src/cmd/go/testdata/script/mod_tidy_convergence_loop.txt - go - Git at Google

 # This test demonstrates a simple case in which 'go mod tidy' may resolve a
 # missing package, only to remove that package when resolving its dependencies.
 #
 # If we naively iterate 'go mod tidy' until the dependency graph converges, this
 # scenario may fail to converge.

 # The import graph used in this test looks like:
 #
 # m --- w
 # |
 # + --- x
 # |
 # + --- y
 # |
 # + --- z
 #
 # The module dependency graph of m initially contains w.1 (and, by extension,
 # y.2-pre and z.2-pre). This is an arbitrary point in the cycle of possible
 # configurations.
 #
 # w.1 requires y.2-pre and z.2-pre
 # x.1 requires z.2-pre and w.2-pre
 # y.1 requires w.2-pre and x.2-pre
 # z.1 requires x.2-pre and y.2-pre
 #
 # At each point, exactly one missing package can be resolved by adding a
 # dependency on the .1 release of the module that provides that package.
 # However, adding that dependency causes the module providing another package to
 # roll over from its .1 release to its .2-pre release, which removes the
 # package. Once the package is removed, 'go mod tidy -e' no longer sees the
 # module as relevant to the main module, and will happily remove the existing
 # dependency on it.
 #
 # The cycle is of length 4 so that at every step only one package can be
 # resolved. This is important because it prevents the iteration from ever
 # reaching a state in which every package is simultaneously over-upgraded — such
 # a state is stable and does not exhibit failure to converge.

 cp go.mod go.mod.orig

 # 'go mod tidy' without -e should fail without modifying go.mod,
 # because it cannot resolve x, y, and z simultaneously.
 ! go mod tidy

 cmp go.mod go.mod.orig

 stderr '^go: finding module for package example\.net/w$'
 stderr '^go: finding module for package example\.net/x$'
 stderr -count=2 '^go: finding module for package example\.net/y$'
 stderr -count=2 '^go: finding module for package example\.net/z$'
 stderr '^go: found example\.net/x in example\.net/x v0.1.0$'

 	# TODO: These error messages should be clearer — it doesn't indicate why v0.2.0-pre is required.
 stderr '^go: example\.net/m imports\n\texample\.net/w: package example\.net/w provided by example\.net/w at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
 stderr '^go: example\.net/m imports\n\texample\.net/y: package example\.net/y provided by example\.net/y at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
 stderr '^go: example\.net/m imports\n\texample\.net/z: package example\.net/z provided by example\.net/z at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'


 # 'go mod tidy -e' should preserve all of the upgrades to modules that could
 # provide the missing packages but don't. That would at least explain why they
 # are missing, and why no individual module can be upgraded in order to satisfy
 # a missing import.
 #
 # TODO(bcmills): Today, it doesn't preserve those upgrades, and instead advances
 # the state by one through the cycle of semi-tidy states.

 go mod tidy -e

 cmp go.mod go.mod.tidye1

 stderr '^go: finding module for package example\.net/w$'
 stderr '^go: finding module for package example\.net/x$'
 stderr -count=2 '^go: finding module for package example\.net/y$'
 stderr -count=2 '^go: finding module for package example\.net/z$'
 stderr '^go: found example\.net/x in example\.net/x v0.1.0$'

 stderr '^go: example\.net/m imports\n\texample\.net/w: package example\.net/w provided by example\.net/w at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
 stderr '^go: example\.net/m imports\n\texample\.net/y: package example\.net/y provided by example\.net/y at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
 stderr '^go: example\.net/m imports\n\texample\.net/z: package example\.net/z provided by example\.net/z at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'


 go mod tidy -e
 cmp go.mod go.mod.tidye2

 go mod tidy -e
 cmp go.mod go.mod.tidye3

 go mod tidy -e
 cmp go.mod go.mod.orig


 # If we upgrade away all of the packages simultaneously, the resulting tidy
 # state converges at "no dependencies", because simultaneously adding all of the
 # packages simultaneously over-upgrades all of the dependencies, and 'go mod
 # tidy' treats "no package can be added" as a terminal state.

 go get example.net/w@v0.2.0-pre example.net/x@v0.2.0-pre example.net/y@v0.2.0-pre example.net/z@v0.2.0-pre
 go mod tidy -e
 cmp go.mod go.mod.postget
 go mod tidy -e
 cmp go.mod go.mod.postget


