How to Suppress Go Vet Warnings About Multiple Percent Signs in Println?

How to Suppress Go Vet Warning for Multiple Percent Signs in Println

Go vet can generate warnings when it encounters potential formatting directives in function calls like Println. This warning can be particularly frustrating when you intentionally want to print multiple percent signs.

Consider the following code:

package main

import (
    "fmt"
)

func main() {
    fmt.Println("%%dude")
}

This code triggers the warning:

./prog.go:8:2: Println call has possible formatting directive %d

To address this issue, you have two options:

Alternative Print Statements:

You can use alternative print statements that do not require percent signs to achieve the same output. For example:

fmt.Println("%" + "dude")
fmt.Println("%\x25dude")
fmt.Printf("%%%%dude\n")
s := "%%dude"
fmt.Println(s)

Custom Go Vet Rules:

While not recommended, you can suppress this specific warning by defining your own custom Go vet rules. However, this approach is discouraged as it could lead to inconsistent or unexpected behavior for other users who build your code.

To create a custom Go vet rule, you can define a new file, typically named custom_rules.go, and edit it to include the following contents:

package govetrules

import (
    "github.com/golangci/go-criticisms"
)

func init() {
    criticisms.Register("suppress-fmt-percent-warning", criticisms.Rule{
        Description: "Suppresses the warning for Println calls with multiple percent signs",
        Validator: func(ctx *criticisms.Context, node ast.Node, s string) {
            // Disable the warning for Println calls with at least two consecutive percent signs
            if call, ok := node.(*ast.CallExpr); ok && call.Fun.Name == "Println" {
                args := call.Args
                if len(args) >= 2 && args[0].String() == "\"\"" && args[1].String() == "\"\"" {
                    ctx.SetResult(criticisms.Invalid)
                }
            }
        },
    })
}

Place this file in your project directory and run go generate to activate the rule. However, as mentioned earlier, using custom rules should be considered a last resort and is not recommended for general use.

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