LibCore+Tests: Unify process handling into Command class

The Test262RunnerHandler class in test-test262 was made in order to
spawn a subprocess, connect to its input/output error pipes, and obtain
its return value.

Later on, a copy of this implementation was added to TestSed with
modifications, such as adding support for reading from the output pipes
as well.

Unify these two implementations into a new Core::Command class. This new
implementation is more closely modeled from the TestSed implementation
due to the extra functionality it implemented.

Userland/Libraries/LibCore/Command.cpp

@@ -1,5 +1,7 @@
 /*
  * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * Copyright (c) 2022, David Tuin <davidot@serenityos.org>
+ * Copyright (c) 2023, Shannon Booth <shannon@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -8,6 +10,7 @@
 #include <AK/Format.h>
 #include <AK/ScopeGuard.h>
 #include <LibCore/File.h>
+#include <LibCore/System.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <sys/wait.h>
@@ -15,6 +18,108 @@
 
 namespace Core {
 
+ErrorOr<OwnPtr<Command>> Command::create(StringView command, char const* const arguments[])
+{
+    auto stdin_fds = TRY(Core::System::pipe2(O_CLOEXEC));
+    auto stdout_fds = TRY(Core::System::pipe2(O_CLOEXEC));
+    auto stderr_fds = TRY(Core::System::pipe2(O_CLOEXEC));
+
+    posix_spawn_file_actions_t file_actions;
+    posix_spawn_file_actions_init(&file_actions);
+    posix_spawn_file_actions_adddup2(&file_actions, stdin_fds[0], STDIN_FILENO);
+    posix_spawn_file_actions_adddup2(&file_actions, stdout_fds[1], STDOUT_FILENO);
+    posix_spawn_file_actions_adddup2(&file_actions, stderr_fds[1], STDERR_FILENO);
+
+    auto pid = TRY(Core::System::posix_spawnp(command, &file_actions, nullptr, const_cast<char**>(arguments), System::environment()));
+
+    posix_spawn_file_actions_destroy(&file_actions);
+    ArmedScopeGuard runner_kill { [&pid] { kill(pid, SIGKILL); } };
+
+    TRY(Core::System::close(stdin_fds[0]));
+    TRY(Core::System::close(stdout_fds[1]));
+    TRY(Core::System::close(stderr_fds[1]));
+
+    auto stdin_file = TRY(Core::File::adopt_fd(stdin_fds[1], Core::File::OpenMode::Write));
+    auto stdout_file = TRY(Core::File::adopt_fd(stdout_fds[0], Core::File::OpenMode::Read));
+    auto stderr_file = TRY(Core::File::adopt_fd(stderr_fds[0], Core::File::OpenMode::Read));
+
+    runner_kill.disarm();
+
+    return make<Command>(pid, move(stdin_file), move(stdout_file), move(stderr_file));
+}
+
+Command::Command(pid_t pid, NonnullOwnPtr<Core::File> stdin_file, NonnullOwnPtr<Core::File> stdout_file, NonnullOwnPtr<Core::File> stderr_file)
+    : m_pid(pid)
+    , m_stdin(move(stdin_file))
+    , m_stdout(move(stdout_file))
+    , m_stderr(move(stderr_file))
+{
+}
+
+ErrorOr<void> Command::write(StringView input)
+{
+    TRY(m_stdin->write_until_depleted(input.bytes()));
+    m_stdin->close();
+    return {};
+}
+
+bool Command::write_lines(Span<DeprecatedString> lines)
+{
+    // It's possible the process dies before we can write everything to the
+    // stdin. So make sure that we don't crash but just stop writing.
+
+    struct sigaction action_handler { };
+    action_handler.sa_handler = SIG_IGN;
+
+    struct sigaction old_action_handler;
+    if (sigaction(SIGPIPE, &action_handler, &old_action_handler) < 0) {
+        perror("sigaction");
+        return false;
+    }
+
+    for (DeprecatedString const& line : lines) {
+        if (m_stdin->write_until_depleted(DeprecatedString::formatted("{}\n", line).bytes()).is_error())
+            break;
+    }
+
+    // Ensure that the input stream ends here, whether we were able to write all lines or not
+    m_stdin->close();
+
+    // It's not really a problem if this signal failed
+    if (sigaction(SIGPIPE, &old_action_handler, nullptr) < 0)
+        perror("sigaction");
+
+    return true;
+}
+
+ErrorOr<Command::ProcessOutputs> Command::read_all()
+{
+    return ProcessOutputs { TRY(m_stdout->read_until_eof()), TRY(m_stderr->read_until_eof()) };
+}
+
+ErrorOr<Command::ProcessResult> Command::status(int options)
+{
+    if (m_pid == -1)
+        return ProcessResult::Unknown;
+
+    m_stdin->close();
+
+    auto wait_result = TRY(Core::System::waitpid(m_pid, options));
+    if (wait_result.pid == 0) {
+        // Attempt to kill it, since it has not finished yet somehow
+        return ProcessResult::Running;
+    }
+    m_pid = -1;
+
+    if (WIFSIGNALED(wait_result.status) && WTERMSIG(wait_result.status) == SIGALRM)
+        return ProcessResult::FailedFromTimeout;
+
+    if (WIFEXITED(wait_result.status) && WEXITSTATUS(wait_result.status) == 0)
+        return ProcessResult::DoneWithZeroExitCode;
+
+    return ProcessResult::Failed;
+}
+
 // Only supported in serenity mode because we use `posix_spawn_file_actions_addchdir`
 #ifdef AK_OS_SERENITY