What I'd like to see in Go 2.0

https://www.sethvargo.com/what-id-like-to-see-in-go-2/

by AtroxDev • 4 years ago

215 219 4 years ago

AtroxDev• 4 years ago

From Rob Pike on reddit regarding this post[0]:

The and and or functions in the template packages do short-circuit, so he's got one thing already. It was a relatively recent change, but it's there.

Non-deterministic select is a critical detail of its design. If you depend on a deterministic order of completion of tasks, you're going to have problems. Now there are cases where determinism might be what you want, but they are peculiar. And given Go's general approach to doing things only one way, you get non-determinism.

A shorthand syntax for trial communication existed. We took it out long ago. Again, you only need one way to do things, and again, it's a rare thing to need. Not worth special syntax.

Some of the other things mentioned may be worth thinking about, and some of them have already (a logging interface for instance), and some we just got wrong (range). But overall this seems like a list of things driven by a particular way of working that is not universal and discounts the cost of creating consensus around the right solutions to some of these problems.

Which is not to discount the author's concerns. This is a thoughtful post.

0: https://old.reddit.com/r/golang/comments/s58ico/what_id_like...

dewey• 4 years ago

Again, you only need one way to do things, and again, it's a rare thing to need. Not worth special syntax.

This really is one of the parts I like the most about Go. It really makes so many things simpler. Discussing code, tutorials and writing it.

Every time I'm trying to do something in JS I have to figure out why every guide has a different way of achieving the same thing and what are the implementation differences.

nightowl_games• 4 years ago

It'd be nice if he had at least hinted towards what 'the way' is for this problem.

tapirl12• 4 years ago

but (deterministic-select cases) hey are peculiar.

It looks for most select blocks in Go code, it doesn't matter whether or not they are non-deterministic or deterministic.

But, if the default is deterministic, user code could simulate non-deterministic, without much performance loss. Not vice versa (the current design).

lanstin5• 4 years ago

Any time there is more than one channel being selected for it needs to cover them all equally.

rplnt6• 4 years ago

user code could simulate non-deterministic

I'm curious how?

Not vice versa

There are pretty common patterns for this. At least for real word cases where you might have one special channel that you always want to check. Ugly, but in relation to the previous question, I don't see how one is doable and one isn't?

usrbinbash7• 4 years ago

Not vice versa (the current design).

    select {
       case: <-chan1_whichIWantToCheckFirst
       default:
    }

    select {
       case: <-chan2_whichItreatTheSameAsChan3
       case: 0xFF ->chan3_whichItreatTheSameAsChan2
    }

uluyol• 4 years ago

Er, when it comes to concurrency, non-determinism is usually cheaper than determinism. As soon as you care about ordering, you almost always have to synchronize, and that has a cost.

Austin Clements (of the Go runtime team) wrote a paper that explores this in detail [1]. That was before joining the Go team, but the concepts are universal.

[1] https://people.csail.mit.edu/nickolai/papers/clements-sc.pdf

maccard• 4 years ago

This is a great post, and I agree with much of what he said (range shouldn't copy - I would love a range that iterates by const-reference by default, to lift a phrase from C++).

Deterministic select I hard disagree with. The code in the blog post is race-y, and needs to be fixed, not select. If anything, making select deterministic will introduce _more_ subtle bugs when developers rely on that behavior only to find out in the real world that things aren't necessarily as quick as they are in development.

sethvargo5• 4 years ago

How would you fix that code?

assbuttbuttass5• 4 years ago

I would write the author's example as follows:

    for ctx.Err() == nil {
        select {
        case <-ctx.Done():
            return nil
        case thing := <-thingCh:
            // Process thing...
        case <-time.After(5*time.Second):
            return errors.New("timeout")
        }
    }

The extra check for ctx.Err before the select statement easily resolves the author's issue.

schrodinger2• 4 years ago

I think you could do which I'd argue is more idiomatic (

    for {
      if _, ok := <- doneCh; ok {
        break
      }
      select {
      case thing := <-thingCh:
        // ... long-running operation
      case <-time.After(5*time.Second):
        return fmt.Errorf("timeout")
      }
    }

Which goes along w/ https://github.com/golang/go/wiki/CodeReviewComments#indent-... of "Indent error flow".

edit: nvm, your break would be blocked until one of the other channels produced a value. you'd need to check for the doneCh redundantly again in the select.

mieubrisse4• 4 years ago

I'd add one more to this list: proper enum types.

We use enums heavily to force devs who use our code into good choices, but the options are currently:

1) Use int-type enums with iota: no human-readable error values, no compile-time guard against illegal enum values, no exhaustive `switch`, and no autogenerated ValidEnumValues for validation at runtime (we instead need to create ValidEnumValues and remember to update it every time a new enum value is added).

2) Use string-type enums: human-readable error values, but same problems with no compile-time guards, exhaustive switch, or validation at runtime.

