[release-branch.go1.19] cmd/go: save checksums for go.mod files needed for go version lines

When we load a package from a module, we need the go version line from
that module's go.mod file to know what language semantics to use for
the package. We need to save a checksum for the go.mod file even if
the module's requirements are pruned out of the module graph.
Previously, we were missing checksums for test dependencies of
packages in 'all' and packages passed to 'go get -t'.

This change preserves the existing bug for 'go mod tidy',
but fixes it for 'go get -t' and flags the missing checksum
with a clearer error in other cases.

Fixes #60000.
Updates #56222.

Change-Id: Icd6acce348907621ae0b02dbeac04fb180353dcf
(cherry picked from CL 489075 and CL 492741)
Reviewed-on: https://go-review.googlesource.com/c/go/+/492983
Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Bryan Mills <bcmills@google.com>

17 files changed, 162 insertions, 27 deletions

diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 0be3d987075..dfb58c28ebf 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -643,7 +643,7 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 				} else {
 					pmain, ptest, pxtest, err = load.TestPackagesFor(ctx, pkgOpts, p, nil)
 					if err != nil {
-						base.Errorf("can't load test package: %s", err)
+						base.Errorf("go: can't load test package: %s", err)
 					}
 				}
 				if pmain != nil {
diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index f2c7592a284..8f77cd7d72d 100644
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -248,7 +248,13 @@ func (e *invalidImportError) Unwrap() error {
 // If the package is present in exactly one module, importFromModules will
 // return the module, its root directory, and a list of other modules that
 // lexically could have provided the package but did not.
-func importFromModules(ctx context.Context, path string, rs *Requirements, mg *ModuleGraph) (m module.Version, modroot, dir string, altMods []module.Version, err error) {
+//
+// If skipModFile is true, the go.mod file for the package is not loaded. This
+// allows 'go mod tidy' to preserve a minor checksum-preservation bug
+// (https://go.dev/issue/56222) for modules with 'go' versions between 1.17 and
+// 1.20, preventing unnecessary go.sum churn and network access in those
+// modules.
+func importFromModules(ctx context.Context, path string, rs *Requirements, mg *ModuleGraph, skipModFile bool) (m module.Version, modroot, dir string, altMods []module.Version, err error) {
 	invalidf := func(format string, args ...interface{}) (module.Version, string, string, []module.Version, error) {
 		return module.Version{}, "", "", nil, &invalidImportError{
 			importPath: path,
@@ -412,6 +418,18 @@ func importFromModules(ctx context.Context, path string, rs *Requirements, mg *M
 		}
 
 		if len(mods) == 1 {
+			// We've found the unique module containing the package.
+			// However, in order to actually compile it we need to know what
+			// Go language version to use, which requires its go.mod file.
+			//
+			// If the module graph is pruned and this is a test-only dependency
+			// of a package in "all", we didn't necessarily load that file
+			// when we read the module graph, so do it now to be sure.
+			if !skipModFile && cfg.BuildMod != "vendor" && mods[0].Path != "" && !MainModules.Contains(mods[0].Path) {
+				if _, err := goModSummary(mods[0]); err != nil {
+					return module.Version{}, "", "", nil, err
+				}
+			}
 			return mods[0], roots[0], dirs[0], altMods, nil
 		}
 
diff --git a/src/cmd/go/internal/modload/init.go b/src/cmd/go/internal/modload/init.go
index f960edd251d..68f5f7ae40e 100644
--- a/src/cmd/go/internal/modload/init.go
+++ b/src/cmd/go/internal/modload/init.go
@@ -1571,7 +1571,8 @@ func commitRequirements(ctx context.Context) (err error) {
 // keepSums returns the set of modules (and go.mod file entries) for which
 // checksums would be needed in order to reload the same set of packages
 // loaded by the most recent call to LoadPackages or ImportFromFiles,
-// including any go.mod files needed to reconstruct the MVS result,
+// including any go.mod files needed to reconstruct the MVS result
+// or identify go versions,
 // in addition to the checksums for every module in keepMods.
 func keepSums(ctx context.Context, ld *loader, rs *Requirements, which whichSums) map[module.Version]bool {
 	// Every module in the full module graph contributes its requirements,
@@ -1593,6 +1594,16 @@ func keepSums(ctx context.Context, ld *loader, rs *Requirements, which whichSums
 				continue
 			}
 
