feat(gatsby): Gatsby Head API

.circleci/config.yml

@@ -320,6 +320,13 @@ jobs:
           test_path: integration-tests/functions
           test_command: yarn test
 
+  integration_tests_head_function_export:
+    executor: node
+    steps:
+      - e2e-test:
+          test_path: integration-tests/head-function-export
+          test_command: yarn test
+
   e2e_tests_path-prefix:
     <<: *e2e-executor
     environment:
@@ -626,6 +633,8 @@ workflows:
           <<: *e2e-test-workflow
       - integration_tests_functions:
           <<: *e2e-test-workflow
+      - integration_tests_head_function_export:
+          <<: *e2e-test-workflow
       - integration_tests_gatsby_cli:
           requires:
             - bootstrap

e2e-tests/development-runtime/cypress/integration/eslint-rules/limited-exports-page-templates.js

@@ -23,7 +23,7 @@ describe(`limited-exports-page-templates`, () => {
   it(`should initially not log to console`, () => {
     cy.get(`@hmrConsoleLog`).should(
       `not.be.calledWithMatch`,
-      /13:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData or config are allowed./i
+      /13:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData, Head or config are allowed./i
     )
   })
   it(`should log warning to console for invalid export`, () => {
@@ -34,11 +34,11 @@ describe(`limited-exports-page-templates`, () => {
 
     cy.get(`@hmrConsoleLog`).should(
       `be.calledWithMatch`,
-      /13:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData or config are allowed./i
+      /13:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData, Head or config are allowed./i
     )
     cy.get(`@hmrConsoleLog`).should(
       `not.be.calledWithMatch`,
-      /15:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData or config are allowed./i
+      /15:1 {2}warning {2}In page templates only a default export of a valid React component and the named exports of a page query, getServerData, Head or config are allowed./i
     )
   })
 })

e2e-tests/development-runtime/cypress/integration/head-function-export/correct-props.js

@@ -0,0 +1,32 @@
+import headFunctionExportSharedData from "../../../shared-data/head-function-export.js"
+
+it(`Head function export receive correct props`, () => {
+  cy.visit(headFunctionExportSharedData.page.correctProps).waitForRouteChange()
+
+  const data = {
+    site: {
+      siteMetadata: {
+        headFunctionExport: {
+          ...headFunctionExportSharedData.data.queried,
+        },
+      },
+    },
+  }
+  const location = {
+    pathname: headFunctionExportSharedData.page.correctProps,
+  }
+
+  const pageContext = headFunctionExportSharedData.data.context
+
+  cy.getTestElement(`pageContext`)
+    .invoke(`attr`, `content`)
+    .should(`equal`, JSON.stringify(pageContext, null, 2))
+
+  cy.getTestElement(`location`)
+    .invoke(`attr`, `content`)
+    .should(`equal`, JSON.stringify(location, null, 2))
+
+  cy.getTestElement(`data`)
+    .invoke(`attr`, `content`)
+    .should(`equal`, JSON.stringify(data, null, 2))
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/fs-route-api.js

@@ -0,0 +1,6 @@
+import { page, data } from "../../../shared-data/head-function-export.js"
+
+it(`Head function export with FS Route API should work`, () => {
+  cy.visit(page.fsRouteApi).waitForRouteChange()
+  cy.getTestElement(`title`).should(`have.text`, data.fsRouteApi.slug)
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/html-insertion.js

