Add openapi3.Unmarshal

Fixes #7442
Fixes #7443

tpl/openapi/openapi3/openapi3.go

@@ -0,0 +1,97 @@
+// Copyright 2020 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package openapi3
+
+import (
+	"io/ioutil"
+
+	gyaml "github.com/ghodss/yaml"
+
+	"github.com/pkg/errors"
+
+	kopenapi3 "github.com/getkin/kin-openapi/openapi3"
+	"github.com/gohugoio/hugo/cache/namedmemcache"
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/parser/metadecoders"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+// New returns a new instance of the openapi3-namespaced template functions.
+func New(deps *deps.Deps) *Namespace {
+	// TODO1 consolidate when merging that "other branch" -- but be aware of the keys.
+	cache := namedmemcache.New()
+	deps.BuildStartListeners.Add(
+		func() {
+			cache.Clear()
+		})
+
+	return &Namespace{
+		cache: cache,
+		deps:  deps,
+	}
+}
+
+// Namespace provides template functions for the "openapi3".
+type Namespace struct {
+	cache *namedmemcache.Cache
+	deps  *deps.Deps
+}
+
+func (ns *Namespace) Unmarshal(r resource.UnmarshableResource) (*kopenapi3.Swagger, error) {
+
+	key := r.Key()
+	if key == "" {
+		return nil, errors.New("no Key set in Resource")
+	}
+
+	v, err := ns.cache.GetOrCreate(key, func() (interface{}, error) {
+		f := metadecoders.FormatFromMediaType(r.MediaType())
+		if f == "" {
+			return nil, errors.Errorf("MIME %q not supported", r.MediaType())
+		}
+
+		reader, err := r.ReadSeekCloser()
+		if err != nil {
+			return nil, err
+		}
+		defer reader.Close()
+
+		b, err := ioutil.ReadAll(reader)
+		if err != nil {
+			return nil, err
+		}
+
+		s := &kopenapi3.Swagger{}
+		switch f {
+		case metadecoders.YAML:
+			err = gyaml.Unmarshal(b, s)
+		default:
+			err = metadecoders.Default.UnmarshalTo(b, f, s)
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		err = kopenapi3.NewSwaggerLoader().ResolveRefsIn(s, nil)
+
+		return s, err
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return v.(*kopenapi3.Swagger), nil
+
+}