+			// We need the checksum for the go.mod file for pkg.mod
+			// so that we know what Go version to use to compile pkg.
+			// However, we didn't do so before Go 1.21, and the bug is relatively
+			// minor, so we maintain the previous (buggy) behavior in 'go mod tidy' to
+			// avoid introducing unnecessary churn.
+			if !ld.Tidy || semver.Compare("v"+ld.GoVersion, tidyGoModSumVersionV) >= 0 {
+				r := resolveReplacement(pkg.mod)
+				keep[modkey(r)] = true
+			}
+
 			if rs.pruning == pruned && pkg.mod.Path != "" {
 				if v, ok := rs.rootSelected(pkg.mod.Path); ok && v == pkg.mod.Version {
 					// pkg was loaded from a root module, and because the main module has
@@ -1648,6 +1659,7 @@ func keepSums(ctx context.Context, ld *loader, rs *Requirements, which whichSums
 		if which == addBuildListZipSums {
 			for _, m := range mg.BuildList() {
 				r := resolveReplacement(m)
+				keep[modkey(r)] = true // we need the go version from the go.mod file to do anything useful with the zipfile
 				keep[r] = true
 			}
 		}
diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index ba85dc2438c..b4c018e8c97 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -842,6 +842,10 @@ type loader struct {
 	// transitively *imported by* the packages and tests in the main module.)
 	allClosesOverTests bool
 
+	// skipImportModFiles indicates whether we may skip loading go.mod files
+	// for imported packages (as in 'go mod tidy' in Go 1.17–1.20).
+	skipImportModFiles bool
+
 	work *par.Queue
 
 	// reset on each iteration
@@ -1022,6 +1026,10 @@ func loadFromRoots(ctx context.Context, params loaderParams) *loader {
 			// version higher than the go.mod version adds nothing.
 			ld.TidyCompatibleVersion = ld.GoVersion
 		}
+
+		if semver.Compare("v"+ld.GoVersion, tidyGoModSumVersionV) < 0 {
+			ld.skipImportModFiles = true
+		}
 	}
 
 	if semver.Compare("v"+ld.GoVersion, narrowAllVersionV) < 0 && !ld.UseVendorAll {
@@ -1402,7 +1410,7 @@ func (ld *loader) updateRequirements(ctx context.Context) (changed bool, err err
 				//
 				// In some sense, we can think of this as ‘upgraded the module providing
 				// pkg.path from "none" to a version higher than "none"’.
-				if _, _, _, _, err = importFromModules(ctx, pkg.path, rs, nil); err == nil {
+				if _, _, _, _, err = importFromModules(ctx, pkg.path, rs, nil, ld.skipImportModFiles); err == nil {
 					changed = true
 					break
 				}
@@ -1613,7 +1621,7 @@ func (ld *loader) preloadRootModules(ctx context.Context, rootPkgs []string) (ch
 			// If the main module is tidy and the package is in "all" — or if we're
 			// lucky — we can identify all of its imports without actually loading the
 			// full module graph.
-			m, _, _, _, err := importFromModules(ctx, path, ld.requirements, nil)
+			m, _, _, _, err := importFromModules(ctx, path, ld.requirements, nil, ld.skipImportModFiles)
 			if err != nil {
 				var missing *ImportMissingError
 				if errors.As(err, &missing) && ld.ResolveMissingImports {
@@ -1701,7 +1709,7 @@ func (ld *loader) load(ctx context.Context, pkg *loadPkg) {
 	}
 
 	var modroot string
-	pkg.mod, modroot, pkg.dir, pkg.altMods, pkg.err = importFromModules(ctx, pkg.path, ld.requirements, mg)
+	pkg.mod, modroot, pkg.dir, pkg.altMods, pkg.err = importFromModules(ctx, pkg.path, ld.requirements, mg, ld.skipImportModFiles)
 	if pkg.dir == "" {
 		return
 	}
@@ -1960,7 +1968,7 @@ func (ld *loader) checkTidyCompatibility(ctx context.Context, rs *Requirements)
 
