fix(gatsby): log config validation errors

packages/gatsby-cli/src/structured-errors/error-map.ts

@@ -244,6 +244,12 @@ const errors = {
     level: Level.ERROR,
   },
   // Config errors
+  "10122": {
+    text: (context): string =>
+      `The site's gatsby-config.js failed validation:\n\n${context.sourceMessage}`,
+    type: Type.CONFIG,
+    level: Level.ERROR,
+  },
   "10123": {
     text: (context): string =>
       `We encountered an error while trying to load your site's ${context.configName}. Please fix the error and try again.`,

packages/gatsby/src/bootstrap/index.js

@@ -15,6 +15,7 @@ import { getBrowsersList } from "../utils/browserslist"
 import { createSchemaCustomization } from "../utils/create-schema-customization"
 import { startPluginRunner } from "../redux/plugin-runner"
 const { store, emitter } = require(`../redux`)
+import { internalActions } from "../redux/actions"
 const loadPlugins = require(`./load-plugins`)
 const loadThemes = require(`./load-themes`)
 const report = require(`gatsby-cli/lib/reporter`)
@@ -154,10 +155,7 @@ module.exports = async (args: BootstrapArgs) => {
     )
   }
 
-  store.dispatch({
-    type: `SET_SITE_CONFIG`,
-    payload: config,
-  })
+  store.dispatch(internalActions.setSiteConfig(config))
 
   activity.end()
 

packages/gatsby/src/joi-schemas/joi.ts

@@ -32,6 +32,9 @@ export const gatsbyConfigSchema: Joi.ObjectSchema<IGatsbyConfig> = Joi.object()
           .replace(/^\/$/, ``)
       )
     ),
+    linkPrefix: Joi.forbidden().error(
+      new Error(`"linkPrefix" should be changed to "pathPrefix"`)
+    ),
     siteMetadata: Joi.object({
       siteUrl: stripTrailingSlash(Joi.string()).uri(),
     }).unknown(),

packages/gatsby/src/redux/actions/__tests__/internal.ts

@@ -0,0 +1,88 @@
+import { setSiteConfig } from "../internal"
+import reporter from "gatsby-cli/lib/reporter"
+
+jest.mock(`gatsby-cli/lib/reporter`, () => {
+  return {
+    panic: jest.fn(),
+  }
+})
+
+beforeEach(() => {
+  reporter.panic.mockClear()
+})
+
+describe(`setSiteConfig`, () => {
+  it(`let's you add a config`, () => {
+    const action = setSiteConfig({
+      siteMetadata: {
+        hi: true,
+      },
+    })
+    expect(action).toMatchInlineSnapshot(`
+      Object {
+        "payload": Object {
+          "pathPrefix": "",
+          "polyfill": true,
+          "siteMetadata": Object {
+            "hi": true,
+          },
+        },
+        "type": "SET_SITE_CONFIG",
+      }
+    `)
+  })
+
+  it(`handles empty configs`, () => {
+    const action = setSiteConfig()
+    expect(action).toMatchInlineSnapshot(`
+      Object {
+        "payload": Object {
+          "pathPrefix": "",
+          "polyfill": true,
+        },
+        "type": "SET_SITE_CONFIG",
+      }
+    `)
+  })
+
+  it(`Validates configs with unsupported options`, () => {
+    setSiteConfig({
+      someRandomThing: `hi people`,
+      plugins: [],
+    })
+
+    expect(reporter.panic).toBeCalledWith({
+      id: `10122`,
+      context: {
+        sourceMessage: `"someRandomThing" is not allowed`,
+      },
+    })
+  })
+
+  it(`It corrects pathPrefixes without a forward slash at beginning`, () => {
+    const action = setSiteConfig({
+      pathPrefix: `prefix`,
+    })
+
+    expect(action.payload.pathPrefix).toBe(`/prefix`)
+  })
+
+  it(`It removes trailing forward slash`, () => {
+    const action = setSiteConfig({
+      pathPrefix: `/prefix/`,
+    })
+    expect(action.payload.pathPrefix).toBe(`/prefix`)
+  })
+
+  it(`It removes pathPrefixes that are a single forward slash`, () => {
+    const action = setSiteConfig({
+      pathPrefix: `/`,
+    })
+    expect(action.payload.pathPrefix).toBe(``)
+  })
+
+  it(`It sets the pathPrefix to an empty string if it's not set`, () => {
+    const action = setSiteConfig({})
+    expect(action.payload.pathPrefix).toBe(``)
+  })
+})

packages/gatsby/src/redux/actions/internal.ts

@@ -1,4 +1,7 @@
+import reporter from "gatsby-cli/lib/reporter"
+
 import {
+  IGatsbyConfig,
   IGatsbyPlugin,
   ProgramStatus,
   ICreatePageDependencyAction,
@@ -12,8 +15,11 @@ import {
   ISetProgramStatusAction,
   IPageQueryRunAction,
   IRemoveStaleJobAction,
+  ISetSiteConfig,
 } from "../types"
 
+import { gatsbyConfigSchema } from "../../joi-schemas/joi"
+
 /**
  * Create a dependency between a page and data. Probably for
  * internal use only.
@@ -217,3 +223,26 @@ export const removeStaleJob = (
     },
   }
 }
+
+/**
+ * Set gatsby config
+ * @private
+ */
+export const setSiteConfig = (config?: unknown): ISetSiteConfig => {
+  const result = gatsbyConfigSchema.validate(config || {})
+  const normalizedPayload: IGatsbyConfig = result.value
+
+  if (result.error) {
+    reporter.panic({
+      id: `10122`,
+      context: {
+        sourceMessage: result.error.message,
+      },
+    })
+  }
+
+  return {
+    type: `SET_SITE_CONFIG`,
+    payload: normalizedPayload,
+  }
+}

packages/gatsby/src/redux/reducers/config.ts

@@ -0,0 +1,14 @@
+import { IGatsbyConfig, ISetSiteConfig } from "../types"
+
+module.exports = (
+  state: IGatsbyConfig = {},
+  action: ISetSiteConfig
+): IGatsbyConfig => {
+  switch (action.type) {
+    case `SET_SITE_CONFIG`: {
+      return action.payload
+    }
+    default:
+      return state
+  }
+}

packages/gatsby/src/redux/types.ts

@@ -47,6 +47,9 @@ export interface IGatsbyConfig {
     title?: string
     author?: string
     description?: string
+    sireUrl?: string
+    // siteMetadata is free form
+    [key: string]: unknown
   }
   // @deprecated
   polyfill?: boolean
@@ -422,3 +425,8 @@ export interface ISetWebpackConfigAction {
   type: `SET_WEBPACK_CONFIG`
   payload: Partial<IGatsbyState["webpack"]>
 }
+
+export interface ISetSiteConfig {
+  type: `SET_SITE_CONFIG`
+  payload: IGatsbyState["config"]
+}