PER-8985 feat: Playwright drop-in baseline seeding — build attributes + exec orchestration

packages/cli-exec/src/baseline.js

@@ -0,0 +1,225 @@
+import fs from 'fs';
+import path from 'path';
+import url from 'url';
+import { createResource, createRootResource } from '@percy/cli-command/utils';
+
+// Playwright drop-in baseline seeding — the `percy exec` side.
+//
+// Generic provider contract (framework knowledge stays in the SDK package, never in the CLI —
+// the same reason command discovery works the way it does): any installed Percy SDK can declare
+//
+//   "@percy/cli": { "baselineProvider": "./path/to/module.js" }
+//
+// in its package.json. The module's default export must be:
+//
+//   {
+//     buildSource,            // drop-in source tag for the head build (e.g. 'playwright-dropin')
+//     async discoverBaselines({ cwd, log })
+//       // -> { baselines: [{ filepath, name, browserFamily, width, height }], degraded?, reason? }
+//   }
+//
+// When the user runs a plain `percy exec -- <cmd>` in a project with committed baseline
+// screenshots and an EMPTY Percy project, the CLI establishes the baseline first (build #1,
+// uploaded directly from the committed files — the user's test suite never runs for it) and only
+// then starts the head build (#2) that runs the real command. The API auto-approves build #1
+// server-side. On an established project nothing is seeded; the user is pointed at the explicit
+// `percy playwright:setup-baseline` command instead.
+
+// Parallel seed-upload cap: fast on large baseline sets without stampeding the API.
+const SEED_CONCURRENCY = 8;
+
+const BASELINE_SOURCE = 'playwright-dropin-baseline';
+
+// Walk up from `dir` collecting @percy/* (and percy-*) package roots from each node_modules on
+// the way — trimmed-down version of @percy/cli's command-discovery walk.
+function findPercyPackages(dir) {
+  let found = [];
+
+  while (dir !== path.dirname(dir)) {
+    let modulesDir = path.join(dir, 'node_modules');
+
+    if (fs.existsSync(modulesDir)) {
+      for (let name of fs.readdirSync(modulesDir)) {
+        if (name === '@percy') {
+          for (let scoped of fs.readdirSync(path.join(modulesDir, name))) {
+            found.push(path.join(modulesDir, name, scoped));
+          }
+        } else if (name.startsWith('percy-')) {
+          found.push(path.join(modulesDir, name));
+        }
+      }
+    }
+
+    dir = path.dirname(dir);
+  }
+
+  return found;
+}
+
+// Find the first installed package declaring a baseline provider and import it. Returns null when
+// none is installed (the overwhelmingly common case — one existsSync walk, negligible cost).
+export async function findBaselineProvider({ cwd = process.cwd(), log } = {}) {
+  for (let pkgPath of findPercyPackages(cwd)) {
+    let pkgFile = path.join(pkgPath, 'package.json');
+
+    try {
+      if (!fs.existsSync(pkgFile)) continue;
+      let pkg = JSON.parse(fs.readFileSync(pkgFile, 'utf-8'));
+      let providerPath = pkg['@percy/cli']?.baselineProvider;
+      if (!providerPath) continue;
+
+      let module = await import(url.pathToFileURL(path.join(pkgPath, providerPath)).href);
+      let provider = module.default || module;
+
+      if (typeof provider.discoverBaselines === 'function') {
+        return { ...provider, packageName: pkg.name };
+      }
+    } catch (err) {
+      log?.debug(`Skipping baseline provider from ${pkgPath}: ${err.message}`);
+    }
+  }
+
+  return null;
+}
+
+// Establish the project's baseline from committed screenshots BEFORE the head build starts.
+// Never throws — a seeding problem must not break `percy exec`. Returns true when a baseline
+// build was created and finalized.
+export async function maybeSeedBaseline(percy, provider, { log }) {
+  try {
+    // Parallel shards would race each other seeding; the head build dedup doesn't apply to the
+    // separate seed build, so leave parallel runs to the explicit setup command.
+    if (process.env.PERCY_PARALLEL_TOTAL) {
+      log.debug('Skipping baseline seeding for a parallel build');
+      return false;
+    }
+
+    let { baselines = [], degraded, reason } =
+      (await provider.discoverBaselines({ cwd: process.cwd(), log })) || {};
+
+    if (degraded) {
+      log.debug(`Baseline discovery degraded (${reason}) — nothing seeded`);
+      return false;
+    }
+    if (!baselines.length) return false;
+
+    // Ask the server. An explicit baseline source on an ESTABLISHED project returns the
+    // baseline-skipped sentinel (no build persisted); on an empty project it creates build #1 as
+    // the baseline. First-ness is decided by the API from the project token — never locally.
+    let res = await percy.client.createBuild({
+      projectType: percy.projectType,
+      source: BASELINE_SOURCE,
+      dropinBaselineCandidate: true
+    });
+
+    if (!res?.data?.id) {
+      log.info(`Found ${baselines.length} committed baseline snapshot(s), but this project ` +
+        'already has builds — skipping baseline setup.');
+      log.info('To (re)establish the baseline from your committed snapshots, run: ' +
+        'npx percy playwright:setup-baseline');
+      return false;
+    }
+
+    let buildId = res.data.id;
+    log.info(`New Percy project with ${baselines.length} committed baseline snapshot(s) ` +
+      'detected — establishing your baseline (build #1) before running tests');
+
+    let seeded = await uploadBaselines(percy.client, buildId, baselines, {
+      log, projectType: percy.projectType
+    });
+
+    await percy.client.finalizeBuild(buildId);
+    log.info(`Baseline established from ${seeded}/${baselines.length} committed snapshot(s) ` +
+      'and auto-approved — this run diffs against it.');
+    return true;
+  } catch (err) {
+    log.warn('Skipping baseline setup');
+    log.debug(err.message);
+    return false;
+  }
+}
+
+// Clamp a pixel dimension to the API's accepted snapshot range (same as `percy upload`).
+function clampDimension(value, fallback) {
+  return Math.max(10, Math.min(value || fallback, 2000));
+}
+
+// A committed baseline PNG becomes a WEB snapshot: a generated root DOM displaying the image at
+// its native size plus the image resource — the exact shape `percy upload` uses for web projects,
+// so Percy renders the baseline in the project's own browsers and it pairs with the head run's
+// DOM snapshots by (name, browser, width).
+async function imageSnapshotResources({ name, filepath, width, height }) {
+  let rootUrl = `http://local/${encodeURIComponent(name)}`;
+  let imageUrl = `http://local/${encodeURIComponent(name)}.png`;
+  let content = await fs.promises.readFile(filepath);
+
+  return [
+    createRootResource(rootUrl, `
+      <!doctype html>
+      <html lang="en">
+        <head>
+          <meta charset="utf-8">
+          <title>${name}</title>
+          <style>
+            *, *::before, *::after { margin: 0; padding: 0; font-size: 0; }
+            html, body { width: 100%; }
+            img { max-width: 100%; }
+          </style>
+        </head>
+        <body>
+          <img src="${imageUrl}" width="${width}px" height="${height}px"/>
+        </body>
+      </html>
+    `),
+    createResource(imageUrl, content, 'image/png')
+  ];
+}
+
+// Bounded-concurrency upload of committed baseline files into `buildId`, shaped by project type:
+//   • web — each PNG becomes a rendered WEB SNAPSHOT (root DOM + image resource); web projects
+//     reject bare comparison tiles ("root resource" validation), and rendering server-side makes
+//     the baseline pair with the head run's DOM snapshots.
+//   • app — each PNG uploads straight through the COMPARISON ingest (tag + tile); no render flow
+//     is triggered, exactly how App Percy ingests screenshots. The tag width is the identity
+//     width (project viewport) so it pairs with the head run's uploads; height comes from the
+//     PNG bytes.
+// Per-file failures are skipped (a partial baseline beats none) and reported in the count.
+export async function uploadBaselines(client, buildId, baselines, { log, projectType = 'web' }) {
+  let queue = [...baselines];
+  let seeded = 0;
+
+  let uploadOne = async b => {
+    if (projectType === 'app') {
+      await client.sendComparison(buildId, {
+        name: b.name,
+        tag: { name: b.browserFamily, width: b.width, height: b.height },
+        tiles: [{ filepath: b.filepath }]
+      });
+    } else {
+      await client.sendSnapshot(buildId, {
+        name: b.name,
+        widths: [clampDimension(b.width, 1280)],
+        minHeight: clampDimension(b.height, 1024),
+        resources: await imageSnapshotResources(b)
+      });
+    }
+  };
+
+  let worker = async () => {
+    for (let b = queue.shift(); b; b = queue.shift()) {
+      try {
+        await uploadOne(b);
+        seeded += 1;
+        log.progress(`Uploading baseline snapshots: ${seeded}/${baselines.length}`, true);
+      } catch (err) {
+        log.warn(`Skipped baseline snapshot "${b.name}": ${err.message}`);
+      }
+    }
+  };
+
+  await Promise.all(
+    Array.from({ length: Math.min(SEED_CONCURRENCY, baselines.length) }, worker)
+  );
+
+  return seeded;
+}

