Add map merging and comparison functions to filter.go

Two new functions have been added to filter.go in the lualib directory. The first function, mergeMaps, merges two maps into one, prioritizing values from the second map in case of duplicate keys. The second function, mapsEqual, compares two maps for equality, returning a boolean result. These functions have been integrated into the filter handling logic.

Signed-off-by: Christian Roessner <c@roessner.co>

server/lualib/filter/filter.go

@@ -492,6 +492,37 @@ func logResult(r *Request, script *LuaFilter, action bool, ret int) {
 	)
 }
 
+// mergeMaps merges 2 maps into one. If same key exists in both maps, value from m2 is used.
+func mergeMaps(m1, m2 map[any]any) map[any]any {
+	result := make(map[any]any)
+
+	for k, v := range m1 {
+		result[k] = v
+	}
+
+	for k, v := range m2 {
+		result[k] = v
+	}
+
+	return result
+}
+
+// mapsEqual checks if two maps are equal by comparing their key-value pairs.
+// It returns true if the maps are equal, and false otherwise.
+func mapsEqual(m1, m2 map[any]any) bool {
+	if len(m1) != len(m2) {
+		return false
+	}
+
+	for k, v := range m1 {
+		if v2, ok := m2[k]; !ok || v != v2 {
+			return false
+		}
+	}
+
+	return true
+}
+
 // CallFilterLua attempts to execute Lua scripts defined in LuaFilters. It returns true if at least
 // one of the scripts executed successfully, otherwise it returns false.
 // The error return value is used to indicate any issues with the Lua filters.
@@ -508,6 +539,9 @@ func (r *Request) CallFilterLua(ctx *gin.Context) (action bool, backendResult *l
 		return false, nil, nil, errors2.ErrNoFiltersDefined
 	}
 
+	backendResult = &lualib.LuaBackendResult{}
+	removeAttributes = make([]string, 0)
+
 	LuaFilters.Mu.RLock()
 
 	defer LuaFilters.Mu.RUnlock()
@@ -520,25 +554,41 @@ func (r *Request) CallFilterLua(ctx *gin.Context) (action bool, backendResult *l
 	globals := setGlobals(ctx, r, L, &backendResult, &removeAttributes)
 	request := setRequest(r, L)
 
+	mergedBackendResult := &lualib.LuaBackendResult{Attributes: make(map[any]any)}
+	mergedRemoveAttributes := config.NewStringSet()
+
 	for _, script := range LuaFilters.LuaScripts {
 		if errors.Is(ctx.Err(), context.Canceled) {
 			return
 		}
 
+		prevBackendResult := backendResult
+
 		result, errLua := executeScriptWithinContext(request, script, r, ctx, L)
 		if errLua != nil {
 			err = errLua
 
 			break
 		}
 
+		if !mapsEqual(prevBackendResult.Attributes, backendResult.Attributes) {
+			mergedBackendResult.Attributes = mergeMaps(mergedBackendResult.Attributes, backendResult.Attributes)
+		}
+
+		for _, attr := range removeAttributes {
+			mergedRemoveAttributes.Set(attr)
+		}
+
 		if result {
 			action = true
 
 			break
 		}
 	}
 
+	backendResult = mergedBackendResult
+	removeAttributes = mergedRemoveAttributes.GetStringSlice()
+
 	lualib.CleanupLTable(request)
 	lualib.CleanupLTable(globals)