add template output (#1051)

* add template output

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* remove dead code

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix template cli flag

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* implement template's own format type

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* simpler code

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix readme link to Go template

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* feedback changes

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* simpler func signature patter

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* nit

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix linter error

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

internal/config/application.go

@@ -38,6 +38,7 @@ type Application struct {
 	// -q, indicates to not show any status output to stderr (ETUI or logging UI)
 	Quiet              bool               `yaml:"quiet" json:"quiet" mapstructure:"quiet"`
 	Outputs            []string           `yaml:"output" json:"output" mapstructure:"output"`                                           // -o, the format to use for output
+	OutputTemplatePath string             `yaml:"output-template-path" json:"output-template-path" mapstructure:"output-template-path"` // -t template file to use for output
 	File               string             `yaml:"file" json:"file" mapstructure:"file"`                                                 // --file, the file to write report output to
 	CheckForAppUpdate  bool               `yaml:"check-for-app-update" json:"check-for-app-update" mapstructure:"check-for-app-update"` // whether to check for an application update on start up or not
 	Anchore            anchore            `yaml:"anchore" json:"anchore" mapstructure:"anchore"`                                        // options for interacting with Anchore Engine/Enterprise

internal/formats/template/encoder.go

@@ -0,0 +1,49 @@
+package template
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"reflect"
+	"text/template"
+
+	"github.com/Masterminds/sprig/v3"
+	"github.com/mitchellh/go-homedir"
+)
+
+func makeTemplateExecutor(templateFilePath string) (*template.Template, error) {
+	if templateFilePath == "" {
+		return nil, errors.New("no template file: please provide a template path")
+	}
+
+	expandedPathToTemplateFile, err := homedir.Expand(templateFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("unable to expand path %s", templateFilePath)
+	}
+
+	templateContents, err := os.ReadFile(expandedPathToTemplateFile)
+	if err != nil {
+		return nil, fmt.Errorf("unable to get template content: %w", err)
+	}
+
+	templateName := expandedPathToTemplateFile
+	tmpl, err := template.New(templateName).Funcs(funcMap).Parse(string(templateContents))
+	if err != nil {
+		return nil, fmt.Errorf("unable to parse template: %w", err)
+	}
+
+	return tmpl, nil
+}
+
+// These are custom functions available to template authors.
+var funcMap = func() template.FuncMap {
+	f := sprig.HermeticTxtFuncMap()
+	f["getLastIndex"] = func(collection interface{}) int {
+		if v := reflect.ValueOf(collection); v.Kind() == reflect.Slice {
+			return v.Len() - 1
+		}
+
+		return 0
+	}
+	return f
+}()

internal/formats/template/encoder_test.go

@@ -0,0 +1,29 @@
+package template
+
+import (
+	"flag"
+	"testing"
+
+	"github.com/anchore/syft/internal/formats/common/testutils"
+	"github.com/stretchr/testify/assert"
+)
+
+var updateTmpl = flag.Bool("update-tmpl", false, "update the *.golden files for json encoders")
+
+func TestFormatWithOption(t *testing.T) {
+	f := OutputFormat{}
+	f.SetTemplatePath("test-fixtures/csv.template")
+
+	testutils.AssertEncoderAgainstGoldenSnapshot(t,
+		f,
+		testutils.DirectoryInput(t),
+		*updateTmpl,
+	)
+
+}
+
+func TestFormatWithoutOptions(t *testing.T) {
+	f := Format()
+	err := f.Encode(nil, testutils.DirectoryInput(t))
+	assert.ErrorContains(t, err, "no template file: please provide a template path")
+}

internal/formats/template/format.go

@@ -0,0 +1,47 @@
+package template
+
+import (
+	"io"
+
+	"github.com/anchore/syft/internal/formats/syftjson"
+	"github.com/anchore/syft/syft/sbom"
+)
+
+const ID sbom.FormatID = "template"
+
+func Format() sbom.Format {
+	return OutputFormat{}
+}
+
+// implementation of sbom.Format interface
+// to make use of format options
+type OutputFormat struct {
+	templateFilePath string
+}
+
+func (f OutputFormat) ID() sbom.FormatID {
+	return ID
+}
+
+func (f OutputFormat) Decode(reader io.Reader) (*sbom.SBOM, error) {
+	return nil, sbom.ErrDecodingNotSupported
+}
+
+func (f OutputFormat) Encode(output io.Writer, s sbom.SBOM) error {
+	tmpl, err := makeTemplateExecutor(f.templateFilePath)
+	if err != nil {
+		return err
+	}
+
+	doc := syftjson.ToFormatModel(s)
+	return tmpl.Execute(output, doc)
+}
+
+func (f OutputFormat) Validate(reader io.Reader) error {
+	return sbom.ErrValidationNotSupported
+}
+
+// SetTemplatePath sets path for template file
+func (f *OutputFormat) SetTemplatePath(filePath string) {
+	f.templateFilePath = filePath
+}

internal/formats/template/test-fixtures/csv.template

@@ -0,0 +1,4 @@
+"Package","Version Installed", "Found by"
+{{- range .Artifacts}}
+"{{.Name}}","{{.Version}}","{{.FoundBy}}"
+{{- end}}

internal/formats/template/test-fixtures/snapshot/TestFormatWithOption.golden

@@ -0,0 +1,3 @@
+"Package","Version Installed", "Found by"
+"package-1","1.0.1","the-cataloger-1"
+"package-2","2.0.1","the-cataloger-2"