Reimplement setup and serialize methods

packages/gatsby-plugin-feed/src/createFeed.js

@@ -1,5 +1,4 @@
 import url from 'url'
-import deepmerge from 'deepmerge'
 import RSS from 'rss'
 
 const defaultOptions = {
@@ -8,17 +7,12 @@ const defaultOptions = {
 }
 
 export default function createFeed({
-  query: {
-    site: {
-      siteMetadata,
-    },
-    entries,
-    ...rest
-  },
+  metadata,
+  entries,
   output,
 }) {
-  // Ensure that siteMetadata is not undefined
-  const metadata = siteMetadata || {}
+  // Provide a couple of defaults that will
+  // override the node-rss defaults
   const options = { ...defaultOptions }
 
   // Assign the default feed options. Note that we can skip existence
@@ -45,11 +39,8 @@ export default function createFeed({
     }
   }
 
-  // @TODO: is this useful? We should think of an example that would use this.
-  const context = deepmerge(rest, options)
-
   // Return an instance of node-rss with our options
-  return new RSS(context)
+  return new RSS(options)
 }
 
 function hasMedia(nodes) {

packages/gatsby-plugin-feed/src/gatsby-node.js

@@ -1,36 +1,42 @@
 import path from 'path'
 import deepmerge from 'deepmerge'
 
-import { defaultOptions, runQuery, writeFile } from './internals'
+import {
+  defaultOptions,
+  isFunction,
+  runQuery,
+  writeFile,
+} from './internals'
 import createFeed from './createFeed'
 import serialize from './serialize'
+import setup from './setup'
 
 const publicPath = `./public`
 
-exports.onPostBuild = async ({ graphql }, pluginOptions) => {
-  delete pluginOptions.plugins
+exports.onPostBuild = async ({ graphql }, userOptions) => {
+  delete userOptions.plugins
 
   // Merge default options with user options,
   // overriding the defaults.
-  const options = {
+  const pluginOptions = {
     ...defaultOptions,
-    ...pluginOptions,
+    ...userOptions,
   }
 
   // If there is a top-level query to execute, do so,
   // and replace the original query with the result.
   // The resulting data will be used to generate the default
   // no-configuration-required feed, or will be deep-merged
   // with the result of any custom feed's query.
-  if (options.query) {
-    options.query = await runQuery(graphql, options.query)
+  if (pluginOptions.query) {
+    pluginOptions.query = await runQuery(graphql, pluginOptions.query)
   }
 
-  return Promise.all(options.feeds.map(async (feed) => {
+  return Promise.all(pluginOptions.feeds.map(async (feed) => {
     // Each feed's inherits the result of the global query
-    const feedOptions = {
+    let feedOptions = {
       ...feed,
-      query: options.query,
+      query: pluginOptions.query,
     }
 
     // Each feed may specify a query of its own. If this
@@ -41,11 +47,24 @@ exports.onPostBuild = async ({ graphql }, pluginOptions) => {
       feedOptions.query = deepmerge(feedOptions.query, feedQuery)
     }
 
+    // Each feed may provide a `setup` function for the purpose
+    // of remapping feed options before they are passed to node-rss
+    const metadata = isFunction(feed.setup) ?
+      feed.setup(feedOptions.query) :
+      setup(feedOptions.query)
+
     // Create the feed instance
-    const outputFeed = createFeed(feedOptions)
+    const outputFeed = createFeed({
+      metadata,
+      entries: feedOptions.query.entries,
+      output: feedOptions.output,
+    })
 
     // Then serialize each feed item and add it to the feed
-    const items = serialize(feedOptions)
+    const items = isFunction(feed.serialize) ?
+      feed.serialize(feedOptions.query) :
+      serialize(feedOptions.query)
+
     items.forEach(i => outputFeed.item(i))
 
     // Finally, write the feed file to disk

packages/gatsby-plugin-feed/src/internals.js

@@ -2,6 +2,7 @@ import fs from "fs"
 import pify from "pify"
 
 export const writeFile = pify(fs.writeFile)
+export const isFunction = f => (f && typeof f === `function`)
 
 export const runQuery = (handler, query) =>
   handler(query).then(r => {

packages/gatsby-plugin-feed/src/serialize.js

@@ -1,8 +1,12 @@
+// Returns the options that will be used to create each item
+// in the feed that is generated by node-rss. Each feed may
+// provide its own `serialize` function, but this provides
+// smart defaults that should work for most folks.
+//
+// The function receives one argument: the result of the feed's query
 export default function serialize({
-  query: {
-    site,
-    entries,
-  },
+  site,
+  entries,
 }) {
   return entries.edges.map(edge => {
     return {

packages/gatsby-plugin-feed/src/setup.js

@@ -0,0 +1,15 @@
+// Returns the options that will be used to initialize the
+// node-rss instance. Each feed may provide its own
+// `setup` function, but by default we just return the siteMetadata
+// merged with the other top-level keys in the result the feed's query
+// (but excluding the `entries` key).
+export default function setup({
+  site: { siteMetadata },
+  entries,
+  ...rest
+}) {
+  return {
+    ...siteMetadata,
+    ...rest,
+  }
+}