structtag

structtag is a library for parsing struct tags in Go during static analysis. It is designed to provide a robust API for extracting metadata from struct fields in Go code. This fork focuses exclusively on reading struct tags and is no longer intended for modifying or rewriting them.

This project is a fork of fatih/structtag, originally created by Fatih Arslan. The primary changes in this fork include a simplified API tailored for read-only access to struct tags, along with enhancements to better support static analysis use cases.

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Install

To install the package:

go get github.com/tylergannon/structtag

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Example Usage

The following example demonstrates how to parse and inspect struct tags using structtag:

package main

import (
	"fmt"
	"reflect"
	"sort"

	"github.com/tylergannon/structtag"
)

func main() {
	type Example struct {
		Field string `json:"foo,omitempty" xml:"bar"`
	}

	// Get the struct tag from the field
	tag := reflect.TypeOf(Example{}).Field(0).Tag

	// Parse the tag using structtag
	tags, err := structtag.Parse(string(tag))
	if err != nil {
		panic(err)
	}

	// Iterate over all tags
	for _, t := range tags.Tags() {
		fmt.Printf("Key: %s, Options: %v\n", t.Key, t.Options)
	}

	// Access a specific tag by key
	jsonTag, err := tags.Get("json")
	if err != nil {
		panic(err)
	}
	fmt.Printf("Key: %s, Options: %v\n", jsonTag.Key, jsonTag.Options)

	// Print the full tag string
	fmt.Println(tags.String()) // Output: json:"foo,omitempty" xml:"bar"

	// Sort tags by key and print them
	sort.Sort(tags)
	fmt.Println(tags.String()) // Output: json:"foo,omitempty" xml:"bar"
}

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Key Features

• Read-Only Access: Extract and inspect struct tags without modifying them.
• Simplified API: A clean interface for retrieving tag keys and options.
• Static Analysis: Ideal for tools that analyze Go code, such as linters or code generators.

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API Overview

Parsing Struct Tags

Use Parse to parse a struct field's tag into a Tags object:

tags, err := structtag.Parse(`json:"foo,omitempty" xml:"bar"`)
if err != nil {
    panic(err)
}

Accessing Tags

• Retrieve all tags:

  allTags := tags.Tags()

• Retrieve a specific tag by key:

  jsonTag, err := tags.Get("json")
  if err != nil {
      // Handle missing tag
  }
  fmt.Println(jsonTag.Key, jsonTag.Options)

Inspecting Tags

• Key: The key of the tag (e.g., json or xml).
• Options: A slice of strings representing the options in the tag (e.g., ["foo", "omitempty"] for json:"foo,omitempty").

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Acknowledgments

This project is based on fatih/structtag, created by Fatih Arslan. While the API and functionality have been modified significantly, the foundation of this library owes much to the original implementation.