Do not close stderr/stdout before program finish

Programs like grep called in '$' command will fail due to SIGPIPE
for example. So we need to keep the pipe open.

src/command_manager.cc

@@ -271,7 +271,7 @@ String expand_token(const Token& token, const Context& context,
     {
     case Token::Type::ShellExpand:
         return ShellManager::instance().eval(content, context, {},
-                                             ShellManager::Flags::ReadOutput,
+                                             ShellManager::Flags::WaitForStdout,
                                              shell_params, env_vars).first;
     case Token::Type::RegisterExpand:
         return context.main_sel_register_value(content).str();

src/commands.cc

@@ -787,7 +787,7 @@ void define_command(const ParametersParser& parser, Context& context)
                 { "pos_in_token",      to_string(pos_in_token) }
             };
             String output = ShellManager::instance().eval(shell_cmd, context, {},
-                                                          ShellManager::Flags::ReadOutput,
+                                                          ShellManager::Flags::WaitForStdout,
                                                           params, vars).first;
             return Completions{ 0_byte, pos_in_token, split(output, '\n', 0) };
         };

src/event_manager.cc

@@ -24,10 +24,13 @@ void FDWatcher::run(EventMode mode)
 }
 
 void FDWatcher::close_fd()
+{
+    if (m_fd != -1)
     {
         close(m_fd);
         m_fd = -1;
     }
+}
 
 Timer::Timer(TimePoint date, Callback callback, EventMode mode)
     : m_date{date}, m_callback{std::move(callback)}, m_mode(mode)

src/normal.cc

@@ -396,7 +396,7 @@ void pipe(Context& context, NormalParams)
                         str += '\n';
                     str = ShellManager::instance().eval(
                         real_cmd, context, str,
-                        ShellManager::Flags::ReadOutput,
+                        ShellManager::Flags::WaitForStdout,
                         {}, EnvVarMap{}).first;
 
                     if ((insert_eol or sel.max() == buffer.back_coord()) and
@@ -441,7 +441,7 @@ void insert_output(Context& context, NormalParams)
                 return;
 
             auto str = ShellManager::instance().eval(real_cmd, context, {},
-                                                     ShellManager::Flags::ReadOutput,
+                                                     ShellManager::Flags::WaitForStdout,
                                                      {}, EnvVarMap{}).first;
             ScopedEdition edition(context);
             context.selections().insert(str, mode);

src/shell_manager.cc

@@ -60,20 +60,18 @@ std::pair<String, int> ShellManager::eval(
             FDWatcher stdout_watcher{read_pipe[0], pipe_reader(child_stdout)};
             FDWatcher stderr_watcher{error_pipe[0], pipe_reader(child_stderr)};
 
-            if (not (flags & Flags::ReadOutput))
+            while (not terminated or
-            {
+                   ((flags & Flags::WaitForStdout) and
-                stdout_watcher.close_fd();
+                    (not stdout_watcher.closed() or
-                stderr_watcher.close_fd();
+                     not stderr_watcher.closed())))
-            }
-
-            while (not stdout_watcher.closed() or
-                   not stderr_watcher.closed() or
-                   not terminated)
             {
                 EventManager::instance().handle_next_events(EventMode::Urgent);
                 if (not terminated)
                     terminated = waitpid(pid, &status, WNOHANG);
             }
+
+            stdout_watcher.close_fd();
+            stderr_watcher.close_fd();
         }
 
         if (not child_stderr.empty())

src/shell_manager.hh

@@ -24,12 +24,12 @@ public:
     enum class Flags
     {
         None = 0,
-        ReadOutput = 1
+        WaitForStdout = 1
     };
 
     std::pair<String, int> eval(StringView cmdline, const Context& context,
                                 StringView input = {},
-                                Flags flags = Flags::ReadOutput,
+                                Flags flags = Flags::WaitForStdout,
                                 ConstArrayView<String> params = {},
                                 const EnvVarMap& env_vars = EnvVarMap{});