[dwattttt]

If the comments impact correctness (which inlining doesn't, but I believe there are other directives that do), saying it's "an implementation detail" waves away "it's an implementation detail that everyone needs" aka part of the spec.

The reason it feels like a kludge is that "comments" are normally understood to be non-impactful. Is a source transformation that removes all comments valid? If comments have no impact per the spec, yes. But that's not the case here.

In practice comments in go are defined to be able to carry semantic meaning extensibly. Whether they're safe to ignore depends on what meaning is given to the directives, e.g. conditional compilation directives.

[scheme271]

There are directives and packages that affect correctness. E.g. the embed package allows you to initialize a variable using a directive. E.g. //go:embed foo.json followed by var jsonFile string initializes the jsonFile variable with the contents of the foo.json file. A compiler or tooling that doesn't support this results in broken code.

[tptacek]

There's nothing unique to Go about this kind of tooling. It exists in C, Java, Rust, Typescript, and probably dozens of other settings as well. It's the standard way of implementing "after-market" opt-in directives.

[dwattttt]

Are we referring to 'go fix' as after market tooling?

It's certainly done in many places. JsDoc is the biggest example I can think of. But they're all walking the line of "this doesn't have an impact, except when it does".

It being done by the language owners just makes them the ones walking the line.

[tptacek]

That's exactly how this works: it doesn't have an impact, except when you ask it to. This is an idiomatic approach to this problem.

[dwattttt]

The part I object to is overloading comments, which aren't meant to be load bearing. A tool developed outside the language has no choice but to take something that has no meaning and overload it, but language owners weren't forced to take this route; they could've made directives not comments.

In practice, the Go language developers carved syntax out of comments, so that a comment is "anything that starts with //, unless the next characters are go:"

[jerf]

Actually, in practice the rule is "The delimiter for a comment is '// '", which to be clear, is slash-slash-space. Slash-slash-(not a space) is in practice a directive. There are several basic tools in the community that work on this principle including one of the basic linters.

If it would make you happier you can imagine this is part of the spec. It wouldn't change much if it was.

[casey2]

The book says "Comments begin with //." and "// +build" is a special comment. It was only replaced with "//go:build" 1.17 (2021) . So your statement incorrectly implied that this strict syntax distinction between directives and comments has always existed, what happened was people started doing this slowly over time and eventually noticed the disconnect and changed "// +build" which they could because all that stuff was implementation-defined behavior. Right now gofmt handles "// +build" "//+build" and "//go:build" by moving them to the top, adding //go:build if it doesn't exist and adding a space to "//+build", which already breaks setups that add a build comment.

Why would millions of programs becoming out of date with the spec make me happy. There is value in the language maintainers and go programmers talking about the same object. I don't disagree that '// ' is standard Go style (and more readable), but it would break all the code that uses //comments /// ////.

I DO agree that it wouldn't change much if by 'it' you mean the go language and it's tooling, a proper spec does prevent arbitrary change. But it should have been added at least 5 years ago.

[YesThatTom2]

So how many angels can you fit on the head of a pin?

[omoikane]

In the listed examples, the compiler will emit a diagnostic upon encountering those comments:

https://go.dev/blog/inliner#example-fixing-api-design-flaws

So these comments carry more weight than how those comment annotations might be consumed by optional tools for other languages.

For most of the listed examples, I think the corresponding C annotation would have been "[[deprecated]]", which has been added to the syntax as of C23.

[ternaryoperator]

It does not exist in Java. Comments in Java do not change code.

[9rx]

It doesn't exist in Go either. https://go.dev/ref/spec

That's why you find it in the comments. That is where tools have found a place to add their own syntax without breaking the Go code.

Absolutely you can do the same in Java. It exists to the exact same degree as it does in Go. I expect it isn't done as often in the Java world because it is much harder to parse Java code so the tools don't get built.

[joshuamorton]

This also does not change th code. It is an advertisement to a linter-loke tool to take some action on the source code. Its most similar to linter directives which usually are comments.

[TheDong]

We're talking about the "//go" comments in general I think here.

Things like "//go:embed" and "//go:build" very much do change the semantics of source code.

The comments above 'import "C"' containing C function definitions and imports change the compilation of go source code.

The "//go" comments contain a mix of ones that must be respected to compile, to being optional, to being entirely ignorable (like generate and fix).

[Patryk27]

There are no comment-based directives in Rust, are there?

[win311fwg]

It provides the feature to use. It’s possible nobody has yet.

[tptacek]

Eh, you're right, they have a structured attribute system.

[joshuamorton]

> The reason it feels like a kludge is that "comments" are normally understood to be non-impactful. Is a source transformation that removes all comments valid? If comments have no impact per the spec, yes. But that's not the case here.

This is not inlining in the compiler. It's a directive to a source transformation (refactoring) tool. So yes, this has no impact on the code. It will do things if you run `go fix` on your codebase, otherwise it won't.

[dwattttt]

And yet it still breaks "comments aren't semantic". That transformation I described is still invalid.

[pastel8739]

I don’t understand why that wouldn’t be valid. As far as I understand if you compile code with these go:fix comments, they will be ignored. But if instead of compiling the code you run ‘go fix’, the source code will be modified to inline the function call. Only after the source code has been modified in this way would compiling reflect the inlining. Do you have a different understanding?

[dwattttt]

I mean that directives other than inlining impact correctness. If you have a source file that only builds for one OS, stripping the build tag will break your build.