On Sun, Jun 27, 2021 at 6:05 PM Victor Giordano <vitucho3...@gmail.com> wrote:
> Thanks to all for the answer, i really try to see any actual reason but i > still don't get it. For me, to my humble acknowledgement, if I define a > type I tend to use everywhere it appears. Period. End of the story. > > > FWIW, arguing that `http.HandleFunc` should take a `http.HandlerFunc` > because there exists a defined type with the same underlying type as the > parameter is a bit like arguing every function that takes an `int64` should > instead take a time.Duration <https://golang.org/pkg/time/#Duration>. > > Allow me to put in different words: if you define `func > doSomething(duration int64)` at least i will argue why don't employ > time.Duration <https://golang.org/pkg/time/#Duration> as a type there, if > the parameter actually represents a Duration that is also a defined > type, ¿you don't?. > Yes. But that's the thing - if what the function actually takes a duration, then the correct type is a duration. But the type `http.HandleFunc` takes is *not* a `http.HandlerFunc`, it's a `func(http.ResponseWriter, *http.Request)`. It's a different type and it's the correct type to describe what that function is for. If the type was `http.HandlerFunc`, then `http.HandleFunc` wouldn't need to exist, because `http.Handle` would suffice. For example, if you had a function // DurationFromMS returns a time.Duration, based on a duration given as an integer in ms. func DurationFromMS(d int64) time.Duration { return time.Duration(d * 1000) } Would you make the parameter type `time.Duration`? After all, it represents a duration, right? But you wouldn't. It would be the wrong type to represent what the function does. Or, a different example: We could introduce a new type in the `filepath` package: // Path is a path, using the OS-specific delimiter type Path string // Verify makes sure that p is a path, using the correct, OS-specific delimiter. // It returns p as a Path, and an error, if p was invalid. func Verify(p string) (Path, error) We could then have `filepath.Join` etc. take `Path`s, instead of `string`s, to represent that the argument actually must be a valid path, using the OS-specific separator. Which would be different from `path.Path`, of course, which would always use "/" as a separator. Meaning you wouldn't be able to accidentally use one as the other, which would add type-safety. But should `Verify` take a `Path` here? Of course not. That would be the wrong type. It just returns its argument converted into the correct type, but semantically, it still takes *a plain string*. Before you pass the path into `Verify`, it doesn't have the semantic association of "this string is an OS-specific path" - that's exactly the semantic association that `Verify` creates. Your argument hinges on the assumption that `http.HandleFunc`s parameter has the semantic interpretation (not only the same underlying type as) as `http.HandlerFunc`. But it doesn't. The semantic interpretation of the argument to `http.HandleFunc` is a plain function. Otherwise, it wouldn't need to exist - because we already *have* a function that can take a `http.HandlerFunc`: `http.Handle`. The plain func is describing *exactly* the type that function should take. `http.HandlerFunc` would be the wrong type. > I won't say the same about other things that hold an int64 that represents > for example an ID of record in a database. > > > > El dom, 27 jun 2021 a las 12:56, 'Axel Wagner' via golang-nuts (< > golang-nuts@googlegroups.com>) escribió: > >> FWIW, arguing that `http.HandleFunc` should take a `http.HandlerFunc` >> because there exists a defined type with the same underlying type as the >> parameter is a bit like arguing every function that takes an `int64` should >> instead take a time.Duration <https://golang.org/pkg/time/#Duration>. >> That's just not how types tend to work. >> >> It makes no sense for `http.HandleFunc` to take a `http.HandlerFunc`, >> because it's purpose is specifically to work on a plain function. If you >> have an `http.HandlerFunc`, you can already just call `http.Handle` - there >> is no need to make a separate function that takes a *specific* >> implementation of `http.Handler`. >> >> On Sun, Jun 27, 2021 at 5:51 PM Axel Wagner < >> axel.wagner...@googlemail.com> wrote: >> >>> On Sun, Jun 27, 2021 at 5:25 PM Victor Giordano <vitucho3...@gmail.com> >>> wrote: >>> >>>> I keep wondering if they code that way for any reason. With "code that >>>> way" I mean: define a type and then not use it. >>>> >>> >>> As I said: It's used plenty of times. Both inside of `net/http` and >>> outside of it. >>> >>>> >>>> - So, ¿why not employ the type defined in the first place? >>>> >>>> I feel like I gave a bunch of reasons for this too. >>> >>> >>>> Don't get me wrong,but if I define a type I tend to use that type where >>>> it appears. That is in fact the basis of making types, to use them. So that >>>> feeds my questioning! >>>> >>>> >>>> El dom, 27 jun 2021 a las 11:46, 'Axel Wagner' via golang-nuts (< >>>> golang-nuts@googlegroups.com>) escribió: >>>> >>>>> If I understand you correctly, you are suggesting to replace the >>>>> parameter type `func(http.ResponseWriter, *http.Request)` with the >>>>> parameter type `http.HandlerFunc`. You've been (correctly) told that we >>>>> can't make that change, because it would break the Go 1 compatibility >>>>> change (as there is code which currently compiles which wouldn't compile >>>>> after that change). But you are wondering if, *ignoring* the compatibility >>>>> guarantee, it would be a good change. Am I getting this right? >>>>> >>>>> If so: I don't think it would be a good change. >>>>> >>>>> First, it's important to realize that the *only* reason, >>>>> `http.HandlerFunc` exists