From 82af250762bf189e0e4980e38e617149a2cc7c1e Mon Sep 17 00:00:00 2001
From: Luca Ruperto <lukelr2000@gmail.com>
Date: Wed, 17 Jun 2026 14:03:29 +0200
Subject: [PATCH 1/2] urlReachable: stub new function and call site

---
 src/GH.hs     | 4 ++++
 src/Update.hs | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/src/GH.hs b/src/GH.hs
index 7df2ae77..a04ed897 100644
--- a/src/GH.hs
+++ b/src/GH.hs
@@ -11,6 +11,7 @@ module GH
     authFromToken,
     checkExistingUpdatePR,
     closedAutoUpdateRefs,
+    urlReachable,
     compareUrl,
     latestVersion,
     pr,
@@ -149,6 +150,9 @@ parseURLMaybe url =
               )
    in url =~ regex
 
+urlReachable :: Text -> IO Bool
+urlReachable _ = pure True -- TODO
+
 parseURL :: MonadIO m => Text -> ExceptT Text m URLParts
 parseURL url =
   tryJust ("GitHub: " <> url <> " is not a GitHub URL.") (parseURLMaybe url)
diff --git a/src/Update.hs b/src/Update.hs
index 64eb3337..89a8646a 100644
--- a/src/Update.hs
+++ b/src/Update.hs
@@ -253,6 +253,12 @@ updateAttrPath log mergeBase updateEnv@UpdateEnv {..} attrPath = do
       "The derivation has no 'version' attribute, so do not know how to figure out the version while doing an updateScript update"
       (not hasUpdateScript || isJust oldVerMay)
 
+    unless hasUpdateScript $
+      when (T.isInfixOf oldVersion oldSrcUrl) do
+        let url = oldVersion `T.replace` newVersion $ oldSrcUrl
+        reachable <- liftIO $ GH.urlReachable url
+        unless reachable $ throwE ("The new url doesn't exist: " <> url)
+
     -- One final filter
     Skiplist.content derivationContents
 

From 5ab9e23fedf7ce1022cc07cfc13822e0f73510c0 Mon Sep 17 00:00:00 2001
From: Luca Ruperto <lukelr2000@gmail.com>
Date: Wed, 17 Jun 2026 14:40:00 +0200
Subject: [PATCH 2/2] urlReachable: use Network.HTTP.Client to make a HEAD
 request to github

---
 src/GH.hs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/GH.hs b/src/GH.hs
index a04ed897..425c7597 100644
--- a/src/GH.hs
+++ b/src/GH.hs
@@ -20,6 +20,7 @@ module GH
 where
 
 import Control.Applicative (liftA2, some)
+import Control.Exception (try)
 import Data.Aeson (FromJSON)
 import Data.Bitraversable (bitraverse)
 import qualified Data.Text as T
@@ -29,7 +30,8 @@ import qualified Data.Vector as V
 import qualified Git
 import qualified GitHub as GH
 import GitHub.Data.Name (Name (..))
-import Network.HTTP.Client (HttpException (..), HttpExceptionContent (..), responseStatus)
+import Network.HTTP.Client
+import Network.HTTP.Client.TLS (tlsManagerSettings)
 import Network.HTTP.Types.Status (statusCode)
 import OurPrelude
 import Text.Regex.Applicative.Text ((=~))
@@ -151,7 +153,18 @@ parseURLMaybe url =
    in url =~ regex
 
 urlReachable :: Text -> IO Bool
-urlReachable _ = pure True -- TODO
+urlReachable url =
+  case parseRequest $ T.unpack url of
+    Nothing -> pure False
+    Just req -> do
+      manager <- newManager tlsManagerSettings
+      res <-
+        try $
+          (httpNoBody (req {method = "HEAD"}) manager) ::
+          IO (Either HttpException (Response ()))
+      case res of
+        Left _ -> pure False
+        Right resp -> pure $ statusCode (responseStatus resp) == 200
 
 parseURL :: MonadIO m => Text -> ExceptT Text m URLParts
 parseURL url =