[7.x](backport #28280) [libbeat] Deprecate common.Float (#28309)

* Deprecate common.Float (#28280)

Deprecate common.Float and stop using it during event normalization within the publishing pipeline.
common.Float has not been used for its original purpose since ~2017 when marshaling to JSON was
handled by go-structform.

This will fix processors that did not previously handle common.Float in type assertions.

Fixes #28279

(cherry picked from commit b891ce2)

* Update CHANGELOG.next.asciidoc

Co-authored-by: Andrew Kroh <andrew.kroh@elastic.co>

CHANGELOG-developer.next.asciidoc

@@ -115,3 +115,7 @@ The list below covers the major changes between 7.0.0-rc2 and master only.
 - Update to go-concert 0.2.0 {pull}27162[27162]
 - Update Go version to 1.16.5. {issue}26182[26182] {pull}26186[26186]
 - Introduce `libbeat/beat.Beat.OutputConfigReloader` {pull}28048[28048]
+
+==== Deprecated
+
+- Deprecated the `common.Float` type. {issue}28279[28279] {pull}28280[28280]

CHANGELOG.next.asciidoc

@@ -135,6 +135,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Preserve annotations in a kubernetes namespace metadata {pull}27045[27045]
 - Allow conditional processing in `decode_xml` and `decode_xml_wineventlog`. {pull}27159[27159]
 - Fix build constraint that caused issues with doc builds. {pull}27381[27381]
+- Fix handling of float data types within processors. {issue}28279[28279] {pull}28280[28280]
 
 *Auditbeat*
 

libbeat/common/event.go

@@ -33,6 +33,11 @@ import (
 
 var textMarshalerType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
 
+// Float is a float64 wrapper that implements the encoding/json Marshaler
+// interface to add a decimal point to all float values.
+//
+// Deprecated: This type should no longer be used and the Marshaler interface
+// is not consulted while marshaling to JSON in libbeat outputs.
 type Float float64
 
 // EventConverter is used to convert MapStr objects for publishing
@@ -208,10 +213,7 @@ func (e *GenericEventConverter) normalizeValue(value interface{}, keys ...string
 		}
 		return tmp, nil
 
-	case float64:
-		return Float(value.(float64)), nil
-	case float32:
-		return Float(value.(float32)), nil
+	case float32, float64:
 	case []float32, []float64:
 	case complex64, complex128:
 	case []complex64, []complex128:
@@ -238,7 +240,7 @@ func (e *GenericEventConverter) normalizeValue(value interface{}, keys ...string
 		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
 			return v.Uint() &^ (1 << 63), nil
 		case reflect.Float32, reflect.Float64:
-			return Float(v.Float()), nil
+			return v.Float(), nil
 		case reflect.Complex64, reflect.Complex128:
 			return v.Complex(), nil
 		case reflect.String:

libbeat/common/event_test.go

@@ -267,7 +267,7 @@ func TestNormalizeValue(t *testing.T) {
 	}
 
 	checkDelta := func(t *testing.T, a, b interface{}) {
-		assert.InDelta(t, a, float64(b.(Float)), 0.000001)
+		assert.InDelta(t, a, b, 0.000001)
 	}
 
 	var nilStringPtr *string