fix(gatsby): better text for missing inferred extension

packages/gatsby/src/schema/infer/__tests__/infer.js

@@ -36,6 +36,7 @@ jest.mock(`gatsby-cli/lib/reporter`, () => {
 const report = require(`gatsby-cli/lib/reporter`)
 afterEach(() => {
   report.error.mockClear()
+  report.warn.mockClear()
 })
 
 const makeNodes = () => [
@@ -1385,4 +1386,54 @@ Object {
       )
     })
   })
+
+  describe(`missing extension warning`, () => {
+    it(`warns when inferred extension is missing in type definition`, async () => {
+      const nodes = [
+        {
+          date: `2012-11-01`,
+          internal: { type: `Test` },
+          id: `1`,
+        },
+        {
+          linked___NODE: `foo`,
+          internal: { type: `Test` },
+          id: `2`,
+        },
+
+        // linked node:
+        { id: `foo`, internal: { type: `Foo` } },
+      ]
+      const typeDefs = [
+        {
+          typeOrTypeDef: `
+            type Test implements Node {
+              linked: Foo
+              date: Date
+            }
+          `,
+        },
+      ]
+      await buildTestSchema(nodes, {}, typeDefs)
+      expect(report.warn.mock.calls.length).toEqual(2)
+      expect(report.warn.mock.calls[0][0]).toEqual(
+        `Deprecation warning: adding inferred extension \`dateformat\` for field \`Test.date\`.\n` +
+          `In Gatsby v3, only fields with an explicit directive/extension will be resolved correctly.\n` +
+          `Add the following type definition to fix this:\n\n` +
+          `  type Test implements Node {\n` +
+          `    date: Date @dateformat\n` +
+          `  }\n\n` +
+          `https://www.gatsbyjs.com/docs/actions/#createTypes`
+      )
+      expect(report.warn.mock.calls[1][0]).toEqual(
+        `Deprecation warning: adding inferred extension \`link\` for field \`Test.linked\`.\n` +
+          `In Gatsby v3, only fields with an explicit directive/extension will be resolved correctly.\n` +
+          `Add the following type definition to fix this:\n\n` +
+          `  type Test implements Node {\n` +
+          `    linked: Foo @link(by: "id", from: "linked___NODE")\n` +
+          `  }\n\n` +
+          `https://www.gatsbyjs.com/docs/actions/#createTypes`
+      )
+    })
+  })
 })

packages/gatsby/src/schema/infer/add-inferred-fields.js

@@ -8,6 +8,7 @@ import { isFile } from "./is-file"
 import { isDate } from "../types/date"
 import { addDerivedType } from "../types/derived-types"
 import { is32BitInteger } from "../../utils/is-32-bit-integer"
+import { printDirectives } from "../print"
 const { getNode, getNodes } = require(`../../redux/nodes`)
 
 const addInferredFields = ({
@@ -120,11 +121,22 @@ const addInferredFieldsImpl = ({
               .forEach(name => {
                 if (!typeComposer.hasFieldExtension(key, name)) {
                   typeComposer.setFieldExtension(key, name, extensions[name])
+
+                  const typeName = typeComposer.getTypeName()
+                  const implementsNode =
+                    unsanitizedFieldPath.length === 1 ? `implements Node ` : ``
+                  const extension = printDirectives(
+                    { [name]: extensions[name] },
+                    schemaComposer.getDirectives()
+                  )
                   report.warn(
-                    `Deprecation warning - adding inferred resolver for field ` +
-                      `${typeComposer.getTypeName()}.${key}. In Gatsby v3, ` +
-                      `only fields with an explicit directive/extension will ` +
-                      `get a resolver.`
+                    `Deprecation warning: adding inferred extension \`${name}\` for field \`${typeName}.${key}\`.\n` +
+                      `In Gatsby v3, only fields with an explicit directive/extension will be resolved correctly.\n` +
+                      `Add the following type definition to fix this:\n\n` +
+                      `  type ${typeComposer.getTypeName()} ${implementsNode}{\n` +
+                      `    ${key}: ${field.type.toString()}${extension}\n` +
+                      `  }\n\n` +
+                      `https://www.gatsbyjs.com/docs/actions/#createTypes`
                   )
                 }
               })

packages/gatsby/src/schema/print.js

@@ -402,4 +402,5 @@ const breakLine = (line, maxLen) => {
 
 module.exports = {
   printTypeDefinitions,
+  printDirectives,
 }