at all, is so that you can write a >>>>> `func(http.ResponseWriter, *http.Request)` and use it as a `http.Handler`, >>>>> in the places where `net/http` expects the latter. You say the type isn't >>>>> used - but it is. It's used by *users* of the `net/http` package, to make >>>>> their plain functions into `http.Handler`s. It is also used in `net/http` >>>>> itself - in the exact function you are referring to >>>>> <https://golang.org/src/net/http/server.go?s=77627:77714#L2487>. That >>>>> is the exact and only purpose of that type, to make a plain function >>>>> implement the `Handler` interface. So, taking a plain function as a >>>>> parameter *is the purpose of having the `HandlerFunc` type*. >>>>> >>>>> You also say that adding types is a good thing. I tend to disagree >>>>> with that as a general statement. Adding types is a good thing, if it >>>>> serves as important documentation or if it serves to catch bugs. I don't >>>>> think either of these would be happening with this change. In terms of >>>>> documentation - well, you don't *have* to pass a `http.HandlerFunc`, so >>>>> there is no reason for the documentation to make it clear that you should. >>>>> You can (and should) just pass a plain `func`. So, using the defined type >>>>> here wouldn't serve as documentation, it would document the *wrong* thing. >>>>> >>>>> As for catching bugs: Making the parameter type a defined type would >>>>> only change one thing in terms of type-safety. It would mean that if you >>>>> define a *different* type `type MyFunc func(http.ResponseWriter, >>>>> *http.Request)`, the compiler would prevent you from writing >>>>> `http.HandleFunc(…, MyFunc(f))`. Preventing a bug would thus require that >>>>> your `MyFunc` type would have to be used semantically differently from >>>>> `http.HandlerFunc`. But that seems *exceedingly* unlikely, given that you >>>>> defined `MyFunc` in terms of the `net/http` package. And it would then >>>>> appear *exceedingly* unlikely, that you'd accidentally mix the two up - >>>>> almost all usages of `http.HandleFunc` will pass the name of some defined >>>>> function and that will always work. >>>>> >>>>> But all of this discussion is really moot. It's a breaking change, so >>>>> it can't happen - whether it's a good change or not doesn't exactly matter >>>>> at that point. Personally, *if* we could "go back in time" and wouldn't >>>>> have to worry about backwards compatibility, my vote would rather be to >>>>> change >>>>> the language to make the HandlerFunc type obsolete >>>>> <https://github.com/golang/go/issues/21670> and remove it altogether. >>>>> >>>>> On Sun, Jun 27, 2021 at 3:53 PM Victor Giordano <vitucho3...@gmail.com> >>>>> wrote: >>>>> >>>>>> Hello gophers! >>>>>> >>>>>> While studing at this source code >>>>>> <https://github.com/golang/go/blob/37f9a8f69d6299783eac8848d87e27eb563500ac/src/net/http/server.go> >>>>>> in search for some knowledge and enlightment, i do note that in some >>>>>> file a >>>>>> type is defined and then is not used in a place where it could be used. >>>>>> This open an interrogant for me, because tipification is often good >>>>>> thing, >>>>>> regardless the language I may state, and I express it via a ticket >>>>>> <https://github.com/golang/go/issues/46926>. I get the idea that due >>>>>> to language grammar changing the code would be a breaking change. >>>>>> >>>>>> But i keep wondering if they actually do this for a reason.. i mean, >>>>>> given the possiblity to get back in time, ¿does the team at golang will >>>>>> write the same source code, definiting a type with a name and then >>>>>> intenttionally not using it? i mean...i keep wondering if there is any >>>>>> reason for defined types and then not use it and using the gitlab >>>>>> channel i >>>>>> probably fail to express my initial intention. I do often read some third >>>>>> party code, in order to view others minds (or try at least..), what i'm >>>>>> asking here is a question in order to get another people point of view. >>>>>> >>>>>> Thanks again! >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "golang-nuts" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to golang-nuts+unsubscr...@googlegroups.com. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/golang-nuts/96369719-6200-4765-aee1-83befce04666n%40googlegroups.com >>>>>> <https://groups.google.com/d/msgid/golang-nuts/96369719-6200-4765-aee1-83befce04666n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- >>>>> You received this message because you are subscribed to a topic in the >>>>> Google Groups "golang-nuts" group. >>>>> To unsubscribe from this topic, visit >>>>> https://groups.google.com/d/topic/golang-nuts/VBQrlI6-zW0/unsubscribe. >>>>> To unsubscribe from this group and all its topics, send an email to >>>>> golang-nuts+unsubscr...@googlegroups.com. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHnCTf_4G5ZhGX0EXBKJRN9LcEWbKWOdPiCTKdX6SDqPA%40mail.gmail.com >>>>> <https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHnCTf_4G5ZhGX0EXBKJRN9LcEWbKWOdPiCTKdX6SDqPA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>> >>>> >>>> -- >>>> V >>>> >>> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "golang-nuts" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/golang-nuts/VBQrlI6-zW0/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> golang-nuts+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHiQP0WEbGPrFkY5gSzaaiQ5OqisySiy8_yUdfVAE-v6w%40mail.gmail.com >> <https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHiQP0WEbGPrFkY5gSzaaiQ5OqisySiy8_yUdfVAE-v6w%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > V > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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