Keep command_fifo read fd open instead of closing/reopening

Closing/reopening the read side seems to sometimes lead to
end-of-file not being received, leaving some extra data unexecuted.

The FDWatcher stays disabled during the executing of the fifo
commands so this should not enable any more commands to be executed
until we get back from the CommandManager and reset the FDWatcher
fd to to fifo read end.

Fixes #4410

1 files changed, 12 insertions, 7 deletions

diff --git a/src/shell_manager.cc b/src/shell_manager.cc
index bd101633..ac0eb43b 100644
--- a/src/shell_manager.cc
+++ b/src/shell_manager.cc
@@ -172,7 +172,8 @@ template<typename OnClose>
 FDWatcher make_reader(int fd, String& contents, OnClose&& on_close)
 {
     return {fd, FdEvents::Read, EventMode::Urgent,
-            [fd, &contents, on_close](FDWatcher& watcher, FdEvents, EventMode) {
+            [&contents, on_close](FDWatcher& watcher, FdEvents, EventMode) {
+        const int fd = watcher.fd();
         char buffer[1024];
         while (fd_readable(fd))
         {
@@ -183,7 +184,7 @@ FDWatcher make_reader(int fd, String& contents, OnClose&& on_close)
                     continue; // try again
 
                 watcher.disable();
-                on_close();
+                on_close(size == 0);
                 return;
             }
             contents += StringView{buffer, buffer+size};
@@ -228,11 +229,15 @@ struct CommandFifos
             mkfifo(command_fifo_path().c_str(), 0600);
             mkfifo(response_fifo_path().c_str(), 0600);
             int fd = open(command_fifo_path().c_str(), O_RDONLY | O_NONBLOCK);
-            return make_reader(fd, command, [&, fd] {
-                close(fd);
+            return make_reader(fd, command, [&, fd](bool graceful) {
+                if (not graceful)
+                {
+                    write_to_debug_buffer(format("error reading from command fifo '{}'", strerror(errno)));
+                    return;
+                }
                 CommandManager::instance().execute(command, context, shell_context);
                 command.clear();
-                command_watcher.reset_fd(open(command_fifo_path().c_str(), O_RDONLY | O_NONBLOCK));
+                command_watcher.reset_fd(fd);
             });
         }())
     {
@@ -313,8 +318,8 @@ std::pair<String, int> ShellManager::eval(
     auto wait_time = Clock::now();
 
     String stdout_contents, stderr_contents;
-    auto stdout_reader = make_reader(child_stdout.read_fd(), stdout_contents, [&]{ child_stdout.close_read_fd(); });
-    auto stderr_reader = make_reader(child_stderr.read_fd(), stderr_contents, [&]{ child_stderr.close_read_fd(); });
+    auto stdout_reader = make_reader(child_stdout.read_fd(), stdout_contents, [&](bool){ child_stdout.close_read_fd(); });
+    auto stderr_reader = make_reader(child_stderr.read_fd(), stderr_contents, [&](bool){ child_stderr.close_read_fd(); });
     auto stdin_writer = make_pipe_writer(child_stdin, input);
 
     // block SIGCHLD to make sure we wont receive it before