 # The 'tidy' logic for a lazy main module requires more iterations to converge,
 # because it is willing to drop dependencies on non-root modules that do not
 # otherwise provide imported packages.
 #
 # On the first iteration, it adds x.1 as a root, which upgrades z and w,
 # dropping w.1's requirement on y. w.1 was initially a root, so the upgraded
 # w.2-pre is retained as a root.
 #
 # On the second iteration, it adds y.1 as a root, which upgrades w and x,
 # dropping x.1's requirement on z. x.1 was added as a root in the previous step,
 # so the upgraded x.2-pre is retained as a root.
 #
 # On the third iteration, it adds z.1 as a root, which upgrades x and y.
 # x and y were already roots (from the previous steps), so their upgraded versions
 # are retained (not dropped) and the iteration stops.
 #
 # At that point, we have z.1 as a root providing package z,
 # and w, x, and y have all been upgraded to no longer provide any packages.
 # So only z is retained as a new root.
 #
 # (From the above, we can see that in a lazy module we still cycle through the
 # same possible root states, but in a different order from the eager case.)
 #
 # TODO(bcmills): if we retained the upgrades on w, x, and y (since they are
 # lexical prefixes for unresolved packages w, x, and y, respectively), then 'go
 # mod tidy -e' itself would become stable and no longer cycle through states.

 cp go.mod.orig go.mod
 go mod edit -go=1.17 go.mod
 cp go.mod go.mod.117
 go mod edit -go=1.17 go.mod.tidye1
 go mod edit -go=1.17 go.mod.tidye2
 go mod edit -go=1.17 go.mod.tidye3
 go mod edit -go=1.17 go.mod.postget

 go list -m all

 go mod tidy -e
 cmp go.mod go.mod.tidye3

 go mod tidy -e
 cmp go.mod go.mod.tidye2

 go mod tidy -e
 cmp go.mod go.mod.tidye1

 go mod tidy -e
 cmp go.mod go.mod.117


 # As in the eager case, for the lazy module the fully-upgraded dependency graph
 # becomes empty, and the empty graph is stable.

 go get example.net/w@v0.2.0-pre example.net/x@v0.2.0-pre example.net/y@v0.2.0-pre example.net/z@v0.2.0-pre
 go mod tidy -e
 cmp go.mod go.mod.postget
 go mod tidy -e
 cmp go.mod go.mod.postget


 -- m.go --
 package m

 import (
 	_ "example.net/w"
 	_ "example.net/x"
 	_ "example.net/y"
 	_ "example.net/z"
 )

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

 go 1.16

 replace (
 	example.net/w v0.1.0 => ./w1
 	example.net/w v0.2.0-pre => ./w2-pre
 	example.net/x v0.1.0 => ./x1
 	example.net/x v0.2.0-pre => ./x2-pre
 	example.net/y v0.1.0 => ./y1
 	example.net/y v0.2.0-pre => ./y2-pre
 	example.net/z v0.1.0 => ./z1
 	example.net/z v0.2.0-pre => ./z2-pre
 )

 require example.net/w v0.1.0
 -- go.mod.tidye1 --
 module example.net/m

 go 1.16

 replace (
 	example.net/w v0.1.0 => ./w1
 	example.net/w v0.2.0-pre => ./w2-pre
 	example.net/x v0.1.0 => ./x1
 	example.net/x v0.2.0-pre => ./x2-pre
 	example.net/y v0.1.0 => ./y1
 	example.net/y v0.2.0-pre => ./y2-pre
 	example.net/z v0.1.0 => ./z1
 	example.net/z v0.2.0-pre => ./z2-pre
 )

 require example.net/x v0.1.0
 -- go.mod.tidye2 --
 module example.net/m

 go 1.16

 replace (
 	example.net/w v0.1.0 => ./w1
 	example.net/w v0.2.0-pre => ./w2-pre
 	example.net/x v0.1.0 => ./x1
 	example.net/x v0.2.0-pre => ./x2-pre
 	example.net/y v0.1.0 => ./y1
 	example.net/y v0.2.0-pre => ./y2-pre
 	example.net/z v0.1.0 => ./z1
 	example.net/z v0.2.0-pre => ./z2-pre
 )

