Sort frontmatter according to the fields order in config file. Closes #215

src/backends/backend.js

@@ -202,7 +202,8 @@ class Backend {
 
   entryToRaw(collection, entry) {
     const format = resolveFormat(collection, entry);
-    return format && format.toFile(entry);
+    const fieldsOrder = collection.get('fields').map(f => f.get('name')).toArray();
+    return format && format.toFile(entry, fieldsOrder);
   }
 }
 

src/formats/yaml-frontmatter.js

@@ -10,7 +10,7 @@ export default class YAMLFrontmatter {
     return obj;
   }
 
-  toFile(data) {
+  toFile(data, sortedKeys) {
     const meta = {};
     let body = '';
     let content = '';
@@ -23,7 +23,7 @@ export default class YAMLFrontmatter {
     }
 
     content += '---\n';
-    content += new YAML().toFile(meta);
+    content += new YAML().toFile(meta, sortedKeys);
     content += '---\n\n';
     content += body;
     return content;

src/formats/yaml.js

@@ -35,12 +35,26 @@ const OutputSchema = new yaml.Schema({
   explicit: yaml.DEFAULT_SAFE_SCHEMA.explicit,
 });
 
+const sortKeys = (sortedKeys = []) => (a, b) => {
+  const idxA = sortedKeys.indexOf(a);
+  const idxB = sortedKeys.indexOf(b);
+  if (idxA === -1 || idxB === -1) {
+    if (a > b) return 1;
+    if (a < b) return -1;
+    return 0;
+  }
+
+  if (idxA > idxB) return 1;
+  if (idxA < idxB) return -1;
+  return 0;
+};
+
 export default class YAML {
   fromFile(content) {
     return yaml.safeLoad(content);
   }
 
-  toFile(data) {
-    return yaml.safeDump(data, { schema: OutputSchema });
+  toFile(data, sortedKeys = []) {
+    return yaml.safeDump(data, { schema: OutputSchema, sortKeys: sortKeys(sortedKeys) });
   }
 }