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import * as path from 'path';
import { fileURLToPath } from 'url';
import { execFileSync } from 'child_process';
import * as dotenv from 'dotenv';
import { Flow, RunnerConfig, DiffScreenshotResult } from './flow';
import { diffCssBundles, changedSelectors, changedRuleProps, sameCss } from './css-diff';
import { buildReportHtml, buildCommentMarkdown, buildOrgUnavailableMarkdown } from './report';
import { FlowRunner, OrgUnavailableError, redact } from './flow-runner';
// --- Flow loading (formerly flow-loader.ts) ---------------------------------
export function substituteEnvVars(content: string): string {
// Values land inside JSON strings, so escape them (a `"` or `\` in a password must not break the flow).
return content.replace(/\$\{(\w+)\}/g, (_, name) => JSON.stringify(process.env[name] || '').slice(1, -1));
}
// The key each Step variant is discriminated on; an unknown key is an unrunnable step.
const STEP_KEYS = [
'goto',
'click',
'blur',
'retry',
'type',
'wait',
'waitForSelector',
'screenshot',
'style',
'cssFile',
'dismiss',
];
function isObject(value: unknown): value is Record<string, unknown> {
return typeof value === 'object' && value !== null && !Array.isArray(value);
}
// Validate shape at load time so a malformed flow fails here (naming the file) rather than later inside the runner.
function assertFlow(value: unknown, filePath: string): asserts value is Flow {
Iif (!isObject(value)) {
throw new Error(
`Invalid flow ${filePath}: expected a JSON object, got ${Array.isArray(value) ? 'array' : typeof value}.`,
);
}
Iif (typeof value.name !== 'string' || value.name.length === 0) {
throw new Error(`Invalid flow ${filePath}: "name" must be a non-empty string.`);
}
Iif (!Array.isArray(value.steps)) {
throw new Error(`Invalid flow ${filePath}: "steps" must be an array.`);
}
value.steps.forEach((step: unknown, i: number) => {
Iif (!isObject(step)) {
throw new Error(`Invalid flow ${filePath}: step ${i} must be an object.`);
}
if (!STEP_KEYS.some((key) => key in step)) {
throw new Error(
`Invalid flow ${filePath}: step ${i} has no recognized action (expected one of ${STEP_KEYS.join(', ')}).`,
);
}
});
}
export function loadFlow(filePath: string): Flow {
const absolutePath = path.resolve(filePath);
const content = fs.readFileSync(absolutePath, 'utf-8');
const substituted = substituteEnvVars(content);
let parsed: unknown;
try {
parsed = JSON.parse(substituted);
} catch (e) {
const detail = e instanceof Error ? e.message : String(e);
throw new Error(`Invalid flow ${absolutePath}: not valid JSON (${detail}).`);
}
assertFlow(parsed, absolutePath);
return parsed;
}
// ----------------------------------------------------------------------------
// Differential VRT: injects bundle A (baseline) then B (candidate) into the SAME page
// load, so anything that isn't the CSS cancels out and every remaining pixel diff is
// CSS-attributable. See --ref/--pr/--css-a/--css-b/--build handling below for options.
// Target repo config — the runner is repo-agnostic, so what/where to build comes from
// the environment (CI has no UI): VRT_REPO_ROOT is the checkout to build in (default cwd),
// VRT_BUILD_CMD builds the CSS bundle, VRT_BUNDLE_REL is the built bundle path relative to
// the repo root, VRT_INSTALL_CMD (optional) installs deps in the ref worktree.
interface TargetConfig {
repoRoot: string;
buildCmd: [string, string[]];
bundleRel: string;
installCmd?: [string, string[]];
}
// execFileSync runs without a shell, so a command string is split into argv on whitespace
// (no shell operators / quoted spaces).
function splitCommand(cmd: string): [string, string[]] {
const parts = cmd.trim().split(/\s+/);
return [parts[0], parts.slice(1)];
}
function resolveTarget(): TargetConfig {
const repoRoot = (process.env.VRT_REPO_ROOT || process.cwd()).trim();
const build = process.env.VRT_BUILD_CMD?.trim();
if (!build) {
throw new Error(
'VRT_BUILD_CMD not set — the command that builds your CSS bundle (e.g. "yarn build:css").',
);
}
const bundleRel = process.env.VRT_BUNDLE_REL?.trim();
if (!bundleRel) {
throw new Error('VRT_BUNDLE_REL not set — the built CSS bundle path, relative to VRT_REPO_ROOT.');
}
const install = process.env.VRT_INSTALL_CMD?.trim();
return {
repoRoot,
buildCmd: splitCommand(build),
bundleRel,
installCmd: install ? splitCommand(install) : undefined,
};
}
// Resolved lazily + memoized: a run with explicit --css-a and --css-b never builds, so it
// needs no target config (and must not fail when it's unset).
