cmd/go/internal/modload: implement the "all" pattern for lazy loading

The new semantics of the "all" package pattern can be implemented
without actually changing module loading per se. This change
implements those semantics, so that the change can be decoupled from
the changes to the module requirement graph.

For #36460

Change-Id: I0ee8b17afa8b728dc470a42a540fcc01764a4442
Reviewed-on: https://go-review.googlesource.com/c/go/+/240623
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

6 files changed, 154 insertions, 12 deletions

diff --git a/doc/go1.16.html b/doc/go1.16.html
index 0ffaecc5a9..95e63d0d5a 100644
--- a/doc/go1.16.html
+++ b/doc/go1.16.html
@@ -52,7 +52,7 @@ Do not send CLs removing the interior tags from such phrases.
   TODO: write and link to tutorial or blog post
 </p>
 
-<p><!-= golang.org/issue/29062 -->
+<p><!-- golang.org/issue/29062 -->
   When using <code>go test</code>, a test that
   calls <code>os.Exit(0)</code> during execution of a test function
   will now be considered to fail.
@@ -62,6 +62,18 @@ Do not send CLs removing the interior tags from such phrases.
   that is still considered to be a passing test.
 </p>
 
+<h4 id="all-pattern">The <code>all</code> pattern</h4>
+
+<p><!-- golang.org/cl/240623 -->
+  When the main module's <code>go.mod</code> file
+  declares <code>go</code> <code>1.16</code> or higher, the <code>all</code>
+  package pattern now matches only those packages that are transitively imported
+  by a package or test found in the main module. (Packages imported by <em>tests
+  of</em> packages imported by the main module are no longer included.) This is
+  the same set of packages retained
+  by <code>go</code> <code>mod</code> <code>vendor</code> since Go 1.11.
+</p>
+
 <p>
   TODO
 </p>
diff --git a/src/cmd/go/internal/modcmd/tidy.go b/src/cmd/go/internal/modcmd/tidy.go
index c7c53d7c0c..4dcb62e02f 100644
--- a/src/cmd/go/internal/modcmd/tidy.go
+++ b/src/cmd/go/internal/modcmd/tidy.go
@@ -40,6 +40,18 @@ func runTidy(ctx context.Context, cmd *base.Command, args []string) {
 		base.Fatalf("go mod tidy: no arguments allowed")
 	}
 
+	// Tidy aims to make 'go test' reproducible for any package in 'all', so we
+	// need to include test dependencies. For modules that specify go 1.15 or
+	// earlier this is a no-op (because 'all' saturates transitive test
+	// dependencies).
+	//
+	// However, with lazy loading (go 1.16+) 'all' includes only the packages that
+	// are transitively imported by the main module, not the test dependencies of
+	// those packages. In order to make 'go test' reproducible for the packages
+	// that are in 'all' but outside of the main module, we must explicitly
+	// request that their test dependencies be included.
+	modload.LoadTests = true
+
 	modload.LoadALL(ctx)
 	modload.TidyBuildList()
 	modload.TrimGoSum()
diff --git a/src/cmd/go/internal/modcmd/why.go b/src/cmd/go/internal/modcmd/why.go
index b16887d318..30b15fc153 100644
--- a/src/cmd/go/internal/modcmd/why.go
+++ b/src/cmd/go/internal/modcmd/why.go
@@ -65,6 +65,8 @@ func runWhy(ctx context.Context, cmd *base.Command, args []string) {
 	loadALL := modload.LoadALL
 	if *whyVendor {
 		loadALL = modload.LoadVendor
+	} else {
+		modload.LoadTests = true
 	}
 	if *whyM {
 		listU := false
diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 2096dfb636..9cedc219b6 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -231,7 +231,7 @@ func ImportPathsQuiet(ctx context.Context, patterns []string, tags map[string]bo
 	loaded = loadFromRoots(loaderParams{
 		tags:               tags,
 		allPatternIsRoot:   allPatternIsRoot,
-		allClosesOverTests: true, // until lazy loading in Go 1.16+
+		allClosesOverTests: index.allPatternClosesOverTests(),
 
