What's the standard practice for naming labels in Go?

Question

Go spec and Effective Go gives guidelines for naming packages, types, functions, and variables. There's also a blog post discussing about package names. But none of articles seem to talk about naming conventions of labels used with goto, break and continue.

I believe the best practice is to avoid labels altogether, but what's the standard convention for those control flow labels in Go?

Please note that this question is not asking for naming recommendations. I just thought it would be good to know what guidelines Google provide about it or how they actually use it.

As has been mentioned before: there is no official convention, guideline, or standard practice for label names. Any other answer will be subjective. — Marc, Sep 24 '20 at 08:21
Yeah, the convention to write label names is just to use `MixedCaps` or `mixedCaps` rather than underscores. — Coconut, Sep 25 '20 at 06:26
@Coconut: So in other words, there is no convention for labels. There's just the existing convention for naming anything in Go. — Jonathan Hall, Sep 25 '20 at 06:58

score 1 · Accepted Answer · answered Sep 24 '20 at 03:38

According to the source code of the Go standard library and internal packages, they tend to name labels in the same manner variables are usually named.

So it's okay for labels to have any combination of either upper or lower-case characters, as long as you don't use underscores for writing anything.

See https://golang.org/doc/effective_go.html#mixed-caps

MixedCaps

Finally, the convention in Go is to use MixedCaps or mixedCaps rather than underscores to write multiword names.

Some examples:

https://golang.org/src/cmd/internal/obj/x86/pcrelative_test.go#L102

continue LOOP

https://golang.org/src/compress/lzw/reader.go#L198

break loop

https://golang.org/src/compress/flate/deflate.go#L402

break Loop

https://golang.org/src/debug/gosym/symtab.go#L429

break countloop

https://golang.org/src/encoding/csv/reader.go#L308

break parseField

https://golang.org/src/crypto/dsa/dsa.go#L128

break GeneratePrimes

https://golang.org/src/go/types/testdata/labels.src

func f3() {
L1:
L2:
L3:
    for {
        break L1 /* ERROR "invalid break label L1" */
        break L2 /* ERROR "invalid break label L2" */
        break L3
        continue L1 /* ERROR "invalid continue label L1" */
        continue L2 /* ERROR "invalid continue label L2" */
        continue L3
        goto L1
        goto L2
        goto L3
    }
}

All sample snippets from Go language spec write all labels in CamelCase. And the word Loop is often abbreviated to L in both the spec and the implementation.

https://golang.org/ref/spec#Break_statements

OuterLoop:
    for i = 0; i < n; i++ {
        for j = 0; j < m; j++ {
            switch a[i][j] {
            case nil:
                state = Error
                break OuterLoop
            case item:
                state = Found
                break OuterLoop
            }
        }
    }

https://golang.org/ref/spec#Continue_statements

RowLoop:
    for y, row := range rows {
        for x, data := range row {
            if data == endOfRow {
                continue RowLoop
            }
            row[x] = data + bias(x, y)
        }
    }

https://golang.org/ref/spec#Goto_statements

goto Error

    goto L  // BAD
    v := 3
L:

if n%2 == 1 {
    goto L1
}
for n > 0 {
    f()
    n--
L1:
    f()
    n--
}

What's the standard practice for naming labels in Go?

1 Answers1

MixedCaps