3) Use struct-based enums per https://threedots.tech/post/safer-enums-in-go/ : human-readable error values and an okay compile-time check (only the all-default-values struct or the values we define), but it still doesn't have exhaustive switch, is a complex pattern so most people don't know to use it, and suffers from the mutable `var` issues the post author detailed.

To my naive eye, it seems like a built-in, compile time-checked enum type with a FromString() function would help the community tremendously.

mseepgood4• 4 years ago

I don't think you would need a 2.0 (backward-incompatible language change) for any of this.

tialaramex• 4 years ago

Exhaustive switch seems likely to be backward incompatible if done well.

What you want here is something akin to Rust's match behaviour on enumerated types. If your alternatives aren't exhaustive, it doesn't compile. Now, Rust is doing that because match is an expression. Your day matching expression needs a value if this is a Thursday, so not handling Thursday in your day matching expression is nonsense - even though often the value of a match isn't used and might be the empty tuple it necessarily must *have a value.

It seems to me that today a Go Switch statement operating on days of the week can omit Thursday and compile just fine. Exhaustive switch means that's a compile error. If your "exhaustive switch" is optional or just emits a warning, it won't catch many of the problems for which exhaustive switch is the appropriate antidote.

smasher164• 4 years ago

Sum types overlap a lot with what interfaces over. So enhancing the language with proper sum-types would benefit from enhancing interfaces and switch statements.

However, zero values throw a wrench into this. The zero value of an interface is nil, so enhancing interfaces would require you to address what happens with an uninitialized variable. One of the current proposals suggests that nil continue as the zero value.

They could introduce a totally different type, like a sealed interface, which doesn't require a zero value, but that distinguishes between different types of interfaces, and I'm not sure how that'll be received.

masklinn16• 4 years ago

We use enums heavily to force devs who use our code into good choices

Beware, tho, that with many languages today you’re not really doing that even when they advertise enums e.g. in both C# and C++, enums are not type-safe (not even `enum class`). Iota is, at least, a fair acknowledgement of that.

with a FromString() function

That seems like way a step too far, is there any such “default method” today? And I don’t think Go has any sort of return-type overloading does it?

amw-zero7• 4 years ago

Really not sure what you're talking about. If you use enums in a real language like Swift, Kotlin, Rust, etc., you can only construct the values of the enum. There are no ways to get around it.

rplnt6• 4 years ago

Every time I see discussion about go and enums there are people who are referencing these mythical C-like enums that had never existed. It's some sort of constructed memory. And I'm sure there are languages that do enums "properly", but it's always C/C++ that is referenced.

lucian1900• 4 years ago

Or even better, proper sum types. They're a superset of enums anyway.

https://github.com/BurntSushi/go-sumtype is great, but a bit unwieldy. Language support would be much better.

catlifeonmars4• 4 years ago

Proper compile time sum types would be great. I find myself reimplementing sum types at runtime far too often, especially when it comes to parsing JSON. My go to is a function with a signature along the lines of the reflect packages dynamic select:

func UnmarshalOneOf(data []byte, args []interface{}) (index int, err error)

Which I use like this:

variants := []interface{}{ &T1{}, &T2{}}

i, err := UnmarshalOneOf(data, variants)

// …

return variants[i]

cle5• 4 years ago

Personally I’ve run into more problems with strict enum types in distributed systems in a team setting, than I have with Go’s lack of them. In that setting, strict enums are usually over-strict and eventually you back yourself into a corner in terms of being able to roll out new enum values.

When there’s no clear winner in terms of tradeoffs, I prefer to leave it out of the language like Go has done.

mseepgood4• 4 years ago

strict enums are usually over-strict and eventually you back yourself into a corner in terms of being able to roll out new enum values.

Yes, they are poison for the evolution of a public API.

amw-zero7• 4 years ago

What problems did an enum cause you, and how was the enum responsible for the problem?

mieubrisse4• 4 years ago

That's a fair concern: if everything is strict, then there's no option to incrementally roll out a new value. Maybe a proper enum type could always have an `Unknown` value, which would allow for the leniency while still forcing the use to think about (and handle) it at compile time?

rplnt6• 4 years ago

no exhaustive `switch`

This is what linters will do for you by default.

we instead need to create ValidEnumValues and remember to update it every time a new enum value is added

Code generators are first class citizens in go, and writing an icky but reliable test won't be too hard either.

donatj3• 4 years ago

Use int-type enums with iota: […] no compile-time guard against illegal enum values

Create a new int type and use that for your enums. While you still can create an illegal enum value, you basically have to be looking for trouble. It’s not going to happen accidentally. It’s even harder if it’s an unpunished type in a different package.

See:

https://github.com/donatj/sqlread/blob/91b4f07370d12d697d18a...

amw-zero7• 4 years ago

This compiles:

  type Test int

  const (
    T1 Test = 0
    T2      = 1
  )

  func TestSomething(t Test) {}

  ...
  
