storage: preserve original error on function fail

test/storage-luatest/storage_1_test.lua

@@ -674,3 +674,28 @@ test_group.test_info_disable_consistency = function(g)
         ilt.assert(res.is_enabled)
     end, {global_cfg})
 end
+
+local function test_error_msg_is_preserved_template(g, add_to_schema)
+    g.replica_1_a:exec(function(add_to_schema)
+        rawset(_G, 'test_fail', function()
+            box.begin()
+            error('test_error')
+        end)
+        if add_to_schema then
+            box.schema.func.create('test_fail')
+        end
+        local status, err = ivshard.storage.call(1, 'read', 'test_fail', {})
+        ilt.assert_not(status)
+        ilt.assert_str_contains(err.message, 'test_error')
+        ilt.assert_not_str_contains(err.message, 'Transaction is active')
+        rawset(_G, 'test_fail', nil)
+        if add_to_schema then
+            box.schema.func.drop('test_fail')
+        end
+    end, {add_to_schema})
+end
+
+test_group.test_error_msg_is_preserved = function(g)
+    test_error_msg_is_preserved_template(g, false)
+    test_error_msg_is_preserved_template(g, true)
+end

vshard/storage/init.lua

@@ -260,6 +260,20 @@ else
     end
 end
 
+--
+-- If the function is called directly, fails, and leaves an uncommitted
+-- transaction, the original error is replaced by the "Transaction is active"
+-- error. We manually check if the function returned an error. If so, we
+-- rollback the transaction to reveal the original error.
+--
+local function handle_results(status, ...)
+    if not status then
+        box.rollback()
+        return status, box.error.new(box.error.PROC_LUA, (...))
+    end
+    return status, ...
+end
+
 --
 -- Invoke a function on this instance. Arguments are unpacked into the function
 -- as arguments.
@@ -284,7 +298,7 @@ local_call = function(func_name, args)
     if not func then
         return pcall(netbox_self_call, netbox_self, func_name, args)
     end
-    return pcall(func.call, func, args)
+    return handle_results(pcall(func.call, func, args))
 end
 
 end