ci: wait for the test simulator before running xcodebuild

.github/workflows/pull_request.yml

@@ -133,6 +133,9 @@ jobs:
         run: |
           mkdir -p dist-test
           echo TEST_FOLDER=$(pwd)/dist-test >> $GITHUB_ENV
+      # Must match the simulator named in the Xcode Tests -destination.
+      - name: Wait for the test simulator
+        run: ./scripts/wait-for-simulator.sh --name "iPhone 16 Pro"
       - name: Xcode Tests
         uses: nick-fields/retry@ad984534de44a9489a53aefd81eb77f87c70dc60 # v4.0.0
         # try to run the tests with xcpretty. If it fails then try again without xcpretty twice for better log output

scripts/wait-for-simulator.sh

@@ -0,0 +1,90 @@
+#!/bin/bash
+# CI-only: waits until an available iOS simulator with the given name is listed.
+# On a fresh runner CoreSimulator can still be enumerating its devices when the
+# test step starts, and an xcodebuild that resolves its -destination then fails
+# with "Unable to find a device matching the provided destination specifier"
+# (exit code 70).
+set -euo pipefail
+
+usage() {
+  echo "Usage: ./scripts/wait-for-simulator.sh --name <device name> [--timeout <seconds>]"
+  echo ""
+  echo "  --name <name>        simulator device name, e.g. \"iPhone 16 Pro\""
+  echo "  --timeout <seconds>  give up after this long (default: 300)"
+  echo "  -h, --help           show this help"
+}
+
+NAME=""
+TIMEOUT=300
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --name)
+      [ $# -ge 2 ] || { echo "--name requires a value" >&2; usage >&2; exit 1; }
+      NAME="$2"
+      shift 2
+      ;;
+    --name=*)
+      NAME="${1#--name=}"
+      shift
+      ;;
+    --timeout)
+      [ $# -ge 2 ] || { echo "--timeout requires a value" >&2; usage >&2; exit 1; }
+      TIMEOUT="$2"
+      shift 2
+      ;;
+    --timeout=*)
+      TIMEOUT="${1#--timeout=}"
+      shift
+      ;;
+    -h|--help)
+      usage
+      exit 0
+      ;;
+    *)
+      echo "Unknown argument: $1" >&2
+      usage >&2
+      exit 1
+      ;;
+  esac
+done
+
+if [ -z "$NAME" ]; then
+  echo "--name is required" >&2
+  usage >&2
+  exit 1
+fi
+case "$TIMEOUT" in
+  ''|*[!0-9]*) echo "--timeout must be a whole number of seconds" >&2; exit 1 ;;
+esac
+
+# Prints the UDID of an available iOS device named $NAME, newest runtime first.
+find_device() {
+  xcrun simctl list devices available -j 2>/dev/null | python3 -c '
+import json, sys
+name = sys.argv[1]
+devices = json.load(sys.stdin).get("devices", {})
+def version(runtime):
+    return [int(p) for p in runtime.rsplit("iOS-", 1)[1].split("-") if p.isdigit()]
+for runtime in sorted((r for r in devices if ".SimRuntime.iOS-" in r), key=version, reverse=True):
+    for device in devices[runtime]:
+        if device.get("name") == name:
+            print(device["udid"], runtime.rsplit(".", 1)[1])
+            sys.exit(0)
+' "$NAME"
+}
+
+deadline=$((SECONDS + TIMEOUT))
+while :; do
+  # simctl itself can fail while CoreSimulator is starting; that counts as "not yet".
+  found="$(find_device || true)"
+  if [ -n "$found" ]; then
+    echo "Found simulator \"$NAME\": $found (after ${SECONDS}s)"
+    exit 0
+  fi
+  if [ "$SECONDS" -ge "$deadline" ]; then
+    echo "::error::No available simulator named \"$NAME\" after ${TIMEOUT}s"
+    xcrun simctl list devices available || true
+    exit 1
+  fi
+  sleep 5
+done