adapter/inotify: support partial rename events

Author: Will

changelog.md

@@ -2,6 +2,8 @@
 
 ## 0.14.4
 
+- Fixed rename event reporting in the inotify adapter when there is no "moved-from" half of the event provided (#105, thanks to @scoueille and @Gautrot for reporting; introduced with fixes for #89).
+- Addsd a regression test for issue #105.
 - Fixed a rare misreporting error in the darwin/fsevents adapter where a rename event very quickly after a creation event on the same path could cause the creation event to be duplicated alongside the rename event.
 - Only add CMake install rules if we are the main project, to be good neighbors when added as a submodule (#111, thanks to @unravel-dev)
 * Fix Windows distribution archive structure to place headers in wtr/ dir (#108, thanks to @dunglas)

devel/include/detail/wtr/watcher/adapter/linux/inotify/watch.hpp

@@ -194,6 +194,7 @@ inline auto peek = [](
 struct parsed {
   static constexpr uint16_t err_pending = 1 << 0;
   static constexpr uint16_t err_overflow = 1 << 1;
+  static constexpr uint16_t err_partial = 1 << 2;
   ::wtr::watcher::event ev{};
   inotify_event* next = nullptr;
   uint16_t err = 0;
@@ -241,7 +242,12 @@ inline auto parse_ev = [](
       return {{ke.fae.evs[i].ev, {path, et, pt}}, next};
     }
   }
-  /* Otherwise, save the current event for later */
+  /* Partial rename events are inferred if the MOVED_FROM
+     half of the event is not adjacent nor previously seen
+     in the associated event buffer. */
+  if (in->mask & IN_MOVED_TO)
+    return {{{"", et, pt}, {path, et, pt}}, next, parsed::err_partial};
+  /* Otherwise, save the current event (MOVED_FROM) for later */
   auto err = ke.fae.evs[ke.fae.idx_rm].cookie != 0
            ? parsed::err_overflow
            : parsed::err_pending;
@@ -385,6 +391,8 @@ inline auto do_ev_recv = [](auto const& cb, sysres& sr) -> result
         auto parsed = parse_ev(sr.ke, in_ev, in_ev_tail);
         if (parsed.err & parsed::err_overflow)
           send_msg(result::w_self_q_overflow, parsed.ev.path_name.c_str(), cb);
+        if (parsed.err & parsed::err_partial)
+          send_msg(result::w_sys_partial, parsed.ev.associated->path_name.c_str(), cb);
         if (msk & IN_ISDIR && msk & IN_CREATE)
           walkdir_do(parsed.ev.path_name.c_str(), [&](auto dir) {
             do_mark(dir, sr.ke.fd, sr.ke.dm, cb);

devel/include/detail/wtr/watcher/adapter/linux/sysres.hpp

@@ -35,6 +35,7 @@ enum class result : unsigned short {
   w_sys_bad_meta,
   w_sys_q_overflow,
   w_self_q_overflow,
+  w_sys_partial,
   complete,
   e,
   e_sys_api_inotify,
@@ -84,6 +85,7 @@ inline constexpr auto to_str(result r)
     case result::w_sys_bad_meta:                     return "w/sys/bad_meta@";
     case result::w_sys_q_overflow:                   return "w/sys/q_overflow@";
     case result::w_self_q_overflow:                  return "w/self/q_overflow@";
+    case result::w_sys_partial:                      return "w/sys/partial@";
     case result::complete:                           return "complete@";
     case result::e:                                  return "e@";
     case result::e_sys_api_inotify:                  return "e/sys/api/inotify@";

