✨ Lazy get (#266)

* ✨ Support first arg currying in get

* ✨ Apply: support function args

* 🐛 fix broken update...

packages/immutadot/src/core/get.js

@@ -2,31 +2,46 @@ import {
   index,
   prop,
 } from 'path/consts'
-import { isNil } from 'util/lang'
+import {
+  isNil,
+  isString,
+} from 'util/lang'
 import { toPath } from 'path/toPath'
 
+const getter = Symbol('getter')
+
 /**
 * Gets the value at <code>path</code> of <code>obj</code>.
 * @memberof core
-* @param {*} obj The object.
+* @param {*} [obj] The object.
 * @param {string|Array} path The path of the property to get.
 * @param {*} defaultValue The default value.
 * @return {*} Returns the value or <code>defaultValue</code>.
 * @example get({ nested: { prop: 'val' } }, 'nested.prop') // => 'val'
 * @example get({ nested: { prop: 'val' } }, 'nested.unknown', 'default') // => 'default'
 * @since 1.0.0
  */
-function get(obj, path, defaultValue) {
-  function walkPath(curObj, remPath) {
-    if (remPath.length === 0) return curObj === undefined ? defaultValue : curObj
-    if (isNil(curObj)) return defaultValue
-    const [[, prop], ...pathRest] = remPath
-    return walkPath(curObj[prop], pathRest)
+function get(...args) {
+  const [firstArg, ...argsRest] = args
+  if (isString(firstArg)) return makeGetter(...args)
+  return makeGetter(...argsRest)(firstArg)
+}
+
+function makeGetter(path, defaultValue) {
+  const getterFn = function(obj) {
+    function walkPath(curObj, remPath) {
+      if (remPath.length === 0) return curObj === undefined ? defaultValue : curObj
+      if (isNil(curObj)) return defaultValue
+      const [[, prop], ...pathRest] = remPath
+      return walkPath(curObj[prop], pathRest)
+    }
+    const parsedPath = toPath(path)
+    if (parsedPath.some(([propType]) => propType !== prop && propType !== index))
+      throw TypeError('get supports only properties and array indexes in path')
+    return walkPath(obj, parsedPath)
   }
-  const parsedPath = toPath(path)
-  if (parsedPath.some(([propType]) => propType !== prop && propType !== index))
-    throw TypeError('get supports only properties and array indexes in path')
-  return walkPath(obj, parsedPath)
+  getterFn[getter] = true
+  return getterFn
 }
 
-export { get }
+export { get, getter }

packages/immutadot/src/core/get.spec.js

@@ -29,4 +29,9 @@ describe('core.get', () => {
   it('should throw an error if path includes something else than props and indexes', () => {
     expect(() => get({}, 'foo[1:2]')).toThrowError('get supports only properties and array indexes in path')
   })
+
+  it('should support currying the object', () => {
+    expect(get('nested2.arr[0].val')(obj)).toBe('arrVal')
+    expect(get('nested2.arr[1].val', 'defaultValue')(obj)).toBe('defaultValue')
+  })
 })

packages/immutadot/src/path/apply.js

@@ -17,6 +17,8 @@ import {
   length,
 } from 'util/lang'
 
+import { getter } from 'core/get'
+
 import { toPath } from './toPath'
 
 /**
@@ -132,7 +134,8 @@ const apply = operation => {
 
         if (remPath.length === 1) {
           const newObj = copyIfNecessary(curObj, propType, doCopy)
-          operation(newObj, propValue, value, ...args)
+          const resolvedArgs = args.map(arg => arg[getter] ? arg(obj) : arg)
+          operation(newObj, propValue, value, ...resolvedArgs)
           return [false, newObj]
         }
 

packages/immutadot/src/path/apply.spec.js

@@ -1,5 +1,6 @@
 /* eslint-env jest */
 import { apply } from './apply'
+import { get } from 'core/get'
 import { immutaTest } from 'test.utils'
 
 describe('path.apply', () => {
@@ -266,4 +267,28 @@ describe('path.apply', () => {
       'nested.prop2.val',
     )
   })
+
+  it('should support lazy function args', () => {
+    immutaTest(
+      input => {
+        const output = inc(input, 'nested.prop1.val', get('nested.prop2.val'))
+        expect(output).toEqual({
+          nested: {
+            prop1: { val: 7 },
+            prop2: { val: 4 },
+          },
+          other: {},
+        })
+        return output
+      },
+      {
+        nested: {
+          prop1: { val: 3 },
+          prop2: { val: 4 },
+        },
+        other: {},
+      },
+      'nested.prop1.val',
+    )
+  })
 })