 		pkg := pkg
 		ld.work.Add(func() {
-			mod, _, _, _, err := importFromModules(ctx, pkg.path, rs, mg)
+			mod, _, _, _, err := importFromModules(ctx, pkg.path, rs, mg, ld.skipImportModFiles)
 			if mod != pkg.mod {
 				mismatches := <-mismatchMu
 				mismatches[pkg] = mismatch{mod: mod, err: err}
diff --git a/src/cmd/go/internal/modload/modfile.go b/src/cmd/go/internal/modload/modfile.go
index 75c278a7dfd..8fe19cc4d9b 100644
--- a/src/cmd/go/internal/modload/modfile.go
+++ b/src/cmd/go/internal/modload/modfile.go
@@ -45,6 +45,13 @@ const (
 	// "// indirect" dependencies are added in a block separate from the direct
 	// ones. See https://golang.org/issue/45965.
 	separateIndirectVersionV = "v1.17"
+
+	// tidyGoModSumVersionV is the Go version (plus leading "v") at which
+	// 'go mod tidy' preserves go.mod checksums needed to build test dependencies
+	// of packages in "all", so that 'go test all' can be run without checksum
+	// errors.
+	// See https://go.dev/issue/56222.
+	tidyGoModSumVersionV = "v1.21"
 )
 
 // ReadModFile reads and parses the mod file at gomod. ReadModFile properly applies the
@@ -566,6 +573,8 @@ func goModSummary(m module.Version) (*modFileSummary, error) {
 		summary := &modFileSummary{
 			module: module.Version{Path: m.Path},
 		}
+
+		readVendorList(MainModules.mustGetSingleMainModule())
 		if vendorVersion[m.Path] != m.Version {
 			// This module is not vendored, so packages cannot be loaded from it and
 			// it cannot be relevant to the build.
@@ -574,8 +583,6 @@ func goModSummary(m module.Version) (*modFileSummary, error) {
 
 		// For every module other than the target,
 		// return the full list of modules from modules.txt.
-		readVendorList(MainModules.mustGetSingleMainModule())
-
 		// We don't know what versions the vendored module actually relies on,
 		// so assume that it requires everything.
 		summary.require = vendorList
@@ -586,7 +593,7 @@ func goModSummary(m module.Version) (*modFileSummary, error) {
 	if HasModRoot() && cfg.BuildMod == "readonly" && !inWorkspaceMode() && actual.Version != "" {
 		key := module.Version{Path: actual.Path, Version: actual.Version + "/go.mod"}
 		if !modfetch.HaveSum(key) {
-			suggestion := fmt.Sprintf("; to add it:\n\tgo mod download %s", m.Path)
+			suggestion := fmt.Sprintf(" for go.mod file; to add it:\n\tgo mod download %s", m.Path)
 			return nil, module.VersionError(actual, &sumMissingError{suggestion: suggestion})
 		}
 	}
diff --git a/src/cmd/go/testdata/mod/example.com_generics_v1.0.0.txt b/src/cmd/go/testdata/mod/example.com_generics_v1.0.0.txt
new file mode 100644
index 00000000000..092241e93b2
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.com_generics_v1.0.0.txt
@@ -0,0 +1,21 @@
+example.com/generics v1.0.0
+written by hand
+
+-- .mod --
+module example.com/generics
+
+go 1.18
+-- .info --
+{"Version":"v1.0.0"}
+-- go.mod --
+module example.com/generics
+
+go 1.18
+-- generics.go --
+package generics
+
+type Int interface {
+	~int
+}
+
+func Bar() {}
\ No newline at end of file
diff --git a/src/cmd/go/testdata/script/list_parse_err.txt b/src/cmd/go/testdata/script/list_parse_err.txt
index 3c5345801a2..0a3eb02c045 100644
--- a/src/cmd/go/testdata/script/list_parse_err.txt
+++ b/src/cmd/go/testdata/script/list_parse_err.txt
@@ -4,9 +4,9 @@ stderr '^p[/\\]b.go:2:2: expected ''package'', found ''EOF''$'
 ! go list -f '{{range .Imports}}{{.}} {{end}}' ./p
 stderr '^p[/\\]b.go:2:2: expected ''package'', found ''EOF''$'
 ! go list -test ./t
-stderr '^can''t load test package: t[/\\]t_test.go:8:1: expected declaration, found ʕ'
+stderr '^go: can''t load test package: t[/\\]t_test.go:8:1: expected declaration, found ʕ'
 ! go list -test -f '{{range .Imports}}{{.}} {{end}}' ./t
-stderr '^can''t load test package: t[/\\]t_test.go:8:1: expected declaration, found ʕ'
+stderr '^go: can''t load test package: t[/\\]t_test.go:8:1: expected declaration, found ʕ'
 