 require example.net/y v0.1.0
 -- go.mod.tidye3 --
 module example.net/m

 go 1.16

 replace (
 	example.net/w v0.1.0 => ./w1
 	example.net/w v0.2.0-pre => ./w2-pre
 	example.net/x v0.1.0 => ./x1
 	example.net/x v0.2.0-pre => ./x2-pre
 	example.net/y v0.1.0 => ./y1
 	example.net/y v0.2.0-pre => ./y2-pre
 	example.net/z v0.1.0 => ./z1
 	example.net/z v0.2.0-pre => ./z2-pre
 )

 require example.net/z v0.1.0
 -- go.mod.postget --
 module example.net/m

 go 1.16

 replace (
 	example.net/w v0.1.0 => ./w1
 	example.net/w v0.2.0-pre => ./w2-pre
 	example.net/x v0.1.0 => ./x1
 	example.net/x v0.2.0-pre => ./x2-pre
 	example.net/y v0.1.0 => ./y1
 	example.net/y v0.2.0-pre => ./y2-pre
 	example.net/z v0.1.0 => ./z1
 	example.net/z v0.2.0-pre => ./z2-pre
 )
 -- w1/go.mod --
 module example.net/w

 go 1.16

 require (
 	example.net/y v0.2.0-pre
 	example.net/z v0.2.0-pre
 )
 -- w1/w.go --
 package w
 -- w2-pre/go.mod --
 module example.net/w

 go 1.16
 -- w2-pre/README.txt --
 Package w has been removed.

 -- x1/go.mod --
 module example.net/x

 go 1.16

 require (
 	example.net/z v0.2.0-pre
 	example.net/w v0.2.0-pre
 )
 -- x1/x.go --
 package x
 -- x2-pre/go.mod --
 module example.net/x

 go 1.16
 -- x2-pre/README.txt --
 Package x has been removed.

 -- y1/go.mod --
 module example.net/y

 go 1.16

 require (
 	example.net/w v0.2.0-pre
 	example.net/x v0.2.0-pre
 )
 -- y1/y.go --
 package y

 -- y2-pre/go.mod --
 module example.net/y

 go 1.16
 -- y2-pre/README.txt --
 Package y has been removed.

 -- z1/go.mod --
 module example.net/z

 go 1.16

 require (
 	example.net/x v0.2.0-pre
 	example.net/y v0.2.0-pre
 )
 -- z1/z.go --
 package z

 -- z2-pre/go.mod --
 module example.net/z

 go 1.16
 -- z2-pre/README.txt --
 Package z has been removed.
	# This test demonstrates a simple case in which 'go mod tidy' may resolve a
	# missing package, only to remove that package when resolving its dependencies.
	#
	# If we naively iterate 'go mod tidy' until the dependency graph converges, this
	# scenario may fail to converge.

	# The import graph used in this test looks like:
	#
	# m --- w
	# \|
	# + --- x
	# \|
	# + --- y
	# \|
	# + --- z
	#
	# The module dependency graph of m initially contains w.1 (and, by extension,
	# y.2-pre and z.2-pre). This is an arbitrary point in the cycle of possible
	# configurations.
	#
	# w.1 requires y.2-pre and z.2-pre
	# x.1 requires z.2-pre and w.2-pre
	# y.1 requires w.2-pre and x.2-pre
	# z.1 requires x.2-pre and y.2-pre
	#
	# At each point, exactly one missing package can be resolved by adding a
	# dependency on the .1 release of the module that provides that package.
	# However, adding that dependency causes the module providing another package to
	# roll over from its .1 release to its .2-pre release, which removes the
	# package. Once the package is removed, 'go mod tidy -e' no longer sees the
	# module as relevant to the main module, and will happily remove the existing
	# dependency on it.
	#
	# The cycle is of length 4 so that at every step only one package can be
	# resolved. This is important because it prevents the iteration from ever
	# reaching a state in which every package is simultaneously over-upgraded — such
	# a state is stable and does not exhibit failure to converge.

	cp go.mod go.mod.orig

	# 'go mod tidy' without -e should fail without modifying go.mod,
	# because it cannot resolve x, y, and z simultaneously.
	! go mod tidy

	cmp go.mod go.mod.orig

	stderr '^go: finding module for package example\.net/w$'
	stderr '^go: finding module for package example\.net/x$'
	stderr -count=2 '^go: finding module for package example\.net/y$'
	stderr -count=2 '^go: finding module for package example\.net/z$'
	stderr '^go: found example\.net/x in example\.net/x v0.1.0$'

