fix(e2e): stop the web backend from outliving Playwright runs (#1747)

apps/web-backend/src/app/project-config.spec.ts

@@ -0,0 +1,63 @@
+import { readdirSync, readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+describe('Playwright web-backend launch', () => {
+    const appsDirectory = join(process.cwd(), 'apps');
+    const launchCommand = 'node --import tsx apps/web-backend/src/main.ts';
+    const configsStartingBackend = ['apps/web-e2e/playwright.config.ts'];
+    const readSource = (path: string) =>
+        readFileSync(join(process.cwd(), path), 'utf8');
+    const serveEnv = (
+        JSON.parse(readSource('apps/web-backend/project.json')) as {
+            targets: { serve: { options: { env: Record<string, string> } } };
+        }
+    ).targets.serve.options.env;
+
+    it('knows every Playwright config that starts the web backend', () => {
+        const configs = readdirSync(appsDirectory, { withFileTypes: true })
+            .filter((entry) => entry.isDirectory())
+            .flatMap((entry) =>
+                readdirSync(join(appsDirectory, entry.name))
+                    .filter((name) =>
+                        /^playwright(\..+)?\.config\.ts$/.test(name)
+                    )
+                    .map((name) => `apps/${entry.name}/${name}`)
+            )
+            .filter((configPath) =>
+                readSource(configPath).includes('web-backend')
+            );
+
+        expect(configs.sort()).toEqual(configsStartingBackend);
+    });
+
+    // Nx starts a run-commands child in its own detached process group, and
+    // Playwright stops a webServer with a process-group SIGKILL, so a backend
+    // launched through Nx outlived the run and kept port 3333.
+    it.each(configsStartingBackend)(
+        'starts the backend in %s as a single node process',
+        (configPath) => {
+            const source = readSource(configPath);
+            const start = source.indexOf(`'${launchCommand}'`);
+
+            expect(source).not.toMatch(/\bnx\b[^'"`\n]*web-backend/);
+            expect(start).toBeGreaterThan(-1);
+            expect(
+                source.indexOf(launchCommand, start + launchCommand.length)
+            ).toBe(-1);
+
+            // WEB_BACKEND_PORT relocates the run; its default is the target's.
+            const { PORT: port, ...fixedEnv } = serveEnv;
+            const entry = source.slice(start, source.indexOf('url:', start));
+            for (const [name, value] of Object.entries(fixedEnv)) {
+                expect(entry).toContain(`${name}: '${value}'`);
+            }
+            expect(source).toContain(
+                `process.env['WEB_BACKEND_PORT'] ?? '${port}'`
+            );
+            expect(entry).toContain('PORT: webBackendPort,');
+            expect(source).toContain(
+                'url: `http://localhost:${webBackendPort}/health`'
+            );
+        }
+    );
+});