Subject: [PATCH v2] fsmonitor-watchman: fix variable reference and remove redundant code

From: "Paul Tarjan via GitGitGadget" <[email-masked]>
Date: Sat, 28 Feb 2026 17:37:57 +0000

From: Paul Tarjan <[email-masked]>

The is_work_tree_watched() function in fsmonitor-watchman.sample has
two bugs:

1. Wrong variable in error check: After calling watchman_clock(), the
   result is stored in $o, but the code checks $output->{error} instead
   of $o->{error}. This means errors from the clock command are silently
   ignored.

2. Double output violates protocol: When the retry path triggers (the
   directory wasn't initially watched), output_result() is called with
   the "/" flag, then launch_watchman() is called recursively which
   calls output_result() again. This outputs two clock tokens to stdout,
   but git's fsmonitor v2 protocol expects exactly one response.

Fix #1 by checking $o->{error} after watchman_clock().

Fix #2 by removing the recursive launch_watchman() call. The "/"
"everything is dirty" flag already tells git to do a full scan, and
git will call the hook again on the next invocation with a valid clock
token.

With the recursive call removed, the $retry guard is no longer needed
since it only existed to prevent infinite recursion. Remove it.

Apply the same fixes to the test helper scripts in t/t7519/.

Signed-off-by: Paul Tarjan <[email-masked]>
---
    fsmonitor-watchman: fix variable reference and remove redundant code
    
    fsmonitor-watchman: fix variable reference and remove redundant code
    
    The is_work_tree_watched() function in fsmonitor-watchman.sample has two
    bugs:
    
     1. Wrong variable in error check: After calling watchman_clock(), the
        result is stored in $o, but the code checks $output->{error} instead
        of $o->{error}. This means errors from the clock command are
        silently ignored.
    
     2. Double output violates protocol: When the retry path triggers (the
        directory wasn't initially watched), output_result() is called with
        the "/" flag, then launch_watchman() is called recursively which
        calls output_result() again. This outputs two clock tokens to
        stdout, but git's fsmonitor v2 protocol expects exactly one
        response.
    
    Fix #1 by checking $o->{error} after watchman_clock().
    
    Fix #2 by removing the recursive launch_watchman() call. The "/"
    "everything is dirty" flag already tells git to do a full scan, and git
    will call the hook again on the next invocation with a valid clock
    token.
    
    Apply the same fixes to the test helper scripts in t/t7519/.
    
    Changes since v1:
    
     * Removed $retry variable and associated logic, which only existed to
       prevent infinite recursion from the now-removed recursive
       launch_watchman() call
     * Fixed commit authorship

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2180%2Fptarjan%2Fclaude%2Ffix-watchman-query-bug-sfbIw-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2180/ptarjan/claude/fix-watchman-query-bug-sfbIw-v2
Pull-Request: https://github.com/git/git/pull/2180

Range-diff vs v1:

 1:  116d26287f ! 1:  b9e00b8ab5 fsmonitor: fix two bugs in watchman hook retry path
     @@
       ## Metadata ##
     -Author: Claude <[email-masked]>
     +Author: Paul Tarjan <[email-masked]>
      
       ## Commit message ##
     -    fsmonitor: fix two bugs in watchman hook retry path
     +    fsmonitor-watchman: fix variable reference and remove redundant code
      
          The is_work_tree_watched() function in fsmonitor-watchman.sample has
          two bugs:
     @@ Commit message
          git will call the hook again on the next invocation with a valid clock
          token.
      
     +    With the recursive call removed, the $retry guard is no longer needed
     +    since it only existed to prevent infinite recursion. Remove it.
     +
          Apply the same fixes to the test helper scripts in t/t7519/.
      
          Signed-off-by: Paul Tarjan <[email-masked]>
      
       ## t/t7519/fsmonitor-watchman ##
     +@@ t/t7519/fsmonitor-watchman: if ($^O =~ 'msys' || $^O =~ 'cygwin') {
     + 	$git_work_tree = Cwd::cwd();
     + }
     + 
     +-my $retry = 1;
     +-
     + launch_watchman();
     + 
     + sub launch_watchman {
     +@@ t/t7519/fsmonitor-watchman: sub launch_watchman {
     + 
     + 	my $o = $json_pkg->new->utf8->decode($response);
     + 
     +-	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
     ++	if ($o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
     + 		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
     +-		$retry--;
     + 		qx/watchman watch "$git_work_tree"/;
     + 		die "Failed to make watchman watch '$git_work_tree'.\n" .
     + 		    "Falling back to scanning...\n" if $? != 0;
      @@ t/t7519/fsmonitor-watchman: sub launch_watchman {
       		close $fh;
       
     @@ t/t7519/fsmonitor-watchman: sub launch_watchman {

       ## t/t7519/fsmonitor-watchman-v2 ##
     +@@ t/t7519/fsmonitor-watchman-v2: if ($version ne 2) {
     + 
     + my $git_work_tree = get_working_dir();
     + 
     +-my $retry = 1;
     +-
     + my $json_pkg;
     + eval {
     + 	require JSON::XS;
     +@@ t/t7519/fsmonitor-watchman-v2: sub watchman_query {
     + sub is_work_tree_watched {
     + 	my ($output) = @_;
     + 	my $error = $output->{error};
     +-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
     +-		$retry--;
     ++	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
     + 		my $response = qx/watchman watch "$git_work_tree"/;
     + 		die "Failed to make watchman watch '$git_work_tree'.\n" .
     + 		    "Falling back to scanning...\n" if $? != 0;
      @@ t/t7519/fsmonitor-watchman-v2: sub is_work_tree_watched {
       		# Watchman query just to get it over with now so we won't pay
       		# the cost in git to look up each individual file.
     @@ t/t7519/fsmonitor-watchman-v2: sub is_work_tree_watched {

