As the title says, is it possible to generate code (with something like //go:generate) after a module dependency is downloaded?
Specifically, let's say there's a repo example.com/protobuf containing some .proto files and a few .sh scripts for generating bindings in different languages, plus a go.mod so it can be used as a dependency from go like so:
module example.com/application
go 1.18
require (
example.com/protobuf v1.0.0
)
However, the generated .go files are not included in this repo, they have to be generated using one of the .sh scripts, so if you try this, you get an error like module example.com/protobuf#latest found (v1.0.0), but does not contain package example.com/protobuf/foo
Is there a way around this without resorting to eg. git submodules?
No this is not possible for obvious security reasons.
Related
I successfully used rules_go to build a gRPC service:
go_proto_library(
name = "processor_go_proto",
compilers = ["#io_bazel_rules_go//proto:go_grpc"],
importpath = "/path/to/proto/package",
proto = ":processor_proto",
deps = ["//services/shared/proto/common:common_go_proto"],
)
However, I'm not sure how to import the resulting file in VSCode. The generated file is nested under bazel_bin and under the original proto file path; so to import this, it seems like I would need to write out the entire path (including the bazel_bin part) to the generated Go file. To my understanding, there doesn't seem to be a way to instruct VSCode to look under certain folders that only contain Go packages/files; everything seems to need a go.mod file. This makes it quite difficult to develop in.
For clarity, my directory structure looks something like this:
WORKSPACE
bazel-bin
- path
- to
- generated_Go_file.go
go.mod
go.sum
proto
- path
- to
- gRPC_proto.proto
main.go
main.go should use the generated_Go_file.go.
Is there a way around this?
I don't use Bazel and so cannot help with the Bazel configuration. It's likely there is a way to specify the generated code location so that you can revise this to reflect you preference.
The outline you provide of the generated code, is workable though and a common pattern. Often the generated proto|gRPC code is placed in a module's gen subdirectory.
This is somewhat similar to vendoring where your code incorporates what may often be a 3rd-party's stubs (client|server) into your code. The stubs must reflect the proto(s) package(s) and, when these are 3rd-party, using gen or bazel-bin provide a way to keep potentially multiple namespaces discrete.
You're correct that the import for main.go, could (!) be prefixed with the module name from go.mod (first line) followed by the folder path to the generated code. This is standard go packaging and treats the generated code in a similar way to vendored modules.
Another approach is to use|place the generated code in a different module.
For code generated from 3rd-party protos, this may be preferable and the generated code may be provided by the 3rd-party in a module that you can go get or add to your go.mod.
An example of this approach is Google Well-Known Types. The proto (sources) are bundled with protoc (lib directory) and, when protoc compiles sources that references any of these, the Go code that is generated includes imports that reference a Google-hosted location of the generated code (!) for these types (google.golang.org/protobuf/types/known).
Alternatively, you can replicate this behavior without having to use an external repo. The bazel-bin folder must be outside of the current module. Each distinct module in bazel-bin, would need its own go.mod file. You would include in a require block in your code's go.mod file references to the modules' (one or more) locations. You don't need to publish the module to a external repo but can simply require ( name => path/to/module ) to provide a local reference.
I've used openapi-generator to generate multiple SDK separately and put it in the same parent dir:
sdks
--- bar-api
------ go.mod
--- foo-api
------ go.mod
I'd like to be able to import bar-api in my client code. Initially there's bar-api's go.mod was generated as:
module github.com/coolrepo/bar-api
go 1.13
but I couldn't fix the imports in my client code:
bar "github.com/cool-repo/bar-api"
so what I did was:
sdks
--- bar-api
------ go.mod
---go.mod
i.e., created sdks/go.mod:
module github.com/coolrepo
go 1.13
and manually edited bar-api's go.mod to:
module github.com/coolrepo/bar-api
require (
...
)
replace github.com/coolrepo => ./..
go 1.15
Is there a better way to fix it? This one seems to work but looks kinda hacky with this replace.
The “better way to fix it” is to put all of the generated Go packages inside a single module, instead of splitting up the repo into multiple modules.
rm bar-api/go.mod
go mod tidy
You only really need to split a repo into separate modules if you need to be able to tag a release for one set of packages independently from another set of packages in the same repo. For generated service APIs, that probably isn't worth the development overhead of juggling versions for multiple modules.
I wrote a program and want to encapsulate some logic.
So I did new module and pull it in my git. Link for git looks like
gitlab.xxx.ru/group/subgroup/proj
but when I tried to get it with go get, I got error
fatal: «https://xxx.ru:#gitlab.xxx.ru/group/subgroup.git/» unreachable: URL using bad/illegal format or missing URL
Go tried to load subgroup instead project.
I made folder gitlab.xxx.ru/group/subgroup/ in $GOPATH/src/ and clone my project.
And now it wrote
could not import gitlab.xxx.ru/group/subgroup/proj (no required module provides package "gitlab.xxx.ru/group/subgroup/proj")
So, if I understand correctly, in Golang 1.16 I can't just put my project in the correct directory and I can't use local packages.