let _target: TargetConfig | undefined;
const target = (): TargetConfig => (_target ??= resolveTarget());
// Base name for traceable temp bundle files, derived from the configured bundle path.
const bundleBase = (): string => path.basename(target().bundleRel).replace(/\.css$/i, '') || 'bundle';
function run(cmd: string, args: string[], cwd: string): void {
console.log(`$ ${cmd} ${args.join(' ')} (cwd: ${cwd})`);
execFileSync(cmd, args, { cwd, stdio: 'inherit' });
}
// PR checkouts have only `origin/<base>` (no local branch), so fall back to the remote-tracking ref.
export function resolveRefSha(ref: string, cwd: string): string {
for (const candidate of [ref, `origin/${ref}`]) {
try {
return execFileSync('git', ['rev-parse', '--verify', '--quiet', `${candidate}^{commit}`], {
cwd,
encoding: 'utf8',
stdio: ['ignore', 'pipe', 'ignore'],
}).trim();
} catch {
/* not found under this name; try the next */
}
}
throw new Error(`Baseline ref "${ref}" not found locally or as origin/${ref}. Fetch it first.`);
}
// Builds the bundle from a commit in an isolated worktree (always cleaned up), then copies it to outPath.
function buildBundleFromRef(ref: string, sha: string, outPath: string, cfg: TargetConfig): void {
const worktree = path.join(cfg.repoRoot, `.vrt-worktree-${ref.replace(/[^\w.-]/g, '_')}`);
// Clean any stale worktree from a previous interrupted run.
try {
run('git', ['worktree', 'remove', '--force', worktree], cfg.repoRoot);
} catch {
/* no-op: nothing to remove */
}
try {
// Detached at the resolved commit, so it works whether or not a local branch exists.
run('git', ['worktree', 'add', '--force', '--detach', worktree, sha], cfg.repoRoot);
// Install (if configured) + build inside the worktree so its deps match that ref.
if (cfg.installCmd) {
run(cfg.installCmd[0], cfg.installCmd[1], worktree);
} else {
console.log('No VRT_INSTALL_CMD set — assuming the worktree builds without a fresh install.');
}
run(cfg.buildCmd[0], cfg.buildCmd[1], worktree);
const built = path.join(worktree, cfg.bundleRel);
if (!fs.existsSync(built)) {
throw new Error(`Bundle not produced in worktree: ${built}`);
}
fs.mkdirSync(path.dirname(outPath), { recursive: true });
fs.copyFileSync(built, outPath);
console.log(`Built ${ref} bundle → ${outPath}`);
} finally {
try {
run('git', ['worktree', 'remove', '--force', worktree], cfg.repoRoot);
} catch {
/* no-op: best-effort cleanup */
}
}
}
// Normalize VRT_BASE_URL to an ORIGIN (scheme + host). A path or trailing slash would mis-join with
// a page's leading-slash path (`.com//lightning/...`), which Lightning silently ignores, so it's trimmed.
function normalizeBaseUrl(raw: string): string {
const trimmed = raw.trim();
let parsed: URL;
try {
parsed = new URL(trimmed);
} catch {
console.error(
`VRT_BASE_URL is not a valid URL. It must be an origin including the scheme, ` +
`e.g. https://my-org.my.salesforce.com (no path, no trailing slash). Page paths live in the flow JSON.`,
);
process.exit(1);
}
if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
console.error(`VRT_BASE_URL must start with http:// or https://.`);
process.exit(1);
}
if ((parsed.pathname && parsed.pathname !== '/') || parsed.search || parsed.hash) {
console.warn(`VRT_BASE_URL had a path; using its origin. Page paths belong in the flow JSON.`);
}
return parsed.origin;
}
// Preflight before opening a browser. Any HTTP response (even 4xx / redirect) counts as reachable;
// only connection/DNS/timeout errors abort. Mirrors the runtime message in flow-runner's goto.
