scope: do not create scope if path is invalid

Signed-off-by: Alfredo Deza <adeza@anchore.com>

syft/scope/scope.go

@@ -2,6 +2,7 @@ package scope
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/anchore/stereoscope"
 
@@ -32,7 +33,11 @@ func NewScope(userInput string, o Option) (Scope, func(), error) {
 
 	switch protocol.Type {
 	case directoryProtocol:
-		// populate the scope object for dir
+		err := isValidPath(protocol.Value)
+		if err != nil {
+			return Scope{}, func() {}, fmt.Errorf("unable to process path, must exist and be a directory: %w", err)
+		}
+
 		s, err := NewScopeFromDir(protocol.Value, o)
 		if err != nil {
 			return Scope{}, func() {}, fmt.Errorf("could not populate scope from path (%s): %w", protocol.Value, err)
@@ -115,3 +120,18 @@ func (s Scope) Source() interface{} {
 
 	return nil
 }
+
+// isValidPath ensures that the user-provided input will correspond to a path
+// that exists and is a directory
+func isValidPath(userInput string) error {
+	fileMeta, err := os.Stat(userInput)
+	if err != nil {
+		return err
+	}
+
+	if fileMeta.IsDir() {
+		return nil
+	}
+
+	return fmt.Errorf("path is not a directory: %s", userInput)
+}

syft/scope/scope_test.go

@@ -213,3 +213,40 @@ func TestFilesByGlob(t *testing.T) {
 		})
 	}
 }
+
+func TestIsValidPath(t *testing.T) {
+	testCases := []struct {
+		desc    string
+		input   string
+		isError bool
+	}{
+		{
+			desc:    "path is valid",
+			input:   "test-fixtures",
+			isError: false,
+		},
+		{
+			desc:    "file is invalid",
+			input:   "test-fixtures/.vimrc",
+			isError: true,
+		},
+		{
+			desc:    "path does not exist",
+			input:   "foo/bar/baz",
+			isError: true,
+		},
+	}
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			err := isValidPath(test.input)
+			if err != nil && !test.isError {
+				t.Errorf("did not expect and error, got: %w", err)
+			}
+
+			if err == nil && test.isError {
+				t.Errorf("expected an error but didn't get one")
+			}
+
+		})
+	}
+}