From 7ec7dd7151c794a86e529e86258059b896142d6b Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Sat, 18 Oct 2025 14:46:18 -0700
Subject: [PATCH] termio: use a union to represent how a process is started

---
 src/termio/Exec.zig | 83 +++++++++++++++++++++++----------------------
 1 file changed, 42 insertions(+), 41 deletions(-)

diff --git a/src/termio/Exec.zig b/src/termio/Exec.zig
index 319ae0ee6..3efcfbf38 100644
--- a/src/termio/Exec.zig
+++ b/src/termio/Exec.zig
@@ -102,24 +102,17 @@ pub fn threadEnter(
     errdefer self.subprocess.stop();
 
     // Watcher to detect subprocess exit
-    var process: ?xev.Process = process: {
+    var process: ?xev.Process = if (self.subprocess.process) |v| switch (v) {
+        .fork_exec => |cmd| try xev.Process.init(
+            cmd.pid orelse return error.ProcessNoPid,
+        ),
+
         // If we're executing via Flatpak then we can't do
         // traditional process watching (its implemented
         // as a special case in os/flatpak.zig) since the
         // command is on the host.
-        if (comptime build_config.flatpak) {
-            if (self.subprocess.flatpak_command != null) {
-                break :process null;
-            }
-        }
-
-        // Get the pid from the subprocess
-        const command = self.subprocess.command orelse
-            return error.ProcessNotStarted;
-        const pid = command.pid orelse
-            return error.ProcessNoPid;
-        break :process try xev.Process.init(pid);
-    };
+        .flatpak => null,
+    } else return error.ProcessNotStarted;
     errdefer if (process) |*p| p.deinit();
 
     // Track our process start time for abnormal exits
@@ -167,17 +160,19 @@ pub fn threadEnter(
         termio.Termio.ThreadData,
         td,
         processExit,
-    ) else if (comptime build_config.flatpak) {
-        // If we're in flatpak and we have a flatpak command
-        // then we can run the special flatpak logic for watching.
-        if (self.subprocess.flatpak_command) |*c| {
-            c.waitXev(
+    ) else if (comptime build_config.flatpak) flatpak: {
+        switch (self.subprocess.process orelse break :flatpak) {
+            // If we're in flatpak and we have a flatpak command
+            // then we can run the special flatpak logic for watching.
+            .flatpak => |*c| c.waitXev(
                 td.loop,
                 &td.backend.exec.flatpak_wait_c,
                 termio.Termio.ThreadData,
                 td,
                 flatpakExit,
-            );
+            ),
+
+            .fork_exec => {},
         }
     }
 
@@ -587,10 +582,18 @@ const Subprocess = struct {
     grid_size: renderer.GridSize,
     screen_size: renderer.ScreenSize,
     pty: ?Pty = null,
-    command: ?Command = null,
-    flatpak_command: ?FlatpakHostCommand = null,
+    process: ?Process = null,
     linux_cgroup: Command.LinuxCgroup = Command.linux_cgroup_default,
 
+    /// Union that represents the running process type.
+    const Process = union(enum) {
+        /// Standard POSIX fork/exec
+        fork_exec: Command,
+
+        /// Flatpak DBus command
+        flatpak: FlatpakHostCommand,
+    };
+
     const ArgsFormatter = struct {
         args: []const [:0]const u8,
 
@@ -883,7 +886,7 @@ const Subprocess = struct {
         read: Pty.Fd,
         write: Pty.Fd,
     } {
-        assert(self.pty == null and self.command == null);
+        assert(self.pty == null and self.process == null);
 
         // This function is funny because on POSIX systems it can
         // fail in the forked process. This is flipped to true if
@@ -959,15 +962,15 @@ const Subprocess = struct {
             }
 
             // Flatpak command must have a stable pointer.
-            self.flatpak_command = .{
+            self.process = .{ .flatpak = .{
                 .argv = self.args,
                 .cwd = cwd,
                 .env = if (self.env) |*env| env else null,
                 .stdin = pty.slave,
                 .stdout = pty.slave,
                 .stderr = pty.slave,
-            };
-            var cmd = &self.flatpak_command.?;
+            } };
+            var cmd = &self.process.?.flatpak;
             const pid = try cmd.spawn(alloc);
             errdefer killCommandFlatpak(cmd);
 
@@ -1046,7 +1049,7 @@ const Subprocess = struct {
             self.env = null;
         }
 
-        self.command = cmd;
+        self.process = .{ .fork_exec = cmd };
         return switch (builtin.os.tag) {
             .windows => .{
                 .read = pty.out_pipe,
@@ -1071,7 +1074,7 @@ const Subprocess = struct {
     /// Called to notify that we exited externally so we can unset our
     /// running state.
     pub fn externalExit(self: *Subprocess) void {
-        self.command = null;
+        self.process = null;
     }
 
     /// Stop the subprocess. This is safe to call anytime. This will wait
@@ -1079,25 +1082,23 @@ const Subprocess = struct {
     /// for it to terminate, so it will not block.
     /// This does not close the pty.
     pub fn stop(self: *Subprocess) void {
-        // Kill our command
-        if (self.command) |*cmd| {
-            // Note: this will also wait for the command to exit, so
-            // DO NOT call cmd.wait
-            killCommand(cmd) catch |err|
-                log.err("error sending SIGHUP to command, may hang: {}", .{err});
-            self.command = null;
-        }
+        switch (self.process orelse return) {
+            .fork_exec => |*cmd| {
+                // Note: this will also wait for the command to exit, so
+                // DO NOT call cmd.wait
+                killCommand(cmd) catch |err|
+                    log.err("error sending SIGHUP to command, may hang: {}", .{err});
+            },
 
-        // Kill our Flatpak command
-        if (comptime build_config.flatpak) {
-            if (self.flatpak_command) |*cmd| {
+            .flatpak => |*cmd| if (comptime build_config.flatpak) {
                 killCommandFlatpak(cmd) catch |err|
                     log.err("error sending SIGHUP to command, may hang: {}", .{err});
                 _ = cmd.wait() catch |err|
                     log.err("error waiting for command to exit: {}", .{err});
-                self.flatpak_command = null;
-            }
+            },
         }
+
+        self.process = null;
     }
 
     /// Resize the pty subprocess. This is safe to call anytime.