add journal_input support mapstructure (#63)

* journalinput config support mapstructure

operator/builtin/input/journald/journald.go

@@ -47,11 +47,11 @@ func NewJournaldInputConfig(operatorID string) *JournaldInputConfig {
 
 // JournaldInputConfig is the configuration of a journald input operator
 type JournaldInputConfig struct {
-	helper.InputConfig `yaml:",inline"`
+	helper.InputConfig `mapstructure:",squash" yaml:",inline"`
 
-	Directory *string  `json:"directory,omitempty" yaml:"directory,omitempty"`
-	Files     []string `json:"files,omitempty"     yaml:"files,omitempty"`
-	StartAt   string   `json:"start_at,omitempty"  yaml:"start_at,omitempty"`
+	Directory *string  `mapstructure:"directory,omitempty" json:"directory,omitempty" yaml:"directory,omitempty"`
+	Files     []string `mapstructure:"files,omitempty"     json:"files,omitempty"     yaml:"files,omitempty"`
+	StartAt   string   `mapstructure:"start_at,omitempty"  json:"start_at,omitempty"  yaml:"start_at,omitempty"`
 }
 
 // Build will build a journald input operator from the supplied configuration

operator/builtin/input/journald/journald_test.go

@@ -24,11 +24,13 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+
 	"github.com/open-telemetry/opentelemetry-log-collection/entry"
 	"github.com/open-telemetry/opentelemetry-log-collection/operator"
+	"github.com/open-telemetry/opentelemetry-log-collection/operator/helper"
 	"github.com/open-telemetry/opentelemetry-log-collection/testutil"
-	"github.com/stretchr/testify/mock"
-	"github.com/stretchr/testify/require"
 )
 
 type fakeJournaldCmd struct{}
@@ -113,3 +115,22 @@ func TestInputJournald(t *testing.T) {
 		require.FailNow(t, "Timed out waiting for entry to be read")
 	}
 }
+
+func TestJournaldInputConfig(t *testing.T) {
+	expect := NewJournaldInputConfig("my_journald_input")
+	expect.WriteTo = entry.NewRecordField("to")
+
+	input := map[string]interface{}{
+		"id":         "my_journald_input",
+		"type":       "journald_input",
+		"start_at":   "end",
+		"write_to":   "$record.to",
+		"attributes": map[string]interface{}{},
+		"resource":   map[string]interface{}{},
+	}
+
+	var actual JournaldInputConfig
+	err := helper.UnmarshalMapstructure(input, &actual)
+	require.NoError(t, err)
+	require.Equal(t, expect, &actual)
+}