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@arp242 arp242 commented Oct 13, 2022

On Windows a FILE_ACTION_MODIFIED event (i.e. a Write event) is triggered on file attribute changes, rather than some dedicates ATTRIBUTE_CHANGED event. Looking at the docs, I don't really see a way to distinguish between "real" write events and attribute changes. This is very odd, but seems to be how the ReadDirectoryChangesW() API works.

The only way I can see to distinguish between the two events is to set up two filters: one with a FILE_NOTIFY_CHANGE_ATTRIBUTES, and one without. But that seems overly complex, and no one asked to get Chmod events for Windows; it's not really all that interesting on Windows anyway.

The problem is that some software (anti-virus, backup software, etc.) can issue lots of attribute changes, causing a lot of "fake" Write events.

So remove the FILE_NOTIFY_CHANGE_ATTRIBUTES and sysFSATTRIB flags.

This was adapted from the tilt-dev/fsnotify fork:
tilt-dev#8

Fixes #487

On Windows a FILE_ACTION_MODIFIED event (i.e. a Write event) is
triggered on file attribute changes, rather than some dedicates
ATTRIBUTE_CHANGED event. Looking at the docs, I don't really see a way
to distinguish between "real" write events and attribute changes. This is
very odd, but seems to be how the ReadDirectoryChangesW() API works.

The only way I can see to distinguish between the two events is to set
up two filters: one with a FILE_NOTIFY_CHANGE_ATTRIBUTES, and one
without. But that seems overly complex, and no one asked to get Chmod
events for Windows; it's not really all that interesting on Windows
anyway.

The problem is that some software (anti-virus, backup software, etc.)
can issue lots of attribute changes, causing a lot of "fake" Write
events.

So remove the FILE_NOTIFY_CHANGE_ATTRIBUTES and sysFSATTRIB flags.

This was adapted from the tilt-dev/fsnotify fork:
tilt-dev#8

Fixes #487
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arp242 commented Oct 14, 2022

FYI @milas @nicks

@arp242 arp242 requested a review from a team October 14, 2022 00:10
@arp242 arp242 merged commit 51c3806 into main Oct 14, 2022
@arp242 arp242 deleted the win-attr branch October 14, 2022 16:34
@shogo82148 shogo82148 mentioned this pull request Mar 6, 2024
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belimawr added a commit to belimawr/fsnotify that referenced this pull request Sep 25, 2024
Release 1.7.0

This version of fsnotify needs Go 1.17.

Additions:

- illumos: add FEN backend to support illumos and Solaris. ([fsnotify#371])

- all: add `NewBufferedWatcher()` to use a buffered channel, which can
  be useful in cases where you can't control the kernel buffer and
  receive a large number of events in bursts. ([fsnotify#550], [fsnotify#572])

- all: add `AddWith()`, which is identical to `Add()` but allows passing
  options. ([fsnotify#521])

- windows: allow setting the ReadDirectoryChangesW() buffer size with
  `fsnotify.WithBufferSize()`; the default of 64K is the highest value
  that works on all platforms and is enough for most purposes, but in
  some cases a highest buffer is needed. ([fsnotify#521])

Changes and fixes:

- inotify: remove watcher if a watched path is renamed ([fsnotify#518])

  After a rename the reported name wasn't updated, or even an empty
  string. Inotify doesn't provide any good facilities to update it, so
  just remove the watcher. This is already how it worked on kqueue and
  FEN.

  On Windows this does work, and remains working.

- windows: don't listen for file attribute changes ([fsnotify#520])

  File attribute changes are sent as `FILE_ACTION_MODIFIED` by the
  Windows API, with no way to see if they're a file write or attribute
  change, so would show up as a fsnotify.Write event. This is never
  useful, and could result in many spurious Write events.

- windows: return `ErrEventOverflow` if the buffer is full ([fsnotify#525])

  Before it would merely return "short read", making it hard to detect
  this error.

- kqueue: make sure events for all files are delivered properly when
  removing a watched directory ([fsnotify#526])

  Previously they would get sent with `""` (empty string) or `"."` as
  the path name.

- kqueue: don't emit spurious Create events for symbolic links ([fsnotify#524])

  The link would get resolved but kqueue would "forget" it already saw
  the link itself, resulting on a Create for every Write event for the
  directory.

- all: return `ErrClosed` on `Add()` when the watcher is closed ([fsnotify#516])

- other: add `Watcher.Errors` and `Watcher.Events` to the no-op
  `Watcher` in `backend_other.go`, making it easier to use on
  unsupported platforms such as WASM, AIX, etc. ([fsnotify#528])

- other: use the `backend_other.go` no-op if the `appengine` build tag
  is set; Google AppEngine forbids usage of the unsafe package so the
  inotify backend won't compile there.

[fsnotify#371]: fsnotify#371
[fsnotify#516]: fsnotify#516
[fsnotify#518]: fsnotify#518
[fsnotify#520]: fsnotify#520
[fsnotify#521]: fsnotify#521
[fsnotify#524]: fsnotify#524
[fsnotify#525]: fsnotify#525
[fsnotify#526]: fsnotify#526
[fsnotify#528]: fsnotify#528
[fsnotify#537]: fsnotify#537
[fsnotify#550]: fsnotify#550
[fsnotify#572]: fsnotify#572
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Consider ignoring CHMOD on Windows

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