  TestSomething(17)

So this isn't a good suggestion, because you can easily pass any int value and will not get a compiler error. You may as well be using strings at that point.

mieubrisse4• 4 years ago

As amw-zero pointed out though, a user could accidentally create the int type and it would only fail if you have runtime checking (which requires you to build it, either via a custom enum constructor that returns `error` or an `IsValid` function, which then require you to maintain the ValidEnums list).

Int types also don't give you any guards when deserializing.

friseurtermin• 4 years ago

One caveat here is serialization. Writing your (or another package's) enum to a database will get you in trouble if you ever want to add another value in the middle. Sure, you can be careful and should document this, but who knows

slx26• 4 years ago

Just adding to the discussion:

I find this comment from Griesemer [0] on one of the github issues for enums in Golang quite insightful:

> [...] all the proposals on enums I've seen so far, including this one, mix way too many things together in my mind. [...] Instead, I suggest that we try to address these (the enum) properties individually. If we had a mechanism in the language for immutable values (a big "if"), and a mechanism to concisely define new values (more on that below), than an "enum" is simply a mechanism to lump together a list of values of a given type such that the compiler can do compile-time validation.

Like with generics, I like the team's approach of taking features seriously, not adding them just because other languages have them, but actually trying to figure out a way for them to work in Go, as cleanly as possible. I think computer science, as a field, benefits from this approach.

And I also dislike many things from Go, and I want "enums" badly too, but that's for another comment.

[0] https://github.com/golang/go/issues/28987#issuecomment-49679...

ibraheemdev• 4 years ago

The type sets proposal for Go has already been accepted as part of the generics proposal [0]:

    type SignedInteger interface {
        ~int | ~int8 | ~int16 | ~int32 | ~int64
    }

Interfaces that contain type sets are only allowed to be used in generic constraints. However, a future extension might permit the use of type sets in regular interface types:

We have proposed that constraints can embed some additional elements. With this proposal, any interface type that embeds anything other than an interface type can only be used as a constraint or as an embedded element in another constraint. A natural next step would be to permit using interface types that embed any type, or that embed these new elements, as an ordinary type, not just as a constraint.
We are not proposing that today. But the rules for type sets and methods set above describe how they would behave. Any type that is an element of the type set could be assigned to such an interface type. A value of such an interface type would permit calling any member of the corresponding method set.
This would permit a version of what other languages call sum types or union types. It would be a Go interface type to which only specific types could be assigned. Such an interface type could still take the value nil, of course, so it would not be quite the same as a typical sum type.
In any case, this is something to consider in a future proposal, not this one.

This along with exhaustive type switches would bring Go something close to the sum types of Rust and Swift.

[0] https://github.com/golang/go/issues/45346

_0w8t• 4 years ago

Another possibility is to use boolean flags. Of cause the compiler then will not enforce that only one of the flags is set. On the other hand on few occasions I observed how initial design with disjoint cases evolved into cases that can be set at the same time modeled with flags.

bstpierre• 4 years ago

Serious question: what are the odds that go 2 ends up like python 3 and it takes the world over a decade of pain to migrate? (I like both python and go, and I’m still maintaining a sizable body of py2 code.)

“Backwards compatibility forever” seems like unnecessary shackles, and the language should be able to grow — I’ve seen some nice proposals for improvements. I just wonder what the strategy is going to be for migrating code from go1 to go2 and how painful that’s going to be.

avg_dev• 4 years ago

It would be nice if there was a tool that re-wrote your Go-1 code in Go-2.

masklinn16• 4 years ago

Go-1 and Go-2 code could even cohabit using something similar to Rust’s editions system e.g. the `range` behaviour could be something like a package opt-in.

And half the article could be fixed by adding new APIs and deprecating the old ones.

szastamasta2• 4 years ago

Nope, this is exactly what has killed Python3. There is only one way forward - old code still has to work or people will simply stay on 1.0 forever.

tapirl12• 4 years ago

I remember that someone in Go core team (Ian?) said Go 1.18 is Go 2. That means Go 2 is back compatible with Go 1.

lolive3• 4 years ago

Not a Go développer here, but let’s take the example of Java when it got (for example) generics or functional features. There was NO going back. These were so fundamental improvements that the past was absolutely outdated as soon as those new features were available. May be the same thing will happen for Go

masklinn16• 4 years ago

Not sure how relevant that is, the old code worked fine in post-generics Java.

chris_overseas• 4 years ago

While I agree with what you're saying, that's not the GP's point. They're talking about backwards compatibility, i.e. old code running on new versions. Java has been extraordinarilly good at that (maybe too much so), with the possible exception of Java 9. Try running Java 1.0 code on JDK 17 and it'll probably run fine. Try running Python 2 code on Python 3 and you're generally going to be in for a very rocky ride.

brnt• 4 years ago

Not so serious question: what is Go2 and Python4 would be the same thing?

kitd• 4 years ago

ie. they both become Nim ;)

norman784• 4 years ago

Rust solved this with editions[0], I don't know if is this feasible with Go.

