fusion/packages/mobile/scripts/patch-android-manifest.ts

/**
 * FNXC:TaskDetailAndroidBack 2026-07-05-11:40:
 * FN-7583: the Android system back GESTURE (predictive back / edge swipe, Android 13+,
 * default-prominent at this project's `targetSdk 35`) was not reaching the same
 * `@capacitor/app` `OnBackPressedCallback` ("backButton" JS event) that the hardware/
 * legacy Back button already routes through — even though both the button and the
 * gesture are supposed to funnel through AndroidX's `OnBackPressedDispatcher`. Per
 * Android's predictive-back docs (https://developer.android.com/guide/navigation/custom-back/predictive-back-gesture)
 * and the confirmed upstream defect (ionic-team/capacitor-plugins#2418, mitigated by
 * ionic-team/capacitor-plugins#2390's `disableBackButtonHandler` toggle shipped in
 * `@capacitor/app@7.1.0`), an app must opt in via `android:enableOnBackInvokedCallback="true"`
 * on the manifest `<application>` tag for the gesture-completion callback to reliably
 * reach a registered `OnBackPressedCallback`. Without that opt-in, the OS falls back to
 * "legacy" gesture dispatch, which silently drops the callback invocation for the
 * gesture while the hardware Back button (delivered via the ordinary Window/Activity
 * input path) keeps working — exactly the divergence this task reported.
 *
 * The native `android/` project is generated by `cap sync` and is git-ignored (see
 * AGENTS.md / `.gitignore`), so durable changes cannot live there directly. Instead this
 * script idempotently patches the generated manifest immediately after every sync, and
 * is wired into Capacitor's own `capacitor:sync:after` npm-script hook (see
 * `package.json`), which the Capacitor CLI runs automatically after `cap sync` — and
 * therefore after `cap run android` (which syncs first) and `build:mobile` too.
 *
 * This keeps a SINGLE dismissal invariant: gesture and button both end up delivered to
 * `AndroidBackButtonManager`'s `backButton` listener in
 * `packages/mobile/src/plugins/native-shell.ts`, which dispatches the cancelable
 * `fusion:native-back` event consumed by the dashboard's shared nav-history stack.
 */
import { existsSync, readFileSync, writeFileSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

const ENABLE_ATTR = 'android:enableOnBackInvokedCallback="true"';

export function patchManifestSource(xml: string): { changed: boolean; xml: string } {
  const applicationTagMatch = xml.match(/<application\b[^>]*>/);
  if (!applicationTagMatch) {
    return { changed: false, xml };
  }

  const applicationTag = applicationTagMatch[0];
  if (applicationTag.includes("android:enableOnBackInvokedCallback")) {
    // Already opted in (idempotent — do not duplicate on repeat `cap sync` runs).
    return { changed: false, xml };
  }

  const patchedTag = applicationTag.replace(/>$/, ` ${ENABLE_ATTR}>`);
  const patchedXml = xml.slice(0, applicationTagMatch.index) + patchedTag + xml.slice((applicationTagMatch.index ?? 0) + applicationTag.length);
  return { changed: true, xml: patchedXml };
}

export function resolveManifestPath(mobilePackageDir: string): string {
  return join(mobilePackageDir, "android", "app", "src", "main", "AndroidManifest.xml");
}

export function patchAndroidManifest(mobilePackageDir: string): { patched: boolean; skipped: boolean; path: string } {
  const manifestPath = resolveManifestPath(mobilePackageDir);

  if (!existsSync(manifestPath)) {
    // No Android platform added yet (e.g. iOS-only sync) — safe no-op, not an error.
    return { patched: false, skipped: true, path: manifestPath };
  }

  const original = readFileSync(manifestPath, "utf8");
  const { changed, xml } = patchManifestSource(original);

  if (changed) {
    writeFileSync(manifestPath, xml, "utf8");
  }

  return { patched: changed, skipped: false, path: manifestPath };
}

function isMainModule(): boolean {
  return process.argv[1] === fileURLToPath(import.meta.url);
}

if (isMainModule()) {
  const mobilePackageDir = dirname(fileURLToPath(import.meta.url)).replace(/[/\\]scripts$/, "");
  const result = patchAndroidManifest(mobilePackageDir);

  if (result.skipped) {
    console.log(`[patch-android-manifest] no android/ project at ${result.path}; skipping (nothing to patch yet)`);
  } else if (result.patched) {
    console.log(`[patch-android-manifest] added android:enableOnBackInvokedCallback="true" to ${result.path}`);
  } else {
    console.log(`[patch-android-manifest] ${result.path} already opts into enableOnBackInvokedCallback; no change`);
  }
}