Module's local transitive dependencies work only with explicit replace directive

[asmundak]

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

$ go version
go version go1.20-pre3 cl/474093167 +a813be86df linux/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
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="$HOME/.cache/go-build"
GOENV="$HOME/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="$HOME/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="$HOME/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/google-golang"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/google-golang/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.20-pre3 cl/474093167 +a813be86df"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2517995585=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.20-pre3 cl/474093167 +a813be86df linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.20-pre3 cl/474093167 +a813be86df
uname -sr: Linux 5.18.16-1rodete4-amd64
Distributor ID:	Debian
Description:	Debian GNU/Linux rodete
Release:	rodete
Codename:	rodete
/lib/x86_64-linux-gnu/libc.so.6: GNU C Library (Debian GLIBC 2.35-1) stable release version 2.35.
gdb --version: GNU gdb (GDB) 10.0-gg5

What did you do?

There are three local modules, with top depending on middle, and middle depending on bottom

$ find . -type f -printf "\n---%P---\n" -exec cat {} \;

---middle/go.mod---
module middle
require _/bottom v0.0.0-00010101000000-000000000000
replace _/bottom => ../bottom
go 1.20

---middle/middle.go---
package middle
import "_/bottom"
var X = bottom.X

---top/go.mod---
module main
require _/middle v0.0.0-00010101000000-000000000000
replace _/middle => ../middle
go 1.20

---top/top.go---
package main
import "_/middle"
func main() {
	println(middle.X)
}

---bottom/go.mod---
module bottom
go 1.20

---bottom/bottom.go---
package bottom
var X int = 1

What did you expect to see?

cd top && go run . should succeed

What did you see instead?

$ (cd top && go run .)
../middle/middle.go:2:8: missing go.sum entry for module providing package _/bottom (imported by _/middle); to add:
	go get _/middle@v0.0.0-00010101000000-000000000000

Doing what is suggested doesn't help:

$ (cd top && go get _/middle@v0.0.0-00010101000000-000000000000)
_/middle imports
	_/bottom: malformed module path "_/bottom": missing dot in first path element

What does help is explicitly adding replace directive to top/go.mod:

(cd top && go mod edit -replace _/bottom=../bottom && go mod tidy)
$ (cd top && go run .)
1

Requesting that a module keeps track of all its transitive local dependencies is IMHO a maintenance problem.

[seankhliao]

Working as intended, replace directives only apply at the main module, if you need to work with multiple modules, consider using workspaces.

Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only.

For questions please refer to https://github.com/golang/go/wiki/Questions

[bcmills]

Hmm, I don't think this is working as intended. go get _/middle@v0.0.0-00010101000000-000000000000 within module top should apply the replace directive from top/go.mod, which should arguably avoid the missing dot in first path element error.

[bcmills]

I suspect we're failing to apply the replacement here:
https://cs.opensource.google/go/go/+/master:src/cmd/go/internal/modload/query.go;l=184-187;drc=c85848a4a62f839427bb56cb2772e008e405cf1f

[seankhliao]

doesn't top have no require / replace for _/bottom, and the error comes from _/bottom being an unretrievable module?

[bcmills]

Ah, you're right! The error message _/bottom: malformed module path "_/bottom": missing dot in first path element is indeed for that module.