feat: support private keys (#102)

* feat: support private keys

* refactor: use `partition`

index.js

@@ -151,7 +151,7 @@ const fields = [
   { key: 'publishConfig', over: sortObject },
 ]
 
-const sortOrder = fields.map(({ key }) => key)
+const defaultSortOrder = fields.map(({ key }) => key)
 
 function editStringJSON(json, over) {
   if (typeof json === 'string') {
@@ -170,11 +170,28 @@ function editStringJSON(json, over) {
   return over(json)
 }
 
+const isPrivateKey = key => key[0] === '_'
+const partition = (array, predicate) =>
+  array.reduce(
+    (result, value) => {
+      result[predicate(value) ? 0 : 1].push(value)
+      return result
+    },
+    [[], []],
+  )
 function sortPackageJson(jsonIsh, options = {}) {
   return editStringJSON(
     jsonIsh,
     onObject(json => {
-      const newJson = sortObjectKeys(json, options.sortOrder || sortOrder)
+      let sortOrder = options.sortOrder ? options.sortOrder : defaultSortOrder
+
+      if (Array.isArray(sortOrder)) {
+        const keys = Object.keys(json)
+        const [privateKeys, publicKeys] = partition(keys, isPrivateKey)
+        sortOrder = [...sortOrder, ...publicKeys.sort(), ...privateKeys.sort()]
+      }
+
+      const newJson = sortObjectKeys(json, sortOrder)
 
       for (const { key, over } of fields) {
         if (over && newJson[key]) newJson[key] = over(newJson[key])
@@ -187,7 +204,7 @@ function sortPackageJson(jsonIsh, options = {}) {
 
 module.exports = sortPackageJson
 module.exports.sortPackageJson = sortPackageJson
-module.exports.sortOrder = sortOrder
+module.exports.sortOrder = defaultSortOrder
 
 if (require.main === module) {
   const fs = require('fs')

test.js

@@ -149,6 +149,22 @@ fs.readFile('./package.json', 'utf8', (error, contents) => {
   )
 })
 
+// fields with '_' prefix should alway at bottom
+assert.deepStrictEqual(
+  Object.keys(
+    sortPackageJson({
+      _foo: '_foo',
+      foo: 'foo',
+      version: '1.0.0',
+      name: 'sort-package-json',
+      bar: 'bar',
+      _id: 'sort-package-json@1.0.0',
+      _bar: '_bar',
+    }),
+  ),
+  ['name', 'version', 'bar', 'foo', '_bar', '_foo', '_id'],
+)
+
 // fields tests
 
 // fields sort as object