feat: add support for toml in addition to json

.golangci.yml

@@ -577,6 +577,7 @@ linters-settings:
       # List of allowed modules.
       # Default: []
       modules:                                                        # List of allowed modules
+        - github.com/pelletier/go-toml/v2
         - github.com/stretchr/testify
         # - gopkg.in/yaml.v2
       # List of allowed module domains.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- Add support for TOML configuration files
+- Use stdlib for tests instead of convey
+- Update golangci-lint config
+
 ## v0.2.0 (2021-12-19)
 
 - Added License
@@ -9,5 +13,5 @@
 - Added a Loadfiles function to load at once several config files
 
 ## v0.1.0 (2020-03-17)
-- Initial varsion
 
+- Initial varsion with support for JSON files

adapters.go

@@ -0,0 +1,86 @@
+package conf
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+type filetype int
+
+const (
+	typeInvalid filetype = iota
+	typeJSON
+	typeTOML
+)
+
+func getType(filename string) filetype {
+	switch {
+	case strings.HasSuffix(filename, ".json"):
+		return typeJSON
+	case strings.HasSuffix(filename, ".toml"):
+		return typeTOML
+	default:
+		return typeInvalid
+	}
+}
+
+func unmarshal(ft filetype, data []byte, v interface{}) error {
+	switch ft {
+	case typeJSON:
+		return unmarshalJSON(data, v)
+	case typeTOML:
+		return unmarshalTOML(data, v)
+	default:
+		return ErrUnsupportedFileType
+	}
+}
+
+func marshal(ft filetype, v interface{}) ([]byte, error) {
+	switch ft {
+	case typeJSON:
+		return marshalJSON(v)
+	case typeTOML:
+		return marshalTOML(v)
+	default:
+		return nil, ErrUnsupportedFileType
+	}
+}
+
+func unmarshalJSON(data []byte, v interface{}) error {
+	err := json.Unmarshal(data, v)
+	if err != nil {
+		return fmt.Errorf("cannot parse config file: %w", err)
+	}
+
+	return nil
+}
+
+func marshalJSON(v interface{}) ([]byte, error) {
+	data, err := json.MarshalIndent(v, "", "  ")
+	if err != nil {
+		return nil, fmt.Errorf("cannot generate config content: %w", err)
+	}
+
+	return data, nil
+}
+
+func unmarshalTOML(data []byte, v interface{}) error {
+	err := toml.Unmarshal(data, v)
+	if err != nil {
+		return fmt.Errorf("cannot parse config file: %w", err)
+	}
+
+	return nil
+}
+
+func marshalTOML(v interface{}) ([]byte, error) {
+	data, err := toml.Marshal(v)
+	if err != nil {
+		return nil, fmt.Errorf("cannot generate config content: %w", err)
+	}
+
+	return data, nil
+}

config.go

@@ -1,15 +1,25 @@
-// Package conf defines utils to simplify configuration
+// Package conf defines utils to simplify configuration management.
-// management.
+//
+// It provides functions to load and save config files.
+//
+// Several formats are supported. The encoders/decoders are selected according
+// to the extension of the paths passed to functions:
+//
+// - JSON: ".json"
+// - TOML: ".toml"
 package conf
 
 import (
-	"encoding/json"
 	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
 )
 
+// ErrUnsupportedFileType is returned when the type of the config file is not
+// supported.
+var ErrUnsupportedFileType = errors.New("unsupported config type")
+
 // LoadFile reads the file at path, parses its json content and fills the struct
 // with the content of the file.
 func LoadFile(path string, data interface{}) error {
@@ -21,7 +31,7 @@ func LoadFile(path string, data interface{}) error {
 // If a path does not exist, it is ignored.
 //
 // It returns an error only if the content of a file is invalid, i.e. it
-// cannot be unmarshaled by json.
+// cannot be unmarshaled to the struct.
 func LoadFiles(data interface{}, paths ...string) error {
 	for _, p := range paths {
 		err := read(p, data)
@@ -78,18 +88,13 @@ func read(path string, data interface{}) error {
 		return fmt.Errorf("cannot read config file: %w", err)
 	}
 