[0] https://doc.rust-lang.org/edition-guide/editions/index.html

asah• 4 years ago

IMHO the long python3 migration was well executed and we're now comfortably on the back side of it. Reminds me of perl4=>5 and other big lifts.

Yes, commercial codebases understaffed for maintenance are kinda stuck, just like any legacy system. IMHO the solution must come from the business model down. Also, security, compliance & cost can help drive priority.

mountainriver3• 4 years ago

I’ve never heard that take, it seemed completely botched to me. The first couple versions of py3 didn’t even work well, and they were still pushing people to cut over

oblio• 4 years ago

It wasn't well executed. The standard migration tool (2to3) was kind of considered a failure and the better one (six) wasn't ready, or even around at the time.

Python came this || close to dying during the migration, its users all having moved to other languages. Primarily data science saved it and then some time passed and libraries moved on, etc, and after a while the cost benefit calculation started swaying towards Python3, probably after 3.3 at least, so 4 years after Python3's launch.

morelisp10• 4 years ago

This is an absolutely implausible take. Perl 4's entire lifetime was about 5 years; released in 1991 and Perl 5 utterly dominant by 1996. Python 2 shows no signs of an actual EOL to this day!

mseepgood4• 4 years ago

Serious question: what are the odds that go 2

The Go maintainers already said that they don't have any plans to do an actual version 2.0 anymore. Generics turned out to be possible without breaking backward-compatibility.

randallsquared• 4 years ago

The issue with the order of range seems like using the same name for satisfying a different requirement: in a template, you're much more likely to want the value than the index, so it makes sense that a looping construct with a single parameter would be putting the value in that parameter. In a loop in normal code, you're more likely to want to do math on the index. So, I'd say the problem is more about punning the name of these two behaviors than the behavior itself being bad.

masklinn16• 4 years ago

In a loop in normal code, you're more likely to want to do math on the index.

It really is not, no. The number of loops using `enumerate` (or working on range / indices directly) in Python or Rust are a small fraction of those just iterating the sequence itself.

That would be even more so for Go, which has no higher-level data-oriented utilities (e.g. HOFs or comprehensions, which would usually replace a number of non-indexed loops, and would thus increase the ratio of indexed to non-indexed loops).

t43562• 4 years ago

Everyone has their own gripes. Modules are what cause me the most pain in Go - especially where they're in github and I need to fork them and now change all the code that references them. I don't know if the problems are even tractable because the way it all works is so incredibly complicated and any change would break a lot.

I would like to remove all the "magic" that's built-in for specific SCMS/repository hosting services and have something that operates in a simple and predictable manner like C includes and include paths (although obviously I don't like preprocessing so not that).

As for the language, I like the range reference idea but my own minor pet peeve is an issue with pre-assignment in if-statements etc which makes a neat feature almost useless:

  // This is nice because err only exists within the if so we don't have to 
  // reuse a variable or invent new names both of which are untidy and have potential 
  // to cause errors (esp when copy-pasting):
  if err := someoperation(); err != nil; {
    // Handle the error
  }


  // This however won't work:  
  func doThing() string {    
     result := "OK" 
     
      if result, err := somethingelse(); err != nil { // result does not need to be created but err does so we cannot do this.
          return "ERROR"  
      }
    

   return result
  }

I don't have any good ideas about how to change the syntax unfortunately.

fastest963• 4 years ago

You should be able to use "replace" to use your forked module instead of the original and you don't have to change anything.

jatone4• 4 years ago

unfortunately replace is not supported well with modules. and they are hell bent on not supporting it well.

jatone4• 4 years ago

yeah it sucks, I think IDEs should help here. 1 click uplift var error to parent scope.

assbuttbuttass5• 4 years ago

The fix is pretty simple, just declare err ahead of time:

    func doThing() string {    
        result := "OK"
        var err error
        if result, err = somethingelse(); err != nil {
            return "ERROR"  
        }

        return result
    }

rocqua• 4 years ago

Part of the reason OP liked the `if assignment` was to avoid polluting the higher-level scope with a variable that is only needed during the if statement.

Your solution fixes the error, but at the cost of losing the upside OP saw.

Gwypaas3• 4 years ago

The issue is now you have a potential nil value hanging around in the code with no real reason for its existence. Three refactors and some moving around later and you manage to hit a runtime panic in production.

usrbinbash7• 4 years ago

Easily fixed using lexical scopes:

    func doThing() string {
        result := "OK"

        {
            var err error
            if result, err = somethingElse(); err != nil {
                return "ERROR"
            }
        }

        return result
    }

`err` is introduced in the lexical scope, `result` isn't so it still refers to the string from the surrounding scope. `err` does not pollute the surrounding scope.

