Fix marking of custom routes for Journey

The Mapper build_path method marks routes where path parameters are part
of a path segment as custom routes by altering the regular expression, e.g:

    get '/foo-:bar', to: 'foo#bar'

There were some edge cases where certain constructs weren't being picked
up and this commit fixes those.

Fixes #23069.

1 files changed, 20 insertions, 14 deletions

diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 522012063d..afbaa45d20 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -184,26 +184,32 @@ module ActionDispatch
         def build_path(ast, requirements, anchor)
           pattern = Journey::Path::Pattern.new(ast, requirements, JOINED_SEPARATORS, anchor)
 
-          # Get all the symbol nodes followed by literals that are not the
-          # dummy node.
-          symbols = ast.find_all { |n|
-            n.cat? && n.left.symbol? && n.right.cat? && n.right.left.literal?
-          }.map(&:left)
-
-          # Get all the symbol nodes preceded by literals.
-          symbols.concat ast.find_all { |n|
-            n.cat? && n.left.literal? && n.right.cat? && n.right.left.symbol?
-          }.map { |n| n.right.left }
-
-          symbols.each { |x|
-            x.regexp = /(?:#{Regexp.union(x.regexp, '-')})+/
+          # Find all the symbol nodes that are adjacent to literal nodes and alter
+          # the regexp so that Journey will partition them into custom routes.
+          ast.find_all { |node|
+            next unless node.cat?
+
+            if node.left.literal? && node.right.symbol?
+              symbol = node.right
+            elsif node.left.literal? && node.right.cat? && node.right.left.symbol?
+              symbol = node.right.left
+            elsif node.left.symbol? && node.right.literal?
+              symbol = node.left
+            elsif node.left.symbol? && node.right.cat? && node.right.left.literal?
+              symbol = node.left
+            else
+              next
+            end
+
+            if symbol
+              symbol.regexp = /(?:#{Regexp.union(symbol.regexp, '-')})+/
+            end
           }
 
           pattern
         end
         private :build_path
 
-
         private
           def add_wildcard_options(options, formatted, path_ast)
             # Add a constraint for wildcard route to make it non-greedy and match the