async function assertReachable(baseUrl: string): Promise<void> {
try {
await fetch(baseUrl, { method: 'HEAD', redirect: 'manual', signal: AbortSignal.timeout(10_000) });
} catch (e) {
const detail = e instanceof Error ? e.message : String(e);
throw new OrgUnavailableError(
`Org unreachable at ${redact(baseUrl)}. If running locally, check VRT_BASE_URL (it defaults to localhost). (${redact(detail)})`,
{ cause: e },
);
}
}
const ORG_DOC = 'packages/design-system-2/scripts/vrt-core/README.md#the-test-org';
async function main() {
const args = process.argv.slice(2);
const flowPath = args.find((a) => !a.startsWith('--'));
if (!flowPath) {
console.error(
'Usage: tsx core/diff.ts <flow.json> [--ref <gitref>] [--css-a p] [--css-b p] [--build]\n' +
'Env (unless both --css-a and --css-b are given): VRT_REPO_ROOT (default cwd),\n' +
'VRT_BUILD_CMD (required), VRT_BUNDLE_REL (required), VRT_INSTALL_CMD (optional).',
);
process.exit(1);
}
const getOpt = (name: string): string | undefined => {
const i = args.indexOf(name);
return i >= 0 ? args[i + 1] : undefined;
};
// Baseline defaults to develop since PRs always target it (main is never a PR base).
const ref = getOpt('--ref') ?? 'develop';
const prOpt = getOpt('--pr');
const cssAOpt = getOpt('--css-a');
const cssBOpt = getOpt('--css-b');
const forceBuild = args.includes('--build');
// candidateLabel names the on-disk bundle file; displayLabel is the human-readable form for the report.
const candidateLabel = prOpt ? `pr${prOpt}` : 'working';
const displayLabel = prOpt ? `PR #${prOpt}` : 'working tree';
// Normalize + validate to a clean origin (fails loudly on a bad URL). Reachability is checked
// only after the CSS compare, so a PR with no CSS changes passes even when the org is down.
const baseUrl = normalizeBaseUrl(process.env.VRT_BASE_URL || 'http://localhost:3000');
const screenshotDir = process.env.VRT_SCREENSHOT_DIR || 'core/screenshots';
const tmpDir = path.join(screenshotDir, 'diff-bundles');
fs.mkdirSync(tmpDir, { recursive: true });
// Resolve bundle B (candidate); copy the working-tree artifact to a source-named file for traceability.
let cssBPath: string;
let labelB: string;
if (cssBOpt) {
cssBPath = path.resolve(cssBOpt);
labelB = path.basename(cssBPath);
} else {
const workingBundle = path.join(target().repoRoot, target().bundleRel);
if (forceBuild || !fs.existsSync(workingBundle)) {
run(target().buildCmd[0], target().buildCmd[1], target().repoRoot);
}
cssBPath = path.join(tmpDir, `${bundleBase()}.${candidateLabel}.css`);
fs.copyFileSync(workingBundle, cssBPath);
labelB = candidateLabel;
}
// Resolve bundle A (baseline = built from --ref, unless overridden).
let cssAPath: string;
let labelA: string;
if (cssAOpt) {
cssAPath = path.resolve(cssAOpt);
labelA = path.basename(cssAPath);
} else {
// Keyed by the ref's commit, so the worktree install + build only reruns when the ref moves.
const sha = resolveRefSha(ref, target().repoRoot);
cssAPath = path.join(tmpDir, `${bundleBase()}.${ref.replace(/[^\w.-]/g, '_')}.${sha.slice(0, 12)}.css`);
if (fs.existsSync(cssAPath)) {
console.log(`Reusing cached ${ref} bundle (${sha.slice(0, 12)}) → ${cssAPath}`);
} else {
buildBundleFromRef(ref, sha, cssAPath, target());
}
labelA = ref;
}
// Tier-1 CSS attribution: exact declarations changed; feeds Tier-2 per-page DOM matching in the runner.
const cssA = fs.readFileSync(cssAPath, 'utf8');
const cssB = fs.readFileSync(cssBPath, 'utf8');
const cssChanges = diffCssBundles(cssA, cssB);
const changedSels = changedSelectors(cssChanges);
console.log('Differential VRT');
console.log(` bundle A (baseline): ${cssAPath} [${labelA}]`);
console.log(` bundle B (candidate): ${cssBPath} [${labelB}]`);
console.log(` flow: ${flowPath}`);
console.log(
` CSS changes: ${cssChanges.length} declaration(s) across ${changedSels.length} selector(s)`,
);
console.log('---');
// Build the CI run URL from GitHub Actions env vars so the PR comment can link to it; undefined locally.
const { GITHUB_SERVER_URL, GITHUB_REPOSITORY, GITHUB_RUN_ID } = process.env;
const runUrl =
GITHUB_SERVER_URL && GITHUB_REPOSITORY && GITHUB_RUN_ID
? `${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}`
: undefined;
// The PR's web URL for the report header to link to; falls back to plain text if server/repo/PR are missing.