You can also try the complete version here: https://go.dev/play/p/kDEB11YdvSs

travisd• 4 years ago

In my experience this isn’t idiomatic Go and would definitely turn heads in a code review. But in such a small function, it’s fine to just not worry about the lifetime of your variables (and in bigger functions you can often decompose into smaller functions).

qaq2• 4 years ago

I have much smaller ask struct type elision in function calls

masklinn16• 4 years ago

I have to say I’ve no idea what you mean. In function definitions I’d interpret it as type inference (and would disagree) but you specifically talk about function calls, and consider it a small change. Can you describe what you’re thinking of?

coder543• 4 years ago

I think I understand what they're asking for. Consider a function that takes in a struct as one of the arguments.[0]

Currently, you would have to invoke it like so:

    svc.GetObjectWithContext(ctx, &s3.GetObjectInput{Bucket: bucket, Key: key})

But... why do you have to type "s3.GetObjectInput"? The function is taking in a concrete type (not an interface) for that argument, and there is only one possible type that you can pass in... so I agree with the person above that it should be possible to elide the type like so:

    svc.GetObjectWithContext(ctx, &{Bucket: bucket, Key: key})

Go already supports type elision in some places, such as...

    []someStruct{{Field: value}, {Field: value}}

instead of having to type

    []someStruct{someStruct{Field: value}, someStruct{Field: value}}

which would be equally pointless repetition.

[0] https://docs.aws.amazon.com/sdk-for-go/api/service/s3/#S3.Ge...

Eun• 4 years ago

I would like to add proper JSON5 support.

The template problem is a real problem. I used it once and it was pain and moved away instantly. I would vote for go inside go as a template system. So you can effectively write go code.

With the help of yaegi[1] a go templating engine can be build e.g here[2].

[1] https://github.com/traefik/yaegi

[2] https://github.com/Eun/yaegi-template

jerf3• 4 years ago

You don't need official Go support for JSON5. Same for templating. The templating library in the standard library isn't anything special, it's just in the standard library. If you don't like it, go get one of the dozens of others on offer.

I think there's a number of language communities you can "grow up" in that teach you that things in the standard library are faster than anything else and have had more attention paid to them than anything else, like Python or Perl, because those languages are slow, and things going into the standard library have generally been converted to C. I think that because I look in my own brain and find that idea knocking about even though nobody ever said it to me directly. But that's not true in the compiled languages, of which Go is one. The vast majority of the Go standard library is written in Go. The vast majority of that vast majority isn't even written in complicated Go, it's just in Go that any Go programmer who has run through a good tutorial can read, it's not like a lot of standard libraries that are fast because they are written impenetrably. (Although the standard library may have subtle performance optimizations because it chooses this way of writing it in Go rather than that way, it's still almost entirely straightforward, comprehensible code.)

If you want JSON5 or a different template library, go get or write one. The Go encoding/json or text/template don't use any special access or have any magical compiler callouts you can't access in a library or anything else; if you grab JSON5 library (if such a thing exists), you've got as much support for it as JSON or text/template.

It's even often good that it's not in the standard library. I've been using the YAML support a lot lately. The biggest Go YAML library is on major version 3, and both of the jumps from 1 to 2 and 2 to 3 were huge, and would have been significantly inhibited if v1 was in the standard library and the backwards compatibility promise applied. v1 definitely resembles encoding/json, but that's missing a lot of things for YAML. If Go "supported YAML" by having v1 in the standard library, everybody would be complaining that it didn't support it well, and by contrast, asking anyone to jump straight to the v3 interface would be an insanely tall ask to do on the first try without any experimentation in the mean time. And I'm not even 100% sure there won't be a v4.

015a• 4 years ago

I disagree with this stance.

To me, the community take on "stdlib vs libraries" is a cyclical thing; we're coming out of a cycle led by JavaScript/NPM, where everything is a library due in no small part to how HORRIBLE JS/NodeJS's standard library is. Go back further, and you run into the Python/Java world which had far more comprehensive stdlibs, and today Go's (and to a lesser degree, Rust's) rising popularity is bringing back more feature-complete stdlibs.

So, it changes. And its alright for different languages to have different stances on how comprehensive their stdlibs should be. Go is absolutely an example of a language that wants tons of stuff in its stdlib; but its also a language which despises change, and thus we got a very awesome stdlib at v1, and limited improvements to it over the years.

I don't feel the "YAML changes a lot" argument is valid. It does; but if an app needs YAML, they can choose to use the stdlib, or a library, and they'll have to keep up regardless.

Putting it in the stdlib has tons of advantages. First: it increases the scope of parties affected by any breaking change, which naturally forces more deliberate thought into the change's necessity and quality. Second: it reduces the number of "things" code consumers need to update; from the go version itself & the YAML library & consuming code, to just the go version & consuming code (this has network productivity effects in only having to source one "breaking changes" changelog for your hit list on what needs updated). Third: it reduces multivariate dependency-dependency issues (eg YAMLv2 requires Go1.14, but we're on Go 1.13, so first we have to upgrade to Go1.14, then we can upgrade to YAMLv2). Fourth: it reduces the number of attack surfaces which security professionals need to monitor (all eyes on the stdlib implementation, versus N community implementations, strength in numbers). Fifth, less about YAML, but: stdlib encourages what I call the "net/http.Request effect"; if I want to write a library that does stuff with http requests, its nearly impossible to do that in a framework-agnostic way in JavaScript, because express does things differently than hapi etc; but in Go, everything is net/http.Request. So even if the stdlib doesn't have everything one needs, plugging in libraries to solve it is easier because everyone is using the same interfaces/structures.

