Fix an issue where we were trying to use a non existing directory whe…

…n generating the fields.go (elastic#8729)

* Fix an issue where we were trying to get use a non existing directory
when generating the fields.go

Functionbeat doesn't have a OSS implementation.

* Add an XPACK_ONLY flag so we can skip some commands in libbeat

dev-tools/mage/fields.go

@@ -18,6 +18,7 @@
 package mage
 
 import (
+	"os"
 	"path/filepath"
 
 	"github.com/magefile/mage/sh"
@@ -40,7 +41,11 @@ func OSSBeatDir(path ...string) string {
 
 	// Check if we need to correct ossDir because it's in x-pack.
 	if parentDir := filepath.Base(filepath.Dir(ossDir)); parentDir == "x-pack" {
-		ossDir = filepath.Join(ossDir, "../..", BeatName)
+		// If the OSS version of the beat exists.
+		tmp := filepath.Join(ossDir, "../..", BeatName)
+		if _, err := os.Stat(tmp); !os.IsNotExist(err) {
+			ossDir = tmp
+		}
 	}
 
 	return filepath.Join(append([]string{ossDir}, path...)...)

libbeat/scripts/Makefile

@@ -213,7 +213,7 @@ system-tests-environment: prepare-tests build-image
 	${DOCKER_COMPOSE} run -e INTEGRATION_TESTS=1 -e TESTING_ENVIRONMENT=${TESTING_ENVIRONMENT} -e DOCKER_COMPOSE_PROJECT_NAME=${DOCKER_COMPOSE_PROJECT_NAME} beat make system-tests
 	#This is a hack to run x-pack/filebeat module tests
 	@XPACKBEAT="${ES_BEATS}/x-pack/${BEAT_NAME}" ; \
-	if [ -e "$$XPACKBEAT/tests/system" ] ; then \
+	if [ -e "$$XPACKBEAT/tests/system" ] && [ $(XPACK_ONLY) = false ]; then \
 	    $(MAKE) -C ../x-pack/${BEAT_NAME} fields; \
 	    ${DOCKER_COMPOSE} run -e INTEGRATION_TESTS=1 -e MODULES_PATH="../../x-pack/${BEAT_NAME}/module" -e TESTING_ENVIRONMENT=${TESTING_ENVIRONMENT} -e DOCKER_COMPOSE_PROJECT_NAME=${DOCKER_COMPOSE_PROJECT_NAME} beat make -C "$$XPACKBEAT" ${BEAT_NAME}.test system-tests ; \
 	    $(MAKE) -C ../x-pack/${BEAT_NAME} fix-permissions; \