 # 'go list -e' should report imports, even if some files have parse errors
 # before the import block.
diff --git a/src/cmd/go/testdata/script/mod_install_pkg_version.txt b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
index e3f59fc1528..53c3e4134b2 100644
--- a/src/cmd/go/testdata/script/mod_install_pkg_version.txt
+++ b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
@@ -16,7 +16,8 @@ env GO111MODULE=auto
 cd m
 cp go.mod go.mod.orig
 ! go list -m all
-stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: reading http.*/mod/example.com/cmd/@v/v1.1.0-doesnotexist.info: 404 Not Found\n\tserver response: 404 page not found$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry for go.mod file; to add it:\n\tgo mod download example.com/cmd$'
 go install example.com/cmd/a@latest
 cmp go.mod go.mod.orig
 exists $GOPATH/bin/a$GOEXE
diff --git a/src/cmd/go/testdata/script/mod_list_sums.txt b/src/cmd/go/testdata/script/mod_list_sums.txt
index 6c2f57c2b2d..cf1c18b575f 100644
--- a/src/cmd/go/testdata/script/mod_list_sums.txt
+++ b/src/cmd/go/testdata/script/mod_list_sums.txt
@@ -29,4 +29,4 @@ stderr '^go: updates to go.sum needed, disabled by -mod=readonly$'
 #
 # TODO(#41297): This should not be an error either.
 ! go list -m -mod=readonly -versions rsc.io/sampler
-stderr '^go: rsc\.io/quote@v1\.5\.1: missing go\.sum entry; to add it:\n\tgo mod download rsc\.io/quote$'
+stderr '^go: rsc\.io/quote@v1\.5\.1: missing go\.sum entry for go.mod file; to add it:\n\tgo mod download rsc\.io/quote$'
diff --git a/src/cmd/go/testdata/script/mod_run_pkg_version.txt b/src/cmd/go/testdata/script/mod_run_pkg_version.txt
index c3a218d553d..969852c1eee 100644
--- a/src/cmd/go/testdata/script/mod_run_pkg_version.txt
+++ b/src/cmd/go/testdata/script/mod_run_pkg_version.txt
@@ -21,7 +21,8 @@ env GO111MODULE=on
 cd m
 cp go.mod go.mod.orig
 ! go list -m all
-stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: reading http.*/mod/example\.com/cmd/@v/v1.1.0-doesnotexist.info: 404 Not Found\n\tserver response: 404 page not found$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry for go.mod file; to add it:\n\tgo mod download example.com/cmd$'
 go run example.com/cmd/a@v1.0.0
 stdout '^a@v1.0.0$'
 cmp go.mod go.mod.orig
diff --git a/src/cmd/go/testdata/script/mod_sum_issue56222.txt b/src/cmd/go/testdata/script/mod_sum_issue56222.txt
new file mode 100644
index 00000000000..841553941e3
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_sum_issue56222.txt
@@ -0,0 +1,67 @@