How to fix loading from my GitLab and load it with ssh?
Thank you.
UDP go.mod in my proj.
module gitlab.xxx.ru/group/subgroup/proj
go 1.16
require (
golang.org/x/sys v0.0.0-20210608053332-aa57babbf139
golang.org/x/text v0.3.6
)
You may be hitting the intended behaviour from Gitlab which will prevent go from fetching the list of subgroups while trying to compute project dependencies. Since go get requests are unauthenticated, existing projects not under the root group are invisible and cannot be found.
To overcome this limitation, which Gitlab has yet to provide a solution, you can use one of the following two approaches:
Have the project located at the root and not in a subgroup (not always possible)
Leverage the .git extension as well as the replace directive in the project which imports your module (see below)
Go is able to fetch the project living under a subgroup if it knows the version control qualifier (.git). To indicate this, make sure you import the project using the following format gitlab.xxx.ru/group/subgroup/proj.git
While this alone works, it would force you to have all those .git in your imports. To overcome this, you also need a replace directive in your go.mod so you can use the original import path.
In the end, the project which imports your module should have a go.mod that look like this:
require(
gitlab.xxx.ru/group/subgroup/proj v1.7.0
)
replace(
gitlab.xxx.ru/group/subgroup/proj => gitlab.xxx.ru/group/subgroup/proj.git v1.7.0
)
I ran into a repo that seems to be a Go module, but there's no go.mod file in it: github.com/confluentinc/confluent-kafka-go.
Is it ok for a go module to have no go.mod file with dependencies, or the authors of that library just didn't migrate to modules yet?
Dependency modules do not need to have explicit go.mod files.
The “main module” in module mode — that is, the module containing the working directory for the go command — must have a go.mod file, so that the go command can figure out the import paths for the packages within that module (based on its module path), and so that it has a place to record its dependencies once resolved.
In addition, any modules slotted in using replace directives must have go.mod files (in order to reduce confusion due to typos or other errors in replacement paths).
However, in general a module that lacks an explicit go.mod file is valid and fine to use. Its effective module path is the path by which it was required, which can be a bit confusing if the same repository ends up in use via multiple paths. Since a module with no go.mod file necessarily doesn't specify its own dependencies, consumers of that module will have to fill in those dependencies themselves (go mod tidy will mark them as // indirect in the consumer's go.mod file).
SHORT SUMMARY OF THE DISCUSSION:
The answer is "No"!
This project contains a set of go packages, but it is not a Go module as it doesn't contain go.mod file (although, it used to be a multi-module repo (Go) previously).
go get can run in both ways: module-aware mode and legacy GOPATH mode (as of Go 1.16).
To read more about this, refer to docs by using the go command:
$ go help gopath-get
and
$ go help module-get
It'd tell about how go get works in both cases.
Also, I noticed that it can download any repository and would treat it as a Go package, even if it contains an arbitrary Python project.
I did a simple test to demonstrate the same:
$ go get github.com/mongoengine/mongoengine
And it surprisingly worked.
Modules are defined by their go.mod file. Without a go.mod file, it is not a module.
See this from the Go Modules Reference
A module is a collection of packages that are released, versioned, and distributed together. Modules may be downloaded directly from version control repositories or from module proxy servers.
A module is identified by a module path, which is declared in a go.mod file, together with information about the module's dependencies. The module root directory is the directory that contains the go.mod file.
And
A module is defined by a UTF-8 encoded text file named go.mod in its root directory.
This repo has 3 go files all begin with "package lumber".
To use this package, I'm supposed to put this in my GOROOT and simply
import lumber
in my program. How do variables and types in this package connect with each other across multiple files? How does the go compiler know which file to begin reading first?
In case I want to read the package, where should I begin reading to understand the package? What exactly is the flow of things here?
To elaborate on jnml's answer:
When you use import "foo/bar" in your code, you are not referring to the source files (which will be located in $GOPATH/src/foo/bar/).
Instead, you are referring to a compiled package file at $GOPATH/pkg/$GOOS_$GOARCH/foo/bar.a. When you build your own code, and the compiler finds that the foo/bar package has not yet been compiled (or is out of date), it will do this for you automatically.
It does this by collating* all the relevant source files in the $GOPATH/src/foo/bar directory and building them into a single bar.a file, which it installs in the pkg directory. Compilation then resumes with your own program.
This process is repeated for all imported packages, and packages imported by those as well, all the way down the dependency chain.
*) How the files are collated, depends on how the file itself is named and what kind of build tags are present inside it.
For a deeper understanding of how this works, refer to the build docs.
No, you're not "supposed to put this in my GOROOT". You're supposed to execute
$ go get github.com/jcelliott/lumber
which will clone the repository into $GOPATH/src/github.com/jcelliott/lumber. Then you can use the package by importing it in your code as
import "github.com/jcelliott/lumber"
About the scoping rules: Declarations and scope