Initialization of fields with zero values

[Abhinav Gupta]

For struct initialization where some of the fields are zero values, we should establish whether we prefer for those fields to be initialized to zero values explicitly or omitted:

foo := Foo{
  Count:   1,
  Items:   nil,
  Default: "",
  Admin:   true,
}

// or

foo := Foo{
  Count: 1,
  Admin: true,
}

Opinion: the latter is preferable because it reduces code noise from things that don't matter at this time. You only specify the things that have meaning/value and everything else is the default.

---

Follow up: When all fields are zero value, do we want to use the explicit struct initialization form or var?

foo := Foo{}
// or
var foo Foo

Opinion: the latter because it scans differently (visually) and differentiates from Foo{} where Foo is a map or slice type (see also, Initializing Maps). It makes it clear that this is something that is probably not going to be used as-is and will be filled separately. ({} form to initialize structs still applies when not stored in a variable or fields are non-zero: do(Stuff{...}).)

[Matt Way]

Agreed on both counts. We also call something similar in the guide already:

However, there are cases where the default value is clearer when the var keyword is used. Declaring Empty Slices, for example.

I think this can be changed to refer more generally to zero values, which would address the 2nd portion of the proposal.

[Prashant Varanasi]

+1 to both.

One caveat for skipping the 0 value in struct initializers is if the 0 value is significant or provides context for the reader. E.g., I often run into test tables where the 0 value is important,

tests := []struct{
  s string
  want int 
}{
  {
    s: "0",
    want: 0,
  },
}