	# TODO: These error messages should be clearer — it doesn't indicate why v0.2.0-pre is required.
	stderr '^go: example\.net/m imports\n\texample\.net/w: package example\.net/w provided by example\.net/w at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
	stderr '^go: example\.net/m imports\n\texample\.net/y: package example\.net/y provided by example\.net/y at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
	stderr '^go: example\.net/m imports\n\texample\.net/z: package example\.net/z provided by example\.net/z at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'


	# 'go mod tidy -e' should preserve all of the upgrades to modules that could
	# provide the missing packages but don't. That would at least explain why they
	# are missing, and why no individual module can be upgraded in order to satisfy
	# a missing import.
	#
	# TODO(bcmills): Today, it doesn't preserve those upgrades, and instead advances
	# the state by one through the cycle of semi-tidy states.

	go mod tidy -e

	cmp go.mod go.mod.tidye1

	stderr '^go: finding module for package example\.net/w$'
	stderr '^go: finding module for package example\.net/x$'
	stderr -count=2 '^go: finding module for package example\.net/y$'
	stderr -count=2 '^go: finding module for package example\.net/z$'
	stderr '^go: found example\.net/x in example\.net/x v0.1.0$'

	stderr '^go: example\.net/m imports\n\texample\.net/w: package example\.net/w provided by example\.net/w at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
	stderr '^go: example\.net/m imports\n\texample\.net/y: package example\.net/y provided by example\.net/y at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'
	stderr '^go: example\.net/m imports\n\texample\.net/z: package example\.net/z provided by example\.net/z at latest version v0\.1\.0 but not at required version v0\.2\.0-pre$'


	go mod tidy -e
	cmp go.mod go.mod.tidye2

	go mod tidy -e
	cmp go.mod go.mod.tidye3

	go mod tidy -e
	cmp go.mod go.mod.orig


	# If we upgrade away all of the packages simultaneously, the resulting tidy
	# state converges at "no dependencies", because simultaneously adding all of the
	# packages simultaneously over-upgrades all of the dependencies, and 'go mod
	# tidy' treats "no package can be added" as a terminal state.

	go get example.net/w@v0.2.0-pre example.net/x@v0.2.0-pre example.net/y@v0.2.0-pre example.net/z@v0.2.0-pre
	go mod tidy -e
	cmp go.mod go.mod.postget
	go mod tidy -e
	cmp go.mod go.mod.postget


	# The 'tidy' logic for a lazy main module requires more iterations to converge,
	# because it is willing to drop dependencies on non-root modules that do not
	# otherwise provide imported packages.
	#
	# On the first iteration, it adds x.1 as a root, which upgrades z and w,
	# dropping w.1's requirement on y. w.1 was initially a root, so the upgraded
	# w.2-pre is retained as a root.
	#
	# On the second iteration, it adds y.1 as a root, which upgrades w and x,
	# dropping x.1's requirement on z. x.1 was added as a root in the previous step,
	# so the upgraded x.2-pre is retained as a root.
	#
	# On the third iteration, it adds z.1 as a root, which upgrades x and y.
	# x and y were already roots (from the previous steps), so their upgraded versions
	# are retained (not dropped) and the iteration stops.
	#
	# At that point, we have z.1 as a root providing package z,
	# and w, x, and y have all been upgraded to no longer provide any packages.
	# So only z is retained as a new root.
	#
	# (From the above, we can see that in a lazy module we still cycle through the
	# same possible root states, but in a different order from the eager case.)
	#
	# TODO(bcmills): if we retained the upgrades on w, x, and y (since they are
	# lexical prefixes for unresolved packages w, x, and y, respectively), then 'go
	# mod tidy -e' itself would become stable and no longer cycle through states.

	cp go.mod.orig go.mod
	go mod edit -go=1.17 go.mod
	cp go.mod go.mod.117
	go mod edit -go=1.17 go.mod.tidye1
	go mod edit -go=1.17 go.mod.tidye2
	go mod edit -go=1.17 go.mod.tidye3
	go mod edit -go=1.17 go.mod.postget

	go list -m all

	go mod tidy -e
	cmp go.mod go.mod.tidye3

	go mod tidy -e
	cmp go.mod go.mod.tidye2

	go mod tidy -e
	cmp go.mod go.mod.tidye1

	go mod tidy -e
	cmp go.mod go.mod.117


	# As in the eager case, for the lazy module the fully-upgraded dependency graph
	# becomes empty, and the empty graph is stable.

