fix issues from @simitt's code review

model/error/event.go

@@ -41,12 +41,6 @@ import (
 
 var (
 	Metrics = monitoring.Default.NewRegistry("apm-server.processor.error", monitoring.PublishExpvar)
-
-	transformations   = monitoring.NewInt(Metrics, "transformations")
-	errorCounter      = monitoring.NewInt(Metrics, "errors")
-	stacktraceCounter = monitoring.NewInt(Metrics, "stacktraces")
-	frameCounter      = monitoring.NewInt(Metrics, "frames")
-	processorEntry    = common.MapStr{"name": processorName, "event": errorDocType}
 )
 
 const (

model/error/payload.go

@@ -24,6 +24,15 @@ import (
 	"github.com/elastic/beats/libbeat/beat"
 	"github.com/elastic/beats/libbeat/common"
 	"github.com/elastic/beats/libbeat/logp"
+	"github.com/elastic/beats/libbeat/monitoring"
+)
+
+var (
+	transformations   = monitoring.NewInt(Metrics, "transformations")
+	errorCounter      = monitoring.NewInt(Metrics, "errors")
+	stacktraceCounter = monitoring.NewInt(Metrics, "stacktraces")
+	frameCounter      = monitoring.NewInt(Metrics, "frames")
+	processorEntry    = common.MapStr{"name": processorName, "event": errorDocType}
 )
 
 type Payload struct {

model/metric/payload_test.go

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/elastic/apm-server/config"
 	m "github.com/elastic/apm-server/model"
@@ -252,7 +253,8 @@ func TestPayloadDecode(t *testing.T) {
 
 		// its ok to ignore the outcome of this cast here because
 		// we assert everything below
-		payload, _ := payloadInterface.(*Payload)
+		payload, ok := payloadInterface.(*Payload)
+		require.True(t, ok)
 
 		// compare metrics separately as they may be ordered differently
 		if test.p != nil && test.p.Metrics != nil {

model/transform/transform.go

@@ -0,0 +1,19 @@
+package transform
+
+import (
+	"regexp"
+
+	"github.com/elastic/apm-server/model"
+	"github.com/elastic/apm-server/sourcemap"
+)
+
+type Context struct {
+	Config   Config
+	Metadata model.Metadata
+}
+
+type Config struct {
+	LibraryPattern      *regexp.Regexp
+	ExcludeFromGrouping *regexp.Regexp
+	SmapMapper          sourcemap.Mapper
+}

processor/error/error.go

@@ -15,7 +15,7 @@
 // specific language governing permissions and limitations
 // under the License.
 
-package processor
+package error
 
 import (
 	err "github.com/elastic/apm-server/model/error"

processor/processor.go

@@ -25,8 +25,6 @@ import (
 	"github.com/elastic/beats/libbeat/monitoring"
 )
 
-type NewProcessor func() Processor
-
 type Processor interface {
 	Validate(map[string]interface{}) error
 	Decode(map[string]interface{}) (model.Payload, error)

processor/sourcemap/sourcemap.go

@@ -30,16 +30,15 @@ import (
 )
 
 var (
-	validateCount = monitoring.NewInt(sm.Metrics, "validation.count")
-	validateError = monitoring.NewInt(sm.Metrics, "validation.errors")
-
 	Processor = &sourcemapProcessor{
 		processor.PayloadProcessor{
 			ProcessorName: "sourcemap",
 			DecodePayload: sm.DecodePayload,
 			PayloadSchema: sm.PayloadSchema(),
 			DecodingCount: monitoring.NewInt(sm.Metrics, "decoding.count"),
 			DecodingError: monitoring.NewInt(sm.Metrics, "decoding.errors"),
+			ValidateCount: monitoring.NewInt(sm.Metrics, "validation.count"),
+			ValidateError: monitoring.NewInt(sm.Metrics, "validation.errors"),
 		},
 	}
 )
@@ -49,7 +48,7 @@ type sourcemapProcessor struct {
 }
 
 func (p *sourcemapProcessor) Validate(raw map[string]interface{}) error {
-	validateCount.Inc()
+	p.PayloadProcessor.ValidateCount.Inc()
 
 	smap, ok := raw["sourcemap"].(string)
 	if !ok {
@@ -67,7 +66,7 @@ func (p *sourcemapProcessor) Validate(raw map[string]interface{}) error {
 
 	err = validation.Validate(raw, p.PayloadSchema)
 	if err != nil {
-		validateError.Inc()
+		p.PayloadProcessor.ValidateError.Inc()
 	}
 	return err
 }