packages/cli-exec/src/exec.js

@@ -5,6 +5,7 @@ import stop from './stop.js';
 import ping from './ping.js';
 import replay from './replay.js';
 import { waitForTimeout } from '@percy/client/utils';
+import { findBaselineProvider, maybeSeedBaseline } from './baseline.js';
 
 export const exec = command('exec', {
   description: 'Start and stop Percy around a supplied command',
@@ -76,6 +77,24 @@ export const exec = command('exec', {
       } else {
         log.debug('Skipping percy project attribute calculation');
       }
+
+      // Drop-in baseline seeding: when an installed SDK declares a baseline provider (e.g. the
+      // @percy/playwright toHaveScreenshot drop-in) and the Percy project is empty, the committed
+      // baseline screenshots are uploaded as an auto-approved build #1 BEFORE the head build
+      // starts — the user's suite doesn't run for the baseline. Never throws. Web projects seed
+      // rendered snapshots; app projects seed raw comparison uploads (no render flow).
+      if (percy.projectType === 'web' || percy.projectType === 'app') {
+        let provider = await findBaselineProvider({ log });
+
+        if (provider) {
+          // Tag the head build so the API can key drop-in behavior on its source.
+          if (provider.buildSource && !process.env.PERCY_BUILD_SOURCE) {
+            process.env.PERCY_BUILD_SOURCE = provider.buildSource;
+          }
+          yield maybeSeedBaseline(percy, provider, { log });
+        }
+      }
+
       yield* percy.yield.start();
     } catch (error) {
       if (error.name === 'AbortError') throw error;

packages/cli-exec/src/index.js

@@ -3,3 +3,6 @@ export { start } from './start.js';
 export { stop } from './stop.js';
 export { ping } from './ping.js';
 export { replay } from './replay.js';
+// Baseline seeding building blocks, reused by SDK-contributed setup commands
+// (e.g. @percy/playwright's `percy playwright:setup-baseline`).
+export { findBaselineProvider, maybeSeedBaseline, uploadBaselines } from './baseline.js';