Obviously not everything can be in stdlib, so it comes down to the question: what belongs there. And in my opinion, every language is too conservative (except maybe Python, which strikes a strong balance). Many language teams will say "we're not including X because X isn't an ISO standard, or because its still changing, or because we're not sure on the implementation". These are all arguments out of cowardice and fear of asserting an opinion. Language designers have developed a deep, deep fear of opinions; because they believe, maybe correctly, that one of their opinions will be bad, and it will hurt adoption. The issue is; having no opinion just hurts productivity, and people will also move from your language toward more productive ones (see: Go's rise in popularity, versus JS's dependency issues).

da39a3ee• 4 years ago

Can someone explain this one? I couldn't see why go gave this result.

What is the value of cp? If you said [A B C], sadly you are incorrect. The value of cp is actually: [C C C]

makapuf• 4 years ago

in the loop, you set cp[i] to a reference to the variable value. value is the same variable through the loop, with different values copied inside it, first A then B then C. So at the end you have cp having three times a reference to value, with the last value in it, namely C.

masklinn16• 4 years ago

The "trap" of the snippet is that `cp` is an array of pointers.

What it shows is that Go doesn't have a `value` per iteration, it has a single `value` for the entire loop which it updates for each iteration. This means if you store a pointer to that, you're going to store a pointer to the loop variable which gets updated, and thus at the end of the loop you'll have stored a bunch of pointers to the last item.

This is most commonly an issue when creating a closure inside a loop, as the closure closes over the binding, and since Go has a single binding for the entire loop all the closures will get the same value.

lanstin5• 4 years ago

This has suprised me twice, once in my own code where i ended up ot really understand the problem but just mutated the code till it worked and then later when I was helping someone with their code and the way they structured the question made the still suprising answer memorable.

A fix wouldn't be unwelcome but it seems it would have a good chance to cause performance regression - a lot more allocated values maybe on a lot of inner loops. I guess escape analysis might help avoid the allovations in the general case. ?

vasergen• 4 years ago

Not go developer, just curious about the language and ecosystem and really like it. For me would be nice to have more functional features. For example - explicitly say that a variable is mutable / immutable, preferably have immutability by default. Also native support for map/filter/reduce/etc. Those are good abstraction and it is easier to read than `for loops`, since you don't need to look over shoulders all the time. Guess latest would be easier to add since there is support for generics already.

jerf3• 4 years ago

"Also native support for map/filter/reduce/etc."

Native support for them in the context of the existing Go spec will be coming with the next release. To reserve the right to evolve the native support before committing it to the backwards compatibility promise, it will initially appear in the https://pkg.go.dev/golang.org/x/exp external repository, but that is the official Go repo for things either too unstable to be included in the standard library, or still experimental. General expectation is it'll be in the standard library in the release after that. It won't be in the standard library, but it's as official as it can be beyond that.

I carefully phrased that with "in the context of the existing Go spec", because I think expectations of this support are wildly out of whack with the reality. It's still going to be a very unpleasant style to work in, with many and manifold problems: http://www.jerf.org/iri/post/2955 . I think people will be crazy to turn to that style in Go. Go wasn't just missing generics to support this style, it was missing many things, and "solving" the generics problem still leaves it missing many things.

rowanseymour• 4 years ago

Hardly important but I hope that in parts of the std lib where they added support for contexts by adding a `FooContext` func for every `Foo` and latter just calls the former with `context.Background()`.. we can just have `Foo` that takes a context argument.

JulianMorrison8• 4 years ago

Alternatively, Go 2.0 could implement "frozen" global variables

A more general change would be to implement the "var" and "val" distinction that exists in some languages.

    const x = 1 // x is a compile time alias for the untyped abstract number 1
    var x := 1  // define x at runtime to be (int)1, x is mutable
    val x := 1  // define x at runtime to be (int)1, x is immutable

Then the globals can be defined with "val".

tapirl12• 4 years ago

No need to invent a new keyword, it is ok to just use "const": https://github.com/go101/go101/wiki/An-immutable-value-propo...

JulianMorrison8• 4 years ago

No, they are very different conceptually.

- A const is an abstracted value.

- A variable is an allocated piece of memory.

avgcorrection2• 4 years ago

I don’t understand why Scala chose “var” for mutable variables. A variable is not defined by being mutable—it is defined by being variable, i.e. not a constant. And it is immutable in math (where we don’t have to care about performance). So “val” is also a “var”, conceptually.

