fix(gatsby-transformer-remark): Revert/remark sources from different …

…sources (#12639)

## Description
This change should happen in core and not in remark itself. I didn't think this through.

I should have read @m-allanson more carefully:
> Thanks @alexkirsz 👍 this is a really useful feature - so much so, that something like it should be added to Gatsby core instead of this being implemented separately across different plugins.

> It'll be particularly useful for the new Gatsby themes functionality that @ChristopherBiscardi is working on. As part of the themes work there's going to be an issue or rfc soon™️ (next week or after) to figure out exactly how this could be added to Gatsby core. Once the rfc has been written I'll add a link here.

> You can check out more info on Gatsby themes here and here.

## Related Issues
#7512

packages/gatsby-transformer-remark/README.md

@@ -14,11 +14,6 @@ plugins: [
   {
     resolve: `gatsby-transformer-remark`,
     options: {
-
-      // Defaults to `() => true`
-      filter: node => node.sourceInstanceName === `blog`,
-      // Defaults to `MarkdownRemark`
-      type: `BlogPost`,
       // CommonMark mode (default: true)
       commonmark: true,
       // Footnotes mode (default: true)

packages/gatsby-transformer-remark/package.json

@@ -8,6 +8,7 @@
   },
   "dependencies": {
     "@babel/runtime": "^7.0.0",
+    "bluebird": "^3.5.0",
     "gray-matter": "^4.0.0",
     "hast-util-raw": "^4.0.0",
     "hast-util-to-html": "^4.0.0",

packages/gatsby-transformer-remark/src/__tests__/extend-node.js

@@ -4,7 +4,7 @@ const {
   GraphQLList,
   GraphQLSchema,
 } = require(`gatsby/graphql`)
-const { onCreateNode, setFieldsOnGraphQLNodeType } = require(`../gatsby-node`)
+const { onCreateNode } = require(`../gatsby-node`)
 const {
   inferObjectStructureFromNodes,
 } = require(`../../../gatsby/src/schema/infer-graphql-type`)
@@ -14,7 +14,7 @@ const extendNodeType = require(`../extend-node-type`)
 async function queryResult(
   nodes,
   fragment,
-  { typeName = `MarkdownRemark`, types = [] } = {},
+  { types = [] } = {},
   { additionalParameters = {}, pluginOptions = {} }
 ) {
   const inferredFields = inferObjectStructureFromNodes({
@@ -51,7 +51,7 @@ async function queryResult(
             name: `LISTNODE`,
             type: new GraphQLList(
               new GraphQLObjectType({
-                name: typeName,
+                name: `MarkdownRemark`,
                 fields: markdownRemarkFields,
               })
             ),
@@ -835,47 +835,3 @@ describe(`Headings are generated correctly from schema`, () => {
     }
   )
 })
-
-describe(`Adding fields to the GraphQL schema`, () => {
-  it(`only adds fields when the GraphQL type matches the provided type`, async () => {
-    const getNode = jest.fn()
-    const getNodesByType = jest.fn()
-
-    expect(
-      setFieldsOnGraphQLNodeType({
-        type: { name: `MarkdownRemark` },
-        getNode,
-        getNodesByType,
-      })
-    ).toBeInstanceOf(Promise)
-
-    expect(
-      setFieldsOnGraphQLNodeType(
-        { type: { name: `MarkdownRemark` }, getNode, getNodesByType },
-        { type: `MarkdownRemark` }
-      )
-    ).toBeInstanceOf(Promise)
-
-    expect(
-      setFieldsOnGraphQLNodeType(
-        { type: { name: `MarkdownRemark` }, getNode, getNodesByType },
-        { type: `GatsbyTestType` }
-      )
-    ).toEqual({})
-
-    expect(
-      setFieldsOnGraphQLNodeType(
-        { type: { name: `GatsbyTestType` }, getNode, getNodesByType },
-        { type: `GatsbyTestType` }
-      )
-    ).toBeInstanceOf(Promise)
-
-    expect(
-      setFieldsOnGraphQLNodeType({
-        type: { name: `GatsbyTestType` },
-        getNode,
-        getNodesByType,
-      })
-    ).toEqual({})
-  })
-})

packages/gatsby-transformer-remark/src/__tests__/on-node-create.js

@@ -1,3 +1,4 @@
+const Promise = require(`bluebird`)
 const _ = require(`lodash`)
 
 const onCreateNode = require(`../on-node-create`)
@@ -119,50 +120,6 @@ yadda yadda
 
       expect(parsed.frontmatter.date).toEqual(new Date(date).toJSON())
     })
-
-    it(`Filters nodes with the given filter function, if provided`, async () => {
-      const content = ``
-
-      node.content = content
-      node.sourceInstanceName = `gatsby-test-source`
-
-      const createNode = jest.fn()
-      const createParentChildLink = jest.fn()
-      const actions = { createNode, createParentChildLink }
-      const createNodeId = jest.fn()
-      createNodeId.mockReturnValue(`uuid-from-gatsby`)
-
-      await onCreateNode(
-        {
-          node,
-          loadNodeContent,
-          actions,
-          createNodeId,
-        },
-        {
-          filter: node =>
-            node.sourceInstanceName === `gatsby-other-test-source`,
-        }
-      ).then(() => {
-        expect(createNode).toHaveBeenCalledTimes(0)
-        expect(createParentChildLink).toHaveBeenCalledTimes(0)
-      })
-
-      await onCreateNode(
-        {
-          node,
-          loadNodeContent,
-          actions,
-          createNodeId,
-        },
-        {
-          filter: node => node.sourceInstanceName === `gatsby-test-source`,
-        }
-      ).then(() => {
-        expect(createNode).toHaveBeenCalledTimes(1)
-        expect(createParentChildLink).toHaveBeenCalledTimes(1)
-      })
-    })
   })
 
   describe(`process graphql correctly`, () => {