include/wtr/watcher.hpp

@@ -861,6 +861,7 @@ enum class result : unsigned short {
   w_sys_bad_meta,
   w_sys_q_overflow,
   w_self_q_overflow,
+  w_sys_partial,
   complete,
   e,
   e_sys_api_inotify,
@@ -910,6 +911,7 @@ inline constexpr auto to_str(result r)
     case result::w_sys_bad_meta:                     return "w/sys/bad_meta@";
     case result::w_sys_q_overflow:                   return "w/sys/q_overflow@";
     case result::w_self_q_overflow:                  return "w/self/q_overflow@";
+    case result::w_sys_partial:                      return "w/sys/partial@";
     case result::complete:                           return "complete@";
     case result::e:                                  return "e@";
     case result::e_sys_api_inotify:                  return "e/sys/api/inotify@";
@@ -1489,6 +1491,7 @@ inline auto peek = [](
 struct parsed {
   static constexpr uint16_t err_pending = 1 << 0;
   static constexpr uint16_t err_overflow = 1 << 1;
+  static constexpr uint16_t err_partial = 1 << 2;
   ::wtr::watcher::event ev{};
   inotify_event* next = nullptr;
   uint16_t err = 0;
@@ -1536,7 +1539,12 @@ inline auto parse_ev = [](
       return {{ke.fae.evs[i].ev, {path, et, pt}}, next};
     }
   }
-  /* Otherwise, save the current event for later */
+  /* Partial rename events are inferred if the MOVED_FROM
+     half of the event is not adjacent nor previously seen
+     in the associated event buffer. */
+  if (in->mask & IN_MOVED_TO)
+    return {{{"", et, pt}, {path, et, pt}}, next, parsed::err_partial};
+  /* Otherwise, save the current event (MOVED_FROM) for later */
   auto err = ke.fae.evs[ke.fae.idx_rm].cookie != 0
            ? parsed::err_overflow
            : parsed::err_pending;
@@ -1680,6 +1688,8 @@ inline auto do_ev_recv = [](auto const& cb, sysres& sr) -> result
         auto parsed = parse_ev(sr.ke, in_ev, in_ev_tail);
         if (parsed.err & parsed::err_overflow)
           send_msg(result::w_self_q_overflow, parsed.ev.path_name.c_str(), cb);
+        if (parsed.err & parsed::err_partial)
+          send_msg(result::w_sys_partial, parsed.ev.associated->path_name.c_str(), cb);
         if (msk & IN_ISDIR && msk & IN_CREATE)
           walkdir_do(parsed.ev.path_name.c_str(), [&](auto dir) {
             do_mark(dir, sr.ke.fd, sr.ke.dm, cb);

tool/test/rename-event-without-source

@@ -0,0 +1,64 @@
+#! /usr/bin/env bash
+# shellcheck source=tool/test/.ctx
+# Regression test for issue #105
+
+ec=0
+
+(
+  desc='Rename from outside watched tree produces partial rename event'
+
+  if [ "$(uname -s)" != Linux ]; then
+    echo "$desc ... [Skipped on non-Linux system]"
+    exit 0
+  fi
+
+  read -r -d '' expect << .
+[
+  {
+    "effect_type": "create",
+    "path_name": "s/self/live@d",
+    "path_type": "watcher"
+  },
+  {
+    "effect_type": "other",
+    "path_name": "w/sys/partial@d/target",
+    "path_type": "watcher"
+  },
+  {
+    "effect_type": "rename",
+    "path_name": "",
+    "path_type": "file",
+    "associated": {
+      "effect_type": "rename",
+      "path_name": "d/target",
+      "path_type": "file"
+    }
+  },
+  {
+    "effect_type": "destroy",
+    "path_name": "s/self/die@d",
+    "path_type": "watcher"
+  }
+]
+.
+
+  echo -n "$desc ... "
+
+  . "$(dirname "$0")/.ctx"
+
+  unwatched=$(mktemp -d -t unwatched-XXXXXX)
+  trap "rm -rf '$unwatched'" EXIT
+
+  actual=$(
+    watch-async "$testdir" -ms 800 > "$testdir.json"
+    echo "test content" > "$unwatched/source"
+    mv "$unwatched/source" "$testdir/target"
+    wait # for the watcher
+    show-events "$testdir" | without-effect-time
+  )
+
+  check-result "$expect" "$actual"
+)
+ec=$((ec + $?))
+
+exit "$ec"