feat: add option to build only active architectures on android (react-native-community#1388)

Author: janicduplessis

packages/platform-android/src/commands/runAndroid/adb.ts

@@ -67,7 +67,29 @@ function getAvailableCPUs(adbPath: string, device: string): Array<string> {
   }
 }
 
+/**
+ * Gets the CPU architecture of a device from ADB
+ */
+function getCPU(adbPath: string, device: string): string | null {
+  try {
+    const cpus = execFileSync(adbPath, [
+      '-s',
+      device,
+      'shell',
+      'getprop',
+      'ro.product.cpu.abi',
+    ])
+      .toString()
+      .trim();
+
+    return cpus.length > 0 ? cpus : null;
+  } catch (e) {
+    return null;
+  }
+}
+
 export default {
   getDevices,
   getAvailableCPUs,
+  getCPU,
 };

packages/platform-android/src/commands/runAndroid/index.ts

@@ -51,6 +51,7 @@ export interface Flags {
   port: number;
   terminal: string;
   jetifier: boolean;
+  activeArchOnly: boolean;
 }
 
 type AndroidProject = NonNullable<Config['project']['android']>;
@@ -380,5 +381,11 @@ export default {
       description:
         'Do not run "jetifier" – the AndroidX transition tool. By default it runs before Gradle to ease working with libraries that don\'t support AndroidX yet. See more at: https://www.npmjs.com/package/jetifier.',
     },
+    {
+      name: '--active-arch-only',
+      description:
+        'Build native libraries only for the current device architecture for debug builds.',
+      default: false,
+    },
   ],
 };

packages/platform-android/src/commands/runAndroid/runOnAllDevices.ts

@@ -63,6 +63,20 @@ async function runOnAllDevices(
       gradleArgs.push('-PreactNativeDevServerPort=' + args.port);
     }
 
+    if (args.activeArchOnly) {
+      const architectures = devices
+        .map((device) => {
+          return adb.getCPU(adbPath, device);
+        })
+        .filter((arch) => arch != null);
+      if (architectures.length > 0) {
+        logger.info(`Detected architectures ${architectures.join(', ')}`);
+        gradleArgs.push(
+          '-PreactNativeDebugArchitectures=' + architectures.join(','),
+        );
+      }
+    }
+
     logger.info('Installing the app...');
     logger.debug(
       `Running command "cd android && ${cmd} ${gradleArgs.join(' ')}"`,