core_dsl: disable Getwd() with environment variable (#1357)

os.Getwd() calls os.Getenv("PWD"), which can change from run to run if
you are using a test suite runner like e.g. Buildkite. Because test
caching relies on environment variables being the same from run to
run, this facile change breaks test caching.

Fixes #1355.

core_dsl.go

@@ -292,7 +292,7 @@ func RunSpecs(t GinkgoTestingT, description string, args ...interface{}) bool {
 
 	err = global.Suite.BuildTree()
 	exitIfErr(err)
-	suitePath, err := os.Getwd()
+	suitePath, err := getwd()
 	exitIfErr(err)
 	suitePath, err = filepath.Abs(suitePath)
 	exitIfErr(err)
@@ -345,6 +345,15 @@ func extractSuiteConfiguration(args []interface{}) Labels {
 	return suiteLabels
 }
 
+func getwd() (string, error) {
+	if !strings.EqualFold(os.Getenv("GINKGO_PRESERVE_CACHE"), "true") {
+		// Getwd calls os.Getenv("PWD"), which breaks test caching if the cache
+		// is shared between two different directories with the same test code.
+		return os.Getwd()
+	}
+	return "", nil
+}
+
 /*
 PreviewSpecs walks the testing tree and produces a report without actually invoking the specs.
 See http://onsi.github.io/ginkgo/#previewing-specs for more information.
@@ -369,7 +378,7 @@ func PreviewSpecs(description string, args ...any) Report {
 
 	err = global.Suite.BuildTree()
 	exitIfErr(err)
-	suitePath, err := os.Getwd()
+	suitePath, err := getwd()
 	exitIfErr(err)
 	suitePath, err = filepath.Abs(suitePath)
 	exitIfErr(err)