+# Regression test for #56222: 'go get -t' and 'go mod tidy'
+# should save enough checksums to run 'go test' on the named
+# packages or any package in "all" respectively.
+
+# At go 1.19 or earlier, 'go mod tidy' should preserve the historical go.sum
+# contents, but 'go test' should flag the missing checksums (instead of trying
+# to build the test dependency with the wrong language version).
+
+cd m1
+go mod tidy
+! go test -o $devnull -c example.com/m2/q
+stderr '^# example.com/m2/q\n'..${/}m2${/}q${/}'q_test.go:3:8: example.com/generics@v1.0.0: missing go.sum entry for go.mod file; to add it:\n\tgo mod download example.com/generics$'
+
+go mod download -json example.com/generics
+go list -f '{{if eq .ImportPath "example.com/generics"}}{{.Module.GoVersion}}{{end}}' -deps -test example.com/m2/q
+stdout 1.18
+
+
+# Even at go 1.19 or earlier, 'go mod tidy' shouldn't need go.mod files or
+# checksums that it won't record.
+
+go mod tidy -go=1.19
+go clean -modcache  # Remove checksums from the module cache, so that only go.sum is used.
+
+env OLDSUMDB=$GOSUMDB
+env GOSUMDB=bad
+go mod tidy
+
+env GOSUMDB=$OLDSUMDB
+
+
+# Regardless of the go version in go.mod, 'go get -t' should fetch
+# enough checksums to run 'go test' on the named package.
+
+rm p
+go mod tidy -go=1.19
+go list -m all
+! stdout example.com/generics
+go get -t example.com/m2/q@v1.0.0
+go list -f '{{if eq .ImportPath "example.com/generics"}}{{.Module.GoVersion}}{{end}}' -deps -test example.com/m2/q
+stdout 1.18
+[!short] go test -o $devnull -c example.com/m2/q
+
+
+-- m1/go.mod --
+module example.com/m1
+
+go 1.19
+
+require example.com/m2 v1.0.0
+replace example.com/m2 => ../m2
+-- m1/p/p.go --
+package p
+
+import _ "example.com/m2/q"
+-- m2/go.mod --
+module example.com/m2
+
+go 1.19
+
+require example.com/generics v1.0.0
+-- m2/q/q.go --
+package q
+-- m2/q/q_test.go --
+package q
+
+import _ "example.com/generics"
diff --git a/src/cmd/go/testdata/script/mod_sum_readonly.txt b/src/cmd/go/testdata/script/mod_sum_readonly.txt
index 57c5bbeefdf..c4260739e27 100644
--- a/src/cmd/go/testdata/script/mod_sum_readonly.txt
+++ b/src/cmd/go/testdata/script/mod_sum_readonly.txt
@@ -4,7 +4,7 @@ env GO111MODULE=on
 # When a sum is needed to load the build list, we get an error for the
 # specific module. The .mod file is not downloaded, and go.sum is not written.
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry for go.mod file; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 ! exists go.sum
 
