feat(core): zip.select and assorted predicates (#113)

Implements the function

const select: (...arguments) => location => Iterable<locations>

The function is in curried form. It expects a variable arg-set that is used to select/filter starting from the current location.

Each argument can be:
- a 'string' which is interpreted as descending into a property. The property should have an element (or child elements)
- an array of strings which is interpreted as the predicate `ofKind` 
- a function returning a list of locations (selector or motion function)
- a predicate function used to filter out nodes

Also implements the functions that can me used in the `select` function, in some of the following categories:
- selectors
  - `ancestors` an iterable of the location's ancestors; nearest parent first
  - `descendants`, an iterable of all descendants, depth-first, right-to-left
  - `children` an iterable of the location's children
  - `childrenAt(key)` an iterable of the location's children for the specified key
- predicates
  - `ofKind(kind)` a predicate function which will return true if the location points to an element the given kind

Closes #53

packages/core/src/__tests__/index.js

@@ -1,6 +1,6 @@
 'use strict'
 
-import { data, log, registry, zip, propNames } from '../'
+import { data, log, registry, zip, skeleZip, propNames } from '../'
 
 const anyFunction = expect.any(Function)
 const anyString = expect.any(String)
@@ -63,6 +63,7 @@ test('core.zip interface', () => {
 
   // edit
   expect(zip.editCond).toEqual(anyFunction)
+  expect(zip.editAt).toEqual(anyFunction)
 
   // walk
   expect(zip.preWalk).toEqual(anyFunction)
@@ -87,6 +88,21 @@ test('core.zip interface', () => {
   expect(zip.replace).toEqual(anyFunction)
   expect(zip.edit).toEqual(anyFunction)
   expect(zip.getChildren).toEqual(anyFunction)
+
+  // predicates
+  expect(zip.ofKind).toEqual(anyFunction)
+  expect(zip.propEq).toEqual(anyFunction)
+
+  // selectors
+  expect(zip.ancestors).toEqual(anyFunction)
+  expect(zip.descendants).toEqual(anyFunction)
+
+  // selectors (skele)
+  expect(skeleZip.children).toEqual(anyFunction)
+  expect(skeleZip.childrenAt).toEqual(anyFunction)
+
+  // select
+  expect(zip.select).toEqual(anyFunction)
 })
 
 test('core.log interface', () => {

packages/core/src/index.js

@@ -3,7 +3,7 @@
 import * as data from './data'
 import * as registry from './registry'
 import * as zip from './zip'
-import skeleZip from './zip/skele'
+import * as skeleZip from './zip/skele'
 import * as log from './log'
 import * as propNames from './propNames'
 import Cursor from './vendor/cursor'

packages/core/src/zip/__tests__/predicate.js

@@ -0,0 +1,60 @@
+'use strict'
+
+import I from 'immutable'
+
+import * as zip from '../'
+import { childrenProperty, flow } from '../../data'
+
+import { propEq } from '../predicate'
+
+const zipper = data => zip.elementZipper({})(data)
+
+const data = {
+  kind: ['navigation', 'tabs'],
+  [childrenProperty]: ['tabs', 'settings'],
+  title: 'App',
+  tabs: [
+    {
+      kind: ['tab'],
+      title: 'Murder Bot',
+    },
+    {
+      kind: ['tab'],
+      title: 'Dr Mensah',
+      [childrenProperty]: ['elements', 'deeplink'],
+      elements: [
+        {
+          kind: ['element'],
+          title: 'robot',
+        },
+        {
+          kind: ['element'],
+          title: 'human',
+        },
+      ],
+      deeplink: {
+        kind: ['link'],
+        title: 'goodreads',
+      },
+    },
+  ],
+  settings: {
+    kind: ['settings'],
+    title: 'Martha Wells',
+  },
+}
+
+describe('zipper predicates', () => {
+  test('propEq', () => {
+    const root = zipper(I.fromJS(data))
+    expect(
+      flow(
+        root,
+        propEq(
+          'settings',
+          I.fromJS({ kind: ['settings'], title: 'Martha Wells' })
+        )
+      )
+    ).toBeTruthy()
+  })
+})