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Description

Bind a a non mandatory file parameter will report an error.

How to reproduce


package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "mime/multipart"
    "net/http"
)

var html = `<!doctype html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>File binding</title>
</head>
<body>
<h1>Bind file with fields</h1>
<form action="/upload" method="post" enctype="multipart/form-data">
    Name: <input type="text" name="name"><br>
    Email: <input type="email" name="email"><br>
    File: <input type="file" name="file"><br><br>
    <input type="submit" value="Submit">
</form>
</body>`

type BindFile struct {
    Name  string                `form:"name" binding:"required"`
    Email string                `form:"email" binding:"required"`
    File  *multipart.FileHeader `form:"file" `
}

func main() {
    router := gin.Default()
    // Set a lower memory limit for multipart forms (default is 32 MiB)
    router.GET("/", func(ctx *gin.Context) {
        ctx.Header("Content-Type", "text/html")
        ctx.String(200, html)
    })
    router.POST("/upload", func(c *gin.Context) {
        var bindFile BindFile
        if err := c.ShouldBind(&bindFile); err != nil {
            // will report an error when file is not uploaded.
            // Can we set it a nil pointer by default ?
            c.String(http.StatusBadRequest, fmt.Sprintf("err: %s", err.Error()))
            return
        }
        // TODO::...
        c.String(http.StatusOK, fmt.Sprintf("File %s uploaded successfully with fields name=%s and email=%s.", file.Filename, bindFile.Name, bindFile.Email))
    })
    router.Run(":8080")
}

Expectations

$ curl 'http://localhost:8080/upload' \
  -H 'Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryK7Skf1qO5bW9JEX0' \
  --data-raw $'------WebKitFormBoundaryK7Skf1qO5bW9JEX0\r\nContent-Disposition: form-data; name="name"\r\n\r\n\r\n------WebKitFormBoundaryK7Skf1qO5bW9JEX0\r\nContent-Disposition: form-data; name="email"\r\n\r\n\r\n------WebKitFormBoundaryK7Skf1qO5bW9JEX0\r\nContent-Disposition: form-data; name="file"; filename=""\r\nContent-Type: application/octet-stream\r\n\r\n\r\n------WebKitFormBoundaryK7Skf1qO5bW9JEX0--\r\n'

Actual result

err: unexpected end of JSON input

Environment

  • go version: go version go1.20.4 darwin/arm64
  • gin version (or commit ref): 53fbf4d
  • operating system: macOS

Comment From: clearcodecn

Error Line is : #L239

can we set it nil by default or using assertions like: time.Time ,

Because we used JSON for him The unmarshal function causes its parsing to fail, and in this scenario, we should not do so