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Go

/*
* Copyright 2025 CloudWeGo Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Package jsonfix provides a ToolMiddleware for Eino's ToolsNode that
// repairs malformed JSON arguments produced by LLMs before tool execution.
//
// Usage:
//
// conf := &compose.ToolsNodeConfig{
// Tools: []tool.BaseTool{yourTool},
// ToolCallMiddlewares: []compose.ToolMiddleware{jsonfix.Middleware()},
// }
//
// Behavior:
// - Fast-path returns original arguments when already valid JSON.
// - Strips common LLM artifacts and isolates the first {...} region.
// - Applies robust fix using jsonrepair only when input is invalid.
// - Safe for both invokable and streamable tools.
package jsonfix
import (
"context"
"encoding/json"
"strings"
"github.com/cloudwego/eino/compose"
"github.com/kaptinlin/jsonrepair"
)
// FixJSON is a helper endpoint that returns repaired JSON for diagnostics
// or standalone use. ToolsNode should prefer Invokable/Streamable middleware.
func FixJSON(ctx context.Context, in *compose.ToolInput) (*compose.ToolOutput, error) {
fixed := repair(in.Arguments)
return &compose.ToolOutput{Result: fixed}, nil
}
// Invokable wraps a non-stream tool endpoint to sanitize JSON arguments.
// Register via ToolCallMiddlewares to apply automatically to invokable tools.
func Invokable(next compose.InvokableToolEndpoint) compose.InvokableToolEndpoint {
return func(ctx context.Context, in *compose.ToolInput) (*compose.ToolOutput, error) {
in.Arguments = repair(in.Arguments)
return next(ctx, in)
}
}
// Streamable wraps a stream tool endpoint to sanitize JSON arguments.
// Register via ToolCallMiddlewares to apply automatically to streamable tools.
func Streamable(next compose.StreamableToolEndpoint) compose.StreamableToolEndpoint {
return func(ctx context.Context, in *compose.ToolInput) (*compose.StreamToolOutput, error) {
in.Arguments = repair(in.Arguments)
return next(ctx, in)
}
}
// Middleware bundles both invokable and streamable wrappers for convenience.
func Middleware() compose.ToolMiddleware {
return compose.ToolMiddleware{Invokable: Invokable, Streamable: Streamable}
}
// repair attempts minimal work first (validity check, region isolation) and
// only uses jsonrepair when necessary. It trims common LLM artifacts.
func repair(input string) string {
s := strings.TrimSpace(input)
// Fast-path: valid JSON as-is
if strings.HasPrefix(s, "{") && strings.HasSuffix(s, "}") && json.Valid([]byte(s)) {
return s
}
// Isolate JSON object region if present; strip noise if object-only is valid
i := strings.IndexByte(s, '{')
j := strings.LastIndexByte(s, '}')
if i >= 0 && j >= i {
sub := s[i : j+1]
if json.Valid([]byte(sub)) {
return sub
}
s = sub
}
// Remove common LLM artifacts
s = strings.TrimPrefix(s, "<|FunctionCallBegin|>")
s = strings.TrimSuffix(s, "<|FunctionCallEnd|>")
s = strings.TrimPrefix(s, "<think>")
// Attempt robust repair only when invalid
if json.Valid([]byte(s)) {
return s
}
// Heuristic: add missing leading/trailing brace if one side exists
if !strings.HasPrefix(s, "{") && strings.HasSuffix(s, "}") {
s = "{" + s
} else if strings.HasPrefix(s, "{") && !strings.HasSuffix(s, "}") {
s = s + "}"
}
out, err := jsonrepair.JSONRepair(s)
if err != nil {
return s
}
return out
}