownloadStrategy < AbstractDownloadStrategy
     @resolved_url_and_basename = [url, parse_basename(url)]
   end
 
+  sig { params(url: String, search_query: T::Boolean).returns(String) }
   def parse_basename(url, search_query: true)
-    uri_path = if url.match?(URI::DEFAULT_PARSER.make_regexp)
+    components = { path: T.let([], T::Array[String]), query: T.let([], T::Array[String]) }
+
+    if url.match?(URI::DEFAULT_PARSER.make_regexp)
       uri = URI(url)
 
       if uri.query
@@ -340,29 +343,32 @@ class AbstractFileDownloadStrategy < AbstractDownloadStrategy
         end
       end
 
-      if uri.query && search_query
-        "#{uri.path}?#{uri.query}"
-      else
-        uri.path
+      if (uri_path = uri.path.presence)
+        components[:path] = uri_path.split("/").map do |part|
+          URI::DEFAULT_PARSER.unescape(part).presence
+        end.compact
+      end
+
+      if search_query && (uri_query = uri.query.presence)
+        components[:query] = URI.decode_www_form(uri_query).map(&:second)
       end
     else
-      url
+      components[:path] = [url]
     end
 
-    uri_path = URI.decode_www_form_component(uri_path)
-    query_regex = /[^?&]+/
-
     # We need a Pathname because we've monkeypatched extname to support double
     # extensions (e.g. tar.gz).
     # Given a URL like https://example.com/download.php?file=foo-1.0.tar.gz
     # the basename we want is "foo-1.0.tar.gz", not "download.php".
-    Pathname.new(uri_path).ascend do |path|
-      ext = path.extname[query_regex]
-      return path.basename.to_s[/#{query_regex.source}#{Regexp.escape(ext)}/] if ext
+    [*components[:path], *components[:query]].reverse_each do |path|
+      path = Pathname(path)
+      return path.basename.to_s if path.extname.present?
     end
 
-    # Strip query string
-    File.basename(uri_path)[query_regex]
+    filename = components[:path].last
+    return "" if filename.blank?
+
+    File.basename(filename)
   end
 end