Fix: avoid matching capture pattern name ( Fixes #291)

Web/Scotty/Route.hs

@@ -20,7 +20,7 @@
 import qualified Text.Regex as Regex
 
 import           Web.Scotty.Action
 import           Web.Scotty.Internal.Types (RoutePattern(..), RouteOptions, ActionEnv(..), ActionT, ScottyState(..), ScottyT(..), ErrorHandler, Middleware, BodyInfo, handler, addRoute, defaultScottyResponse)
 import           Web.Scotty.Util (decodeUtf8Lenient)
 import Web.Scotty.Body (cloneBodyInfo, getBodyAction, getBodyChunkAction, getFormParamsAndFilesAction)
 
@@ -140,10 +140,10 @@
                        | otherwise           = Nothing  -- request string is longer than pattern
           go p  [] prs | T.null (mconcat p)  = Just prs -- in case pattern has trailing slashes
                        | otherwise           = Nothing  -- request string is not long enough
-          go (p:ps) (r:rs) prs | p == r          = go ps rs prs -- equal literals, keeping checking
-                               | T.null p        = Nothing      -- p is null, but r is not, fail
-                               | T.head p == ':' = go ps rs $ (T.tail p, r) : prs -- p is a capture, add to params
-                               | otherwise       = Nothing      -- both literals, but unequal, fail
+          go (p:ps) (r:rs) prs = case T.uncons p of
+                        Just (':', name) -> go ps rs $ (name, r) : prs -- p is a capture, add to params
+                        _ | p == r       -> go ps rs prs -- equal literals, keeping checking
+                          | otherwise    -> Nothing      -- both literals, but unequal, fail
           compress ("":rest@("":_)) = compress rest
           compress (x:xs) = x : compress xs
           compress [] = []

changelog.md

@@ -1,5 +1,8 @@
 ## next [????.??.??]
 
+### Fixes
+* Path parameters with value matching the parameter name prefixed by colon will properly populate `pathParams` with their literal value : `/:param` will match `/:param` and add a `Param` with value `("param", ":param")` (#301)
+
 
 ## 0.21 [2023.12.17]
 ### New

test/Web/ScottySpec.hs

@@ -57,6 +57,8 @@ spec = do
             makeRequest "//scotty" `shouldRespondWith` 200
 
         withApp (route "/:paramName" $ captureParam "paramName" >>= text) $ do
+          it ("captures route parameters for " ++ method ++ " requests when parameter matches its name") $ do
+            makeRequest "/:paramName" `shouldRespondWith` ":paramName"
           it ("captures route parameters for " ++ method ++ " requests with url encoded '/' in path") $ do
             makeRequest "/a%2Fb" `shouldRespondWith` "a/b"