Inline env variables if the underlying struct is YAML inlined

Signed-off-by: evanebb <git@evanus.nl>

configuration/parser.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"reflect"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -205,6 +206,25 @@ func (p *Parser) overwriteStruct(v reflect.Value, fullpath string, path []string
 	byUpperCase := make(map[string]int)
 	for i := 0; i < v.NumField(); i++ {
 		sf := v.Type().Field(i)
+
+		// For fields inlined in the YAML configuration file, the environment variables also need to be inlined
+		// Example struct tag for inlined field: `yaml:",inline"`
+		yamlTag := sf.Tag.Get("yaml")
+		split := strings.Split(yamlTag, ",")
+		// Skip the first entry, which is the field name
+		isInlined := slices.Contains(split[1:], "inline")
+
+		if isInlined && sf.Type.Kind() == reflect.Struct {
+			// Inlined struct, check whether the env variable corresponds to a field inside this struct
+			// Maps could also be inlined, but since we don't need it right now it is not supported
+			inlined := v.Field(i)
+			for j := 0; j < inlined.NumField(); j++ {
+				if strings.ToUpper(inlined.Type().Field(j).Name) == path[0] {
+					return p.overwriteFields(inlined, fullpath, path, payload)
+				}
+			}
+		}
+
 		upper := strings.ToUpper(sf.Name)
 		if _, present := byUpperCase[upper]; present {
 			panic(fmt.Sprintf("field name collision in configuration object: %s", sf.Name))

configuration/parser_test.go

@@ -11,12 +11,18 @@ type localConfiguration struct {
 	Version       Version `yaml:"version"`
 	Log           *Log    `yaml:"log"`
 	Notifications []Notif `yaml:"notifications,omitempty"`
+	Inlined       Inlined `yaml:",inline"`
 }
 
 type Notif struct {
 	Name string `yaml:"name"`
 }
 
+type Inlined struct {
+	FirstValue  string `yaml:"firstValue"`
+	SecondValue string `yaml:"secondValue"`
+}
+
 var expectedConfig = localConfiguration{
 	Version: "0.1",
 	Log: &Log{
@@ -89,3 +95,41 @@ func TestParseOverwriteUnininitializedPoiner(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, expectedConfig, config)
 }
+
+const testConfig3 = `version: "0.1"
+log:
+  formatter: "text"`
+
+func TestParseInlinedStruct(t *testing.T) {
+	config := localConfiguration{}
+
+	expected := localConfiguration{
+		Version: "0.1",
+		Log: &Log{
+			Formatter: "text",
+		},
+		Inlined: Inlined{
+			FirstValue:  "foo",
+			SecondValue: "bar",
+		},
+	}
+
+	// Test without inlined struct name in the env variable name
+	t.Setenv("REGISTRY_FIRSTVALUE", "foo")
+	// Test with the inlined struct name in the env variable name, for backward compatibility
+	t.Setenv("REGISTRY_INLINED_SECONDVALUE", "bar")
+
+	p := NewParser("registry", []VersionedParseInfo{
+		{
+			Version: "0.1",
+			ParseAs: reflect.TypeOf(config),
+			ConversionFunc: func(c interface{}) (interface{}, error) {
+				return c, nil
+			},
+		},
+	})
+
+	err := p.Parse([]byte(testConfig3), &config)
+	require.NoError(t, err)
+	require.Equal(t, expected, config)
+}