Linter for field order in struct initialization

[begelundmuller]

Hello, do you know of a linter that will error if a struct is initialized with a different field order than the struct definition?

For example:

// Given this struct definition:
type Foobar struct {
  Foo int
  Bar int
}

// This should succeed:
var a = Foobar{
  Foo: 3,
  Bar: 14,
}

// But this should fail:
var b = Foobar{
  Bar: 14,
  Foo: 3,
}

[ldez]

Hello,

I don't think a linter exists for that as it's a pure "style" linter.

Can you explain the need behind this? Why the order is important for you?

[begelundmuller]

Hello @ldez, thank you for responding!

Yes it's definitely only a style/readability matter. Here are two reasons why it would be useful:

1. Struct fields are usually ordered in a meaningful way to improve code readability. For example, the fields in url.URL are roughly ordered by where they appear in the string representation of a URL. I find that using the same field order when initializing a struct similarly improves the readability of the initialization code.
2. When comparing a struct initialization to its type definition, having a consistent field order makes it easier to check if a specific field is set or not. This is particularly useful when auditing large options/config/request types (for example, git.CloneOptions or s3.GetObjectInput).

[manuelarte]

Hi @begelundmuller,

I created a linter that does what you want here: https://github.com/manuelarte/structinit

In the README.md you should find the instructions on how to run it. Let me know how it goes if you use it.

After some talks with the maintainers of golangci-lint, I don't think this linter will be included in it.

[arkriny]

Thank you for your linter, it's really helpful!
I'm also curious why it won't be included in golangci-lint. It seems quite useful, even if it's mainly about style - there are already style-focused linters included, wsl for example. Additionally, this linter complements the "fill struct" code action very well, which often used to initialize all fields in the declared order. Paired with exhaustruct, this linter can ensures readability and consistency in every place.
Even if it remains like that, it would still be great to use it as a plugin, would that be possible? Thanks again for your work!

[manuelarte]

Hi @arkriny I updated the repository and also the README to indicate how to use it as a plugin. Let me know if you find it useful.