Optionally capture packager logs during RNTester Xcode build

Summary:
Changelog: [Internal]

* Sets a default custom reporter in `scripts/packager.sh` that redirects Metro's logs to a JSON file when the `RCT_PACKAGER_LOG_PATH` environment variable is set. Otherwise we use Metro's `TerminalReporter`, [like the CLI does by default](https://github.com/react-native-community/cli/blob/0993f627869f4de0e5a8a9a950d38a9f15e18fb2/packages/cli-plugin-metro/src/commands/start/runServer.ts#L124).
* Modifies `scripts/launchPackager.command` to write logs to `$RCT_PACKAGER_LOGS_DIR` (and in particular use the JSON reporter) if this environment var is set.
* Uses [`open -n`](https://ss64.com/osx/open.html#:~:text=Open%20a%20new%20instance%20of%20the%20application) to execute `launchPackager.command` from Xcode, so that environment variables are reliably passed to the script even if a Terminal process is already running.

Reviewed By: yungsters

Differential Revision: D32295290

fbshipit-source-id: 4d783e1f94d122d3a35c104b2b02dbfaf8e1a1a3

packages/rn-tester/RNTesterPods.xcodeproj/project.pbxproj

@@ -594,7 +594,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "set -x\n\nexport RCT_METRO_PORT=\"${RCT_METRO_PORT:=8081}\"\necho \"export RCT_METRO_PORT=${RCT_METRO_PORT}\" > \"${SRCROOT}/../../scripts/.packager.env\"\nif [ -z \"${RCT_NO_LAUNCH_PACKAGER+xxx}\" ] ; then\n  if nc -w 5 -z localhost ${RCT_METRO_PORT} ; then\n    if ! curl -s \"http://localhost:${RCT_METRO_PORT}/status\" | grep -q \"packager-status:running\" ; then\n      echo \"Port ${RCT_METRO_PORT} already in use, packager is either not running or not running correctly\"\n      exit 2\n    fi\n  else\n    open \"$SRCROOT/../../scripts/launchPackager.command\" || echo \"Can't start packager automatically\"\n  fi\nfi\n";
+			shellScript = "set -x\n\nexport RCT_METRO_PORT=\"${RCT_METRO_PORT:=8081}\"\necho \"export RCT_METRO_PORT=${RCT_METRO_PORT}\" > \"${SRCROOT}/../../scripts/.packager.env\"\nif [ -z \"${RCT_NO_LAUNCH_PACKAGER+xxx}\" ] ; then\n  if nc -w 5 -z localhost ${RCT_METRO_PORT} ; then\n    if ! curl -s \"http://localhost:${RCT_METRO_PORT}/status\" | grep -q \"packager-status:running\" ; then\n      echo \"Port ${RCT_METRO_PORT} already in use, packager is either not running or not running correctly\"\n      exit 2\n    fi\n  else\n    open -n \"$SRCROOT/../../scripts/launchPackager.command\" || echo \"Can't start packager automatically\"\n  fi\nfi\n";
 			showEnvVarsInLog = 0;
 		};
 		68CD48B71D2BCB2C007E06A9 /* Build JS Bundle */ = {

scripts/launchPackager.command

@@ -10,9 +10,17 @@ clear
 
 THIS_DIR=$(cd -P "$(dirname "$(readlink "${BASH_SOURCE[0]}" || echo "${BASH_SOURCE[0]}")")" && pwd)
 
-# shellcheck source=/dev/null
-. "$THIS_DIR/packager.sh"
-
+if [ -n "${RCT_PACKAGER_LOGS_DIR}" ] ; then
+  echo "Writing logs to $RCT_PACKAGER_LOGS_DIR"
+  # shellcheck source=/dev/null
+  RCT_PACKAGER_LOG_PATH="$RCT_PACKAGER_LOGS_DIR/metro.log" \
+  . "$THIS_DIR/packager.sh" \
+    > "$RCT_PACKAGER_LOGS_DIR/packager.stdout.log" \
+    2> "$RCT_PACKAGER_LOGS_DIR/packager.stderr.log"
+else
+  # shellcheck source=/dev/null
+  . "$THIS_DIR/packager.sh"
+fi
 if [[ -z "$CI" ]]; then
   echo "Process terminated. Press <enter> to close the window"
   read -r

scripts/packager-reporter.js

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+'use strict';
+
+const logPath = process.env.RCT_PACKAGER_LOG_PATH;
+if (logPath != null && logPath !== '') {
+  const JsonReporter = require('metro/src/lib/JsonReporter');
+  const fs = require('fs');
+  const path = require('path');
+  module.exports = class extends JsonReporter {
+    constructor() {
+      fs.mkdirSync(path.dirname(logPath), {
+        recursive: true,
+      });
+      super(fs.createWriteStream(logPath));
+    }
+  };
+} else {
+  module.exports = require('metro/src/lib/TerminalReporter');
+}

scripts/packager.sh

@@ -21,4 +21,4 @@ then
 fi
 # Start packager from PROJECT_ROOT
 cd "$PROJECT_ROOT" || exit
-"$NODE_BINARY" "$REACT_NATIVE_ROOT/cli.js" start "$@"
+"$NODE_BINARY" "$REACT_NATIVE_ROOT/cli.js" start --custom-log-reporter-path "$THIS_DIR/packager-reporter.js" "$@"