Enable reading from and writing to empty config files

internal/config/config_file.go

@@ -76,8 +76,11 @@ func parseConfigFile(fn string) ([]byte, *yaml.Node, error) {
 	if err != nil {
 		return data, nil, err
 	}
-	if len(root.Content) < 1 {
-		return data, &root, fmt.Errorf("malformed config")
+	if len(root.Content) == 0 {
+		return data, &yaml.Node{
+			Kind:    yaml.DocumentNode,
+			Content: []*yaml.Node{{Kind: yaml.MappingNode}},
+		}, nil
 	}
 	if root.Content[0].Kind != yaml.MappingNode {
 		return data, &root, fmt.Errorf("expected a top level map")

internal/config/config_file_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"reflect"
 	"testing"
 
@@ -94,3 +95,16 @@ github.com:
 
 	eq(t, buf.String(), expected)
 }
+
+func Test_parseConfigFile(t *testing.T) {
+	fileContents := []string{"", " ", "\n"}
+	for _, contents := range fileContents {
+		t.Run(fmt.Sprintf("contents: %q", contents), func(t *testing.T) {
+			defer StubConfig(contents, "")()
+			_, yamlRoot, err := parseConfigFile("config.yml")
+			eq(t, err, nil)
+			eq(t, yamlRoot.Content[0].Kind, yaml.MappingNode)
+			eq(t, len(yamlRoot.Content[0].Content), 0)
+		})
+	}
+}

internal/config/config_type.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 
@@ -172,6 +173,10 @@ func (c *fileConfig) Write() error {
 		return err
 	}
 
+	if bytes.Equal(marshalled, []byte("{}\n")) {
+		marshalled = []byte{}
+	}
+
 	return WriteConfigFile(ConfigFile(), marshalled)
 }
 

internal/config/config_type_test.go

@@ -27,3 +27,13 @@ hosts:
         editor: vim
 `, cb.String())
 }
+
+func Test_fileConfig_Write(t *testing.T) {
+	cb := bytes.Buffer{}
+	StubWriteConfig(&cb, nil)
+
+	c := NewBlankConfig()
+	assert.NoError(t, c.Write())
+
+	assert.Equal(t, "", cb.String())
+}