dont export structs used for unmarshaling

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

syft/presenter/json/artifact.go

@@ -9,11 +9,11 @@ import (
 )
 
 type Artifact struct {
-	ArtifactBasicMetadata
-	ArtifactCustomMetadata
+	artifactBasicMetadata
+	artifactCustomMetadata
 }
 
-type ArtifactBasicMetadata struct {
+type artifactBasicMetadata struct {
 	Name      string            `json:"name"`
 	Version   string            `json:"version"`
 	Type      pkg.Type          `json:"type"`
@@ -23,12 +23,12 @@ type ArtifactBasicMetadata struct {
 	Language  pkg.Language      `json:"language"`
 }
 
-type ArtifactCustomMetadata struct {
+type artifactCustomMetadata struct {
 	MetadataType pkg.MetadataType `json:"metadataType"`
 	Metadata     interface{}      `json:"metadata,omitempty"`
 }
 
-type ArtifactMetadataUnpacker struct {
+type artifactMetadataUnpacker struct {
 	MetadataType string          `json:"metadataType"`
 	Metadata     json.RawMessage `json:"metadata"`
 }
@@ -36,7 +36,7 @@ type ArtifactMetadataUnpacker struct {
 func NewArtifact(p *pkg.Package) (Artifact, error) {
 
 	return Artifact{
-		ArtifactBasicMetadata: ArtifactBasicMetadata{
+		artifactBasicMetadata: artifactBasicMetadata{
 			Name:      p.Name,
 			Version:   p.Version,
 			Type:      p.Type,
@@ -45,7 +45,7 @@ func NewArtifact(p *pkg.Package) (Artifact, error) {
 			Licenses:  p.Licenses,
 			Language:  p.Language,
 		},
-		ArtifactCustomMetadata: ArtifactCustomMetadata{
+		artifactCustomMetadata: artifactCustomMetadata{
 			MetadataType: p.MetadataType,
 			Metadata:     p.Metadata,
 		},
@@ -68,13 +68,13 @@ func (a Artifact) ToPackage() pkg.Package {
 }
 
 func (a *Artifact) UnmarshalJSON(b []byte) error {
-	var basic ArtifactBasicMetadata
+	var basic artifactBasicMetadata
 	if err := json.Unmarshal(b, &basic); err != nil {
 		return err
 	}
-	a.ArtifactBasicMetadata = basic
+	a.artifactBasicMetadata = basic
 
-	var unpacker ArtifactMetadataUnpacker
+	var unpacker artifactMetadataUnpacker
 	if err := json.Unmarshal(b, &unpacker); err != nil {
 		return err
 	}

syft/presenter/json/distribution.go

@@ -2,13 +2,14 @@ package json
 
 import "github.com/anchore/syft/syft/distro"
 
-// Distribution provides information about a detected Linux Distribution
+// Distribution provides information about a detected Linux Distribution.
 type Distribution struct {
-	Name    string `json:"name"`
-	Version string `json:"version"`
-	IDLike  string `json:"idLike"`
+	Name    string `json:"name"`    // Name of the Linux distribution
+	Version string `json:"version"` // Version of the Linux distribution (major or major.minor version)
+	IDLike  string `json:"idLike"`  // the ID_LIKE field found within the /etc/os-release file
 }
 
+// NewDistribution creates a struct with the Linux distribution to be represented in JSON.
 func NewDistribution(d distro.Distro) Distribution {
 	distroName := d.Name()
 	if distroName == "UnknownDistroType" {

syft/presenter/json/document.go

@@ -8,13 +8,15 @@ import (
 	"github.com/anchore/syft/syft/source"
 )
 
+// Document represents the syft cataloging findings as a JSON document
 type Document struct {
-	Artifacts  []Artifact   `json:"artifacts"`
-	Source     Source       `json:"source"`
-	Distro     Distribution `json:"distro"`
-	Descriptor Descriptor   `json:"descriptor"`
+	Artifacts  []Artifact   `json:"artifacts"`  // Artifacts is the list of packages discovered and placed into the catalog
+	Source     Source       `json:"source"`     // Source represents the original object that was cataloged
+	Distro     Distribution `json:"distro"`     // Distro represents the Linux distribution that was detected from the source
+	Descriptor Descriptor   `json:"descriptor"` // Descriptor is a block containing self-describing information about syft
 }
 
+// NewDocument creates and populates a new JSON document struct from the given cataloging results.
 func NewDocument(catalog *pkg.Catalog, srcMetadata source.Metadata, d distro.Distro) (Document, error) {
 	src, err := NewSource(srcMetadata)
 	if err != nil {

syft/presenter/json/presenter.go

@@ -9,12 +9,14 @@ import (
 	"github.com/anchore/syft/syft/source"
 )
 
+// Presenter is a JSON presentation object for the syft results
 type Presenter struct {
 	catalog     *pkg.Catalog
 	srcMetadata source.Metadata
 	distro      distro.Distro
 }
 
+// NewPresenter creates a new JSON presenter object for the given cataloging results.
 func NewPresenter(catalog *pkg.Catalog, s source.Metadata, d distro.Distro) *Presenter {
 	return &Presenter{
 		catalog:     catalog,
@@ -23,6 +25,7 @@ func NewPresenter(catalog *pkg.Catalog, s source.Metadata, d distro.Distro) *Pre
 	}
 }
 
+// Present the catalog results to the given writer.
 func (pres *Presenter) Present(output io.Writer) error {
 	doc, err := NewDocument(pres.catalog, pres.srcMetadata, pres.distro)
 	if err != nil {

syft/presenter/json/source.go

@@ -7,16 +7,19 @@ import (
 	"github.com/anchore/syft/syft/source"
 )
 
+// Source object represents the thing that was cataloged
 type Source struct {
 	Type   string      `json:"type"`
 	Target interface{} `json:"target"`
 }
 
-type SourceUnpacker struct {
+// sourceUnpacker is used to unmarshal Source objects
+type sourceUnpacker struct {
 	Type   string          `json:"type"`
 	Target json.RawMessage `json:"target"`
 }
 
+// NewSource creates a new source object to be represented into JSON.
 func NewSource(src source.Metadata) (Source, error) {
 	switch src.Scheme {
 	case source.ImageScheme:
@@ -34,8 +37,9 @@ func NewSource(src source.Metadata) (Source, error) {
 	}
 }
 
+// UnmarshalJSON populates a source object from JSON bytes.
 func (s *Source) UnmarshalJSON(b []byte) error {
-	var unpacker SourceUnpacker
+	var unpacker sourceUnpacker
 	if err := json.Unmarshal(b, &unpacker); err != nil {
 		return err
 	}
@@ -57,6 +61,7 @@ func (s *Source) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
+// ToSourceMetadata takes a source object represented from JSON and creates a source.Metadata object.
 func (s *Source) ToSourceMetadata() source.Metadata {
 	var metadata source.Metadata
 	switch s.Type {