feat(ioscompanion): pair the legacy companion with the in-simulator runner

internal/driver/ioscompanion/runnerspawn.go

@@ -0,0 +1,89 @@
+package ioscompanion
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"syscall"
+
+	"github.com/priyanshujain/sanderling/internal/driver/ioscompanion/runnerassets"
+)
+
+// runnerPortPlaceholder is the marker the prepare script plants in the
+// packaged test configuration's environment. The spawner substitutes the
+// session's port before launching.
+const runnerPortPlaceholder = "__COMPANION_PORT__"
+
+// realSpawnRunner extracts the embedded runner bundle, writes a test
+// configuration bound to the session's port, and starts the hosting test
+// session against the configured simulator. Cancel sends SIGTERM so the
+// session tears down its in-simulator children cleanly.
+func (d *Driver) realSpawnRunner(ctx context.Context, address string) (*exec.Cmd, error) {
+	extractDirectory := filepath.Join(os.TempDir(), "sanderling-runner")
+	testRunPath, err := runnerassets.Extract(extractDirectory)
+	if err != nil {
+		return nil, fmt.Errorf("extract runner: %w", err)
+	}
+	_, port, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+	boundTestRunPath, err := bindTestRunPort(testRunPath, port)
+	if err != nil {
+		return nil, err
+	}
+
+	logPath := filepath.Join(extractDirectory, "runner-session-"+port+".log")
+	logFile, err := os.Create(logPath)
+	if err != nil {
+		return nil, fmt.Errorf("create runner log: %w", err)
+	}
+
+	command := exec.CommandContext(ctx, "xcrun", "xcodebuild", "test-without-building",
+		"-xctestrun", boundTestRunPath,
+		"-destination", "platform=iOS Simulator,id="+d.udid)
+	// The session log stays out of the run output: the build tool is noisy
+	// and would pollute the run's error scan. The path is reported once so a
+	// failed startup is diagnosable.
+	command.Stdout = logFile
+	command.Stderr = logFile
+	command.Env = []string{
+		"HOME=" + os.Getenv("HOME"),
+		"PATH=/usr/bin:/bin",
+		"TMPDIR=" + os.TempDir(),
+	}
+	command.Cancel = func() error { return command.Process.Signal(syscall.SIGTERM) }
+	command.WaitDelay = shutdownGrace
+	startErr := command.Start()
+	// The child holds its own descriptor after Start, so the parent's copy
+	// closes either way.
+	logFile.Close()
+	if startErr != nil {
+		return nil, fmt.Errorf("start runner session: %w", startErr)
+	}
+	fmt.Fprintf(d.output, "runner session pid=%d listening on %s (log: %s)\n", command.Process.Pid, address, logPath)
+	return command, nil
+}
+
+// bindTestRunPort writes a copy of the extracted test configuration with the
+// port placeholder substituted, next to the original so its relative paths
+// keep resolving. Returns the bound copy's path.
+func bindTestRunPort(testRunPath, port string) (string, error) {
+	configuration, err := os.ReadFile(testRunPath)
+	if err != nil {
+		return "", fmt.Errorf("read test configuration: %w", err)
+	}
+	if !bytes.Contains(configuration, []byte(runnerPortPlaceholder)) {
+		return "", fmt.Errorf("test configuration %s carries no %s placeholder", testRunPath, runnerPortPlaceholder)
+	}
+	bound := bytes.ReplaceAll(configuration, []byte(runnerPortPlaceholder), []byte(port))
+	boundPath := filepath.Join(filepath.Dir(testRunPath), "runner-"+port+".xctestrun")
+	if err := os.WriteFile(boundPath, bound, 0o644); err != nil {
+		return "", fmt.Errorf("write bound test configuration: %w", err)
+	}
+	return boundPath, nil
+}