cmd/go: populate build info for test mains

Before this change, test binaries didn't have build info populated on them
unless they were tests for package main. Now we generate them for all
test binaries so that they can be inspected like other binaries.

We don't need to add the default GODEBUG in printLinkerConfig because it
will now always be present on the build info, and when build info is
present we use it to generate the hash.

Fixes #33976

Change-Id: Ib4f51c04f87df3c7f2f21c400ab446e70d66a101
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-windows-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/613096
Auto-Submit: Michael Matloob <[email protected]>
Reviewed-by: Sam Thanawalla <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: matloob

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

@@ -293,14 +293,13 @@ func TestPackagesAndErrors(ctx context.Context, done func(), opts PackageOpts, p
 
 	pb := p.Internal.Build
 	pmain.DefaultGODEBUG = defaultGODEBUG(pmain, pb.Directives, pb.TestDirectives, pb.XTestDirectives)
-	if pmain.Internal.BuildInfo != nil && pmain.DefaultGODEBUG != p.DefaultGODEBUG {
-		// The DefaultGODEBUG used to build the test main package is different from the DefaultGODEBUG
-		// used to build the package under test. That makes the BuildInfo assigned above from the package
-		// under test incorrect for the test main package. Recompute the build info for the test main
-		// package to incorporate the test main's DefaultGODEBUG value.
-		// Most test binaries do not have build info: p.Internal.BuildInfo is only computed for main
-		// packages, so ptest only inherits a non-nil BuildInfo value if the test is for package main.
-		// See issue #68053.
+	if 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, opts.AutoVCS)
 	}
 

src/cmd/go/internal/work/exec.go

@@ -1425,14 +1425,6 @@ func (b *Builder) printLinkerConfig(h io.Writer, p *load.Package) {
 			fmt.Fprintf(h, "GOEXPERIMENT=%q\n", cfg.CleanGOEXPERIMENT)
 		}
 
-		// The default godebug is embedded in the binary. For main packages it's
-		// already taken into account for the action id through the build info. But
-		// to make sure it's included for tests of other packages, where there's no
-		// build info, use it as part of the action id. See issue #69203.
-		if p != nil {
-			fmt.Fprintf(h, "default GODEBUG %q\n", p.DefaultGODEBUG)
-		}
-
 		// The linker writes source file paths that refer to GOROOT,
 		// but only if -trimpath is not specified (see [gctoolchain.ld] in gc.go).
 		gorootFinal := cfg.GOROOT

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

@@ -0,0 +1,24 @@
+# Ensure buildinfo is populated on test binaries even if they
+# are not tests for package main. See issue #33976.
+
+[short] skip 'invokes go test'
+
+go mod init foo
+go test -v
+stdout '(devel)'
+
+-- foo_test.go --
+package foo_test
+
+import (
+        "runtime/debug"
+        "testing"
+)
+
+func TestBuildInfo(t *testing.T) {
+        info, ok := debug.ReadBuildInfo()
+        if !ok {
+                t.Fatal("no debug info")
+        }
+        t.Log(info.Main.Version)
+}