@@ -0,0 +1,99 @@
+import { page, data } from "../../../shared-data/head-function-export.js"
+
+describe(`Head function export html insertion`, () => {
+  it(`should work with static data`, () => {
+    cy.visit(page.basic).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.base)
+    cy.getTestElement(`title`).should(`have.text`, data.static.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.static.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.static.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.link)
+  })
+
+  it(`should work with data from a page query`, () => {
+    cy.visit(page.pageQuery).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.base)
+    cy.getTestElement(`title`).should(`have.text`, data.queried.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.queried.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.queried.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.queried.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.link)
+  })
+
+  it(`should work when a head function with static data is re-exported from the page`, () => {
+    cy.visit(page.reExport).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.base)
+    cy.getTestElement(`title`).should(`have.text`, data.static.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.static.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.static.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.link)
+  })
+
+  it(`should work when an imported Head component with queried data is used`, () => {
+    cy.visit(page.staticQuery).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.base)
+    cy.getTestElement(`title`).should(`have.text`, data.queried.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.queried.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.queried.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.queried.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.link)
+  })
+
+  it(`should work in a DSG page (exporting function named config)`, () => {
+    cy.visit(page.dsg).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.dsg.base)
+    cy.getTestElement(`title`).should(`have.text`, data.dsg.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.dsg.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.dsg.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.dsg.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.dsg.link)
+  })
+
+  it(`should work in an SSR page (exporting function named getServerData)`, () => {
+    cy.visit(page.ssr).waitForRouteChange()
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.ssr.base)
+    cy.getTestElement(`title`).should(`have.text`, data.ssr.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.ssr.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.ssr.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.ssr.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.ssr.link)
+  })
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/invalid-elements.js

@@ -0,0 +1,13 @@
+import { page, data } from "../../../shared-data/head-function-export.js"
+
+it(`Head function export should not include invalid elements`, () => {
+  cy.visit(page.invalidElements).waitForRouteChange()
+
+  cy.get(`head > h1`).should(`not.exist`)
+  cy.get(`head > div`).should(`not.exist`)
+  cy.get(`head > audio`).should(`not.exist`)
+  cy.get(`head > video`).should(`not.exist`)
+  cy.get(`head > title`)
+    .should(`exist`)
+    .and(`have.text`, data.invalidElements.title)
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/navigation.js

@@ -0,0 +1,114 @@
+import { page, data } from "../../../shared-data/head-function-export.js"
+
+// No need to test SSR navigation (anchor tags) because it's effectively covered in the html insertion tests
+
+describe(`Head function export behavior during CSR navigation (Gatsby Link)`, () => {
+  it(`should remove tags not on next page`, () => {
+    cy.visit(page.basic).waitForRouteChange()
+
+    cy.getTestElement(`extra-meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.extraMeta)
+
+    cy.getTestElement(`gatsby-link`).click().waitForRouteChange()
+
+    cy.get(`[data-testid="extra-meta"]`).should(`not.exist`)
+  })
+
+  it(`should add tags not on next page`, () => {
+    cy.visit(page.basic).waitForRouteChange()
+
+    cy.get(`[data-testid="extra-meta-2"]`).should(`not.exist`)
+
+    cy.getTestElement(`gatsby-link`).click().waitForRouteChange()
+
+    cy.getTestElement(`extra-meta-2`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.queried.extraMeta2)
+  })
+
+  it(`should not contain tags from old tags when we navigate to page without Head export`, () => {
+    cy.visit(page.basic).waitForRouteChange()
+
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.base)
+    cy.getTestElement(`title`).should(`have.text`, data.static.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.static.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.static.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.link)
+
+    cy.getTestElement(`navigate-to-page-without-head-export`)
+      .click()
+      .waitForRouteChange()
+
+    cy.getTestElement(`base`).should(`not.exist`)
+    cy.getTestElement(`title`).should(`not.exist`)
+    cy.getTestElement(`meta`).should(`not.exist`)
+    cy.getTestElement(`noscript`).should(`not.exist`)
+    cy.getTestElement(`style`).should(`not.exist`)
+    cy.getTestElement(`link`).should(`not.exist`)
+  })
+
+  /**
+   * Technically nodes are always removed from the DOM and new ones added (in other words nodes are not reused with different data),
+   * but since this is an implementation detail we'll still test the behavior we expect as if we didn't know that.
+   */
+  it(`should change meta tag values`, () => {
+    // Initial load
+    cy.visit(page.basic).waitForRouteChange()
+
+    // Validate data from initial load
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.base)
+    cy.getTestElement(`title`).should(`have.text`, data.static.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.static.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.static.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.link)
+
+    // Navigate to a different page via Gatsby Link
+    cy.getTestElement(`gatsby-link`).click()
+
+    // Validate data on navigated-to page
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.base)
+    cy.getTestElement(`title`).should(`have.text`, data.queried.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.queried.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.queried.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.queried.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.queried.link)
+
+    // Navigate back to original page via Gatsby Link
+    cy.getTestElement(`gatsby-link`).click().waitForRouteChange()
+
+    // Validate data is same as initial load
+    cy.getTestElement(`base`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.base)
+    cy.getTestElement(`title`).should(`have.text`, data.static.title)
+    cy.getTestElement(`meta`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, data.static.meta)
+    cy.getTestElement(`noscript`).should(`have.text`, data.static.noscript)
+    cy.getTestElement(`style`).should(`contain`, data.static.style)
+    cy.getTestElement(`link`)
+      .invoke(`attr`, `href`)
+      .should(`equal`, data.static.link)
+  })
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/typescript.js

