feat: use parser to load dynamic config from file.

pkg/config/file/file.go

@@ -2,7 +2,11 @@
 package file
 
 import (
+	"fmt"
+
+	"github.com/BurntSushi/toml"
 	"github.com/containous/traefik/v2/pkg/config/parser"
+	"gopkg.in/yaml.v2"
 )
 
 // Decode decodes the given configuration file into the given element.
@@ -22,11 +26,57 @@ func Decode(filePath string, element interface{}) error {
 		return err
 	}
 
-	metaOpts := parser.MetadataOpts{TagName: parser.TagLabel, AllowSliceAsStruct: true}
+	metaOpts := parser.MetadataOpts{TagName: parser.TagFile, AllowSliceAsStruct: false}
 	err = parser.AddMetadata(element, root, metaOpts)
 	if err != nil {
 		return err
 	}
 
-	return parser.Fill(element, root, parser.FillerOpts{AllowSliceAsStruct: true})
+	return parser.Fill(element, root, parser.FillerOpts{AllowSliceAsStruct: false})
+}
+
+// DecodeContent decodes the given configuration file content into the given element.
+// The operation goes through three stages roughly summarized as:
+// file contents -> tree of untyped nodes
+// untyped nodes -> nodes augmented with metadata such as kind (inferred from element)
+// "typed" nodes -> typed element.
+func DecodeContent(content string, extension string, element interface{}) error {
+	data := make(map[string]interface{})
+
+	switch extension {
+	case ".toml":
+		_, err := toml.Decode(content, &data)
+		if err != nil {
+			return err
+		}
+
+	case ".yml", ".yaml":
+		var err error
+		err = yaml.Unmarshal([]byte(content), &data)
+		if err != nil {
+			return err
+		}
+
+	default:
+		return fmt.Errorf("unsupported file extension: %s", extension)
+	}
+
+	filters := getRootFieldNames(element)
+
+	node, err := decodeRawToNode(data, parser.DefaultRootName, filters...)
+	if err != nil {
+		return err
+	}
+
+	if len(node.Children) == 0 {
+		return nil
+	}
+
+	metaOpts := parser.MetadataOpts{TagName: parser.TagFile, AllowSliceAsStruct: false}
+	err = parser.AddMetadata(element, node, metaOpts)
+	if err != nil {
+		return err
+	}
+
+	return parser.Fill(element, node, parser.FillerOpts{AllowSliceAsStruct: false})
 }

pkg/config/file/file_test.go

@@ -42,6 +42,32 @@ fii = "bir"
 	assert.Equal(t, expected, element)
 }
 
+func TestDecodeContent_TOML(t *testing.T) {
+	content := `
+foo = "bar"
+fii = "bir"
+[yi]
+`
+
+	element := &Yo{
+		Fuu: "test",
+	}
+
+	err := DecodeContent(content, ".toml", element)
+	require.NoError(t, err)
+
+	expected := &Yo{
+		Foo: "bar",
+		Fii: "bir",
+		Fuu: "test",
+		Yi: &Yi{
+			Foo: "foo",
+			Fii: "fii",
+		},
+	}
+	assert.Equal(t, expected, element)
+}
+
 func TestDecode_YAML(t *testing.T) {
 	f, err := ioutil.TempFile("", "traefik-config-*.yaml")
 	require.NoError(t, err)
@@ -74,3 +100,29 @@ yi: {}
 	}
 	assert.Equal(t, expected, element)
 }
+
+func TestDecodeContent_YAML(t *testing.T) {
+	content := `
+foo: bar
+fii: bir
+yi: {}
+`
+
+	element := &Yo{
+		Fuu: "test",
+	}
+
+	err := DecodeContent(content, ".yaml", element)
+	require.NoError(t, err)
+
+	expected := &Yo{
+		Foo: "bar",
+		Fii: "bir",
+		Fuu: "test",
+		Yi: &Yi{
+			Foo: "foo",
+			Fii: "fii",
+		},
+	}
+	assert.Equal(t, expected, element)
+}

pkg/config/file/fixtures_test.go

@@ -6,7 +6,7 @@ type Yo struct {
 	Foo string
 	Fii string
 	Fuu string
-	Yi  *Yi `label:"allowEmpty"`
+	Yi  *Yi `file:"allowEmpty"`
 }
 
 func (y *Yo) SetDefaults() {