feat(gatsby): invite (1%) of Gatsby users to try out develop ssr (#28139)

* feat(gatsby): invite (1%) of Gatsby users to try out develop ssr

* fix

Author: KyleAMathews

packages/gatsby/src/services/initialize.ts

@@ -9,6 +9,8 @@ import telemetry from "gatsby-telemetry"
 
 import apiRunnerNode from "../utils/api-runner-node"
 import { getBrowsersList } from "../utils/browserslist"
+import { showExperimentNoticeAfterTimeout } from "../utils/show-experiment-notice"
+import sampleSiteForExperiment from "../utils/sample-site-for-experiment"
 import { Store, AnyAction } from "redux"
 import { preferDefault } from "../bootstrap/prefer-default"
 import * as WorkerPool from "../utils/worker/pool"
@@ -30,6 +32,31 @@ interface IPluginResolution {
   options: IPluginInfoOptions
 }
 
+if (
+  process.env.gatsby_executing_command === `develop` &&
+  !process.env.GATSBY_EXPERIMENTAL_DEV_SSR &&
+  !isCI() &&
+  sampleSiteForExperiment(`DEV_SSR`, 1)
+) {
+  showExperimentNoticeAfterTimeout(
+    `devSSR`,
+    `
+Your dev experience is about to get better, faster, and stronger!
+
+We'll soon be shipping support for SSR in development.
+
+This will help the dev environment more closely mimic builds so you'll catch build errors earlier and fix them faster.
+
+Try out develop SSR *today* by running your site with it enabled:
+
+GATSBY_EXPERIMENT_DEV_SSR=true gatsby develop
+
+Please let us know how it goes good, bad, or otherwise at gatsby.dev/dev-ssr-feedback
+      `,
+    1 // Show this immediately to the subset of sites selected.
+  )
+}
+
 // Show stack trace on unhandled promises.
 process.on(`unhandledRejection`, (reason: unknown) => {
   // https://github.com/DefinitelyTyped/DefinitelyTyped/issues/33636

packages/gatsby/src/utils/__tests__/__snapshots__/sample-site-for-experiment.ts.snap

@@ -0,0 +1,17 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 1`] = `true`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 2`] = `false`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 3`] = `true`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 4`] = `true`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 5`] = `false`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 6`] = `true`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 7`] = `false`;
+
+exports[`sampleSiteForExperiment returns true or false depending on if they randomly are bucketed in or not 8`] = `false`;

packages/gatsby/src/utils/__tests__/sample-site-for-experiment.ts

@@ -0,0 +1,12 @@
+import sampleSiteForExperiment from "../sample-site-for-experiment"
+
+describe(`sampleSiteForExperiment`, () => {
+  it(`returns true or false depending on if they randomly are bucketed in or not`, () => {
+    const experiments = [`a`, `b`, `c`, `d`, `e`, `f`, `h`, `i`]
+    experiments.forEach(experiment => {
+      expect(sampleSiteForExperiment(experiment, 0)).toBeFalsy()
+      expect(sampleSiteForExperiment(experiment, 50)).toMatchSnapshot()
+      expect(sampleSiteForExperiment(experiment, 100)).toBeTruthy()
+    })
+  })
+})

packages/gatsby/src/utils/sample-site-for-experiment.ts

@@ -0,0 +1,11 @@
+import { getRepositoryId } from "gatsby-telemetry/lib/repository-id"
+import { murmurhash } from "babel-plugin-remove-graphql-queries"
+
+const sampleSite = (experimentName: string, percentage: number): boolean =>
+  murmurhash(
+    experimentName + `` + JSON.stringify(getRepositoryId().repositoryId)
+  ) %
+    100 <
+  percentage
+
+export default sampleSite