@@ -12,7 +12,7 @@ stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod dow
 # we should see the same error.
 cp go.sum.h2only go.sum
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry for go.mod file; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 cmp go.sum go.sum.h2only
 rm go.sum
@@ -21,7 +21,7 @@ rm go.sum
 cp go.mod go.mod.orig
 go mod edit -replace rsc.io/quote@v1.5.2=rsc.io/quote@v1.5.1
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry for go.mod file; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.1.mod
 ! exists go.sum
 cp go.mod.orig go.mod
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat.txt b/src/cmd/go/testdata/script/mod_tidy_compat.txt
index 18b297da60e..724c83e14ee 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat.txt
@@ -50,7 +50,7 @@ cmp stdout m_all.txt
 
 go mod edit -go=1.16
 ! go list -m all
-stderr '^go: example.net/lazy@v0.1.0 requires\n\texample.com/version@v1.0.1: missing go.sum entry; to add it:\n\tgo mod download example.com/version$'
+stderr '^go: example.net/lazy@v0.1.0 requires\n\texample.com/version@v1.0.1: missing go.sum entry for go.mod file; to add it:\n\tgo mod download example.com/version$'
 
 
 -- go.mod --
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt b/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
index a45de5ad8cd..8f29f74875a 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
@@ -62,7 +62,7 @@ cmp stdout all-m.txt
 
 go mod edit -go=1.16
 ! go list -m all
-stderr '^go: example\.net/indirect@v0\.1\.0 requires\n\texample\.net/ambiguous@v0\.1\.0: missing go\.sum entry; to add it:\n\tgo mod download example\.net/ambiguous\n'
+stderr '^go: example\.net/indirect@v0\.1\.0 requires\n\texample\.net/ambiguous@v0\.1\.0: missing go\.sum entry for go\.mod file; to add it:\n\tgo mod download example\.net/ambiguous\n'
 
 
 -- go.mod --
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat_implicit.txt b/src/cmd/go/testdata/script/mod_tidy_compat_implicit.txt
index 186a3f8e672..8b5869780c2 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat_implicit.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat_implicit.txt
@@ -45,14 +45,14 @@ go mod tidy -compat=1.17
 ! stderr .
 cmp go.mod go.mod.orig
 
-go list -deps -test -f $MODFMT all
-stdout '^example\.com/retract/incompatible v1\.0\.0$'
+go list -deps -test -f $MODFMT ./...
+stdout '^example.net/lazy v0.1.0$'
 
 go mod edit -go=1.16
-! go list -deps -test -f $MODFMT all
+! go list -deps -test -f $MODFMT ./...
 
 	# TODO(#46160): -count=1 instead of -count=2.
-stderr -count=2 '^go: example\.net/lazy@v0\.1\.0 requires\n\texample\.com/retract/incompatible@v1\.0\.0: missing go\.sum entry; to add it:\n\tgo mod download example\.com/retract/incompatible$'
+stderr -count=2 '^go: example\.net/lazy@v0\.1\.0 requires\n\texample\.com/retract/incompatible@v1\.0\.0: missing go\.sum entry for go\.mod file; to add it:\n\tgo mod download example\.com/retract/incompatible$'
 
 
 # If we combine a Go 1.16 go.sum file...
@@ -63,7 +63,7 @@ cp go.mod.orig go.mod
 
 # ...then Go 1.17 no longer works. 😞
 ! go list -deps -test -f $MODFMT all
-stderr -count=1 '^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$'
+stderr -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$'
 
 
 # However, if we take the union of the go.sum files...
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat_incompatible.txt b/src/cmd/go/testdata/script/mod_tidy_compat_incompatible.txt
index 11313f144c3..1fef4b629c6 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat_incompatible.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat_incompatible.txt
@@ -49,7 +49,7 @@ cmp go.mod go.mod.orig
 go mod edit -go=1.16
 ! go list -f $MODFMT -deps ./...
 	# TODO(#46160): -count=1 instead of -count=2.
-stderr -count=2 '^go: example\.net/lazy@v0\.1\.0 requires\n\texample\.net/requireincompatible@v0\.1\.0 requires\n\texample\.com/retract/incompatible@v2\.0\.0\+incompatible: missing go.sum entry; to add it:\n\tgo mod download example.com/retract/incompatible$'
+stderr -count=2 '^go: example\.net/lazy@v0\.1\.0 requires\n\texample\.net/requireincompatible@v0\.1\.0 requires\n\texample\.com/retract/incompatible@v2\.0\.0\+incompatible: missing go.sum entry for go.mod file; to add it:\n\tgo mod download example.com/retract/incompatible$'
 
 
 # There are two ways for the module author to bring the two into alignment.
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat_irrelevant.txt b/src/cmd/go/testdata/script/mod_tidy_compat_irrelevant.txt
index 7c22fca6c0f..59926d06d69 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat_irrelevant.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat_irrelevant.txt
@@ -48,7 +48,7 @@ cmp stdout out-117.txt
 go mod edit -go=1.16
 ! go list -deps -test -f $MODFMT all
 	# TODO(#46160): -count=1 instead of -count=2.
-stderr -count=2 '^go: example.net/lazy@v0.1.0 requires\n\texample.com/retract/incompatible@v1.0.0: missing go.sum entry; to add it:\n\tgo mod download example.com/retract/incompatible$'
+stderr -count=2 '^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$'
 
 
 -- go.mod --