Fixes bug in error handling within the VerifyFileExists method

Fixes bug in error handling within the `VerifyFileExists` method that resulted in a panic when the error from os.Stat` was not `ErrNotExist`. The fix includes introducing the `CAKC058` error and log message for when the path to a file exists but is not a regular file.

CHANGELOG.md

@@ -5,6 +5,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+## Fixed
+- Fixes bug in error handling within the `VerifyFileExists` method that resulted in a
+  panic when the error from `os.Stat` was not `ErrNotExist`. The fix includes introducing
+  the `CAKC058` error and log message for when the path to a file exists but is not a
+  regular file.
+  [cyberark/conjur-authn-k8s-client#252](https://github.com/cyberark/conjur-authn-k8s-client/issues/252)
 
 ## [0.19.1] - 2021-02-08
 ### Changed

pkg/log/log_messages.go

@@ -70,3 +70,4 @@ const CAKC054 string = "CAKC054 Failed to delete file %s"
 const CAKC055 string = "CAKC055 Cert placement failed with the following error:\n%s"
 const CAKC056 string = "CAKC056 File %s does not exist"
 const CAKC057 string = "CAKC057 Removing file %s"
+const CAKC058 string = "CAKC058 Path exists but does not contain regular file: %s"

pkg/utils/file.go

@@ -47,10 +47,9 @@ func WaitForFile(
 
 func VerifyFileExists(path string) error {
 	info, err := os.Stat(path)
-	if !os.IsNotExist(err) && info.Mode().IsRegular() {
-		// No error, the file exists
-		return nil
+	if err == nil && !info.Mode().IsRegular() {
+		// Path exists but is not a regular file
+		err = log.RecordedError(log.CAKC058, path)
 	}
-
 	return err
 }

pkg/utils/file_test.go

@@ -73,12 +73,30 @@ func TestFile(t *testing.T) {
 			So(err, ShouldBeNil)
 		})
 
-		Convey("A non-existing file returns the error", func() {
+		Convey("A folder at the path returns an error", func() {
+			path := "/"
+			expectedOutput := fmt.Errorf(
+				"CAKC058 Path exists but does not contain regular file: %s",
+				path,
+			)
+
+			err := VerifyFileExists(path)
+
+			So(err, ShouldResemble, expectedOutput)
+		})
+
+		Convey("A non-existing file returns an error", func() {
 			path := "non/existing/path"
 
 			err := VerifyFileExists(path)
 
 			So(os.IsNotExist(err), ShouldBeTrue)
 		})
+
+		Convey("A non-ErrNotExist error is returned", func() {
+			err := VerifyFileExists("\000invalid")
+
+			So(err.Error(), ShouldResemble, "stat \x00invalid: invalid argument")
+		})
 	})
 }