1# https://golang.org/issue/46141: 'go mod tidy' for a Go 1.17 module should by
2# default preserve enough checksums for the module to be used by Go 1.16.
3#
4# We don't have a copy of Go 1.16 handy, but we can simulate it by editing the
5# 'go' version in the go.mod file to 1.16, without actually updating the
6# requirements to match.
7
8[short] skip
9
10env MODFMT='{{with .Module}}{{.Path}} {{.Version}}{{end}}'
11
12
13# For this module, Go 1.16 selects the same versions of all explicit dependencies
14# as Go 1.17 does. However, Go 1.16 selects a higher version of an *implicit*
15# dependency, imported by a test of one of the (external) imported packages.
16# As a result, Go 1.16 also needs checksums for the module sources for that higher
17# version.
18#
19# The Go 1.16 module graph looks like:
20#
21# m ---- lazy v0.1.0 ---- incompatible v1.0.0
22# |
23# + ------------- requireincompatible v0.1.0 ---- incompatible v2.0.0+incompatible
24#
25# The Go 1.17 module graph is the same except that the dependencies of
26# requireincompatible are pruned out (because the module that requires
27# it — lazy v0.1.0 — specifies 'go 1.17', and it is not otherwise relevant to
28# the main module).
29
30# 'go mod tidy' should by default diagnose the difference in dependencies as an
31# error, with useful suggestions about how to resolve it.
32
33cp go.mod go.mod.orig
34! go mod tidy
35stderr '^go: example\.com/m imports\n\texample\.net/lazy tested by\n\texample\.net/lazy.test imports\n\texample\.com/retract/incompatible loaded from example\.com/retract/incompatible@v1\.0\.0,\n\tbut go 1\.16 would select v2\.0\.0\+incompatible\n\n'
36stderr '\n\nTo upgrade to the versions selected by go 1\.16:\n\tgo mod tidy -go=1\.16 && go mod tidy -go=1\.17\nIf reproducibility with go 1.16 is not needed:\n\tgo mod tidy -compat=1.17\nFor other options, see:\n\thttps://golang\.org/doc/modules/pruning\n'
37
38cmp go.mod go.mod.orig
39
40# The suggested '-compat' flag to ignore differences should silence the error
41# and leave go.mod unchanged, resulting in checksum errors when Go 1.16 tries
42# to load a module pruned out by Go 1.17.
43
44go mod tidy -compat=1.17
45! stderr .
46cmp go.mod go.mod.orig
47
48go list -deps -test -f $MODFMT ./...
49stdout '^example.net/lazy v0.1.0$'
50
51go mod edit -go=1.16
52! go list -deps -test -f $MODFMT ./...
53
54stderr -count=1 '^go: example\.net/lazy@v0\.1\.0 requires\n\texample\.com/retract/incompatible@v1\.0\.0: missing go\.sum entry for go\.mod file; to add it:\n\tgo mod download example\.com/retract/incompatible$'
55
56
57# If we combine a Go 1.16 go.sum file...
58go mod tidy -go=1.16
59
60# ...with a Go 1.17 go.mod file...
61cp go.mod.orig go.mod
62
63# ...then Go 1.17 no longer works. 😞
64! go list -deps -test -f $MODFMT all
65stderr -count=1 '^go: can''t load test package: lazy[/\\]lazy_test.go:3:8: missing go\.sum entry for module providing package example\.com/retract/incompatible \(imported by example\.net/lazy\); to add:\n\tgo get -t example.net/lazy@v0\.1\.0$'
66
67
68# However, if we take the union of the go.sum files...
69go list -mod=mod -deps -test all
70cmp go.mod go.mod.orig
71
72# ...then Go 1.17 continues to work...
73go list -deps -test -f $MODFMT all
74stdout '^example\.com/retract/incompatible v1\.0\.0$'
75
76# ...and 1.16 also works(‽), but selects a different version for the
77# external-test dependency.
78go mod edit -go=1.16
79go list -deps -test -f $MODFMT all
80stdout '^example\.com/retract/incompatible v2\.0\.0\+incompatible$'
81
82
83-- go.mod --
84// Module m imports packages from the same versions under Go 1.17
85// as under Go 1.16, but under 1.16 its (implicit) external test dependencies
86// are higher.
87module example.com/m
88
89go 1.17
90
91replace (
92 example.net/lazy v0.1.0 => ./lazy
93 example.net/requireincompatible v0.1.0 => ./requireincompatible
94)
95
96require example.net/lazy v0.1.0
97-- implicit.go --
98package implicit
99
100import _ "example.net/lazy"
101-- lazy/go.mod --
102// Module lazy requires example.com/retract/incompatible v1.0.0.
103//
104// When viewed from the outside it also has a transitive dependency
105// on v2.0.0+incompatible, but in lazy mode that transitive dependency
106// is pruned out.
107module example.net/lazy
108
109go 1.17
110
111exclude example.com/retract/incompatible v2.0.0+incompatible
112
113require (
114 example.com/retract/incompatible v1.0.0
115 example.net/requireincompatible v0.1.0
116)
117-- lazy/lazy.go --
118package lazy
119-- lazy/lazy_test.go --
120package lazy_test
121
122import _ "example.com/retract/incompatible"
123-- requireincompatible/go.mod --
124module example.net/requireincompatible
125
126go 1.15
127
128require example.com/retract/incompatible v2.0.0+incompatible
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