cmd/go: include test deps in buildinfo

Fixes #76926

Change-Id: I822dd6363dea1c4ad73df5958964c1bfe2c46d19
Reviewed-on: https://go-review.googlesource.com/c/go/+/756240
Reviewed-by: Michael Matloob <matloob@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/go/internal/load/test.go

@@ -294,15 +294,6 @@ func TestPackagesAndErrors(loaderstate *modload.State, ctx context.Context, done
 
 	pb := p.Internal.Build
 	pmain.DefaultGODEBUG = defaultGODEBUG(loaderstate, pmain, pb.Directives, pb.TestDirectives, pb.XTestDirectives)
-	if !opts.SuppressBuildInfo && (pmain.Internal.BuildInfo == nil || pmain.DefaultGODEBUG != p.DefaultGODEBUG) {
-		// Either we didn't generate build info for the package under test (because it wasn't package main), or
-		// the DefaultGODEBUG used to build the test main package is different from the DefaultGODEBUG
-		// used to build the package under test. If we didn't set build info for the package under test
-		// pmain won't have buildinfo set (since we copy it from the package under test). If the default GODEBUG
-		// used for the package under test is different from that of the test main, the BuildInfo assigned above from the package
-		// under test incorrect for the test main package. Either set or correct pmain's build info.
-		pmain.setBuildInfo(ctx, loaderstate.Fetcher(), opts.AutoVCS)
-	}
 
 	// The generated main also imports testing, regexp, and os.
 	// Also the linker introduces implicit dependencies reported by LinkerDeps.
@@ -379,6 +370,15 @@ func TestPackagesAndErrors(loaderstate *modload.State, ctx context.Context, done
 			ptest.Incomplete = true
 		}
 
+		if !opts.SuppressBuildInfo {
+			// Now that pmain.Internal.Imports includes the test dependencies,
+			// regenerate build info for the test binary. We can't reuse p's
+			// build info because the test variants of packages can add
+			// packages from modules that don't already have transitive
+			// imports from p.
+			pmain.setBuildInfo(ctx, loaderstate.Fetcher(), opts.AutoVCS)
+		}
+
 		if cover != nil {
 			// Here ptest needs to inherit the proper coverage mode (since
 			// it contains p's Go files), whereas pmain contains only

src/cmd/go/testdata/script/test_buildinfo.txt

@@ -4,15 +4,20 @@
 [short] skip 'invokes go test'
 
 go mod init foo
+go get example.com/version@v1.0.0
+
 go test -v
 stdout '(devel)'
+stdout 'example.com/version v1.0.0'
 
 -- foo_test.go --
-package foo_test
+package foo
 
 import (
         "runtime/debug"
         "testing"
+
+        _ "example.com/version"
 )
 
 func TestBuildInfo(t *testing.T) {
@@ -21,4 +26,8 @@ func TestBuildInfo(t *testing.T) {
                 t.Fatal("no debug info")
         }
         t.Log(info.Main.Version)
-}
+
+        for _, d := range info.Deps {
+                t.Log(d.Path, d.Version)
+        }
+}