cmd/go: add option to run "go mod tidy" recursively on nested modules

[echarrod]

What version of Go are you using (go version)?

$ go version 1.13.12 windows/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\harroded\AppData\Local\go-build
set GOENV=C:\Users\harroded\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\harroded\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=C:\Users\harroded\repos\yoti-go-sdk\go.mod
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\harroded\AppData\Local\Temp\go-build068344166=/tmp/go-build -gno-record-gcc-switches

What did you do?

go mod tidy ./...
With a file structure like:

• mypackage
  • go.mod
  • _examples
    • one
      • go.mod
    • two
      • go.mod
    • three
      • go.mod

What did you expect to see?

Recursively run go mod tidy on subfolders

What did you see instead?

go mod tidy: no arguments allowed

Although having multiple modules inside doesn't seem to be always wise for everyone, and I know some people are against it, taking the advice from https://github.com/golang/go/wiki/Modules#should-i-have-multiple-modules-in-a-single-repository, there are still cases where it is useful, and it would be good to support this option

[bcmills]

The ... wildcard in arguments to the go command is a package pattern, not a directory pattern. That package pattern matches only packages in the main module — so go mod tidy ./... would mean the same thing as go mod tidy.

And this is pretty easy to do as a bash command or script if you so desire:

for f in $(find . -name go.mod)
do (cd $(dirname $f); go mod tidy)
done

[bcmills]

CC @jayconrod @matloob, but I don't think this carries its weight in the go command — especially given how rarely nested modules should be used in the first place.

[jayconrod]

I don't think we should support this. Go commands generally operate in the context of a specific "main" module. Running go mod tidy across multiple main modules would be very different from anything done today.

[echarrod]

I understand it's quite rare. We took this approach after seeing it done in https://github.com/cucumber/godog, as the use case of having multiple modules seems to suit our needs, I seem to remember seeing it in other places too, although can't remember where right now

EDIT: more examples

• https://github.com/FluuxIO/go-xmpp/tree/master/_examples
• https://github.com/elastic/go-elasticsearch/tree/master/_examples/fasthttp

[mvdan]

And this is pretty easy to do as a bash command or script if you so desire:

I agree with Bryan. I've been doing something similar, with a bit more care about ignoring huge directories:

go-modules() {
        find . \( -name vendor -o -name '[._].*' -o -name node_modules \) -prune -o -name go.mod -print | sed 's:/go.mod$::'
}

Then, I can just do something like: for m in $(go-modules); do (cd $m && go mod tidy); done