feat(jsonnet): import .yaml (#106)

Allows to directly import `.yaml` files from `.jsonnet`, as if they were JSON:

   local whatever = import "foo.yaml"

pkg/jsonnet/eval.go

@@ -27,12 +27,8 @@ func EvaluateFile(jsonnetFile string) (string, error) {
 
 // Evaluate renders the given jsonnet into a string
 func Evaluate(sonnet string, jpath []string) (string, error) {
-	importer := jsonnet.FileImporter{
-		JPaths: jpath,
-	}
-
 	vm := jsonnet.MakeVM()
-	vm.Importer(&importer)
+	vm.Importer(NewExtendedImporter(jpath))
 	for _, nf := range native.Funcs() {
 		vm.NativeFunction(nf)
 	}

pkg/jsonnet/importer.go

@@ -0,0 +1,50 @@
+package jsonnet
+
+import (
+	"encoding/json"
+	"path/filepath"
+
+	jsonnet "github.com/google/go-jsonnet"
+	"github.com/pkg/errors"
+	"gopkg.in/yaml.v3"
+)
+
+// ExtendedImporter wraps jsonnet.FileImporter to add additional functionality:
+// - `import "file.yaml"`
+type ExtendedImporter struct {
+	fi *jsonnet.FileImporter
+}
+
+// NewExtendedImporter returns a new instance of ExtendedImporter with the
+// correct jpaths set up
+func NewExtendedImporter(jpath []string) *ExtendedImporter {
+	return &ExtendedImporter{
+		fi: &jsonnet.FileImporter{
+			JPaths: jpath,
+		},
+	}
+}
+
+func (i *ExtendedImporter) Import(importedFrom, importedPath string) (contents jsonnet.Contents, foundAt string, err error) {
+	// regularly import
+	contents, foundAt, err = i.fi.Import(importedFrom, importedPath)
+	if err != nil {
+		return jsonnet.Contents{}, "", err
+	}
+
+	// if yaml -> convert to json
+	ext := filepath.Ext(foundAt)
+	if ext == ".yaml" || ext == ".yml" {
+		var data map[string]interface{}
+		if err := yaml.Unmarshal([]byte(contents.String()), &data); err != nil {
+			return jsonnet.Contents{}, "", errors.Wrapf(err, "unmarshalling yaml import '%s'", foundAt)
+		}
+		out, err := json.Marshal(data)
+		if err != nil {
+			return jsonnet.Contents{}, "", errors.Wrapf(err, "converting '%s' to json", foundAt)
+		}
+		contents = jsonnet.MakeContents(string(out))
+	}
+
+	return
+}

pkg/jsonnet/imports.go

@@ -24,12 +24,9 @@ func TransitiveImports(filename string) ([]string, error) {
 	if err != nil {
 		return nil, errors.Wrap(err, "resolving JPATH")
 	}
-	importer := jsonnet.FileImporter{
-		JPaths: jpath,
-	}
 
 	vm := jsonnet.MakeVM()
-	vm.Importer(&importer)
+	vm.Importer(NewExtendedImporter(jpath))
 	for _, nf := range native.Funcs() {
 		vm.NativeFunction(nf)
 	}