create combined file path if doesnt exist

apisix/cli/util.lua

@@ -174,11 +174,36 @@ do
 end
 
 
+local function ensure_dir(path)
+    -- Extract directory from path
+    local dir = path:match("(.*/)")
+    if dir then
+        -- Try to create directory recursively.
+        -- This uses "mkdir -p" to avoid error if the directory already exists.
+        local ok = os.execute("mkdir -p " .. dir)
+        if not ok then
+            error("Failed to create directory: " .. dir)
+        end
+    end
+end
+
 function _M.gen_trusted_certs_combined_file(combined_filepath, paths)
-    local combined_file = assert(io.open(combined_filepath, "w"))
+    -- Ensure the directory for combined_filepath exists.
+    ensure_dir(combined_filepath)
+
+    local combined_file, err = io.open(combined_filepath, "w")
+    if not combined_file then
+        error("Failed to open or create combined file at " .. combined_filepath .. 
+              ". Error: " .. tostring(err))
+    end
+
     for _, path in ipairs(paths) do
-        local cert_file = assert(io.open(path, "r"))
-        combined_file:write(cert_file:read("*a"))
+        local cert_file, cert_err = io.open(path, "r")
+        if not cert_file then
+            error("Failed to open certificate file " .. path .. ": " .. tostring(cert_err))
+        end
+        local data = cert_file:read("*a") or ""
+        combined_file:write(data)
         combined_file:write("\n")
         cert_file:close()
     end