flatpak: use host-spawn to find default shell

com.mitchellh.ghostty.yml

@@ -41,6 +41,26 @@ modules:
         only-arches:
           - aarch64
 
+  # We use this to get a proper PTY on our host spawn. We should eventually
+  # replace this with using dbus directly.
+  - name: host-spawn
+    buildsystem: simple
+    build-commands:
+      - mkdir -p /app/bin
+      - mv ./host-spawn-* /app/bin/host-spawn
+      - chmod +x /app/bin/host-spawn
+    sources:
+      - type: file
+        url: https://github.com/1player/host-spawn/releases/download/1.4.1/host-spawn-x86_64
+        sha256: d81bb6125ec73a9a2e26266c48787367fbcb665d67c2e7fb42217f0981106cf7
+        only-arches:
+          - x86_64
+      - type: file
+        url: https://github.com/1player/host-spawn/releases/download/1.4.1/host-spawn-aarch64
+        sha256: 29bff846d72e37093b3fdf7859bae16addd64acc98087f8c059548df3c2273c4
+        only-arches:
+          - aarch64
+
   - name: ghostty
     buildsystem: simple
     build-commands:

src/config.zig

@@ -344,6 +344,9 @@ pub const Config = struct {
             if (self.command == null or wd_home) command: {
                 const alloc = self._arena.?.allocator();
 
+                // We don't do this in flatpak because SHELL in Flatpak is
+                // always set to /bin/sh
+                if (!internal_os.isFlatpak()) {
                     // First look up the command using the SHELL env var.
                     if (std.process.getEnvVarOwned(alloc, "SHELL")) |value| {
                         log.debug("default shell source=env value={s}", .{value});
@@ -352,6 +355,7 @@ pub const Config = struct {
                         // If we don't need the working directory, then we can exit now.
                         if (!wd_home) break :command;
                     } else |_| {}
+                }
 
                 // We need the passwd entry for the remainder
                 const pw = try passwd.get(alloc);

src/passwd.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const builtin = @import("builtin");
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
+const internal_os = @import("os/main.zig");
 
 const log = std.log.scoped(.passwd);
 
@@ -45,6 +46,39 @@ pub fn get(alloc: Allocator) !Entry {
 
     var result: Entry = .{};
 
+    // If we're in flatpak then our entry is always empty so we grab it
+    // by shelling out to the host. note that we do HAVE an entry in the
+    // sandbox but only the username is correct.
+    //
+    // Note: we wrap our getent call in a /bin/sh login shell because
+    // some operating systems (NixOS tested) don't set the PATH for various
+    // utilities properly until we get a login shell.
+    if (internal_os.isFlatpak()) {
+        log.info("flatpak detected, will use host-spawn to get our entry", .{});
+        const exec = try std.ChildProcess.exec(.{
+            .allocator = alloc,
+            .argv = &[_][]const u8{
+                "/app/bin/host-spawn",
+                "-pty",
+                "/bin/sh",
+                "-l",
+                "-c",
+                try std.fmt.allocPrint(
+                    alloc,
+                    "getent passwd {s}",
+                    .{std.mem.sliceTo(pw.pw_name, 0)},
+                ),
+            },
+        });
+        if (exec.term == .Exited) {
+            // Shell and home are the last two entries
+            var it = std.mem.splitBackwards(u8, exec.stdout, ":");
+            result.shell = it.next() orelse null;
+            result.home = it.next() orelse null;
+            return result;
+        }
+    }
+
     if (pw.pw_shell) |ptr| {
         const source = std.mem.sliceTo(ptr, 0);
         const sh = try alloc.alloc(u8, source.len);