       ## templates/hooks/fsmonitor-watchman.sample ##
     +@@ templates/hooks/fsmonitor-watchman.sample: if ($version ne 2) {
     + 
     + my $git_work_tree = get_working_dir();
     + 
     +-my $retry = 1;
     +-
     + my $json_pkg;
     + eval {
     + 	require JSON::XS;
     +@@ templates/hooks/fsmonitor-watchman.sample: sub watchman_query {
     + sub is_work_tree_watched {
     + 	my ($output) = @_;
     + 	my $error = $output->{error};
     +-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
     +-		$retry--;
     ++	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
     + 		my $response = qx/watchman watch "$git_work_tree"/;
     + 		die "Failed to make watchman watch '$git_work_tree'.\n" .
     + 		    "Falling back to scanning...\n" if $? != 0;
      @@ templates/hooks/fsmonitor-watchman.sample: sub is_work_tree_watched {
       		# Watchman query just to get it over with now so we won't pay
       		# the cost in git to look up each individual file.

 t/t7519/fsmonitor-watchman                |  6 +-----
 t/t7519/fsmonitor-watchman-v2             | 10 ++--------
 templates/hooks/fsmonitor-watchman.sample | 10 ++--------
 3 files changed, 5 insertions(+), 21 deletions(-)

diff --git a/t/t7519/fsmonitor-watchman b/t/t7519/fsmonitor-watchman
index 264b9daf83..bcc055c1e0 100755
--- a/t/t7519/fsmonitor-watchman
+++ b/t/t7519/fsmonitor-watchman
@@ -38,8 +38,6 @@ if ($^O =~ 'msys' || $^O =~ 'cygwin') {
 	$git_work_tree = Cwd::cwd();
 }
 
-my $retry = 1;
-
 launch_watchman();
 
 sub launch_watchman {
@@ -92,9 +90,8 @@ sub launch_watchman {
 
 	my $o = $json_pkg->new->utf8->decode($response);
 
-	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
+	if ($o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
 		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
-		$retry--;
 		qx/watchman watch "$git_work_tree"/;
 		die "Failed to make watchman watch '$git_work_tree'.\n" .
 		    "Falling back to scanning...\n" if $? != 0;
@@ -109,7 +106,6 @@ sub launch_watchman {
 		close $fh;
 
 		print "/\0";
-		eval { launch_watchman() };
 		exit 0;
 	}
 
diff --git a/t/t7519/fsmonitor-watchman-v2 b/t/t7519/fsmonitor-watchman-v2
index 14ed0aa42d..368604c278 100755
--- a/t/t7519/fsmonitor-watchman-v2
+++ b/t/t7519/fsmonitor-watchman-v2
@@ -29,8 +29,6 @@ if ($version ne 2) {
 
 my $git_work_tree = get_working_dir();
 
-my $retry = 1;
-
 my $json_pkg;
 eval {
 	require JSON::XS;
@@ -122,8 +120,7 @@ sub watchman_query {
 sub is_work_tree_watched {
 	my ($output) = @_;
 	my $error = $output->{error};
-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
-		$retry--;
+	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
 		my $response = qx/watchman watch "$git_work_tree"/;
 		die "Failed to make watchman watch '$git_work_tree'.\n" .
 		    "Falling back to scanning...\n" if $? != 0;
@@ -141,15 +138,12 @@ sub is_work_tree_watched {
 		# Watchman query just to get it over with now so we won't pay
 		# the cost in git to look up each individual file.
 		my $o = watchman_clock();
-		$error = $output->{error};
+		$error = $o->{error};
 
 		die "Watchman: $error.\n" .
 		"Falling back to scanning...\n" if $error;
 
 		output_result($o->{clock}, ("/"));
-		$last_update_token = $o->{clock};
-
-		eval { launch_watchman() };
 		return 0;
 	}
 
diff --git a/templates/hooks/fsmonitor-watchman.sample b/templates/hooks/fsmonitor-watchman.sample
index 23e856f5de..429e0a51c1 100755
--- a/templates/hooks/fsmonitor-watchman.sample
+++ b/templates/hooks/fsmonitor-watchman.sample
@@ -29,8 +29,6 @@ if ($version ne 2) {
 
 my $git_work_tree = get_working_dir();
 
-my $retry = 1;
-
 my $json_pkg;
 eval {
 	require JSON::XS;
@@ -123,8 +121,7 @@ sub watchman_query {
 sub is_work_tree_watched {
 	my ($output) = @_;
 	my $error = $output->{error};
-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
-		$retry--;
+	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
 		my $response = qx/watchman watch "$git_work_tree"/;
 		die "Failed to make watchman watch '$git_work_tree'.\n" .
 		    "Falling back to scanning...\n" if $? != 0;
@@ -142,15 +139,12 @@ sub is_work_tree_watched {
 		# Watchman query just to get it over with now so we won't pay
 		# the cost in git to look up each individual file.
 		my $o = watchman_clock();
-		$error = $output->{error};
+		$error = $o->{error};
 
 		die "Watchman: $error.\n" .
 		"Falling back to scanning...\n" if $error;
 
 		output_result($o->{clock}, ("/"));
-		$last_update_token = $o->{clock};
-
-		eval { launch_watchman() };
 		return 0;
 	}

base-commit: 68cb7f9e92a5d8e9824f5b52ac3d0a9d8f653dbe
-- 
gitgitgadget