[8.18](backport #45747) Does not emit warning log if V2 config do not have an ID (#45877)

Inputs V2 CheckConfig was emitting warning logs for every input
without an ID.

This commit fixes it by not requiring an ID to exist when calling
CheckConfig.

(cherry picked from commit 240c010)

* Fix merge conflicts

---------

Co-authored-by: Tiago Queiroz <[email protected]>

Author: mergify[bot]

CHANGELOG.next.asciidoc

@@ -122,6 +122,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Journald input now works on Docker containers (except Wolfi) {issue}41278[41278] {issue}44040[44040] {pull}44056[44056]
 - Fix endpoint path typo in Okta entity analytics provider. {pull}44147[44147]
 - Fixed a websocket panic scenario which would occur after exhausting max retries. {pull}44342[44342]
+- Fix wrongly emitted missing input ID warning {issue}42969[42969] {pull}45747[45747]
 - Fix handling of unnecessary BOM in UTF-8 text received by o365audit input. {issue}44327[44327] {pull}45739[45739]
 - Fix reading journald messages with more than 4kb. {issue}45511[45511] {pull}46017[46017]
 - Restore the Streaming input on Windows. {pull}46031[46031]

filebeat/input/v2/compat/compat.go

@@ -192,18 +192,23 @@ func (f *factory) generateCheckConfig(config *conf.C) (*conf.C, error) {
 		return nil, fmt.Errorf("failed to create new config: %w", err)
 	}
 
-	// let's try to override the `id` field, if it fails, give up
-	inputID, err := testCfg.String("id", -1)
+	uid, err := uuid.NewV4()
 	if err != nil {
-		return nil, fmt.Errorf("failed to get 'id': %w", err)
+		return nil, fmt.Errorf("failed to generate check config id: %w", err)
 	}
 
-	id, err := uuid.NewV4()
-	if err != nil {
-		return nil, fmt.Errorf("failed to generate check congig id: %w", err)
+	finalID := uid.String()
+	// if 'id' is present, use it as a prefix
+	if testCfg.HasField("id") {
+		inputID, err := testCfg.String("id", -1)
+		if err != nil {
+			return nil, fmt.Errorf("failed to get 'id': %w", err)
+		}
+
+		finalID = inputID + "-" + finalID
 	}
-	err = testCfg.SetString("id", -1, inputID+"-"+id.String())
-	if err != nil {
+
+	if err := testCfg.SetString("id", -1, finalID); err != nil {
 		return nil, fmt.Errorf("failed to set 'id': %w", err)
 	}
 

filebeat/input/v2/compat/compat_test.go

@@ -20,6 +20,7 @@ package compat
 import (
 	"errors"
 	"fmt"
+	"strings"
 	"sync"
 	"testing"
 
@@ -193,27 +194,36 @@ func TestGenerateCheckConfig(t *testing.T) {
 		cfg       *conf.C
 		want      *conf.C
 		wantErr   error
-		assertCfg func(t assert.TestingT, expected interface{}, actual interface{}, msgAndArgs ...interface{}) bool
+		assertCfg func(t assert.TestingT, expected any, actual *conf.C, msgAndArgs ...any)
 	}{
 		{
-			name:      "id is present",
-			cfg:       conf.MustNewConfigFrom("id: some-id"),
-			assertCfg: assert.NotEqual,
+			name: "id is present",
+			cfg:  conf.MustNewConfigFrom("id: some-id"),
+			assertCfg: func(t assert.TestingT, expect any, got *conf.C, msgAndArgs ...any) {
+				id, _ := got.String("id", -1)
+				if !strings.HasPrefix(id, "some-id") {
+					t.Errorf("'id' field must start with the original id, got %q", id)
+				}
+				assert.NotEqual(t, expect, got, msgAndArgs)
+			},
 		},
 		{
-			name:    "absent id",
-			cfg:     conf.MustNewConfigFrom(""),
-			wantErr: errors.New("failed to get 'id'"),
-			assertCfg: func(t assert.TestingT, _ interface{}, got interface{}, msgAndArgs ...interface{}) bool {
-				return assert.Nil(t, got, msgAndArgs...)
+			name: "absent id",
+			cfg:  conf.MustNewConfigFrom(""),
+			assertCfg: func(t assert.TestingT, expect any, got *conf.C, msgAndArgs ...any) {
+				if !got.HasField("id") {
+					t.Errorf("expecting 'id' to be present in %s", conf.DebugString(got, true))
+				}
+				assert.NotNil(t, got, msgAndArgs...)
+				assert.NotEqual(t, expect, got, msgAndArgs)
 			},
 		},
 		{
 			name:    "invalid config",
 			cfg:     nil,
 			wantErr: errors.New("failed to create new config"),
-			assertCfg: func(t assert.TestingT, _ interface{}, got interface{}, msgAndArgs ...interface{}) bool {
-				return assert.Nil(t, got, msgAndArgs...)
+			assertCfg: func(t assert.TestingT, _ any, got *conf.C, msgAndArgs ...any) {
+				assert.Nil(t, got, msgAndArgs...)
 			},
 		},
 	}