From 47a2cce03de7c2bf2322d515504ef1bb9cd37ad0 Mon Sep 17 00:00:00 2001
From: Chase Geigle <sky@skystrife.com>
Date: Tue, 24 Jan 2017 00:10:55 -0600
Subject: [PATCH] fix: Ensure reloading when IN_IGNORED fired on config (#371)

This fixes a "bug" where polybar wouldn't reload on a configuration
file change on some configurations of vim, which don't actually issue
any IN_MODIFY events because they choose to move the file, replace it
with a new one, and then delete the file instead.

To work around this, we now also listen for IN_IGNORED which fires when
the file we are watching is destroyed. When this happens, we re-attach
the configuration file watcher to the new file and reload.
---
 include/utils/inotify.hpp     |  2 +-
 src/components/controller.cpp | 19 +++++++++++++++++--
 src/utils/inotify.cpp         |  5 +++--
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/include/utils/inotify.hpp b/include/utils/inotify.hpp
index 9a964eb7..207d7b02 100644
--- a/include/utils/inotify.hpp
+++ b/include/utils/inotify.hpp
@@ -26,7 +26,7 @@ class inotify_watch {
   void remove(bool force = false);
   bool poll(int wait_ms = 1000) const;
   unique_ptr<inotify_event> get_event() const;
-  bool await_match() const;
+  unique_ptr<inotify_event> await_match() const;
   const string path() const;
   int get_file_descriptor() const;
 
diff --git a/src/components/controller.cpp b/src/components/controller.cpp
index 125b7723..08907273 100644
--- a/src/components/controller.cpp
+++ b/src/components/controller.cpp
@@ -246,7 +246,7 @@ void controller::read_events() {
 
   if (m_confwatch) {
     m_log.trace("controller: Attach config watch");
-    m_confwatch->attach(IN_MODIFY);
+    m_confwatch->attach(IN_MODIFY | IN_IGNORED);
     fds.emplace_back((fd_confwatch = m_confwatch->get_file_descriptor()));
   }
 
@@ -281,7 +281,22 @@ void controller::read_events() {
     }
 
     // Process event on the config inotify watch fd
-    if (fd_confwatch > -1 && FD_ISSET(fd_confwatch, &readfds) && m_confwatch->await_match()) {
+    unique_ptr<inotify_event> confevent;
+    if (fd_confwatch > -1 && FD_ISSET(fd_confwatch, &readfds) && (confevent = m_confwatch->await_match())) {
+      if (confevent->mask & IN_IGNORED) {
+        // IN_IGNORED: file was deleted or filesystem was unmounted
+        //
+        // This happens in some configurations of vim when a file is saved,
+        // since it is not actually issuing calls to write() but rather
+        // moves a file into the original's place after moving the original
+        // file to a different location (and subsequently deleting it).
+        //
+        // We need to re-attach the watch to the new file in this case.
+        fds.erase(std::remove_if(fds.begin(), fds.end(), [fd_confwatch](int fd) { return fd == fd_confwatch; }), fds.end());
+        m_confwatch = inotify_util::make_watch(m_confwatch->path());
+        m_confwatch->attach(IN_MODIFY | IN_IGNORED);
+        fds.emplace_back((fd_confwatch = m_confwatch->get_file_descriptor()));
+      }
       m_log.info("Configuration file changed");
       g_terminate = 1;
       g_reload = 1;
diff --git a/src/utils/inotify.cpp b/src/utils/inotify.cpp
index 5ece28fb..e5f1bed6 100644
--- a/src/utils/inotify.cpp
+++ b/src/utils/inotify.cpp
@@ -98,8 +98,9 @@ unique_ptr<inotify_event> inotify_watch::get_event() const {
 /**
  * Wait for matching event
  */
-bool inotify_watch::await_match() const {
-  return (get_event()->mask & m_mask) == m_mask;
+unique_ptr<inotify_event> inotify_watch::await_match() const {
+  auto event = get_event();
+  return event->mask & m_mask ? std::move(event) : nullptr;
 }
 
 /**