 		listRoots: func() (roots []string) {
 			updateMatches(nil)
@@ -450,7 +450,7 @@ func ImportFromFiles(ctx context.Context, gofiles []string) {
 			roots = append(roots, testImports...)
 			return roots
 		},
-		allClosesOverTests: true, // until lazy loading.
+		allClosesOverTests: index.allPatternClosesOverTests(),
 	})
 	WriteGoMod()
 }
@@ -501,7 +501,7 @@ func ReloadBuildList() []module.Version {
 	loaded = loadFromRoots(loaderParams{
 		tags:               imports.Tags(),
 		listRoots:          func() []string { return nil },
-		allClosesOverTests: true, // until lazy loading, but doesn't matter because the root list is empty.
+		allClosesOverTests: index.allPatternClosesOverTests(), // but doesn't matter because the root list is empty.
 	})
 	return buildList
 }
@@ -512,9 +512,13 @@ func ReloadBuildList() []module.Version {
 // It adds modules to the build list as needed to satisfy new imports.
 // This set is useful for deciding whether a particular import is needed
 // anywhere in a module.
+//
+// In modules that specify "go 1.16" or higher, ALL follows only one layer of
+// test dependencies. In "go 1.15" or lower, ALL follows the imports of tests of
+// dependencies of tests.
 func LoadALL(ctx context.Context) []string {
 	InitMod(ctx)
-	return loadAll(ctx, true)
+	return loadAll(ctx, index.allPatternClosesOverTests())
 }
 
 // LoadVendor is like LoadALL but only follows test dependencies
@@ -523,7 +527,9 @@ func LoadALL(ctx context.Context) []string {
 // This set is useful for identifying the which packages to include in a vendor directory.
 func LoadVendor(ctx context.Context) []string {
 	InitMod(ctx)
-	return loadAll(ctx, false)
+	// 'go mod vendor' has never followed test dependencies since Go 1.11.
+	const closeOverTests = false
+	return loadAll(ctx, closeOverTests)
 }
 
 func loadAll(ctx context.Context, closeOverTests bool) []string {
diff --git a/src/cmd/go/internal/modload/modfile.go b/src/cmd/go/internal/modload/modfile.go
index a45c4a63be..18dd293ac9 100644
--- a/src/cmd/go/internal/modload/modfile.go
+++ b/src/cmd/go/internal/modload/modfile.go
@@ -25,6 +25,11 @@ import (
 	"golang.org/x/mod/semver"
 )
 
+// lazyLoadingVersion is the Go version (plus leading "v") at which lazy module
+// loading takes effect.
+const lazyLoadingVersionV = "v1.16"
+const go116EnableLazyLoading = true
+
 var modFile *modfile.File
 
 // A modFileIndex is an index of data corresponding to a modFile
@@ -249,6 +254,23 @@ func indexModFile(data []byte, modFile *modfile.File, needsFix bool) *modFileInd
 	return i
 }
 
+// allPatternClosesOverTests reports whether the "all" pattern includes
+// dependencies of tests outside the main module (as in Go 1.11–1.15).
+// (Otherwise — as in Go 1.16+ — the "all" pattern includes only the packages
+// transitively *imported by* the packages and tests in the main module.)
+func (i *modFileIndex) allPatternClosesOverTests() bool {
+	if !go116EnableLazyLoading {
+		return true
+	}
+	if i != nil && semver.Compare(i.goVersionV, lazyLoadingVersionV) < 0 {
+		// The module explicitly predates the change in "all" for lazy loading, so
+		// continue to use the older interpretation. (If i == nil, we not in any
+		// module at all and should use the latest semantics.)
+		return true
+	}
+	return false
+}
+
 // modFileIsDirty reports whether the go.mod file differs meaningfully
 // from what was indexed.
 // If modFile has been changed (even cosmetically) since it was first read,
diff --git a/src/cmd/go/testdata/script/mod_all.txt b/src/cmd/go/testdata/script/mod_all.txt
index 9f4b0a4e4d..aac66292d6 100644
--- a/src/cmd/go/testdata/script/mod_all.txt
+++ b/src/cmd/go/testdata/script/mod_all.txt
@@ -187,17 +187,105 @@ stdout '^example.com/main_test \[example.com/main.test\]$'
 stdout '^example.com/main/testonly.test$'
 stdout '^example.com/main/testonly_test \[example.com/main/testonly.test\]$'
 
-# TODO(#36460):
+rm vendor
+
+# Convert all modules to go 1.16 to enable lazy loading.
+go mod edit -go=1.16 a/go.mod
+go mod edit -go=1.16 b/go.mod
+go mod edit -go=1.16 c/go.mod
+go mod edit -go=1.16 d/go.mod
+go mod edit -go=1.16 q/go.mod
+go mod edit -go=1.16 r/go.mod
+go mod edit -go=1.16 s/go.mod
+go mod edit -go=1.16 t/go.mod
+go mod edit -go=1.16 u/go.mod
+go mod edit -go=1.16 w/go.mod
+go mod edit -go=1.16 x/go.mod
+go mod edit -go=1.16
+
+# With lazy loading, 'go list all' with neither -mod=vendor nor -test should
+# match -mod=vendor without -test in 1.15.
 