-	err = json.Unmarshal(content, &data)
+	return unmarshal(getType(path), content, data)
-	if err != nil {
-		return fmt.Errorf("cannot parse config file: %w", err)
-	}
-
-	return nil
 }
 
 func write(path string, data interface{}) error {
-	content, err := json.MarshalIndent(data, "", "  ")
+	content, err := marshal(getType(path), data)
 	if err != nil {
-		return fmt.Errorf("cannot generate config content: %w", err)
+		return err
 	}
 
 	err = os.WriteFile(path, content, 0o600)

config_test.go

@@ -11,6 +11,68 @@ import (
 	"code.bcarlin.xyz/go/conf"
 )
 
+func TestJSONFiles(t *testing.T) {
+	t.Parallel()
+
+	runTestSuite(t, "json")
+}
+
+func TestTOMLFiles(t *testing.T) {
+	t.Parallel()
+
+	runTestSuite(t, "toml")
+}
+
+func TestUnknownFiles(t *testing.T) {
+	t.Parallel()
+
+	t.Run("LoadFile", func(t *testing.T) {
+		t.Parallel()
+
+		s := struct{}{}
+
+		err := conf.LoadFile("test_data/valid.unknown", &s)
+		if assert.Error(t, err) {
+			assert.ErrorIs(t, err, conf.ErrUnsupportedFileType)
+		}
+	})
+
+	t.Run("SaveFile", func(t *testing.T) {
+		t.Parallel()
+
+		s := struct{}{}
+
+		err := conf.SaveFile("test.unknown", &s)
+		if assert.Error(t, err) {
+			assert.ErrorIs(t, err, conf.ErrUnsupportedFileType)
+		}
+
+		assert.NoFileExists(t, "test.unknown")
+	})
+
+	t.Run("LoadAndUpdateFile", func(t *testing.T) {
+		t.Parallel()
+
+		s := struct{}{}
+
+		err := conf.LoadAndUpdateFile("test.unknown", &s)
+		if assert.Error(t, err) {
+			assert.ErrorIs(t, err, conf.ErrUnsupportedFileType)
+		}
+
+		assert.NoFileExists(t, "test.unknown")
+	})
+}
+
+func runTestSuite(t *testing.T, ext string) {
+	t.Helper()
+
+	testLoadFile(t, ext)
+	testLoadFiles(t, ext)
+	testSaveFile(t, ext)
+	testLoadAndUpdateFile(t, ext)
+}
+
 type testconf struct {
 	inUpdate  func()
 	String    string
@@ -24,374 +86,352 @@ func (t testconf) Update() {
 	}
 }
 
-func TestLoadFile(t *testing.T) {
+func testLoadFile(t *testing.T, ext string) {
-	t.Parallel()
+	t.Helper()
 
-	t.Run("with a valid file", func(t *testing.T) {
+	t.Run("LoadFile", func(t *testing.T) {
 		t.Parallel()
 
-		c := testconf{
+		t.Run("with a valid file", func(t *testing.T) {
-			String:    "default string",
+			t.Parallel()
-			Int:       1,
-			Invariant: "should not change",
-		}
 
-		file := "test_data/valid.json"
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+			}
 
-		err := conf.LoadFile(file, &c)
+			file := "test_data/valid." + ext
-		require.NoError(t, err)
 
-		assert.Equal(t, "config string", c.String)
+			err := conf.LoadFile(file, &c)
-		assert.Equal(t, 42, c.Int)
+			require.NoError(t, err)
-		assert.Equal(t, "should not change", c.Invariant)
-	})
 
-	t.Run("with an invalid file", func(t *testing.T) {
+			assert.Equal(t, "config string", c.String)
-		t.Parallel()
+			assert.Equal(t, 42, c.Int)
+			assert.Equal(t, "should not change", c.Invariant)
+		})
 
-		c := testconf{
+		t.Run("with an invalid file", func(t *testing.T) {
-			String:    "default string",
+			t.Parallel()
-			Int:       1,
-			Invariant: "should not change",
-		}
 
-		file := "test_data/invalid.json"
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+			}
 
-		err := conf.LoadFile(file, &c)
+			file := "test_data/invalid." + ext
-		require.Error(t, err)
 
-		assert.Equal(t, "default string", c.String)
+			err := conf.LoadFile(file, &c)
-		assert.Equal(t, 1, c.Int)
+			require.Error(t, err)
-		assert.Equal(t, "should not change", c.Invariant)
-	})
 
-	t.Run("with a non existent file", func(t *testing.T) {
+			assert.Equal(t, "default string", c.String)
-		t.Parallel()
+			assert.Equal(t, 1, c.Int)
+			assert.Equal(t, "should not change", c.Invariant)
+		})
 
