feat(pkg): add support to empty bracket syntax

Adds ability to using empty bracket syntax as a shortcut to appending
items to the end of an array when using `npm pkg set`, e.g:

npm pkg set keywords[]=foo

Relates to: npm/rfcs#402

docs/content/commands/npm-pkg.md

@@ -98,6 +98,13 @@ Returned values are always in **json** format.
     npm pkg set contributors[0].name='Foo' contributors[0].email='foo@bar.ca'
     ```
 
+    You may also append items to the end of an array using the special
+    empty bracket notation:
+
+    ```bash
+    npm pkg set contributors[].name='Foo' contributors[].name='Bar'
+    ```
+
     It's also possible to parse values as json prior to saving them to your
     `package.json` file, for example in order to set a `"private": true`
     property:

lib/utils/queryable.js

@@ -1,14 +1,27 @@
 const util = require('util')
 const _data = Symbol('data')
 const _delete = Symbol('delete')
+const _append = Symbol('append')
 
-const sqBracketsMatcher = str => str.match(/(.+)\[([^\]]+)\](.*)$/)
+const sqBracketsMatcher = str => str.match(/(.+)\[([^\]]+)\]\.?(.*)$/)
 
-const cleanLeadingDot = str =>
-  str && str.startsWith('.') ? str.substr(1) : str
+// replaces any occurence of an empty-brackets (e.g: []) with a special
+// Symbol(append) to represent it, this is going to be useful for the setter
+// method that will push values to the end of the array when finding these
+const replaceAppendSymbols = str => {
+  const matchEmptyBracket = str.match(/^(.*)\[\]\.?(.*)$/)
+
+  if (matchEmptyBracket) {
+    const [, pre, post] = matchEmptyBracket
+    return [...replaceAppendSymbols(pre), _append, post].filter(Boolean)
+  }
+
+  return [str]
+}
 
 const parseKeys = (key) => {
   const sqBracketItems = new Set()
+  sqBracketItems.add(_append)
   const parseSqBrackets = (str) => {
     const index = sqBracketsMatcher(str)
 
@@ -21,7 +34,7 @@ const parseKeys = (key) => {
       // foo.bar[foo.bar] should split into { foo: { bar: { 'foo.bar': {} } }
       /* eslint-disable-next-line no-new-wrappers */
       const foundKey = new String(index[2])
-      const postSqBracketPortion = cleanLeadingDot(index[3])
+      const postSqBracketPortion = index[3]
 
       // we keep track of items found during this step to make sure
       // we don't try to split-separate keys that were defined within
@@ -43,7 +56,11 @@ const parseKeys = (key) => {
       ]
     }
 
-    return [str]
+    // at the end of parsing, any usage of the special empty-bracket syntax
+    // (e.g: foo.array[]) has  not yet bene parsed, here we'll take care
+    // of parsing it and adding a special symbol to represent it in
+    // the resulting list of keys
+    return replaceAppendSymbols(str)
   }
 
   const res = []
@@ -79,6 +96,14 @@ const getter = ({ data, key }) => {
   let label = ''
 
   for (const k of keys) {
+    // empty-bracket-shortcut-syntax is not supported on getter
+    if (k === _append) {
+      throw Object.assign(
+        new Error('Empty brackets are not valid syntax for retrieving values.'),
+        { code: 'EINVALIDSYNTAX' }
+      )
+    }
+
     // extra logic to take into account printing array, along with its
     // special syntax in which using a dot-sep property name after an
     // arry will expand it's results, e.g:
@@ -119,13 +144,39 @@ const setter = ({ data, key, value, force }) => {
   // ['foo', 'bar', 'baz'] -> { foo: { bar: { baz:  {} } }
   const keys = parseKeys(key)
   const setKeys = (_data, _key) => {
-    // handles array indexes, making sure the new array is created if
-    // missing and properly casting the index to a number
-    const maybeIndex = Number(_key)
-    if (!Number.isNaN(maybeIndex)) {
+    // handles array indexes, converting valid integers to numbers,
+    // note that occurences of Symbol(append) will throw,
+    // so we just ignore these for now
+    let maybeIndex = Number.NaN
+    try {
+      maybeIndex = Number(_key)
+    } catch (err) {}
+    if (!Number.isNaN(maybeIndex))
       _key = maybeIndex
-      if (!Object.keys(_data).length)
-        _data = []
+
+    // creates new array in case key is an index
+    // and the array obj is not yet defined
+    const keyIsAnArrayIndex = _key === maybeIndex || _key === _append
+    const dataHasNoItems = !Object.keys(_data).length
+    if (keyIsAnArrayIndex && dataHasNoItems && !Array.isArray(_data))
+      _data = []
+
+    // converting from array to an object is also possible, in case the
+    // user is using force mode, we should also convert existing arrays
+    // to an empty object if the current _data is an array
+    if (force && Array.isArray(_data) && !keyIsAnArrayIndex)
+      _data = { ..._data }
+
+    // the _append key is a special key that is used to represent
+    // the empty-bracket notation, e.g: arr[] -> arr[arr.length]
+    if (_key === _append) {
+      if (!Array.isArray(_data)) {
+        throw Object.assign(
+          new Error(`Can't use append syntax in non-Array element`),
+          { code: 'ENOAPPEND' }
+        )
+      }
+      _key = _data.length
     }
 
     // retrieves the next data object to recursively iterate on,
@@ -141,20 +192,30 @@ const setter = ({ data, key, value, force }) => {
       // appended to the resulting obj is not an array index, then it
       // should throw since we can't append arbitrary props to arrays
       const shouldNotAddPropsToArrays =
+        typeof keys[0] !== 'symbol' &&
         Array.isArray(_data[_key]) &&
         Number.isNaN(Number(keys[0]))
 
       const overrideError =
         haveContents &&
-        (shouldNotOverrideLiteralValue || shouldNotAddPropsToArrays)
-
+        shouldNotOverrideLiteralValue
       if (overrideError) {
         throw Object.assign(
-          new Error(`Property ${key} already has a value in place.`),
+          new Error(`Property ${_key} already exists and is not an Array or Object.`),
           { code: 'EOVERRIDEVALUE' }
         )
       }
 
+      const addPropsToArrayError =
+        haveContents &&
+        shouldNotAddPropsToArrays
+      if (addPropsToArrayError) {
+        throw Object.assign(
+          new Error(`Can't add property ${key} to an Array.`),
+          { code: 'ENOADDPROP' }
+        )
+      }
+
       return typeof _data[_key] === 'object' ? _data[_key] || {} : {}
     }
 

test/lib/pkg.js

@@ -291,6 +291,38 @@ t.test('set single field', t => {
   })
 })
 
+t.test('push to array syntax', t => {
+  const json = {
+    name: 'foo',
+    version: '1.1.1',
+    keywords: [
+      'foo',
+    ],
+  }
+  npm.localPrefix = t.testdir({
+    'package.json': JSON.stringify(json),
+  })
+
+  pkg.exec(['set', 'keywords[]=bar', 'keywords[]=baz'], err => {
+    if (err)
+      throw err
+
+    t.strictSame(
+      readPackageJson(),
+      {
+        ...json,
+        keywords: [
+          'foo',
+          'bar',
+          'baz',
+        ],
+      },
+      'should append to arrays using empty bracket syntax'
+    )
+    t.end()
+  })
+})
+
 t.test('set multiple fields', t => {
   const json = {
     name: 'foo',