templates/hooks--fsmonitor-watchman.sample

   1 #!/usr/bin/perl
   2
   3 use strict;
   4 use warnings;
   5 use IPC::Open2;
   6
   7 # An example hook script to integrate Watchman
   8 # (https://facebook.github.io/watchman/) with git to speed up detecting
   9 # new and modified files.
  10 #
  11 # The hook is passed a version (currently 2) and last update token
  12 # formatted as a string and outputs to stdout a new update token and
  13 # all files that have been modified since the update token. Paths must
  14 # be relative to the root of the working tree and separated by a single NUL.
  15 #
  16 # To enable this hook, rename this file to "query-watchman" and set
  17 # 'git config core.fsmonitor .git/hooks/query-watchman'
  18 #
  19 my ($version, $last_update_token) = @ARGV;
  20
  21 # Uncomment for debugging
  22 # print STDERR "$0 $version $last_update_token\n";
  23
  24 # Check the hook interface version
  25 if ($version ne 2) {
  26         die "Unsupported query-fsmonitor hook version '$version'.\n" .
  27             "Falling back to scanning...\n";
  28 }
  29
  30 my $git_work_tree = get_working_dir();
  31
  32 my $retry = 1;
  33
  34 my $json_pkg;
  35 eval {
  36         require JSON::XS;
  37         $json_pkg = "JSON::XS";
  38         1;
  39 } or do {
  40         require JSON::PP;
  41         $json_pkg = "JSON::PP";
  42 };
  43
  44 launch_watchman();
  45
  46 sub launch_watchman {
  47         my $o = watchman_query();
  48         if (is_work_tree_watched($o)) {
  49                 output_result($o->{clock}, @{$o->{files}});
  50         }
  51 }
  52
  53 sub output_result {
  54         my ($clockid, @files) = @_;
  55
  56         # Uncomment for debugging watchman output
  57         # open (my $fh, ">", ".git/watchman-output.out");
  58         # binmode $fh, ":utf8";
  59         # print $fh "$clockid\n@files\n";
  60         # close $fh;
  61
  62         binmode STDOUT, ":utf8";
  63         print $clockid;
  64         print "\0";
  65         local $, = "\0";
  66         print @files;
  67 }
  68
  69 sub watchman_clock {
  70         my $response = qx/watchman clock "$git_work_tree"/;
  71         die "Failed to get clock id on '$git_work_tree'.\n" .
  72                 "Falling back to scanning...\n" if $? != 0;
  73
  74         return $json_pkg->new->utf8->decode($response);
  75 }
  76
  77 sub watchman_query {
  78         my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
  79         or die "open2() failed: $!\n" .
  80         "Falling back to scanning...\n";
  81
  82         # In the query expression below we're asking for names of files that
  83         # changed since $last_update_token but not from the .git folder.
  84         #
  85         # To accomplish this, we're using the "since" generator to use the
  86         # recency index to select candidate nodes and "fields" to limit the
  87         # output to file names only. Then we're using the "expression" term to
  88         # further constrain the results.
  89         if (substr($last_update_token, 0, 1) eq "c") {
  90                 $last_update_token = "\"$last_update_token\"";
  91         }
  92         my $query = <<" END";
  93                 ["query", "$git_work_tree", {
  94                         "since": $last_update_token,
  95                         "fields": ["name"],
  96                         "expression": ["not", ["dirname", ".git"]]
  97                 }]
  98         END
  99
 100         # Uncomment for debugging the watchman query
 101         # open (my $fh, ">", ".git/watchman-query.json");
 102         # print $fh $query;
 103         # close $fh;
 104
 105         print CHLD_IN $query;
 106         close CHLD_IN;
 107         my $response = do {local $/; <CHLD_OUT>};
 108
 109         # Uncomment for debugging the watch response
 110         # open ($fh, ">", ".git/watchman-response.json");
 111         # print $fh $response;
 112         # close $fh;
 113
 114         die "Watchman: command returned no output.\n" .
 115         "Falling back to scanning...\n" if $response eq "";
 116         die "Watchman: command returned invalid output: $response\n" .
 117         "Falling back to scanning...\n" unless $response =~ /^\{/;
 118
 119         return $json_pkg->new->utf8->decode($response);
 120 }
 121
 122 sub is_work_tree_watched {
 123         my ($output) = @_;
 124         my $error = $output->{error};
 125         if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
 126                 $retry--;
 127                 my $response = qx/watchman watch "$git_work_tree"/;
 128                 die "Failed to make watchman watch '$git_work_tree'.\n" .
 129                     "Falling back to scanning...\n" if $? != 0;
 130                 $output = $json_pkg->new->utf8->decode($response);
 131                 $error = $output->{error};
 132                 die "Watchman: $error.\n" .
 133                 "Falling back to scanning...\n" if $error;
 134
 135                 # Uncomment for debugging watchman output
 136                 # open (my $fh, ">", ".git/watchman-output.out");
 137                 # close $fh;
 138
 139                 # Watchman will always return all files on the first query so
 140                 # return the fast "everything is dirty" flag to git and do the
 141                 # Watchman query just to get it over with now so we won't pay
 142                 # the cost in git to look up each individual file.
 143                 my $o = watchman_clock();
 144                 $error = $output->{error};
 145
 146                 die "Watchman: $error.\n" .
 147                 "Falling back to scanning...\n" if $error;
 148
 149                 output_result($o->{clock}, ("/"));
 150                 $last_update_token = $o->{clock};
 151
 152                 eval { launch_watchman() };
 153                 return 0;
 154         }
 155
 156         die "Watchman: $error.\n" .
 157         "Falling back to scanning...\n" if $error;
 158
 159         return 1;
 160 }
 161
 162 sub get_working_dir {
 163         my $working_dir;
 164         if ($^O =~ 'msys' || $^O =~ 'cygwin') {
 165                 $working_dir = Win32::GetCwd();
 166                 $working_dir =~ tr/\\/\//;
 167         } else {
 168                 require Cwd;
 169                 $working_dir = Cwd::cwd();
 170         }
 171
 172         return $working_dir;
 173 }