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mkdoc.zsh
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mkdoc.zsh
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#!/usr/bin/env zsh
[ "${ZSH_VERSION:-}" = "" ] && echo >&2 "Only works with zsh" && exit 1
setopt err_exit no_unset pipefail extended_glob
# Simple script to update the godoc comments on all watchers. Probably took me
# more time to write this than doing it manually, but ah well 🙃
watcher=$(<<EOF
// Watcher watches a set of files, delivering events to a channel.
//
// A watcher should not be copied (e.g. pass it by pointer, rather than by
// value).
//
// # Linux notes
//
// When a file is removed a Remove event won't be emitted until all file
// descriptors are closed, and deletes will always emit a Chmod. For example:
//
// fp := os.Open("file")
// os.Remove("file") // Triggers Chmod
// fp.Close() // Triggers Remove
//
// The fs.inotify.max_user_watches sysctl variable specifies the upper limit
// for the number of watches per user, and fs.inotify.max_user_instances
// specifies the maximum number of inotify instances per user. Every Watcher you
// create is an "instance", and every path you add is a "watch".
//
// These are also exposed in /proc as /proc/sys/fs/inotify/max_user_watches and
// /proc/sys/fs/inotify/max_user_instances
//
// To increase them you can use sysctl or write the value to the /proc file:
//
// # Default values on Linux 5.18
// sysctl fs.inotify.max_user_watches=124983
// sysctl fs.inotify.max_user_instances=128
//
// To make the changes persist on reboot edit /etc/sysctl.conf or
// /usr/lib/sysctl.d/50-default.conf (on some systemd systems):
//
// fs.inotify.max_user_watches=124983
// fs.inotify.max_user_instances=128
//
// Reaching the limit will result in a "no space left on device" or "too many open
// files" error.
//
// # kqueue notes (macOS, BSD)
//
// kqueue requires opening a file descriptor for every file that's being watched;
// so if you're watching a directory with five files then that's six file
// descriptors. You will run in to your system's "max open files" limit faster on
// these platforms.
//
// The sysctl variables kern.maxfiles and kern.maxfilesperproc can be used to
// control the maximum number of open files, as well as /etc/login.conf on BSD
// systems.
//
// # macOS notes
//
// Spotlight indexing on macOS can result in multiple events (see [#15]). A
// temporary workaround is to add your folder(s) to the "Spotlight Privacy
// Settings" until we have a native FSEvents implementation (see [#11]).
//
// [#11]: https://github.com/fsnotify/fsnotify/issues/11
// [#15]: https://github.com/fsnotify/fsnotify/issues/15
EOF
)
new=$(<<EOF
// NewWatcher creates a new Watcher.
EOF
)
add=$(<<EOF
// Add starts monitoring the path for changes.
//
// A path can only be watched once; attempting to watch it more than once will
// return an error. Paths that do not yet exist on the filesystem cannot be
// added. A watch will be automatically removed if the path is deleted.
//
// A path will remain watched if it gets renamed to somewhere else on the same
// filesystem, but the monitor will get removed if the path gets deleted and
// re-created.
//
// Notifications on network filesystems (NFS, SMB, FUSE, etc.) or special
// filesystems (/proc, /sys, etc.) generally don't work.
//
// # Watching directories
//
// All files in a directory are monitored, including new files that are created
// after the watcher is started. Subdirectories are not watched (i.e. it's
// non-recursive).
//
// # Watching files
//
// Watching individual files (rather than directories) is generally not
// recommended as many tools update files atomically. Instead of "just" writing
// to the file a temporary file will be written to first, and if successful the
// temporary file is moved to to destination, removing the original, or some
// variant thereof. The watcher on the original file is now lost, as it no
// longer exists.
//
// Instead, watch the parent directory and use [Event.Name] to filter out files
// you're not interested in. There is an example of this in cmd/fsnotify/file.go
EOF
)
remove=$(<<EOF
// Remove stops monitoring the path for changes.
//
// Directories are always removed non-recursively. For example, if you added
// /tmp/dir and /tmp/dir/subdir then you will need to remove both.
//
// Removing a path that has not yet been added returns [ErrNonExistentWatch].
EOF
)
close=$(<<EOF
// Close removes all watches and closes the events channel.
EOF
)
watchlist=$(<<EOF
// WatchList returns all paths added with Add() (and are not yet removed).
EOF
)
events=$(<<EOF
// Events sends the filesystem change events.
//
// fsnotify can send the following events; a "path" here can refer to a
// file, directory, symbolic link, or special files like a FIFO.
//
// fsnotify.Create A new path was created; this may be followed by one
// or more Write events if data also gets written to a
// file.
//
// fsnotify.Remove A path was removed.
//
// fsnotify.Rename A path was renamed. A rename is always sent with the
// old path as [Event.Name], and a Create event will be
// sent with the new name. Renames are only sent for
// paths that are currently watched; e.g. moving an
// unmonitored file into a monitored directory will
// show up as just a Create. Similarly, renaming a file
// to outside a monitored directory will show up as
// only a Rename.
//
// fsnotify.Write A file or named pipe was written to. A Truncate will
// also trigger a Write. A single "write action"
// initiated by the user may show up as one or multiple
// writes, depending on when the system syncs things to
// disk. For example when compiling a large Go program
// you may get hundreds of Write events, so you
// probably want to wait until you've stopped receiving
// them (see the dedup example in cmd/fsnotify).
//
// fsnotify.Chmod Attributes were changes (never sent on Windows). On
// Linux this is also sent when a file is removed (or
// more accurately, when a link to an inode is
// removed), and on kqueue when a file is truncated.
EOF
)
errors=$(<<EOF
// Errors sends any errors.
EOF
)
set-cmt() {
local pat=$1
local cmt=$2
IFS=$'\n' local files=($(grep -n $pat backend_*~*_test.go))
for f in $files; do
IFS=':' local fields=($=f)
local file=$fields[1]
local end=$(( $fields[2] - 1 ))
# Find start of comment.
local start=0
IFS=$'\n' local lines=($(head -n$end $file))
for (( i = 1; i <= $#lines; i++ )); do
local line=$lines[-$i]
if ! grep -q '^[[:space:]]*//' <<<$line; then
start=$(( end - (i - 2) ))
break
fi
done
head -n $(( start - 1 )) $file >/tmp/x
print -r -- $cmt >>/tmp/x
tail -n+$(( end + 1 )) $file >>/tmp/x
mv /tmp/x $file
done
}
set-cmt '^type Watcher struct ' $watcher
set-cmt '^func NewWatcher(' $new
set-cmt '^func (w \*Watcher) Add(' $add
set-cmt '^func (w \*Watcher) Remove(' $remove
set-cmt '^func (w \*Watcher) Close(' $close
set-cmt '^func (w \*Watcher) WatchList(' $watchlist
set-cmt '^[[:space:]]*Events *chan Event$' $events
set-cmt '^[[:space:]]*Errors *chan error$' $errors