-		c := testconf{
+		t.Run("with a non existent file", func(t *testing.T) {
-			String:    "default string",
+			t.Parallel()
-			Int:       1,
-			Invariant: "should not change",
-		}
 
-		file := "does-not-exist.conf"
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+			}
 
-		err := conf.LoadFile(file, &c)
+			file := "does-not-exist." + ext
-		require.Error(t, err)
 
-		assert.Equal(t, "default string", c.String)
+			err := conf.LoadFile(file, &c)
-		assert.Equal(t, 1, c.Int)
+			require.Error(t, err)
-		assert.Equal(t, "should not change", c.Invariant)
+
+			assert.Equal(t, "default string", c.String)
+			assert.Equal(t, 1, c.Int)
+			assert.Equal(t, "should not change", c.Invariant)
+		})
 	})
 }
 
-func TestLoadFiles(t *testing.T) {
+func testLoadFiles(t *testing.T, ext string) {
-	t.Parallel()
+	t.Helper()
 
-	t.Run("with two valid files with different options", func(t *testing.T) {
+	t.Run("LoadFiles", func(t *testing.T) {
 		t.Parallel()
 
-		c := testconf{}
+		t.Run("with two valid files with different options", func(t *testing.T) {
-		tmpDir := t.TempDir()
+			t.Parallel()
 
-		content1 := []byte(`{"String": "foo"}`)
+			c := testconf{}
-		content2 := []byte(`{"Int": 42}`)
+			err := conf.LoadFiles(&c, "test_data/part1."+ext, "test_data/part2."+ext)
-		paths := []string{
+			require.NoError(t, err)
-			filepath.Join(tmpDir, "file1.json"),
-			filepath.Join(tmpDir, "file2.json"),
-		}
 
-		err := os.WriteFile(paths[0], content1, 0o600)
+			assert.Equal(t, "foo", c.String)
-		require.NoError(t, err)
+			assert.Equal(t, 42, c.Int)
-		err = os.WriteFile(paths[1], content2, 0o600)
+		})
-		require.NoError(t, err)
 
-		err = conf.LoadFiles(&c, paths...)
+		t.Run("with two valid files with the same option", func(t *testing.T) {
-		require.NoError(t, err)
+			t.Parallel()
 
-		assert.Equal(t, "foo", c.String)
+			c := testconf{}
-		assert.Equal(t, 42, c.Int)
-	})
 
-	t.Run("with two valid files with the same option", func(t *testing.T) {
+			err := conf.LoadFiles(&c, "test_data/same1."+ext, "test_data/same2."+ext)
-		t.Parallel()
+			require.NoError(t, err)
 
-		c := testconf{}
+			assert.Equal(t, "bar", c.String)
-		tmpDir := t.TempDir()
+		})
 
-		content1 := []byte(`{"String": "foo"}`)
+		t.Run("with one non-existing and one existing file", func(t *testing.T) {
-		content2 := []byte(`{"String": "bar"}`)
+			t.Parallel()
-		paths := []string{
-			filepath.Join(tmpDir, "file1.json"),
-			filepath.Join(tmpDir, "file2.json"),
-		}
 
-		err := os.WriteFile(paths[0], content1, 0o600)
+			c := testconf{}
-		require.NoError(t, err)
-		err = os.WriteFile(paths[1], content2, 0o600)
-		require.NoError(t, err)
 
-		err = conf.LoadFiles(&c, paths...)
+			err := conf.LoadFiles(&c, "does-not-exist."+ext, "test_data/valid."+ext)
-		require.NoError(t, err)
+			require.NoError(t, err)
 
-		assert.Equal(t, "bar", c.String)
+			assert.Equal(t, "config string", c.String)
-	})
+		})
 
-	t.Run("with one non-existing and one existing file", func(t *testing.T) {
+		t.Run("with one invalid and one valid file", func(t *testing.T) {
-		t.Parallel()
+			t.Parallel()
 
-		c := testconf{}
+			c := testconf{}
-		tmpDir := t.TempDir()
 
-		content2 := []byte(`{"String": "bar"}`)
+			err := conf.LoadFiles(&c, "test_data/invalid."+ext, "test_data/valid."+ext)
-		paths := []string{
+			require.Error(t, err)
-			"does-not-exist.json",
-			filepath.Join(tmpDir, "file2.json"),
-		}
 