JulianMorrison8• 4 years ago

I think it was Fortran which introduced the equivalence between programming variables (that are a mutable piece of memory) and mathematical variables (which describe a relationship). But they aren't really the same. And "variable" has become too fixed in computer science usage to be repaired back to its earlier mathematical meaning.

bruce3434342• 4 years ago

if it is not constant, it must be variable i.e. changing. Mutation = change.

maerF0x02• 4 years ago

could be interesting, however I'd hope for something more visually distinctive that val/var as it took about 2-3 reads for me notice what was even the diff between L2 and L3.

JulianMorrison8• 4 years ago

Fair point. "value" and "var" then, perhaps?

catlifeonmars4• 4 years ago

How about `mut var`?

Edit: this likely wouldn’t fly as it would be completely backwards incompatible

bruce3434342• 4 years ago

the val and const cases should hardly be different if the compiler has constant folding, except maybe for the typing.

JulianMorrison8• 4 years ago

From the language reference

Constant expressions may contain only constant operands and are evaluated at compile time.

and a "const" can only be defined with a constant expression.

So the difference would be that a "val" can be assigned a value that is evaluated at runtime.

mountainriver3• 4 years ago

I would really love to see default parameters and struct values. I jump between Python and Go in my day job and Go is a much better language overall but things like this make it painful

geenat2• 4 years ago

This is also my #1.

Parameter / Option ergonomics.

The current best practice of "functional options" and long function chains results in far too many function stubs ... its a minimum of 3 extra lines per parameter. Parameter structs require a whole extra struct...

Borrowing optional / named parameters from Python would cut down length and complexity of Go code drastically.

Jeff_Brown3• 4 years ago

Default parameters have always struck me as dangerous. (And for my day job I use Python.)

mountainriver3• 4 years ago

I always hear this argument but I’ve never seen it be dangerous in my day to day. We deal with defaults all the time in programming and it’s generally fine

geenat2• 4 years ago

I'd like to see ergonomics improvements, particularly to function parameters.

Suggestion: Just borrow named / optional parameters from Python. It would cut down length and complexity of Go code drastically.

tgv2• 4 years ago

What would you need those for? For checking exhaustive type switches? Seems like an extra keyword on "interface" would do the trick.

exdsq• 4 years ago

Is this comment meant for this article? I can't for the life of me grok what you mean!

FreeFull• 4 years ago

Guessing it was meant to go on https://news.ycombinator.com/item?id=30205232 ? No idea how it ended up here

conaclos• 4 years ago

About the optimization of the regex package: a talk is scheduled tomorrow [0] to FOSDEM 2022.

[0] https://fosdem.org/2022/schedule/event/go_finite_automata/

mariusor• 4 years ago

To expand on the logging improvements, I would like to see a `context.WithLogger` context function, to allow cross package passing of a common logger instance.

the_gipsy• 4 years ago

Proper sum types, if only for proper error handling. The if err != nil dance is extremely verbose and error prone with consecutive checks.

Jeff_Brown3• 4 years ago

That could also alleviate the no-exhaustive-enum-checking problem mentioned in another top-level comment.

sdevonoes2• 4 years ago

A better template library would be a killer feature. Similar to what PHP has been since forever; the ability to write HTML using all the Go language's features.

sdevonoes2• 4 years ago

I would add: an extended standard library for "common stuff". I don't want to import a third-party library nor write my own "utils.go" to do:

    func contains(s []int, e int) bool {
        for _, a := range s {
            if a == e {
                return true
            }
        }
        return false
    }

Mawr• 4 years ago

If you need to look up or worse, delete, a value in a slice, then you probably shouldn't be using a slice in the first place. You probably want to replace your slice with a set.

arccy• 4 years ago

soon-ish https://cs.opensource.google/go/x/exp/+/master:slices/slices...

rank0• 4 years ago

I think Golang is awesome, but I have two major gripes that I hope can be fixed:

Dependency management:

Go mods is a dumpster fire. `go get` and `go install` is finicky and inconsistent across systems.

It's difficult to import local code as a dependency. Using mods with replace feels like a shitty hack, and requires me to maintain a public repo for something I may not want to be public. I end up using ANOTHER hack that replaces mod references to private repos and I have to mess with my git config to properly authenticate.

I've never used another language that made it so difficult to import local code. Rust's cargo is so much easier to use!

Sane dynamic json parsing:

Having to create a perfectly specified struct for every single json object I need to touch is terrible UX. Using `map[string]interface{}` is just gross.

Again, I think Go should copy the existing rust solution from serde. With serde, I define the struct I need, and when I parse an object, the extra fields just get thrown out.

If anyone thinks I'm misunderstanding something, please enlighten me. I hope reasonable solutions already exist and I just haven't found them yet.

