Fix problems with reading config files using --config (apigee#1230)

* Fix problems with reading config files using `--config`
* Add test to verify that we can read config files outside of ~/.config

pkg/config/config.go

@@ -37,7 +37,7 @@ var (
 	// `cmd.PersistentFlags().AddFlagSet(connection.Flags)`
 	Flags *pflag.FlagSet = CreateFlagSet()
 
-	// Directory is $HOME/config/registry
+	// Directory is $HOME/.config/registry
 	Directory             string
 	ErrCannotDeleteActive = fmt.Errorf("cannot delete active configuration")
 	ErrReservedConfigName = fmt.Errorf("%q is reserved", ActivePointerFilename)
@@ -100,10 +100,6 @@ func ValidateName(name string) error {
 	if name == ActivePointerFilename {
 		return ErrReservedConfigName
 	}
-
-	if dir, _ := filepath.Split(name); dir != "" {
-		return fmt.Errorf("%q must not include a path", name)
-	}
 	return nil
 }
 
@@ -199,9 +195,10 @@ func ReadValid(name string) (c Configuration, err error) {
 }
 
 // Read loads a Configuration from yaml file matching `name`. If name
-// contains a path, the file will be read from that path, otherwise
-// the path is assumed as: ~/.config/registry. Does a simple read from the
-// file: does not bind to env vars or flags, resolve, or validate.
+// contains a path or refers to a local file, the file will be read
+// using name, otherwise the path is assumed as: ~/.config/registry.
+// Does a simple read from the file: does not bind to env vars or flags,
+// resolve, or validate.
 // See also: ReadValid()
 func Read(name string) (c Configuration, err error) {
 	if err = ValidateName(name); err != nil {
@@ -210,7 +207,11 @@ func Read(name string) (c Configuration, err error) {
 
 	dir, file := filepath.Split(name)
 	if dir == "" {
-		name = filepath.Join(Directory, file)
+		// If name refers to a local file, preferentially read the local file.
+		// Otherwise assume name refers to a file in the config directory.
+		if info, err := os.Stat(file); errors.Is(err, os.ErrNotExist) || info.IsDir() {
+			name = filepath.Join(Directory, file)
+		}
 	}
 	var r io.Reader
 	if r, err = os.Open(name); err != nil {

pkg/config/configuration_test.go

@@ -15,6 +15,7 @@
 package config_test
 
 import (
+	"log"
 	"os"
 	"path"
 	"path/filepath"
@@ -24,6 +25,7 @@ import (
 	"github.com/apigee/registry/pkg/config"
 	"github.com/apigee/registry/pkg/config/test"
 	"github.com/google/go-cmp/cmp"
+	"gopkg.in/yaml.v2"
 )
 
 func TestMissingDirectory(t *testing.T) {
@@ -476,3 +478,40 @@ func TestResolve(t *testing.T) {
 		t.Errorf("want: %s, got: %s", "hello", c.Registry.Token)
 	}
 }
+
+func TestReadExternalFile(t *testing.T) {
+	c := config.Configuration{
+		Registry: config.Registry{Address: "example.com:443"},
+	}
+	bytes, err := yaml.Marshal(c)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.CreateTemp(".", "tmpfile-")
+	if err != nil {
+		log.Fatal(err)
+	}
+	if _, err = f.Write(bytes); err != nil {
+		log.Fatal(err)
+	}
+	if err = f.Close(); err != nil {
+		log.Fatal(err)
+	}
+	defer os.Remove(f.Name())
+	// Verify that we can read a file using its full path name.
+	c2, err := config.Read(f.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c2.Registry.Address != c.Registry.Address {
+		t.Errorf("want: %s, got: %s", c2.Registry.Address, c.Registry.Address)
+	}
+	// Verify that we can read a local file using its base name.
+	c3, err := config.Read(filepath.Base(f.Name()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c3.Registry.Address != c.Registry.Address {
+		t.Errorf("want: %s, got: %s", c3.Registry.Address, c.Registry.Address)
+	}
+}