The go.mod file format is described in detail at
https://golang.org/ref/mod#go-mod-file.

To create a new go.mod file, use 'go mod init'. For details see
'go help mod init' or https://golang.org/ref/mod#go-mod-init.

To add missing module requirements or remove unneeded requirements,
use 'go mod tidy'. For details, see 'go help mod tidy' or
https://golang.org/ref/mod#go-mod-tidy.

github.com/tinylib/msgp v1.1.9/go.mod h1:BCXGB54lDD8qUEPmiG0cQQUANC4IUQyB2ItS2UDlO/k=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20200302210943-78000ba7a073/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
golang.org/x/crypto v0.23.0 h1:dIJU/v2J8Mdglj/8rJ6UUOM3Zc9zLZxVZwwxMooUSAI=
golang.org/x/crypto v0.23.0/go.mod h1:CKFgDieR+mRhux2Lsu27y0fO304Db0wZe70UKqHu0v8=

stdout $GOPATH[\\/]src[\\/]b

# vendor directory produced for module, module mode
# runs in mod=vendor
go mod vendor
cmp vendor/modules.txt want_module_modules_txt
go list -f {{.Dir}} example.com/b
stdout $GOPATH[\\/]src[\\/]vendor[\\/]example.com[\\/]b

# vendor directory produced for module, workspace mode
# runs in mod=readonly
env GOWORK=
go list -f {{.Dir}} example.com/b
stdout $GOPATH[\\/]src[\\/]b

cmp go.mod go.mod.115-2

cp go.mod.orig go.mod
go mod tidy -go=''
cmpenv go.mod go.mod.latest

# Repeat with go get go@ instead of mod tidy.

# Go 1.16 -> 1.17 should be a no-op.
cp go.mod.116 go.mod
go get go@1.16
cmp go.mod go.mod.116

# Go 1.17 -> 1.16 should leave b (go get is not tidy).
cp go.mod.117 go.mod
go get go@1.16
cmp go.mod go.mod.116from117

# Go 1.15 -> 1.16 should leave d (go get is not tidy).

mkdir dir dir/dir
cp go.mod.new go.mod
cp go.mod.new dir/go.mod
cp go.mod.new dir/dir/go.mod
cp p.go dir/p.go
cp p.go dir/dir/p.go
go get -C dir rsc.io/needgo124
stderr '^go: rsc.io/needgo124@v0.0.1 requires go >= 1.24; switching to go1.24rc1$'
stderr '^go: upgraded go 1.1 => 1.24$'
stderr '^go: added toolchain go1.24rc1$'
cmp go.mod.new go.mod
cmp go.mod.new dir/dir/go.mod
grep 'go 1.24$' dir/go.mod

cp go.mod.orig go.mod
go mod download
go mod download example.com@v1.0.0
go mod download example.com/badchain/a@v1.1.0
go mod download example.com/badchain/b@v1.1.0
go mod download example.com/badchain/c@v1.1.0

# Try to update example.com/badchain/a (and its dependencies).
! go get example.com/badchain/a
cmp stderr update-a-expected
cmp go.mod go.mod.orig

cmp go.mod.orig go.mod
! exists vendor


# 'go mod tidy' still logs the errors, but succeeds and updates go.mod.

go mod tidy -e
stderr -count=4 'cannot find module providing package'
cmp go.mod.final go.mod


# 'go mod vendor -e' still logs the errors, but creates a vendor directory
# and exits with status 0.
# 'go mod vendor -e' does not update go.mod and will not vendor packages that

cp go.mod.21 go.mod
go list -f '{{.Module.GoVersion}} {{.DefaultGODEBUG}}'
! stdout panicnil
stdout randautoseed=0

# Go 1.21 work module should NOT set panicnil=1 in Go 1.20 dependency.
cp go.mod.21 go.mod
go list -f '{{.Module.GoVersion}} {{.DefaultGODEBUG}}' q
! stdout panicnil=1
! stdout randautoseed

go mod download rsc.io/panicnil # for go.sum

# leading to an infinite loop.

cp go.mod go.mod.orig
go mod tidy
cmp go.mod go.mod.orig

go get -u=patch ./...
cmp go.mod go.mod.want

-- go.mod --
module example.net/m

go 1.16

replace (
	example.net/a v0.1.0 => ./a
	example.net/b v0.1.0 => ./b
	example.net/b v0.1.1 => ./b
	example.net/m v0.1.0 => ./m1
)

require example.net/a v0.1.0
-- go.mod.want --
module example.net/m

go 1.16

# 'go mod tidy' should not leave duplicate lines when re-writing the file.

go mod tidy
cmp go.sum golden.sum

-- go.mod --
module use

go 1.16

require rsc.io/quote v1.5.2

-- go.sum --
rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
rsc.io/quote v1.5.2 h1:3fEykkD9k7lYzXqCYrwGAf7iNhbk4yCjHmKBN9td4L0=
rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=