Always attempt to set RUNFILES_DIR and JAVA_RUNFILES in runfiles.Env

These variables are needed by e.g. the Java launcher even when running
with a manifest file. Match the logic of the Bazel-provided runfiles
libraries.

go/runfiles/directory.go

@@ -23,8 +23,11 @@ type Directory string
 
 func (d Directory) new(sourceRepo SourceRepo) (*Runfiles, error) {
 	r := &Runfiles{
-		impl:       d,
-		env:        directoryVar + "=" + string(d),
+		impl: d,
+		env: []string{
+			directoryVar + "=" + string(d),
+			legacyDirectoryVar + "=" + string(d),
+		},
 		sourceRepo: string(sourceRepo),
 	}
 	err := r.loadRepoMapping()

go/runfiles/manifest.go

@@ -33,9 +33,24 @@ func (f ManifestFile) new(sourceRepo SourceRepo) (*Runfiles, error) {
 	if err != nil {
 		return nil, err
 	}
+	env := []string{
+		manifestFileVar + "=" + string(f),
+	}
+	// Certain tools (e.g., Java tools) may need the runfiles directory, so try to find it even if
+	// running with a manifest file.
+	if strings.HasSuffix(string(f), ".runfiles_manifest") ||
+		strings.HasSuffix(string(f), "/MANIFEST") ||
+		strings.HasSuffix(string(f), "\\MANIFEST") {
+		// Cut off either "_manifest" or "/MANIFEST" or "\\MANIFEST", all of length 9, from the end
+		// of the path to obtain the runfiles directory.
+		d := string(f)[:len(string(f))-len("_manifest")]
+		env = append(env,
+			directoryVar+"="+d,
+			legacyDirectoryVar+"="+d)
+	}
 	r := &Runfiles{
 		impl:       m,
-		env:        manifestFileVar + "=" + string(f),
+		env:        env,
 		sourceRepo: string(sourceRepo),
 	}
 	err = r.loadRepoMapping()

go/runfiles/runfiles.go

@@ -14,19 +14,19 @@
 
 // Package runfiles provides access to Bazel runfiles.
 //
-// Usage
+// # Usage
 //
 // This package has two main entry points, the global functions Rlocation and Env,
 // and the Runfiles type.
 //
-// Global functions
+// # Global functions
 //
 // For simple use cases that don’t require hermetic behavior, use the Rlocation and
 // Env functions to access runfiles.  Use Rlocation to find the filesystem location
 // of a runfile, and use Env to obtain environmental variables to pass on to
 // subprocesses.
 //
-// Runfiles type
+// # Runfiles type
 //
 // If you need hermetic behavior or want to change the runfiles discovery
 // process, use New to create a Runfiles object.  New accepts a few options to
@@ -45,8 +45,9 @@ import (
 )
 
 const (
-	directoryVar    = "RUNFILES_DIR"
-	manifestFileVar = "RUNFILES_MANIFEST_FILE"
+	directoryVar       = "RUNFILES_DIR"
+	legacyDirectoryVar = "JAVA_RUNFILES"
+	manifestFileVar    = "RUNFILES_MANIFEST_FILE"
 )
 
 type repoMappingKey struct {
@@ -62,7 +63,7 @@ type Runfiles struct {
 	// We don’t need concurrency control since Runfiles objects are
 	// immutable once created.
 	impl        runfiles
-	env         string
+	env         []string
 	repoMapping map[repoMappingKey]string
 	sourceRepo  string
 }
@@ -198,10 +199,7 @@ func (r *Runfiles) loadRepoMapping() error {
 // The return value is a newly-allocated slice; you can modify it at will.  If
 // r is the zero Runfiles object, the return value is nil.
 func (r *Runfiles) Env() []string {
-	if r.env == "" {
-		return nil
-	}
-	return []string{r.env}
+	return r.env
 }
 
 // WithSourceRepo returns a Runfiles instance identical to the current one,

tests/runfiles/runfiles_test.go

@@ -19,6 +19,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strings"
 	"testing"
@@ -147,3 +148,42 @@ func TestRunfiles_manifestWithDir(t *testing.T) {
 		})
 	}
 }
+
+func TestRunfiles_dirEnv(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Windows doesn't have a runfiles directory by default")
+	}
+
+	dir := t.TempDir()
+	r, err := runfiles.New(runfiles.Directory(dir))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := []string{"RUNFILES_DIR=" + dir, "JAVA_RUNFILES=" + dir}
+	if !reflect.DeepEqual(r.Env(), want) {
+		t.Errorf("Env: got %v, want %v", r.Env(), want)
+	}
+}
+
+func TestRunfiles_manifestEnv(t *testing.T) {
+	tmp := t.TempDir()
+	dir := filepath.Join(tmp, "foo.runfiles")
+	err := os.Mkdir(dir, 0o755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	manifest := filepath.Join(tmp, "foo.runfiles_manifest")
+	if err = os.WriteFile(manifest, []byte("foo/dir path/to/foo/dir\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	r, err := runfiles.New(runfiles.ManifestFile(manifest))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := []string{"RUNFILES_MANIFEST_FILE=" + manifest, "RUNFILES_DIR=" + dir, "JAVA_RUNFILES=" + dir}
+	if !reflect.DeepEqual(r.Env(), want) {
+		t.Errorf("Env: got %v, want %v", r.Env(), want)
+	}
+}