[preview] Expose a default materializePaths function (#492)

packages/@sanity/base/src/preview/index.js

@@ -1,2 +1,2 @@
 export {SanityPreview as default, PreviewSubscriber, PreviewFields} from '@sanity/preview/components'
-export {observeForPreview, observeWithPaths} from '@sanity/preview'
+export {observeForPreview, observeWithPaths, materializePaths} from '@sanity/preview'

packages/@sanity/preview/index.js

@@ -1,2 +1,3 @@
 exports.observeForPreview = require('./lib/observeForPreview').default
 exports.observeWithPaths = require('./lib/observeWithPaths').default
+exports.materializePaths = require('./lib/materializePaths').default

packages/@sanity/preview/src/createPreviewObserver.js → packages/@sanity/preview/src/createPathMaterializer.js

@@ -1,13 +1,9 @@
-import {uniq, isObject, isArray} from 'lodash'
+import {isArray, isObject, uniq} from 'lodash'
 import Observable from '@sanity/observable'
 import {configure} from 'observable-props'
 
 const props = configure({Observable})
 
-function resolveMissingHeads(value, paths) {
-  return paths.filter(path => !(path[0] in value))
-}
-
 function isReference(value) {
   return '_ref' in value
 }
@@ -23,9 +19,12 @@ function createEmpty(keys) {
   }, {})
 }
 
-export default function createPreviewObserver(observeWithPaths) {
+function resolveMissingHeads(value, paths) {
+  return paths.filter(path => !(path[0] in value))
+}
 
-  function follow(value, paths) {
+export default function createPathMaterializer(observeWithPaths) {
+  return function materializePaths(value, paths) {
     if (!isArray(value) && !isObject(value)) {
       // Reached a leaf. Don't blow up
       return Observable.of(value)
@@ -41,7 +40,7 @@ export default function createPreviewObserver(observeWithPaths) {
         const id = isReference(value) ? value._ref : value._id
         return observeWithPaths(id, nextHeads)
           .switchMap(snapshot => {
-            return follow({...createEmpty(nextHeads), ...value, ...snapshot}, paths)
+            return materializePaths({...createEmpty(nextHeads), ...value, ...snapshot}, paths)
           })
       }
     }
@@ -60,13 +59,11 @@ export default function createPreviewObserver(observeWithPaths) {
       if (tails.every(tail => tail.length === 0)) {
         res[head] = value[head]
       } else {
-        res[head] = follow(value[head], tails)
+        res[head] = materializePaths(value[head], tails)
       }
       return res
     }, {...value})
 
     return props(Observable.of(next), {wait: true})
   }
-
-  return follow
 }

packages/@sanity/preview/src/materializePaths.js

@@ -0,0 +1,4 @@
+import observeWithPaths from './observeWithPaths'
+import createPathMaterializer from './createPathMaterializer'
+
+export default createPathMaterializer(observeWithPaths)

packages/@sanity/preview/src/observeForPreview.js

@@ -1,10 +1,7 @@
-import createPreviewObserver from './createPreviewObserver'
-import observeWithPaths from './observeWithPaths'
 import resolveRefType from './resolveRefType'
 import prepareForPreview, {invokePrepare} from './prepareForPreview'
 import Observable from '@sanity/observable'
-
-const observe = createPreviewObserver(observeWithPaths)
+import materializePaths from './materializePaths'
 
 function is(typeName, type) {
   return type.name === typeName || (type.type && is(typeName, type.type))
@@ -34,7 +31,7 @@ export default function observeForPreview(value, type, fields, viewOptions) {
     const configFields = Object.keys(selection)
     const targetFields = fields ? configFields.filter(fieldName => fields.includes(fieldName)) : configFields
     const paths = targetFields.map(key => selection[key].split('.'))
-    return observe(value, paths)
+    return materializePaths(value, paths)
       .map(snapshot => ({
         type: type,
         snapshot: prepareForPreview(snapshot, type, viewOptions)