Support arbitrary data unter the key custom in meta.yaml or meta.js…

…on is accessible via the api

References #62, #71, #73

This will enable creators of custom frontends to use custom data fields / values
/ configuration defined in metadata. Data needs to be evaluated and validated in
the frontend.

- Expose custom data through api
- Add custom data synonyms example
- Demostrate custom data and synonyms in yaml

With the help of dyno:
https://stackoverflow.com/questions/40737122/convert-yaml-to-json-without-struct/40737676#40737676

apiv1.go

@@ -59,6 +59,7 @@ type APIv1Node struct {
 	Modified    int64              `json:"modified"`
 	Version     string             `json:"version"`
 	Tags        []string           `json:"tags"`
+	Custom      interface{}        `json:"custom"`
 	Docs        []*APIv1NodeDoc    `json:"docs"`
 	Assets      []*APIv1NodeAsset  `json:"assets"`
 	Crumbs      []*APIv1RefNode    `json:"crumbs"`
@@ -263,6 +264,7 @@ func (api APIv1) NewNode(n *Node) (*APIv1Node, error) {
 		Related:     related,
 		Prev:        prev,
 		Next:        next,
+		Custom:      n.Custom(),
 
 		// Deprecated, to be removed in APIv3:
 		Downloads: assets,

example/02_Components/Displaying Content/List/meta.yaml

@@ -8,4 +8,9 @@ tags:
   - Progress/Draft
   - Release/0.6
 
+custom:
+  synonyms:
+    - Listing
+    - Index
+
 version: 1

example/02_Components/Input/Textfield/meta.yaml

@@ -8,3 +8,8 @@ tags:
   - Build 8
 
 version: 1
+
+custom:
+  synonyms:
+    - Inputfield
+    - Entryfield

frontend/src/Page/index.js

@@ -133,6 +133,12 @@ function Page(props) {
     authors = <Meta title={title}>{authorLinks}</Meta>;
   }
 
+  let synonyms;
+  if (props.custom && props.custom.synonyms) {
+    let synonymText = Array.isArray(props.custom.synonyms) ? props.custom.synonyms.join(", ") : props.custom.synonyms
+    synonyms = <Meta title="Synonyms">{synonymText}</Meta>;
+  }
+
   return (
     <div className="page">
       <div className="page__header">
@@ -150,6 +156,7 @@ function Page(props) {
           <div className="page__meta">
             <Meta title="Last Changed">{new Date(props.modified * 1000).toLocaleDateString()}</Meta>
             {authors}
+            {synonyms}
           </div>
         </div>
       </div>

node.go

@@ -218,6 +218,10 @@ func (n *Node) Description() string {
 	return n.meta.Description
 }
 
+func (n *Node) Custom() interface{} {
+	return n.meta.Custom
+}
+
 // Returns a list of related nodes.
 func (n *Node) Related(get NodeGetter) []*Node {
 	nodes := make([]*Node, 0, len(n.meta.Related))

node_meta.go

@@ -12,17 +12,19 @@ import (
 	"path/filepath"
 
 	"github.com/go-yaml/yaml"
+	"github.com/icza/dyno"
 )
 
 // Metadata parsed from node configuration.
 type NodeMeta struct {
 	path string
 
 	// Email addresses of node authors.
-	Authors     []string `json:"authors,omitempty" yaml:"authors,omitempty"`
-	Description string   `json:"description,omitempty" yaml:"description,omitempty"`
-	Related     []string `json:"related,omitempty" yaml:"related,omitempty"`
-	Tags        []string `json:"tags,omitempty" yaml:"tags,omitempty"`
+	Authors     []string    `json:"authors,omitempty" yaml:"authors,omitempty"`
+	Description string      `json:"description,omitempty" yaml:"description,omitempty"`
+	Related     []string    `json:"related,omitempty" yaml:"related,omitempty"`
+	Tags        []string    `json:"tags,omitempty" yaml:"tags,omitempty"`
+	Custom      interface{} `json:"custom,omitempty" yaml:"custom,omitempty"`
 
 	// Freeform version string.
 	Version string `json:"version,omitempty" yaml:"version,omitempty"`
@@ -59,7 +61,11 @@ func (m *NodeMeta) Load() error {
 	case ".json":
 		return json.Unmarshal(contents, &m)
 	case ".yaml", ".yml":
-		return yaml.Unmarshal(contents, &m)
+		if err := yaml.Unmarshal(contents, &m); err != nil {
+			return err
+		}
+		m.Custom = dyno.ConvertMapI2MapS(m.Custom)
+		return nil
 	default:
 		return fmt.Errorf("Unsupported format: %s", prettyPath(m.path))
 	}