@@ -0,0 +1,11 @@
+describe(`Tsx Pages`, () => {
+  it(`Works with Head export`, () => {
+    cy.visit(`/head-function-export/tsx-page`)
+
+    cy.getTestElement(`title`).should(`contain`, `TypeScript`)
+
+    cy.getTestElement(`name`)
+      .invoke(`attr`, `content`)
+      .should(`equal`, `TypeScript`)
+  })
+})

e2e-tests/development-runtime/cypress/integration/head-function-export/warnings.js

@@ -0,0 +1,28 @@
+import { VALID_NODE_NAMES } from "gatsby/cache-dir/head/constants"
+import { page } from "../../../shared-data/head-function-export.js"
+
+describe(`Head function export should warn`, () => {
+  beforeEach(() => {
+    cy.visit(page.warnings, {
+      onBeforeLoad(win) {
+        cy.stub(win.console, `warn`).as(`consoleWarn`)
+      },
+    }).waitForRouteChange()
+  })
+
+  it(`for elements that belong in the body`, () => {
+    cy.get(`@consoleWarn`).should(
+      `be.calledWith`,
+      `<h1> is not a valid head element. Please use one of the following: ${VALID_NODE_NAMES.join(
+        `, `
+      )}`
+    )
+  })
+
+  it(`for scripts that could use the script component`, () => {
+    cy.get(`@consoleWarn`).should(
+      `be.calledWith`,
+      `Do not add scripts here. Please use the <Script> component in your page template instead. For more info see: https://www.gatsbyjs.com/docs/reference/built-in-components/gatsby-script/`
+    )
+  })
+})

e2e-tests/development-runtime/cypress/integration/hot-reloading/head-export.js

@@ -0,0 +1,28 @@
+const { data } = require("../../../shared-data/head-function-export")
+
+const TEST_ID = `extra-meta-for-hot-reloading`
+
+describe(`hot reloading Head export`, () => {
+  beforeEach(() => {
+    cy.visit(`/head-function-export/basic`).waitForRouteChange()
+  })
+
+  it(`displays placeholder content on launch`, () => {
+    cy.getTestElement(TEST_ID)
+      .invoke(`attr`, `content`)
+      .should(`contain.equal`, "%SOME_EXTRA_META%")
+  })
+
+  it(`hot reloads with new content`, () => {
+    const text = `New Title by HMR`
+    cy.exec(
+      `npm run update -- --file src/pages/head-function-export/basic.js --replacements "SOME_EXTRA_META:${text}"`
+    )
+
+    cy.waitForHmr()
+
+    cy.getTestElement(TEST_ID)
+      .invoke(`attr`, `content`)
+      .should(`contain.equal`, text)
+  })
+})