const prUrl =
GITHUB_SERVER_URL && GITHUB_REPOSITORY && prOpt
? `${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/pull/${prOpt}`
: undefined;
const prLabel = cssBOpt ? labelB : displayLabel;
const commentMd = path.join(screenshotDir, 'pr-comment.md');
// Identical CSS can't change a page: pass without touching the org.
if (sameCss(cssA, cssB)) {
fs.writeFileSync(
commentMd,
buildCommentMarkdown({ prLabel, baselineLabel: labelA, results: [], changes: [], runUrl, prUrl }),
);
console.log(`No SLDS CSS changes between ${labelA} and ${labelB}; no pages tested.`);
console.log(`Wrote ${commentMd}`);
return;
}
const config: RunnerConfig = {
baseUrl,
headless: process.env.VRT_HEADLESS !== 'false',
screenshotDir,
};
const runner = new FlowRunner(config);
const flow = loadFlow(flowPath);
let results: DiffScreenshotResult[] = [];
try {
await assertReachable(baseUrl);
await runner.init();
results = await runner.runFlowDifferential(flow, {
cssAPath,
cssBPath,
labelA,
labelB,
changedSelectors: changedSels,
changedRules: changedRuleProps(cssChanges),
});
} catch (e) {
// Say so on the PR; the job still fails.
if (e instanceof OrgUnavailableError) {
const docUrl =
GITHUB_SERVER_URL && GITHUB_REPOSITORY
? `${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/blob/develop/${ORG_DOC}`
: undefined;
fs.writeFileSync(
commentMd,
buildOrgUnavailableMarkdown({ prLabel, baselineLabel: labelA, reason: e.message, docUrl }),
);
}
throw e;
} finally {
await runner.close();
}
console.log('---');
console.log('Differential results:');
let anyChange = false;
for (const r of results) {
if (r.missed) {
console.log(
` ⛔ ${r.name}: ${r.missed.error ? `NOT CAPTURED (${r.missed.error})` : `skipped (depends on ${r.missed.dependsOn})`}`,
);
} else if (r.dimensionMismatch) {
console.log(
` ⚠ ${r.name}: REFLOW (A=${r.dimensionMismatch.a.join('x')} B=${r.dimensionMismatch.b.join('x')}) — review ${r.diffPath ?? r.shotBPath}`,
);
anyChange = true;
} else {
const pct = (r.ratio * 100).toFixed(3);
const flag = r.noise ? '≈ noise (ignored)' : r.changedPixels > 0 ? '✗ CHANGED' : '✓ identical';
console.log(
` ${flag} ${r.name}: ${r.changedPixels}/${r.totalPixels} px (${pct}%) → ${r.diffPath ?? '(no diff img)'}`,
);
if (r.changedPixels > 0 && !r.noise) anyChange = true;
}
}
// Emit machine-readable results for CI surfacing (PR comment / summary).
const outJson = path.join(config.screenshotDir!, 'diff-results.json');
fs.writeFileSync(outJson, JSON.stringify(results, null, 2));
console.log(`\nWrote ${outJson}`);
const reportInput = {
prLabel,
baselineLabel: labelA,
results,
changes: cssChanges,
runUrl,
prUrl,
};
const reportHtml = path.join(config.screenshotDir!, 'visual-report.html');
fs.writeFileSync(reportHtml, buildReportHtml(reportInput));
fs.writeFileSync(commentMd, buildCommentMarkdown(reportInput));
console.log(`Wrote ${reportHtml}`);
console.log(`Wrote ${commentMd}`);
console.log(
anyChange ? '\nDifferences found (see visual-report.html).' : '\nNo CSS-attributable differences.',
);
// Job stays green; the report and PR comment carry the "incomplete" status.
const missedCount = results.filter((r) => r.missed).length;
if (missedCount) console.log(`Incomplete: ${missedCount} of ${results.length} page(s) not captured.`);
}
// Run only as the entrypoint, so tests can import the helpers above without starting a run.
const self = fileURLToPath(import.meta.url);
Iif (process.argv[1] && path.resolve(process.argv[1]) === self) {
// Load local .env (gitignored; no-op in CI).
dotenv.config({ path: path.resolve(path.dirname(self), '.env') });
main().catch((err) => {
console.error(redact(err instanceof Error ? (err.stack ?? err.message) : String(err)));
process.exitCode = 1;
});
}
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