Read gqlgen.yml from io.Reader. (#2607)

* Update config.go

Add ReadConfig

* Add tests

* Update config_test.go

remove extra space to fix lint checks

* Update config.go

Need to return the config

codegen/config/config.go

@@ -3,6 +3,7 @@ package config
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -100,14 +101,18 @@ var path2regex = strings.NewReplacer(
 
 // LoadConfig reads the gqlgen.yml config file
 func LoadConfig(filename string) (*Config, error) {
-	config := DefaultConfig()
-
 	b, err := os.ReadFile(filename)
 	if err != nil {
 		return nil, fmt.Errorf("unable to read config: %w", err)
 	}
 
-	dec := yaml.NewDecoder(bytes.NewReader(b))
+	return ReadConfig(bytes.NewReader(b))
+}
+
+func ReadConfig(cfgFile io.Reader) (*Config, error) {
+	config := DefaultConfig()
+
+	dec := yaml.NewDecoder(cfgFile)
 	dec.KnownFields(true)
 
 	if err := dec.Decode(config); err != nil {

codegen/config/config_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -21,19 +22,29 @@ func TestLoadConfig(t *testing.T) {
 		_, err := LoadConfig("doesnotexist.yml")
 		require.Error(t, err)
 	})
+}
+
+func TestReadConfig(t *testing.T) {
+	t.Run("empty config", func(t *testing.T) {
+		_, err := ReadConfig(strings.NewReader(""))
+		require.EqualError(t, err, "unable to parse config: EOF")
+	})
 
 	t.Run("malformed config", func(t *testing.T) {
-		_, err := LoadConfig("testdata/cfg/malformedconfig.yml")
+		cfgFile, _ := os.Open("testdata/cfg/malformedconfig.yml")
+		_, err := ReadConfig(cfgFile)
 		require.EqualError(t, err, "unable to parse config: yaml: unmarshal errors:\n  line 1: cannot unmarshal !!str `asdf` into config.Config")
 	})
 
 	t.Run("unknown keys", func(t *testing.T) {
-		_, err := LoadConfig("testdata/cfg/unknownkeys.yml")
+		cfgFile, _ := os.Open("testdata/cfg/unknownkeys.yml")
+		_, err := ReadConfig(cfgFile)
 		require.EqualError(t, err, "unable to parse config: yaml: unmarshal errors:\n  line 2: field unknown not found in type config.Config")
 	})
 
 	t.Run("globbed filenames", func(t *testing.T) {
-		c, err := LoadConfig("testdata/cfg/glob.yml")
+		cfgFile, _ := os.Open("testdata/cfg/glob.yml")
+		c, err := ReadConfig(cfgFile)
 		require.NoError(t, err)
 
 		if runtime.GOOS == "windows" {
@@ -46,7 +57,8 @@ func TestLoadConfig(t *testing.T) {
 	})
 
 	t.Run("unwalkable path", func(t *testing.T) {
-		_, err := LoadConfig("testdata/cfg/unwalkable.yml")
+		cfgFile, _ := os.Open("testdata/cfg/unwalkable.yml")
+		_, err := ReadConfig(cfgFile)
 		if runtime.GOOS == "windows" {
 			require.EqualError(t, err, "failed to walk schema at root not_walkable/: CreateFile not_walkable/: The system cannot find the file specified.")
 		} else {