Fix VAGRANT_CWD handling

VAGRANT_CWD was not being honored in the Go-side Vagrantfile-finding
code. Add that in and also fix a couple of bugs in the path walking
logic.

internal/config/path.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"fmt"
 	"os"
 
 	"github.com/hashicorp/vagrant-plugin-sdk/helper/path"
@@ -25,25 +26,37 @@ func GetVagrantfileName() string {
 // filename is empty, it will default to the Filename constant.
 func FindPath(dir path.Path, filename string) (p path.Path, err error) {
 	if dir == nil {
-		cwd, err := os.Getwd()
-		if err != nil {
-			return nil, err
+		cwd, ok := os.LookupEnv("VAGRANT_CWD")
+		if ok {
+			if _, err := os.Stat(cwd); os.IsNotExist(err) {
+				return nil, fmt.Errorf("VAGRANT_CWD set to path (%s) that does not exist", cwd)
+			} else {
+				dir = path.NewPath(cwd)
+			}
+		} else {
+			cwd, err := os.Getwd()
+			if err != nil {
+				return nil, err
+			}
+			dir = path.NewPath(cwd)
 		}
-		dir = path.NewPath(cwd)
 	}
 
 	if filename == "" {
 		filename = GetVagrantfileName()
 	}
 
+	p = dir
 	for {
-		p = dir.Join(filename)
+		p = p.Join(filename)
 		if _, err = os.Stat(p.String()); err == nil || !os.IsNotExist(err) {
 			return
 		}
-		if p.String() == p.Parent().String() {
+		// since we just tacked a filename on above, the first Parent() call is
+		// the directory of the file and the  second is the actual parent dir
+		if p.Parent().String() == p.Parent().Parent().String() {
 			return nil, nil
 		}
-		p = p.Parent()
+		p = p.Parent().Parent()
 	}
 }

internal/config/path_test.go

@@ -0,0 +1,127 @@
+package config
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/hashicorp/vagrant-plugin-sdk/helper/path"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFindPath(t *testing.T) {
+	t.Run("uses dir and filename args if passed and file exists", func(t *testing.T) {
+		require := require.New(t)
+
+		dir, err := ioutil.TempDir("", "test")
+		require.NoError(err)
+		defer os.RemoveAll(dir)
+
+		p := filepath.Join(dir, "MyCoolFile")
+		file, err := os.Create(p)
+		require.NoError(err)
+		file.Close()
+
+		out, err := FindPath(path.NewPath(dir), "MyCoolFile")
+		require.NoError(err)
+		require.Equal(p, out.String())
+	})
+
+	t.Run("when VAGRANT_CWD is not set", func(t *testing.T) {
+		oldVcwd, ok := os.LookupEnv("VAGRANT_CWD")
+		if ok {
+			os.Unsetenv("VAGRANT_CWD")
+			defer os.Setenv("VAGRANT_CWD", oldVcwd)
+		}
+
+		t.Run("uses cwd and Vagrantfile when blank args passed", func(t *testing.T) {
+			require := require.New(t)
+
+			dir, err := ioutil.TempDir("", "test")
+			require.NoError(err)
+			defer os.RemoveAll(dir)
+
+			p := filepath.Join(dir, "Vagrantfile")
+			file, err := os.Create(p)
+			require.NoError(err)
+			file.Close()
+
+			oldCwd, err := os.Getwd()
+			require.NoError(err)
+			os.Chdir(dir)
+			defer os.Chdir(oldCwd)
+
+			out, err := FindPath(nil, "")
+			require.NoError(err)
+			require.Equal(p, out.String())
+		})
+
+		t.Run("walks parent dirs looking for Vagrantfile", func(t *testing.T) {
+			require := require.New(t)
+
+			dir, err := ioutil.TempDir("", "test")
+			require.NoError(err)
+			defer os.RemoveAll(dir)
+
+			deepPath := path.NewPath(filepath.Join(dir, "a", "b"))
+			err = os.MkdirAll(deepPath.String(), 0700)
+			require.NoError(err)
+
+			notDeepFile := filepath.Join(dir, "Vagrantfile")
+			file, err := os.Create(notDeepFile)
+			require.NoError(err)
+			file.Close()
+
+			out, err := FindPath(deepPath, "")
+			require.NoError(err)
+			require.Equal(notDeepFile, out.String())
+		})
+
+		t.Run("returns nil if parent walk comes up empty", func(t *testing.T) {
+			require := require.New(t)
+
+			dir, err := ioutil.TempDir("", "test")
+			require.NoError(err)
+			defer os.RemoveAll(dir)
+
+			deepPath := path.NewPath(filepath.Join(dir, "a", "b"))
+			err = os.MkdirAll(deepPath.String(), 0700)
+			require.NoError(err)
+
+			out, err := FindPath(deepPath, "")
+			require.NoError(err)
+			require.Nil(out)
+		})
+	})
+
+	t.Run("honors VAGRANT_CWD if set and exists", func(t *testing.T) {
+		require := require.New(t)
+
+		dir, err := ioutil.TempDir("", "test")
+		require.NoError(err)
+		defer os.RemoveAll(dir)
+
+		os.Setenv("VAGRANT_CWD", dir)
+		defer os.Unsetenv("VAGRANT_CWD")
+
+		file, err := os.Create(filepath.Join(dir, "Vagrantfile"))
+		require.NoError(err)
+		file.Close()
+
+		out, err := FindPath(nil, "")
+		require.NoError(err)
+		require.Equal(filepath.Join(dir, "Vagrantfile"), out.String())
+	})
+
+	t.Run("errors if VAGRANT_CWD is set and does not exist", func(t *testing.T) {
+		require := require.New(t)
+
+		os.Setenv("VAGRANT_CWD", filepath.Join(os.TempDir(), "idontexit"))
+		defer os.Unsetenv("VAGRANT_CWD")
+
+		_, err := FindPath(nil, "")
+		require.Error(err)
+		require.Contains(err.Error(), "does not exist")
+	})
+}