HackStudio: Separate master & slave PTY setup in TerminalWrapper

Previously the setup for both the master and slave pseudoterminals was
done in TerminalWrapper::run_command.

This commit separates the relevant logic into
TerminalWrapper::setup_master_pseudoterminal
and TerminalWrapper::setup_slave_pseudoterminal.

Userland/DevTools/HackStudio/TerminalWrapper.cpp

@@ -32,6 +32,44 @@ void TerminalWrapper::run_command(const String& command)
         return;
     }
 
+    auto ptm_res = setup_master_pseudoterminal();
+    if (ptm_res.is_error()) {
+        perror("setup_master_pseudoterminal");
+        return;
+    }
+
+    int ptm_fd = ptm_res.value();
+
+    m_pid = fork();
+    if (m_pid < 0) {
+        perror("fork");
+        return;
+    }
+
+    if (m_pid > 0)
+        return;
+
+    if (setup_slave_pseudoterminal(ptm_fd).is_error()) {
+        perror("setup_pseudoterminal");
+        exit(1);
+    }
+
+    auto parts = command.split(' ');
+    VERIFY(!parts.is_empty());
+    const char** args = (const char**)calloc(parts.size() + 1, sizeof(const char*));
+    for (size_t i = 0; i < parts.size(); i++) {
+        args[i] = parts[i].characters();
+    }
+    auto rc = execvp(args[0], const_cast<char**>(args));
+    if (rc < 0) {
+        perror("execve");
+        exit(1);
+    }
+    VERIFY_NOT_REACHED();
+}
+
+ErrorOr<int> TerminalWrapper::setup_master_pseudoterminal(WaitForChildOnExit wait_for_child)
+{
     int ptm_fd = posix_openpt(O_RDWR | O_CLOEXEC);
     if (ptm_fd < 0) {
         perror("posix_openpt");
@@ -47,7 +85,8 @@ void TerminalWrapper::run_command(const String& command)
     }
 
     m_terminal_widget->set_pty_master_fd(ptm_fd);
-    m_terminal_widget->on_command_exit = [this] {
+    m_terminal_widget->on_command_exit = [this, wait_for_child] {
+        if (wait_for_child == WaitForChildOnExit::Yes) {
             int wstatus;
             int rc = waitpid(m_pid, &wstatus, 0);
             if (rc < 0) {
@@ -61,33 +100,30 @@ void TerminalWrapper::run_command(const String& command)
             } else if (WIFSIGNALED(wstatus)) {
                 m_terminal_widget->inject_string(String::formatted("\033[34;1m(Command signaled with {}!)\033[0m\r\n", strsignal(WTERMSIG(wstatus))));
             }
+        }
         m_pid = -1;
 
         if (on_command_exit)
             on_command_exit();
     };
 
-    m_pid = fork();
-    if (m_pid < 0) {
-        perror("fork");
-        return;
-    }
+    terminal().scroll_to_bottom();
 
-    if (m_pid == 0) {
-        // Create a new process group.
+    return ptm_fd;
+}
+
+ErrorOr<void> TerminalWrapper::setup_slave_pseudoterminal(int master_fd)
+{
     setsid();
 
-        const char* tty_name = ptsname(ptm_fd);
-        if (!tty_name) {
-            perror("ptsname");
-            exit(1);
-        }
-        close(ptm_fd);
+    const char* tty_name = ptsname(master_fd);
+    if (!tty_name)
+        return Error::from_errno(errno);
+
+    close(master_fd);
     int pts_fd = open(tty_name, O_RDWR);
-        if (pts_fd < 0) {
-            perror("open");
-            exit(1);
-        }
+    if (pts_fd < 0)
+        return Error::from_errno(errno);
 
     tcsetpgrp(pts_fd, getpid());
 
@@ -99,49 +135,28 @@ void TerminalWrapper::run_command(const String& command)
     close(2);
 
     rc = dup2(pts_fd, 0);
-        if (rc < 0) {
-            perror("dup2");
-            exit(1);
-        }
+    if (rc < 0)
+        return Error::from_errno(errno);
+
     rc = dup2(pts_fd, 1);
-        if (rc < 0) {
-            perror("dup2");
-            exit(1);
-        }
+    if (rc < 0)
+        return Error::from_errno(errno);
+
     rc = dup2(pts_fd, 2);
-        if (rc < 0) {
-            perror("dup2");
-            exit(1);
-        }
+    if (rc < 0)
+        return Error::from_errno(errno);
+
     rc = close(pts_fd);
-        if (rc < 0) {
-            perror("close");
-            exit(1);
-        }
+    if (rc < 0)
+        return Error::from_errno(errno);
+
     rc = ioctl(0, TIOCSCTTY);
-        if (rc < 0) {
-            perror("ioctl(TIOCSCTTY)");
-            exit(1);
-        }
+    if (rc < 0)
+        return Error::from_errno(errno);
 
     setenv("TERM", "xterm", true);
 
-        auto parts = command.split(' ');
-        VERIFY(!parts.is_empty());
-        const char** args = (const char**)calloc(parts.size() + 1, sizeof(const char*));
-        for (size_t i = 0; i < parts.size(); i++) {
-            args[i] = parts[i].characters();
-        }
-        rc = execvp(args[0], const_cast<char**>(args));
-        if (rc < 0) {
-            perror("execve");
-            exit(1);
-        }
-        VERIFY_NOT_REACHED();
-    }
-
-    // (In parent process)
-    terminal().scroll_to_bottom();
+    return {};
 }
 
 void TerminalWrapper::kill_running_command()

Userland/DevTools/HackStudio/TerminalWrapper.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/Error.h>
 #include <LibGUI/Widget.h>
 #include <LibVT/TerminalWidget.h>
 
@@ -23,6 +24,13 @@ public:
     bool user_spawned() const { return m_user_spawned; }
     VT::TerminalWidget& terminal() { return *m_terminal_widget; }
 
+    enum class WaitForChildOnExit {
+        No,
+        Yes,
+    };
+    ErrorOr<int> setup_master_pseudoterminal(WaitForChildOnExit = WaitForChildOnExit::Yes);
+    static ErrorOr<void> setup_slave_pseudoterminal(int master_fd);
+
     Function<void()> on_command_exit;
 
 private: