add the result of calling lstat() to the processed paths log

Summary:
To understand why Watchman is reporting deleted files as existing, log
the results of `getFileInformation()` to the processed paths log.

Reviewed By: kmancini

Differential Revision: D28300181

fbshipit-source-id: 39e7f3fdc1669f8ba0473491d884c081a86b862a

InMemoryView.cpp

@@ -403,18 +403,29 @@ void ViewDatabase::insertAtHeadOfFileList(struct watchman_file* file) {
 }
 
 InMemoryView::PendingChangeLogEntry::PendingChangeLogEntry(
-    const PendingChange& pc) noexcept {
-  now = pc.now;
-  flags = pc.flags;
-  storeTruncatedTail(path_tail, pc.path);
+    const PendingChange& pc,
+    std::error_code errcode,
+    const FileInformation& st) noexcept {
+  this->now = pc.now;
+  this->pending_flags = pc.flags;
+  storeTruncatedTail(this->path_tail, pc.path);
+
+  this->errcode = errcode.value();
+  this->mode = st.mode;
+  this->size = st.size;
+  this->mtime = st.mtime.tv_sec;
 }
 
 json_ref InMemoryView::PendingChangeLogEntry::asJsonValue() const {
   return json_object({
       {"now", json_integer(now.time_since_epoch().count())},
-      {"flags", json_integer(flags)},
+      {"pending_flags", json_integer(pending_flags)},
       {"path",
        w_string_to_json(w_string{path_tail, strnlen(path_tail, kPathLength)})},
+      {"errcode", json_integer(errcode)},
+      {"mode", json_integer(mode)},
+      {"size", json_integer(size)},
+      {"mtime", json_integer(mtime)},
   });
 }
 

InMemoryView.h

@@ -340,19 +340,29 @@ class InMemoryView : public QueryableView {
     PendingChangeLogEntry() noexcept {
       // time_point is not noexcept so this can't be defaulted.
     }
-    explicit PendingChangeLogEntry(const PendingChange& pc) noexcept;
+    explicit PendingChangeLogEntry(
+        const PendingChange& pc,
+        std::error_code errcode,
+        const FileInformation& st) noexcept;
 
     json_ref asJsonValue() const;
 
     // 55 should cover many filenames.
     static constexpr size_t kPathLength = 55;
 
+    // fields from PendingChange
     std::chrono::system_clock::time_point now;
-    unsigned char flags;
+    unsigned char pending_flags;
     char path_tail[kPathLength];
+
+    // results of calling getFileInformation
+    int32_t errcode;
+    mode_t mode;
+    off_t size;
+    time_t mtime;
   };
 
-  static_assert(64 == sizeof(PendingChangeLogEntry));
+  static_assert(88 == sizeof(PendingChangeLogEntry));
 
   // If set, paths processed by processPending are logged here.
   std::unique_ptr<folly::LockFreeRingBuffer<PendingChangeLogEntry>>

root/iothread.cpp

@@ -267,10 +267,6 @@ void InMemoryView::processPath(
       pending.path.size() >= rootPath_.size(),
       "full_path must be a descendant of the root directory\n");
 
-  if (processedPaths_) {
-    processedPaths_->write(PendingChangeLogEntry{pending});
-  }
-
   /* From a particular query's point of view, there are four sorts of cookies we
    * can observe:
    * 1. Cookies that this query has created. This marks the end of this query's

root/stat.cpp

@@ -113,6 +113,10 @@ void InMemoryView::statPath(
     }
   }
 
+  if (processedPaths_) {
+    processedPaths_->write(PendingChangeLogEntry{pending, errcode, st});
+  }
+
   if (errcode == watchman::error_code::no_such_file_or_directory ||
       errcode == watchman::error_code::not_a_directory) {
     /* it's not there, update our state */