Metadata

ID: go-best-practices/unnecessary-blank-identifier

Language: Go

Severity: Info

Category: Best Practices

Description

In Go, when using range iterations or receiving values from channels, it is recommended to avoid assigning the iteration or received value to the blank identifier _. Instead, it is preferred to omit the assignment entirely.

Here’s why it is best to use for range s {}, x = someMap[key], and <-ch instead of using the blank identifier _:

1. Clarity and Readability: By omitting the assignment entirely, it makes the code more readable and self-explanatory. Using _ can introduce confusion and make it less clear what the purpose of the assignment is or if the value is discarded intentionally or accidentally.
2. Avoiding Variable Pollution: Using _ as an assignment can unnecessarily pollute the variable space. Although Go allows the use of the blank identifier _ to disregard a value, it is a good practice to avoid introducing unnecessary variables, especially if they are never used.
3. Linting and static analysis: Some linting tools and static analyzers may flag the use of varName = _ as an indication of accidental assignment or failure to handle errors or returned values properly. Removing these assignments eliminates such warnings or false-positive detections.

For example, consider the following code snippets:

for _ = range aSlice {}
x, _ = something()
_ = <- aChannel

for range aSlice {}
x = something()
<-aChannel

Both snippets achieve the same result, but the second one that omits the assignments using _ is preferred for its simplicity, readability, and adherence to Go’s best practices.

By using for range s {}, x = someMap[key], and <-ch instead of assigning to _, you can write cleaner and more readable Go code while avoiding unnecessary variable assignments and potential confusion.

Non-Compliant Code Examples

func main() {
    for _ = range aSlice {
        
    }
    x, _ = myMap[key]
    _ = <- aChannel

    x, _ = myFunction()

    for key, _ = range myMap {
        
    }

    for _, _ = range myMap {
        
    }
}

Compliant Code Examples

func main() {
    for aSlice {
        
    }
    x = myMap[key]
    <- aChannel

    for _, val = range mySlice {
        
    }
}