Looking for mvn-golang example with multi-module using go-module dependency management

[dantran]

My apology if this is asked at the wrong place.

basically my go-module A depends on mvn-golang package B, and mvn build fails with

 cannot find module providing package xxxxxx/yyyyyy  

xxxxx/yyyy is from my mvn-golang dependency

and xxxx/yyyy does show up under target/.dep/ dir

I do have GO111MODULE = on

[raydac]

I have a multi-module example among examples. Am I correct that you have both maven dependencies and golang module dependencies in your project?

[dantran]

Yes that is the example, without using mvn-golang dependency and with GO111MODULE=on

[raydac]

making some experiments but still no success, single module works well but multi-module still can't process "on" , golang team made very strange stupid implementation of module mechanism. internet full of messages "how to read another module from local folder?!" and there is still no good answer for the question

[dantran]

Thank you for looking into this. I am able to create a POC

• Use go.mod's 'replace' to provide path to depending module with the maven reactor
• For external mvn-golang, use go.mod's 'replace' to provide path to depending module under target/.dep/artifact-xxxx/. This is not clean, but it works. Another way is use maven-dependency-plugin to unpack 'mvn-golang' dependencies to ${goPath}

[raydac]

yes, it looks like that auto-generation of replacement in go.mod is only way to get it working, I will try today to make some autogenerator
replacement directly to depending module will not be working because sources and resources can be situated in different folders, not only in src, but with __dep__ it can work

[raydac]

I have made some experiments with preprocessing of go.mod, it adds replace into all such files with relative path, visually looks good but still can't build with on flag
you can try with 2.3.3-snapshot, just add

  <properties>
    <mvn.golang.preprocess.gomod>true</mvn.golang.preprocess.gomod>
    <mvn.golang.restore.gomod>false</mvn.golang.restore.gomod>
  </properties>

to enable processing and disable removing of generated go.mod after build, may be you can give some recommendations what is wrong in my case

[dantran]

do you have a sample multi module maven project with GO Module, or I need to come up one?

[raydac]

looks like that found some solution, may be today will get working version

[raydac]

I made solution and now go.mod files are supported, there is example of maven-module mixed project, to activate module support you should either add <moduleMode>true</moduleMode> into configuration or add project property <mvn.golang.module.mode>true</mvn.golang.module.mode>, GO111MODULE non needed because plugin will turn on the mode and inject this environment value automatically

[dantran]

How does it work behind the scene?

[raydac]

it is preprocessing all go.mod files to provide local paths to dependency modules through replace directive and restore all go.mod files from backup after work

[dantran]

this works from maven perspective, how it will confuse the IDE which would not be able to reference dependencies. Can we have an option to not restore. I am OK with commit changes of go.mod into source control

[raydac]

restoration of go.mod can be turned off if project property mvn.golang.restore.go.mod is false

[dantran]

I build the provided examples Golang module build with -Dmvn.golang.restore.go.mod=false

do see this log

[WARNING] Restoring of go.mod from backup is disabled

but go.mod are not modified at end of build

also, can you set gitignore for go.sum?

[raydac]

I have moved the message into debugging log
processing of git config files (as and IDE options) is out of bound of responsibility of the plugin, I will not be surprised if there is some maven git plugin which allows to modify gitignore

[dantran]

i am expecting go.mod updated by mvn-golang, but sofar i dont see any update

just want to see how you manage to get multi maven modules working with Go mod

[raydac]

if you have maven mvn-golang dependencies to golang modules then your go.mod will be temporary changed from (example)

module main

require (
	com.igormaznitsa/testmixproxy v1.0.0
	com.igormaznitsa/testmixterminal v1.0.0
)

to

module main
require com.igormaznitsa/testmixproxy v1.0.0
require com.igormaznitsa/testmixterminal v1.0.0
replace com.igormaznitsa/testmixproxy => ../bin/.__deps__/mvn-go-test-mix-proxy-1.0.0-SNAPSHOT/src/com.igormaznitsa/testmixproxy
replace com.igormaznitsa/testmixterminal => ../bin/.__deps__/mvn-go-test-mix-terminal-1.0.0-SNAPSHOT/src/com.igormaznitsa/testmixterminal

in the end of work go.mod will be restored to the original one
if you want keep changes after work then use -Dmvn.golang.restore.go.mod=false as parameter of command line in maven or provide it as project property (but in the case you have to remove backup version else it will be restored automatically before work), keep changed file is very strange because paths to dependencies can be changed and it should be refreshed every time

[dantran]

Now I see why you have to restore go.mod file. I have developers :) insist on working with Go command line instead of maven. The only way is to setup go.mod and commit to source control. Best i can do is to have them run maven the first time to populate dependencies, then run Go and cli