Fix /log/ endpoint

The old logic would fail to return a result if a later
substituter didn't have the log file, even if an older

This also simplifies the logic.

cbits/nix.cpp

@@ -176,30 +176,26 @@ void dumpPath(char const * const hashPart, struct string * const output) {
     }
 }
 
-void dumpLog(char const * const hashPart, struct string * const output) {
+void dumpLog(char const * const baseName, struct string * const output) {
     ref<Store> store = getStore();
 
-    std::optional<StorePath> storePath =
+    StorePath storePath(baseName);
-        store->queryPathFromHashPart(hashPart);
 
-    if (storePath.has_value()) {
+    auto subs = getDefaultSubstituters();
-        auto subs = getDefaultSubstituters();
 
-        subs.push_front(store);
+    subs.push_front(store);
 
-        for (auto & sub : subs) {
+    *output = emptyString;
-            LogStore * logStore = dynamic_cast<LogStore *>(&*sub);
 
-            std::optional<std::string> log = logStore->getBuildLog(storePath.value());
+    for (auto & sub : subs) {
+        LogStore * logStore = dynamic_cast<LogStore *>(&*sub);
 
-            if (log.has_value()) {
+        std::optional<std::string> log = logStore->getBuildLog(storePath);
-                copyString(log.value(), output);
+
-            } else {
+        if (log.has_value()) {
-                *output = emptyString;
+            copyString(log.value(), output);
-            }
         }
-    } else {
-        *output = emptyString;
     }
 }
+
 }

src/Main.hs

@@ -88,23 +88,26 @@ makeApplication ApplicationOptions{..} request respond = do
 
             done response
 
+    let invalidPath = do
+            let headers = [ ("Content-Type", "text/plain") ]
+
+            let builder = "Invalid path.\n"
+
+            let response =
+                    Wai.responseBuilder
+                        Types.status400
+                        headers
+                        builder
+
+            done response
+
     result <- Except.runExceptT do
         let rawPath = Wai.rawPathInfo request
 
         if  | Just prefix <- ByteString.stripSuffix ".narinfo" rawPath
             , Just hashPart <- ByteString.stripPrefix "/" prefix -> do
                 Monad.unless (ByteString.length hashPart == 32 && validHashPart hashPart) do
-                    let headers = [ ("Content-Type", "text/plain") ]
+                    invalidPath
-
-                    let builder = "Invalid hash part.\n"
-
-                    let response =
-                            Wai.responseBuilder
-                                Types.status400
-                                headers
-                                builder
-
-                    done response
 
                 maybeStorePath <- liftIO (Nix.queryPathFromHashPart hashPart)
 
@@ -219,30 +222,10 @@ makeApplication ApplicationOptions{..} request respond = do
                         return (interior, Nothing)
 
                     | otherwise -> do
-                        let headers = [ ("Content-Type", "text/plain") ]
+                        invalidPath
-
-                        let builder = "Invalid path component.\n"
-
-                        let response =
-                                Wai.responseBuilder
-                                    Types.status400
-                                    headers
-                                    builder
-
-                        done response
 
                 Monad.unless (validHashPart hashPart) do
-                    let headers = [ ("Content-Type", "text/plain") ]
+                    invalidPath
-
-                    let builder = "Invalid hash part.\n"
-
-                    let response =
-                            Wai.responseBuilder
-                                Types.status400
-                                headers
-                                builder
-
-                    done response
 
                 maybeStorePath <- liftIO (Nix.queryPathFromHashPart hashPart)
 
@@ -281,11 +264,14 @@ makeApplication ApplicationOptions{..} request respond = do
 
                 done response
 
-            | Just suffix <- ByteString.stripPrefix "/log/" rawPath
+            | Just suffix <- ByteString.stripPrefix "/log/" rawPath -> do
-            , 32 <= ByteString.length suffix -> do
                 let hashPart = ByteString.take 32 suffix
 
-                maybeBytes <- liftIO (Nix.dumpLog hashPart)
+                Monad.unless (ByteString.length hashPart == 32 && validHashPart hashPart) do
+                    invalidPath
+
+                liftIO (print suffix)
+                maybeBytes <- liftIO (Nix.dumpLog suffix)
 
                 bytes <- case maybeBytes of
                     Nothing    -> noSuchPath

src/Nix.hsc

@@ -280,10 +280,10 @@ foreign import ccall "dumpLog" dumpLog_
     :: CString -> Ptr String_ -> IO ()
 
 dumpLog :: ByteString -> IO (Maybe ByteString)
-dumpLog hashPart = do
+dumpLog baseName = do
-    ByteString.useAsCString hashPart \cHashPart -> do
+    ByteString.useAsCString baseName \cBaseName -> do
         Foreign.alloca \output -> do
-            let open = dumpLog_ cHashPart output
+            let open = dumpLog_ cBaseName output
             let close = freeString output
             Exception.bracket_ open close do
                 string_@String_{ data_} <- peek output