fix: stage libffmpeg for Linux AppImage child processes

scripts/electron-builder-after-pack.cjs

@@ -0,0 +1,41 @@
+const fs = require('node:fs/promises');
+const path = require('node:path');
+
+const LINUX_FFMPEG_LIBRARY = 'libffmpeg.so';
+
+async function stageLinuxAppImageSharedLibrary(
+  context,
+  deps = {
+    access: (filePath) => fs.access(filePath),
+    mkdir: (dirPath) => fs.mkdir(dirPath, { recursive: true }),
+    copyFile: (from, to) => fs.copyFile(from, to),
+  },
+) {
+  if (context.electronPlatformName !== 'linux') return false;
+
+  const sourceLibraryPath = path.join(context.appOutDir, LINUX_FFMPEG_LIBRARY);
+
+  try {
+    await deps.access(sourceLibraryPath);
+  } catch {
+    return false;
+  }
+
+  const targetLibraryDir = path.join(context.appOutDir, 'usr', 'lib');
+  const targetLibraryPath = path.join(targetLibraryDir, LINUX_FFMPEG_LIBRARY);
+
+  await deps.mkdir(targetLibraryDir);
+  await deps.copyFile(sourceLibraryPath, targetLibraryPath);
+
+  return true;
+}
+
+async function afterPack(context) {
+  await stageLinuxAppImageSharedLibrary(context);
+}
+
+module.exports = {
+  LINUX_FFMPEG_LIBRARY,
+  stageLinuxAppImageSharedLibrary,
+  default: afterPack,
+};

scripts/electron-builder-after-pack.test.ts

@@ -0,0 +1,84 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import test from 'node:test';
+
+const {
+  LINUX_FFMPEG_LIBRARY,
+  stageLinuxAppImageSharedLibrary,
+} = require('./electron-builder-after-pack.cjs') as {
+  LINUX_FFMPEG_LIBRARY: string;
+  stageLinuxAppImageSharedLibrary: (context: {
+    appOutDir: string;
+    electronPlatformName: string;
+  }) => Promise<boolean>;
+};
+
+function createWorkspace(name: string): string {
+  return fs.mkdtempSync(path.join(os.tmpdir(), `${name}-`));
+}
+
+test('stageLinuxAppImageSharedLibrary copies libffmpeg.so into usr/lib for Linux packaging', async () => {
+  const workspace = createWorkspace('subminer-after-pack-linux');
+  const appOutDir = path.join(workspace, 'SubMiner-linux-x64');
+  const sourceLibraryPath = path.join(appOutDir, LINUX_FFMPEG_LIBRARY);
+  const targetLibraryPath = path.join(appOutDir, 'usr', 'lib', LINUX_FFMPEG_LIBRARY);
+
+  fs.mkdirSync(appOutDir, { recursive: true });
+  fs.writeFileSync(sourceLibraryPath, 'bundled ffmpeg', 'utf8');
+
+  try {
+    const staged = await stageLinuxAppImageSharedLibrary({
+      appOutDir,
+      electronPlatformName: 'linux',
+    });
+
+    assert.equal(staged, true);
+    assert.equal(fs.readFileSync(targetLibraryPath, 'utf8'), 'bundled ffmpeg');
+  } finally {
+    fs.rmSync(workspace, { recursive: true, force: true });
+  }
+});
+
+test('stageLinuxAppImageSharedLibrary skips non-Linux packaging contexts', async () => {
+  const workspace = createWorkspace('subminer-after-pack-non-linux');
+  const appOutDir = path.join(workspace, 'SubMiner-darwin-arm64');
+  const sourceLibraryPath = path.join(appOutDir, LINUX_FFMPEG_LIBRARY);
+  const targetLibraryPath = path.join(appOutDir, 'usr', 'lib', LINUX_FFMPEG_LIBRARY);
+
+  fs.mkdirSync(appOutDir, { recursive: true });
+  fs.writeFileSync(sourceLibraryPath, 'bundled ffmpeg', 'utf8');
+
+  try {
+    const staged = await stageLinuxAppImageSharedLibrary({
+      appOutDir,
+      electronPlatformName: 'darwin',
+    });
+
+    assert.equal(staged, false);
+    assert.equal(fs.existsSync(targetLibraryPath), false);
+  } finally {
+    fs.rmSync(workspace, { recursive: true, force: true });
+  }
+});
+
+test('stageLinuxAppImageSharedLibrary no-ops when libffmpeg.so is absent', async () => {
+  const workspace = createWorkspace('subminer-after-pack-missing-library');
+  const appOutDir = path.join(workspace, 'SubMiner-linux-x64');
+  const targetLibraryPath = path.join(appOutDir, 'usr', 'lib', LINUX_FFMPEG_LIBRARY);
+
+  fs.mkdirSync(appOutDir, { recursive: true });
+
+  try {
+    const staged = await stageLinuxAppImageSharedLibrary({
+      appOutDir,
+      electronPlatformName: 'linux',
+    });
+
+    assert.equal(staged, false);
+    assert.equal(fs.existsSync(targetLibraryPath), false);
+  } finally {
+    fs.rmSync(workspace, { recursive: true, force: true });
+  }
+});