-		err := os.WriteFile(paths[1], content2, 0o600)
+			assert.Equal(t, "", c.String)
-		require.NoError(t, err)
+		})
-
-		err = conf.LoadFiles(&c, paths...)
-		require.NoError(t, err)
-
-		assert.Equal(t, "bar", c.String)
-	})
-
-	t.Run("with one valid and one invalid file", func(t *testing.T) {
-		t.Parallel()
-
-		c := testconf{}
-		tmpDir := t.TempDir()
-
-		content1 := []byte(`{"`)
-		content2 := []byte(`{"String": "bar"}`)
-		paths := []string{
-			filepath.Join(tmpDir, "file1.json"),
-			filepath.Join(tmpDir, "file2.json"),
-		}
-
-		err := os.WriteFile(paths[0], content1, 0o600)
-		require.NoError(t, err)
-		err = os.WriteFile(paths[1], content2, 0o600)
-		require.NoError(t, err)
-
-		err = conf.LoadFiles(&c, paths...)
-		require.Error(t, err)
-
-		assert.Equal(t, "", c.String)
 	})
 }
 
-func TestSaveFile(t *testing.T) {
+func testSaveFile(t *testing.T, ext string) {
-	t.Parallel()
+	t.Helper()
 
-	t.Run("with a valid path", func(t *testing.T) {
+	t.Run("SaveFile", func(t *testing.T) {
 		t.Parallel()
 
-		c := testconf{
+		t.Run("with a valid path", func(t *testing.T) {
-			String:    "default string",
+			t.Parallel()
-			Invariant: "should not change",
-			Int:       1,
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		err := conf.SaveFile(file, &c)
+			c := testconf{
-		require.NoError(t, err)
+				String:    "default string",
+				Invariant: "should not change",
+				Int:       1,
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "test."+ext)
 
-		assert.FileExists(t, file)
+			err := conf.SaveFile(file, &c)
+			require.NoError(t, err)
 
-		expected := "{\n  \"String\": \"default string\",\n  \"Invariant\": \"should not change\",\n  \"Int\": 1\n}"
+			require.FileExists(t, file)
-		got, err := os.ReadFile(file)
-		require.NoError(t, err)
-		assert.Equal(t, expected, string(got))
-	})
 
-	t.Run("with a valid path and invalid data", func(t *testing.T) {
+			expected, err := os.ReadFile("test_data/full." + ext)
-		t.Parallel()
+			require.NoError(t, err)
+			got, err := os.ReadFile(file)
+			require.NoError(t, err)
 
-		tmpDir := t.TempDir()
+			assert.Equal(t, string(expected), string(got))
-		file := filepath.Join(tmpDir, "test.conf")
+		})
 
-		err := conf.SaveFile(file, func() error { return nil })
+		t.Run("with a valid path and invalid data", func(t *testing.T) {
-		require.Error(t, err)
+			t.Parallel()
 
-		assert.NoFileExists(t, file)
+			tmpDir := t.TempDir()
-	})
+			file := filepath.Join(tmpDir, "test."+ext)
 
-	t.Run("with an invalid path", func(t *testing.T) {
+			err := conf.SaveFile(file, func() error { return nil })
-		t.Parallel()
+			require.Error(t, err)
 
-		c := testconf{
+			assert.NoFileExists(t, file)
-			String:    "default string",
+		})
-			Invariant: "should not change",
-			Int:       1,
-		}
-		file := "cannot/write/here.conf"
 
-		err := conf.SaveFile(file, &c)
+		t.Run("with an invalid path", func(t *testing.T) {
-		require.Error(t, err)
+			t.Parallel()
 
-		assert.NoFileExists(t, file)
+			c := testconf{
+				String:    "default string",
+				Invariant: "should not change",
+				Int:       1,
+			}
+			file := "cannot/write/here." + ext
+
+			err := conf.SaveFile(file, &c)
+			require.Error(t, err)
+
+			assert.NoFileExists(t, file)
+		})
 	})
 }
 
-func TestLoadAndUpdateFile(t *testing.T) {
+func testLoadAndUpdateFile(t *testing.T, ext string) {
-	t.Parallel()
+	t.Helper()
 
-	t.Run("when the target file does not exist", func(t *testing.T) {
+	t.Run("LoadAndUpdateFile", func(t *testing.T) {
 		t.Parallel()
 
-		updated := false
+		t.Run("when the target file does not exist", func(t *testing.T) {
-		c := testconf{
+			t.Parallel()
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		err := conf.LoadAndUpdateFile(file, &c)
+			updated := false
-		require.NoError(t, err)
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "does-not-exist."+ext)
 
