Try a temporary directory if the user cache fails

Since commit 58c17f6 ("addr.Suggest should lock a file instead of
memory"), pkg/internal/testing/addr/manager.go’s init() function tries
to create a directory using either os.UserCacheDir() or os.TempDir(),
whichever succeeds first. In many build environments, $HOME is
non-empty but points to an unusable directory; in such cases,
os.UserCacheDir() returns an unusable directory, which causes init()
to panic.

This changes init() to first try os.UserCacheDir(), including creating
the desired directory; if that fails, the whole operation is tried
again with os.TempDir().

Fixes: #1799
Signed-off-by: Stephen Kitt <skitt@redhat.com>

pkg/internal/testing/addr/manager.go

@@ -42,16 +42,30 @@ var (
 )
 
 func init() {
-	baseDir, err := os.UserCacheDir()
+	var err error
+	cacheDir, err = tryUserCacheDir()
 	if err != nil {
-		baseDir = os.TempDir()
+		// Either we didn't get a cache directory, or we can't use it
+		cacheDir, err = tryCacheInDir(os.TempDir())
 	}
-	cacheDir = filepath.Join(baseDir, "kubebuilder-envtest")
-	if err := os.MkdirAll(cacheDir, 0750); err != nil {
+	if err != nil {
 		panic(err)
 	}
 }
 
+func tryUserCacheDir() (string, error) {
+	baseDir, err := os.UserCacheDir()
+	if err != nil {
+		return "", err
+	}
+	return tryCacheInDir(baseDir)
+}
+
+func tryCacheInDir(dir string) (string, error) {
+	dir = filepath.Join(dir, "kubebuilder-envtest")
+	return dir, os.MkdirAll(dir, 0o750)
+}
+
 type portCache struct{}
 
 func (c *portCache) add(port int) (bool, error) {