如何解组具有对节点的完全访问权限的 YAML v3

Question

我正在尝试学习使用 YAML v3 解组，并具有对复杂嵌入式结构中节点的完全访问权限。

The announcement 帖子解释了如何使用 yaml.Node，但没有给出一个严肃的例子。并且documentation 也没有显示使用节点。主要目的似乎是在 YAML 文件中出色地保存 cmets。

例如，使用公告文章的扩展，我有

package main

import(
    "fmt"
    "gopkg.in/yaml.v3"
    "os"
)

func main() {

    type Person struct {
        Name    string
        Address yaml.Node
    }

    data := `
name: John Doe
address: 
    street: 123 E 3rd St # street is like an avenue
    city: Denver  # A city might be a town as well
    state: CO  # A state might be a province or administrative unit
    zip: 81526 # zip might be "postal_code"
`

    var person Person
    err := yaml.Unmarshal([]byte(data), &person)
    if (err != nil) {
        fmt.Printf("Failed to unmarshall: %v", err)
        os.Exit(1)
    }
    fmt.Printf("Marshalled person=%v", person)

}

但如果我尝试使用地址项，我会发现它们每个都列为节点内的内容数组；那里没有实际有用的信息。 cmets 在那里，但不清楚它们与什么相关联。

Modify existing yaml file and add new data and comments 也处理相同的区域，但在解组到结构后不显示导航结构。

如何在解组后导航“地址”节点，并在再次编组时保留 cmets？

Answer 1

所以 Node 结构有三个字段：

// HeadComment holds any comments in the lines preceding the node and
// not separated by an empty line.
HeadComment string

// LineComment holds any comments at the end of the line where the node is in.
LineComment string

// FootComment holds any comments following the node and before empty lines.
FootComment string

此 ^ 取自文档 here。对上面的例子进行了轻微的扩充：

package main

import (
    "fmt"
    "os"

    "gopkg.in/yaml.v3"
)

func main() {
    type Person struct {
        Name    yaml.Node
        Address yaml.Node
    }

    data := `
name: John Doe
#comment here
address: 
    street: 123 E 3rd St
    city: Denver
    state: CO
    zip: 81526
`

    var person Person
    err := yaml.Unmarshal([]byte(data), &person)
    if err != nil {
        fmt.Printf("Failed to unmarshall: %v", err)
        os.Exit(1)
    }
    address := &yaml.Node{}

    decErr := person.Address.Decode(address)
    if decErr != nil {
        fmt.Printf("Failed to decode: %v", decErr)
        os.Exit(1)
    }
    fmt.Printf("%v", address.HeadComment)
}

在我们的例子中

#comment here
address: 
    street: 123 E 3rd St
    city: Denver
    state: CO
    zip: 81526

可以称为 Node，它的 cmets 可以从 Node 结构中的字段访问。但是我仍然无法获得节点上方的评论，尽管我能够访问文档中指出的其他字段。

Answer 2

你必须声明完整的 struct 而不是使用 yaml.Node

package main

import (
    "fmt"
    "gopkg.in/yaml.v3"
    "os"
)

func main() {
    type Address struct {
        Street string
        City   string
        State  string
        Zip    string
    }
    type Person struct {
        Name    string
        Address Address
    }



data := `
    name: John Doe
    address: 
        street: 123 E 3rd St
        city: Denver
        state: CO
        zip: 81526
    `

    var person Person
    err := yaml.Unmarshal([]byte(data), &person)
    if (err != nil) {
        fmt.Printf("Failed to unmarshall: %v", err)
        os.Exit(1)
    }
    fmt.Printf("Marshalled person=%v", person)
}

yaml.Node 似乎是一个中间表示。 必须对其进行解码才能获取值。

package main

import (
    "fmt"
    "gopkg.in/yaml.v3"
    "os"
)

func main() {
    type Address struct {
        Street string
        City   string
        State  string
        Zip    string
    }
type Person struct {
    Name    string
    Address yaml.Node
}

data := `
name: John Doe
address: 
    street: 123 E 3rd St
    city: Denver
    state: CO
    zip: 81526
`

var person Person
err := yaml.Unmarshal([]byte(data), &person)
if (err != nil) {
    fmt.Printf("Failed to unmarshall: %v", err)
    os.Exit(1)
}
address := &Address{}
_ = person.Address.Decode(address)
fmt.Printf("Marshalled person=%v\n %v", person, *address)

}