	go get example.net/w@v0.2.0-pre example.net/x@v0.2.0-pre example.net/y@v0.2.0-pre example.net/z@v0.2.0-pre
	go mod tidy -e
	cmp go.mod go.mod.postget
	go mod tidy -e
	cmp go.mod go.mod.postget


	-- m.go --
	package m

	import (
	_ "example.net/w"
	_ "example.net/x"
	_ "example.net/y"
	_ "example.net/z"
	)

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

	go 1.16

	replace (
	example.net/w v0.1.0 => ./w1
	example.net/w v0.2.0-pre => ./w2-pre
	example.net/x v0.1.0 => ./x1
	example.net/x v0.2.0-pre => ./x2-pre
	example.net/y v0.1.0 => ./y1
	example.net/y v0.2.0-pre => ./y2-pre
	example.net/z v0.1.0 => ./z1
	example.net/z v0.2.0-pre => ./z2-pre
	)

	require example.net/w v0.1.0
	-- go.mod.tidye1 --
	module example.net/m

	go 1.16

	replace (
	example.net/w v0.1.0 => ./w1
	example.net/w v0.2.0-pre => ./w2-pre
	example.net/x v0.1.0 => ./x1
	example.net/x v0.2.0-pre => ./x2-pre
	example.net/y v0.1.0 => ./y1
	example.net/y v0.2.0-pre => ./y2-pre
	example.net/z v0.1.0 => ./z1
	example.net/z v0.2.0-pre => ./z2-pre
	)

	require example.net/x v0.1.0
	-- go.mod.tidye2 --
	module example.net/m

	go 1.16

	replace (
	example.net/w v0.1.0 => ./w1
	example.net/w v0.2.0-pre => ./w2-pre
	example.net/x v0.1.0 => ./x1
	example.net/x v0.2.0-pre => ./x2-pre
	example.net/y v0.1.0 => ./y1
	example.net/y v0.2.0-pre => ./y2-pre
	example.net/z v0.1.0 => ./z1
	example.net/z v0.2.0-pre => ./z2-pre
	)

	require example.net/y v0.1.0
	-- go.mod.tidye3 --
	module example.net/m

	go 1.16

	replace (
	example.net/w v0.1.0 => ./w1
	example.net/w v0.2.0-pre => ./w2-pre
	example.net/x v0.1.0 => ./x1
	example.net/x v0.2.0-pre => ./x2-pre
	example.net/y v0.1.0 => ./y1
	example.net/y v0.2.0-pre => ./y2-pre
	example.net/z v0.1.0 => ./z1
	example.net/z v0.2.0-pre => ./z2-pre
	)

	require example.net/z v0.1.0
	-- go.mod.postget --
	module example.net/m

	go 1.16

	replace (
	example.net/w v0.1.0 => ./w1
	example.net/w v0.2.0-pre => ./w2-pre
	example.net/x v0.1.0 => ./x1
	example.net/x v0.2.0-pre => ./x2-pre
	example.net/y v0.1.0 => ./y1
	example.net/y v0.2.0-pre => ./y2-pre
	example.net/z v0.1.0 => ./z1
	example.net/z v0.2.0-pre => ./z2-pre
	)
	-- w1/go.mod --
	module example.net/w

	go 1.16

	require (
	example.net/y v0.2.0-pre
	example.net/z v0.2.0-pre
	)
	-- w1/w.go --
	package w
	-- w2-pre/go.mod --
	module example.net/w

	go 1.16
	-- w2-pre/README.txt --
	Package w has been removed.

	-- x1/go.mod --
	module example.net/x

	go 1.16

	require (
	example.net/z v0.2.0-pre
	example.net/w v0.2.0-pre
	)
	-- x1/x.go --
	package x
	-- x2-pre/go.mod --
	module example.net/x

	go 1.16
	-- x2-pre/README.txt --
	Package x has been removed.

	-- y1/go.mod --
	module example.net/y

	go 1.16

	require (
	example.net/w v0.2.0-pre
	example.net/x v0.2.0-pre
	)
	-- y1/y.go --
	package y

	-- y2-pre/go.mod --
	module example.net/y

	go 1.16
	-- y2-pre/README.txt --
	Package y has been removed.

	-- z1/go.mod --
	module example.net/z

	go 1.16

	require (
	example.net/x v0.2.0-pre
	example.net/y v0.2.0-pre
	)
	-- z1/z.go --
	package z

	-- z2-pre/go.mod --
	module example.net/z

	go 1.16
	-- z2-pre/README.txt --
	Package z has been removed.