1 files changed, 60 insertions, 0 deletions
diff --git a/go/tools/bzltestutil/init.go b/go/tools/bzltestutil/init.go
new file mode 100644
index 00000000..ca9852ed
--- /dev/null
+++ b/go/tools/bzltestutil/init.go
@@ -0,0 +1,60 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package bzltestutil
+
+// This package must have no deps beyond Go SDK.
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+var (
+	// Initialized by linker.
+	RunDir string
+
+	// Initial working directory.
+	testExecDir string
+)
+
+// This initializer runs before any user packages.
+func init() {
+	var err error
+	testExecDir, err = os.Getwd()
+	if err != nil {
+		panic(err)
+	}
+
+	// Check if we're being run by Bazel and change directories if so.
+	// TEST_SRCDIR and TEST_WORKSPACE are set by the Bazel test runner, so that makes a decent proxy.
+	testSrcDir, hasSrcDir := os.LookupEnv("TEST_SRCDIR")
+	testWorkspace, hasWorkspace := os.LookupEnv("TEST_WORKSPACE")
+	if hasSrcDir && hasWorkspace && RunDir != "" {
+		abs := RunDir
+		if !filepath.IsAbs(RunDir) {
+			abs = filepath.Join(testSrcDir, testWorkspace, RunDir)
+		}
+		err := os.Chdir(abs)
+		// Ignore the Chdir err when on Windows, since it might have have runfiles symlinks.
+		// https://github.com/bazelbuild/rules_go/pull/1721#issuecomment-422145904
+		if err != nil && runtime.GOOS != "windows" {
+			panic(fmt.Sprintf("could not change to test directory: %v", err))
+		}
+		if err == nil {
+			os.Setenv("PWD", abs)
+		}
+	}
+}