CamouflagedKiwi• 4 years ago

What you describe for JSON is already the case in Go; the stdlib json parser does simply throw out any extra fields on deserialisation.

morelisp10• 4 years ago

In fact it's difficult-to-impossible to get the opposite (only json.Decoder supports a strict mode, and as soon as one intermediate type implements UnmarshalJSON it stops getting propagated).

tyree731• 4 years ago

It's difficult to import local code as a dependency. Using mods with replace feels like a shitty hack, and requires me to maintain a public repo for something I may not want to be public. I end up using ANOTHER hack that replaces mod references to private repos and I have to mess with my git config to properly authenticate.

With regards to this concern at least go 1.18 is adding workspaces, which should help (https://sebastian-holstein.de/post/2021-11-08-go-1.18-featur...).

hpx7• 4 years ago

Go's templating packages should support compile time type checking.

Does anyone know of a decent type safe templating package out there (for any language)?

Strom• 4 years ago

React with TypeScript. Very popular and unlike Go's templates has proper type checking.

itgkbcdfhb• 4 years ago

I want golang to stay as minimal as possible. I think of go as 2020s version of C. If you want all the madness of templating, reflection and (arguably) needless features can some privileged PhD student out there please make 2020s C++… go++?

ternaryoperator• 4 years ago

Mine would be a much larger collections library. Having come to go from Java and finding that the standard go library has no trees, no stack, no skip list, etc. was quite a surprise. Possibly the advent of generics will stimulate development of a more robust standard collections library.

christophilus2• 4 years ago

It does have a doubly-linked list which can easily serve as a stack, though. And it has a heap which is a poor man's replacement for some uses of tree. I've found that I can get quite a bit farther with the built-in Go slices, maps, and lists than I thought.

But yeah. Now that generics are in, I do hope they add a handful of common collections.

[0] https://pkg.go.dev/container/list@go1.17.6

[1] https://pkg.go.dev/container/heap@go1.17.6

[2] https://pkg.go.dev/container/ring@go1.17.6

pipeline_peak• 4 years ago

I’ve heard Go program’s execution performance is near Java.

Is this true because I can’t think of anything more useless than that.

honkycat• 4 years ago

What I would like to see:

- Enun Types

- A special operator to cut down on `if err != nil { return err }` and just return at that point.

- Named arguments, and optional params with defaults

- Default values on structs

- ...macros? We already have `go generate ./...`

( edit: Removed unformatted source code )

Jeff_Brown3• 4 years ago

Sum types would satisfy the first two on that list, as well as making an ergonomic optional type trivial to define.

christophilus2• 4 years ago

This was a surprisingly good list. Most of these kinds of articles just consist of someone bemoaning the fact that Go isn't Haskell or whatever language they like more. But this is a legitimate list of things that could and should (in my opinion) be changed without turning Go into not-Go.

synergy20• 4 years ago

Most important items in my plate

    1. a unified improved *error* in stdlib with stack trace support.
    2. a unified log interface(mentioned)
    3. a STL library like c++
    4. shared library support so we dont have 100 static binaries that among them each have 90% of duplicated content. go shall support shared libraries/modules officially.

cpeterso• 4 years ago

Two Go 2 proposals that interested me were:

* nillability annotations: https://github.com/golang/go/issues/49202

* Change int from a machine word size (int32 or int64) to arbitrary precision (bigint): https://github.com/golang/go/issues/19623

Sadly the nillability annotations were rejected because they weren't backwards compatible. The bigint change is also unlikely to be accepted because the issue is already five years old and there are concerns about performance.

usrbinbash7• 4 years ago

If this was implemented:

    func foo(a, b int) int {
        return a * b
    }

At compile time, what is the return type of foo? Answer: Unknown. The compiler has no way of determining if the resulting type will be small or big int. This has to be taken into account not just in foo, but in every function calling foo, and every function that is called with the return of foo as a param.

One of the best things about golang, is how little "magic" there is. Everything that happens is immediately obvious from the code. An int that is upgraded to a completely different type when it reaches certain values, goes directly counter to that; it would be hidden behaviour, not immediately obvious from the code.

Should golang have a builtin arbitrary sized integer type? Maybe. Using math/big can become cumbersome. But a much better solution would be to introduce a new builtin type like `num`

Seb-C• 4 years ago

My biggest annoyance so far is the inability (and inconsistency) to have a one-liner to get a pointer to something else than a struct.

I can write x = &Foo{...} but somehow x = &42 and x = &foo() are not allowed, which forces me in some cases to declare useless variables that hurts readability.

crnkofe• 4 years ago

Oddly enough the list doesn't resonate much with me.

I'd love to see better mocking support. Doing mock.On("fun name", ...) is so backwards, confusing and brittle. It's also a great source of confusion for teammates when tests fail.

I miss better transaction management. I regularly juggle db, transactions and related interfaces and it's a continuous pain.

Then there's the "workaround" for enforcing interface implementation: _ InterfaceType = &struct . This could be easily part of struct def. rather than having it in var section.

As was mentioned by others doing x := 5 only to later do JsonField: &x is just a waste of intellectual firepower. Maybe this can be alleviated by generics but the lang should be able to make this a one liner.

What I'd like to see in Go 2.0

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