golang get comments

With the continuous development of the Go programming language, more and more programmers choose Go as their main programming language. Starting from Go 1.17, a new go/doc package has been added to the Go language standard library, which makes it easier and more convenient for Golang to obtain comments.

In this article, we will explore how to get comments in Golang source code using the go/doc package. We will explain it from the following aspects:

1. go/doc Basic use of packages
2. How to get comments on methods and functions
3. How to get comments on structures and interfaces
4. Nesting and filtering of comments

1. go/doc Basic use of packages

## The

#go/doc package is a package that comes with the Go language standard library and can be used without installation. This package provides a very simple way to parse annotation information from Golang source code.

First, we need to import the

go/doc package and use go/doc.New(pak *ast.Package, importPath string, mode Mode ) function to create an object of type go/doc.Package. The first parameter of this function is a pointer of type *ast.Package, which represents the Go package we want to get the annotation from; the second parameter is a string type, which represents the path to import the package. ;The third parameter is a go/doc.Mode type, used to specify the information we want to query.

package main

import (
    "go/ast"
    "go/doc"
    "go/parser"
    "go/token"
)

func main() {
    // 从本地源码文件解析 Go 代码
    fset := token.NewFileSet()
    astFile, _ := parser.ParseFile(fset, "example.go", nil, parser.ParseComments)
    packageName := "example"
    pkg := &ast.Package{
        Name: packageName,
        Files: map[string]*ast.File {
            "example.go": astFile,
        },
    }

    // 创建一个 go/doc.Package 对象
    targetPkg := doc.New(pkg, packageName, 0)
}

The above code creates a

go/doc.Package object named targetPkg, which contains all the information of the example package. Below we will explain step by step how to use this object to obtain annotation information.

2. How to get comments on methods and functions

In Golang, methods and functions are common code elements. Below we'll explain how to get their annotations.

Get the comments of the function

In the

go/doc.Package type, there is a function named The Funcs field contains annotation information for all functions and methods. This field is a map with the function name as the key and the go/doc.Func type value as the value.

func Example() {
    targetPkg := ...

    // 获取函数的注释
    f := targetPkg.Funcs["foo"]
    fmt.Println(f.Doc)  // 输出函数 foo 的注释
}

In the above code, we obtain the annotation information of the

foo function through targetPkg.Funcs["foo"] and print it to the console.

Get the annotation of the method

In Golang, a method refers to the function associated with the structure. If we want to get the annotation of a method, we can use the

Types field in the go/doc.Package type. Each *go/doc.Type object contains all annotation information related to it, including methods.

We can use the

Name() method to get the name of the type, and then traverse its method list to get the annotation information of each method.

func Example() {
    targetPkg := ...

    // 获取结构体的注释和方法的注释
    for _, t := range targetPkg.Types {
        fmt.Println(t.Doc)  // 输出结构体的注释
        for _, m := range t.Methods {
            fmt.Println(m.Doc)  // 输出方法的注释
        }
    }
}

In the above code, we use

targetPkg.Types to obtain the annotations of all structures and methods. Traverse targetPkg.Types, for each type, we can use t.Doc to get its annotation information, and traverse t.Methods to get the annotations of each method information.

3. How to get comments on structures and interfaces

In Golang, structures and interfaces are also common code elements. Similar to functions and methods, we can also get their annotation information.

Get the comments of the structure

In the

go/doc.Package type, there is a file named Types field, which contains all structure and interface information. This field is a map with type names as keys and values ​​of type go/doc.Type as values.

We can use the

Doc field in the go/doc.Type type to obtain the annotation information of the structure.

func Example() {
    targetPkg := ...

    // 获取结构体的注释
    typ := targetPkg.Types["MyStruct"]
    fmt.Println(typ.Doc)
}

In the above code, we obtain the annotation information of the structure named

MyStruct through targetPkg.Types["MyStruct"] and print it to console.

Get the comments of the interface

Similar to the structure, we can also use the ## in the

go/doc.Type type The #Doc` field obtains the annotation information of the interface. <pre class='brush:php;toolbar:false;'>func Example() { targetPkg := ... // 获取接口的注释 typ := targetPkg.Types[&quot;MyInterface&quot;] fmt.Println(typ.Doc) }</pre>In the above code, we obtain the annotation information of the interface named

MyInterface

through targetPkg.Types["MyInterface"] and print it to the control tower. 4. Nesting and filtering of comments

In Golang, comments can be nested in other comments, which means that we can find nested comments by traversing the comments. Furthermore, sometimes we are only interested in annotations containing specific text. In this case, we can use regular expressions or other filters to filter comments.

Get nested comments

1. In the

go/doc

.Package type, the comment information is nested in in other notes. We can find nested comments by looping through them. The following example code demonstrates how to traverse annotation information to find nested annotations. <pre class='brush:php;toolbar:false;'>func Example() { targetPkg := ... // 遍历注释来查找嵌套的注释 for _, f := range targetPkg.Funcs { ast.Inspect(f.Decl, func(node ast.Node) bool { switch n := node.(type) { case *ast.CommentGroup: for _, c := range n.List { if strings.Contains(c.Text, &quot;TODO&quot;) { fmt.Println(c) } } } return true }) } }</pre><p>上述代码中，我们使用 <code>targetPkg.Funcs 获取所有函数和方法的注释。然后，我们使用 go/ast.Inspect 函数将注释树作为根节点输入，并遍历树中的所有注释。如果找到了包含特定文本的注释，则将其打印到控制台。在上述示例中，我们打印了所有包含 TODO 的注释。

2. 使用过滤器来过滤注释

有时候我们只对包含特定文本的注释感兴趣。在这种情况下，我们可以使用正则表达式或其他过滤器来过滤注释。下面示例代码演示了如何使用正则表达式过滤注释。

func Example() {
    targetPkg := ...

    // 使用正则表达式过滤注释
    pattern, _ := regexp.Compile(`@deprecated`)
    for _, f := range targetPkg.Funcs {
        if pattern.MatchString(f.Doc) {
            fmt.Printf("Function %s is deprecated: %s
", f.Name, f.Doc)
        }
    }
}

上述代码中，我们创建了一个名为 pattern 的正则表达式。然后，我们遍历 targetPkg.Funcs，并使用 pattern 过滤所有包含 @deprecated 的注释。对于匹配的注释，我们将其打印到控制台。

总结

在本文中，我们探讨了如何使用 go/doc 包获取 Golang 源代码中的注释。我们介绍了基本的使用方法，并讲解了如何获取函数和方法、结构体和接口的注释。此外，我们还讨论了如何遍历注释以查找嵌套的注释，以及如何使用正则表达式或其他过滤器来过滤注释。希望本文能够帮助你更好地理解 Golang 的注释机制，并在实践中发挥作用。

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