-# With lazy loading, 'go list all' without -mod=vendor should match
-# 'go mod vendor'.
+go list -f $PKGFMT all
+stdout -count=8 '^.'
+stdout '^example.com/a$'
+stdout '^example.com/b$'
+stdout '^example.com/main$'
+stdout '^example.com/main/testonly$'
+stdout '^example.com/q$'
+stdout '^example.com/r$'
+stdout '^example.com/t$'
+stdout '^example.com/u$'
 
-# 'go list -test all' should expand that to cover test dependencies
-# of packages imported by the main module.
+# 'go list -test all' should expand that to include the test variants of the
+# packages in 'all', but not the dependencies of outside tests.
 
-# 'go list -m all' should cover the packages in 'go list -test all'.
+go list -test -f $PKGFMT all
+stdout -count=25 '^.'
+stdout '^example.com/a$'
+stdout '^example.com/b$'
+stdout '^example.com/main$'
+stdout '^example.com/main/testonly$'
+stdout '^example.com/q$'
+stdout '^example.com/r$'
+stdout '^example.com/t$'
+stdout '^example.com/u$'
+stdout '^example.com/a.test$'
+stdout '^example.com/a_test \[example.com/a.test\]$'
+stdout '^example.com/b.test$'
+stdout '^example.com/b_test \[example.com/b.test\]$'
+stdout '^example.com/main.test$'
+stdout '^example.com/main \[example.com/main.test\]$'
+stdout '^example.com/main_test \[example.com/main.test\]$'
+stdout '^example.com/main/testonly.test$'
+stdout '^example.com/main/testonly_test \[example.com/main/testonly.test\]$'
+stdout '^example.com/q.test$'
+stdout '^example.com/q_test \[example.com/q.test\]$'
+stdout '^example.com/r.test$'
+stdout '^example.com/r_test \[example.com/r.test\]$'
+stdout '^example.com/t.test$'
+stdout '^example.com/t_test \[example.com/t.test\]$'
+stdout '^example.com/u.test$'
+stdout '^example.com/u_test \[example.com/u.test\]$'
+
+# 'go list -test -deps all' should include the dependencies of those tests,
+# but not the tests of the dependencies of outside tests.
+
+go list -test -deps -f $PKGFMT all
+stdout -count=28 '^.'
+stdout '^example.com/a$'
+stdout '^example.com/b$'
+stdout '^example.com/c$'
+stdout '^example.com/main$'
+stdout '^example.com/main/testonly$'
+stdout '^example.com/q$'
+stdout '^example.com/r$'
+stdout '^example.com/s$'
+stdout '^example.com/t$'
+stdout '^example.com/u$'
+stdout '^example.com/w$'
+stdout '^example.com/a.test$'
+stdout '^example.com/a_test \[example.com/a.test\]$'
+stdout '^example.com/b.test$'
+stdout '^example.com/b_test \[example.com/b.test\]$'
+stdout '^example.com/main.test$'
+stdout '^example.com/main \[example.com/main.test\]$'
+stdout '^example.com/main_test \[example.com/main.test\]$'
+stdout '^example.com/main/testonly.test$'
+stdout '^example.com/main/testonly_test \[example.com/main/testonly.test\]$'
+stdout '^example.com/q.test$'
+stdout '^example.com/q_test \[example.com/q.test\]$'
+stdout '^example.com/r.test$'
+stdout '^example.com/r_test \[example.com/r.test\]$'
+stdout '^example.com/t.test$'
+stdout '^example.com/t_test \[example.com/t.test\]$'
+stdout '^example.com/u.test$'
+stdout '^example.com/u_test \[example.com/u.test\]$'
 
 
+# TODO(#36460):
+# 'go list -m all' should exactly cover the packages in 'go list -test all'.
+
 -- go.mod --
 module example.com/main