-		var c2 testconf
+			err := conf.LoadAndUpdateFile(file, &c)
-		err = conf.LoadFile(file, &c2)
+			require.NoError(t, err)
-		require.NoError(t, err)
-		assert.Equal(t, c.String, c2.String)
-		assert.Equal(t, c.Int, c2.Int)
-		assert.Equal(t, c.Invariant, c2.Invariant)
 
-		assert.False(t, updated)
+			require.FileExists(t, file)
-	})
 
-	t.Run("when the path cannot be written", func(t *testing.T) {
+			var c2 testconf
-		t.Parallel()
+			err = conf.LoadFile(file, &c2)
+			require.NoError(t, err)
+			assert.Equal(t, c.String, c2.String)
+			assert.Equal(t, c.Int, c2.Int)
+			assert.Equal(t, c.Invariant, c2.Invariant)
 
-		updated := false
+			assert.False(t, updated)
-		c := testconf{
+		})
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "does-not-exist", "test.conf")
 
-		err := conf.LoadAndUpdateFile(file, &c)
+		t.Run("when the path cannot be written", func(t *testing.T) {
-		require.Error(t, err)
+			t.Parallel()
 
-		assert.NoFileExists(t, file)
+			updated := false
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "does-not-exist", "test."+ext)
 
-		assert.False(t, updated)
+			err := conf.LoadAndUpdateFile(file, &c)
-	})
+			require.Error(t, err)
 
-	t.Run("when the config file is invalid", func(t *testing.T) {
+			assert.NoFileExists(t, file)
-		t.Parallel()
 
-		updated := false
+			assert.False(t, updated)
-		c := testconf{
+		})
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		content := []byte(`String: not json`)
+		t.Run("when the config file is invalid", func(t *testing.T) {
-		err := os.WriteFile(file, content, 0o644)
+			t.Parallel()
-		require.NoError(t, err)
 
-		err = conf.LoadAndUpdateFile(file, &c)
+			updated := false
-		require.Error(t, err)
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "test."+ext)
 
-		assert.False(t, updated)
+			content, err := os.ReadFile("test_data/invalid." + ext)
-	})
+			require.NoError(t, err)
 
-	t.Run("when the config file is valid", func(t *testing.T) {
+			err = os.WriteFile(file, content, 0o600)
-		t.Parallel()
+			require.NoError(t, err)
 
-		updated := false
+			err = conf.LoadAndUpdateFile("test_data/invalid."+ext, &c)
-		c := testconf{
+			require.Error(t, err)
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		content := []byte(`{"String": "config string", "Int": 42}`)
+			assert.False(t, updated)
-		err := os.WriteFile(file, content, 0o644)
+		})
-		require.NoError(t, err)
 
-		err = conf.LoadAndUpdateFile(file, &c)
+		t.Run("when the config file is valid", func(t *testing.T) {
-		require.NoError(t, err)
+			t.Parallel()
 
-		var c2 testconf
+			updated := false
-		err = conf.LoadFile(file, &c2)
+			c := testconf{
-		require.NoError(t, err)
+				String:    "default string",
-		assert.Equal(t, "config string", c2.String)
+				Int:       1,
-		assert.Equal(t, 42, c2.Int)
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "test."+ext)
 
-		assert.True(t, updated)
+			content, err := os.ReadFile("test_data/valid." + ext)
-	})
+			require.NoError(t, err)
 
-	t.Run("when the config file is missing options", func(t *testing.T) {
+			err = os.WriteFile(file, content, 0o600)
-		t.Parallel()
+			require.NoError(t, err)
 
-		updated := false
+			err = conf.LoadAndUpdateFile(file, &c)
-		c := testconf{
+			require.NoError(t, err)
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		content := []byte(`{"String": "config string"}`)
+			var c2 testconf
-		err := os.WriteFile(file, content, 0o644)
+			err = conf.LoadFile(file, &c2)
-		require.NoError(t, err)
+			require.NoError(t, err)
+			assert.Equal(t, "config string", c2.String)
+			assert.Equal(t, 42, c2.Int)
+			assert.Equal(t, "should not change", c2.Invariant)
 
-		err = conf.LoadAndUpdateFile(file, &c)
+			assert.True(t, updated)
-		require.NoError(t, err)
+		})
 
-		newContent, err := os.ReadFile(file)
+		t.Run("when the config file is missing options", func(t *testing.T) {
-		require.NoError(t, err)
+			t.Parallel()
 
