Track pages/layouts without queries fixes #3139 #3148 #3094 (#3218)

* Track pages/layouts without queries fixes #3139 #3148 #3094

This bug was hard to track down as it manifested itself in a weird way.

Gatsby tracks external changes which indicate a need to re-run GraphQL
queries. Which is normally fine since Gatsby also is tracking which
queries would be dirtied by the external change (e.g. a query depends
on a file — when that file is changed, the query is "dirty" and needs
run again). But pages/layouts *without* queries weren't being tracked
which meant that on every external change, Gatsby would think it needed
to run those queries again.

During the build process. Gatsby assumes that external data won't change
so during the bootstrap, it waits for the initials set of queries to
finish running but during later stages, it doesn't.

Because sites with lots of pages with no queries were running their
queries over and over, this meant that occassionally webpack would try
to load a JSON file (queries are written out as JSON files) that wasn't
finished writing.

This PR fixes the problem as now during build, Gatsby only attempts to
run queries for page/layout components without queries during the
initial bootstrap.

* Fix formatting

packages/gatsby/src/internal-plugins/query-runner/page-query-runner.js

@@ -62,6 +62,7 @@ const runQueuedActions = async () => {
 // query things in a 1/2 finished state.
 emitter.on(`API_RUNNING_QUEUE_EMPTY`, runQueuedActions)
 
+let seenIdsWithoutDataDependencies = []
 const findIdsWithoutDataDependencies = () => {
   const state = store.getState()
   const allTrackedIds = _.uniq(
@@ -75,13 +76,22 @@ const findIdsWithoutDataDependencies = () => {
 
   // Get list of paths not already tracked and run the queries for these
   // paths.
-  return _.difference(
+  const notTrackedIds = _.difference(
     [
       ...state.pages.map(p => p.path),
       ...state.layouts.map(l => `LAYOUT___${l.id}`),
     ],
-    allTrackedIds
+    [...allTrackedIds, ...seenIdsWithoutDataDependencies]
   )
+
+  // Add new IDs to our seen array so we don't keep trying to run queries for them.
+  // Pages/Layouts without queries can't be tracked.
+  seenIdsWithoutDataDependencies = _.uniq([
+    ...notTrackedIds,
+    ...seenIdsWithoutDataDependencies,
+  ])
+
+  return notTrackedIds
 }
 
 const runQueriesForIds = ids => {
@@ -105,8 +115,9 @@ const runQueriesForIds = ids => {
             result => callback(null, result),
             error => callback(error)
           )
+        } else {
+          return callback(null, null)
         }
-        return callback(null, null)
       },
       (error, result) => {
         error ? reject(error) : resolve(result)