-		assert.Contains(t, string(newContent), "Int") //nolint:usestdlibvars // not the constant here
+			updated := false
-		assert.Contains(t, string(newContent), "Invariant")
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "test."+ext)
 
-		assert.True(t, updated)
+			content, err := os.ReadFile("test_data/valid." + ext)
-	})
+			require.NoError(t, err)
 
-	t.Run("when the config contains unknown options", func(t *testing.T) {
+			err = os.WriteFile(file, content, 0o600)
-		t.Parallel()
+			require.NoError(t, err)
 
-		updated := false
+			err = conf.LoadAndUpdateFile(file, &c)
-		c := testconf{
+			require.NoError(t, err)
-			String:    "default string",
-			Int:       1,
-			Invariant: "should not change",
-			inUpdate:  func() { updated = true },
-		}
-		tmpDir := t.TempDir()
-		file := filepath.Join(tmpDir, "test.conf")
 
-		content := []byte(`{"String": "config string", "Foo": "blah"}`)
+			newContent, err := os.ReadFile(file)
-		err := os.WriteFile(file, content, 0o644)
+			require.NoError(t, err)
-		require.NoError(t, err)
 
-		err = conf.LoadAndUpdateFile(file, &c)
+			assert.Contains(t, string(newContent), "Invariant")
-		require.NoError(t, err)
 
-		newContent, err := os.ReadFile(file)
+			assert.True(t, updated)
-		require.NoError(t, err)
+		})
-		assert.NotContains(t, string(newContent), "Foo")
 
-		assert.True(t, updated)
+		t.Run("when the config contains unknown options", func(t *testing.T) {
+			t.Parallel()
+
+			updated := false
+			c := testconf{
+				String:    "default string",
+				Int:       1,
+				Invariant: "should not change",
+				inUpdate:  func() { updated = true },
+			}
+			tmpDir := t.TempDir()
+			file := filepath.Join(tmpDir, "test."+ext)
+
+			content, err := os.ReadFile("test_data/unknown." + ext)
+			require.NoError(t, err)
+
+			err = os.WriteFile(file, content, 0o600)
+			require.NoError(t, err)
+
+			err = conf.LoadAndUpdateFile(file, &c)
+			require.NoError(t, err)
+
+			newContent, err := os.ReadFile(file)
+			require.NoError(t, err)
+			assert.NotContains(t, string(newContent), "Unknown")
+
+			assert.True(t, updated)
+		})
 	})
 }

go.mod

@@ -6,6 +6,7 @@ require github.com/stretchr/testify v1.9.0
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,6 +1,8 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pelletier/go-toml/v2 v2.2.2 h1:aYUidT7k73Pcl9nb2gScu7NSrKCSHIDE89b3+6Wq+LM=
+github.com/pelletier/go-toml/v2 v2.2.2/go.mod h1:1t835xjRzz80PqgE6HHgN2JOsmgYu/h4qDAS4n929Rs=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

test_data/full.json

@@ -0,0 +1,5 @@
+{
+  "String": "default string",
+  "Invariant": "should not change",
+  "Int": 1
+}

test_data/full.toml

@@ -0,0 +1,3 @@
+String = 'default string'
+Invariant = 'should not change'
+Int = 1

test_data/invalid.toml

@@ -0,0 +1 @@
+String: not toml

test_data/part1.json

@@ -0,0 +1 @@
+{"String": "foo"}

test_data/part1.toml

@@ -0,0 +1 @@
+String = "foo"

test_data/part2.json

@@ -0,0 +1 @@
+{"Int": 42}

test_data/part2.toml

@@ -0,0 +1 @@
+Int = 42

test_data/same1.json

@@ -0,0 +1 @@
+{"String": "foo"}

test_data/same1.toml

@@ -0,0 +1 @@
+String = "foo"

test_data/same2.json

@@ -0,0 +1 @@
+{"String": "bar"}

test_data/same2.toml

@@ -0,0 +1 @@
+String = "bar"

test_data/unknown.json

@@ -0,0 +1,5 @@
+{
+    "String": "config string",
+    "Int": 42,
+    "Unknown": "foo"
+}

test_data/unknown.toml

@@ -0,0 +1,3 @@
+String = "config string"
+Int = 42
+Unknown = "foo"

test_data/valid.toml

@@ -0,0 +1,2 @@
+string = "config string"
+int = 42

test_data/valid.unknown

@@ -0,0 +1 @@
+String: not json