[PATCH 13/18] chainlint.pl: allow `|| echo` to signal failure upstream of a pipe

From: Eric Sunshine via GitGitGadget <gitgitgadget@gmail.com>
Date: Sep 1, 2022, 00:29 UTC
Message-ID: <7179972013825de50bddb6a68a17f0b83d5f35a8.1661992197.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1322.git.git.1661992197.gitgitgadget@gmail.com>

From: Eric Sunshine <sunshine@sunshineco.com>

The use of `|| return` (or `|| exit`) to signal failure within a loop isn't effective when the loop is upstream of a pipe since the pipe swallows all upstream exit codes and returns only the exit code of the final command in the pipeline.

To work around this limitation, tests may adopt an alternative strategy of signaling failure by emitting text which would never be emitted in the non-failing case. For instance:

    while condition
    do
        command1 &&
        command2 ||
        echo "impossible text"
    done |
    sort >actual &&

Such usage indicates deliberate thought about failure cases by the test author, thus flagging them as missing `|| return` (or `|| exit`) is not helpful. Therefore, take this case into consideration when checking for explicit loop termination.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---
 t/chainlint.pl                        |  3 +++
 t/chainlint/loop-upstream-pipe.expect | 10 ++++++++++
 t/chainlint/loop-upstream-pipe.test   | 11 +++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 t/chainlint/loop-upstream-pipe.expect
 create mode 100644 t/chainlint/loop-upstream-pipe.test

diff --git a/t/chainlint.pl b/t/chainlint.pl
index 674b3ddf696..386999ce65d 100755
--- a/t/chainlint.pl
+++ b/t/chainlint.pl
@@ -487,6 +487,9 @@ sub parse_loop_body {
 	my @tokens = $self->SUPER::parse_loop_body(@_);
 	# did loop signal failure via "|| return" or "|| exit"?
 	return @tokens if !@tokens || grep(/^(?:return|exit|\$\?)$/, @tokens);
+	# did loop upstream of a pipe signal failure via "|| echo 'impossible
+	# text'" as the final command in the loop body?
+	return @tokens if ends_with(\@tokens, [qr/^\|\|$/, "\n", qr/^echo$/, qr/^.+$/]);
 	# flag missing "return/exit" handling explicit failure in loop body
 	my $n = find_non_nl(\@tokens);
 	splice(@tokens, $n + 1, 0, '?!LOOP?!');
diff --git a/t/chainlint/loop-upstream-pipe.expect b/t/chainlint/loop-upstream-pipe.expect
new file mode 100644
index 00000000000..0b82ecc4b96
--- /dev/null
+++ b/t/chainlint/loop-upstream-pipe.expect
@@ -0,0 +1,10 @@
+(
+	git rev-list --objects --no-object-names base..loose |
+	while read oid
+	do
+		path="$objdir/$(test_oid_to_path "$oid")" &&
+		printf "%s %d\n" "$oid" "$(test-tool chmtime --get "$path")" ||
+		echo "object list generation failed for $oid"
+	done |
+	sort -k1
+) >expect &&
diff --git a/t/chainlint/loop-upstream-pipe.test b/t/chainlint/loop-upstream-pipe.test
new file mode 100644
index 00000000000..efb77da897c
--- /dev/null
+++ b/t/chainlint/loop-upstream-pipe.test
@@ -0,0 +1,11 @@
+(
+	git rev-list --objects --no-object-names base..loose |
+	while read oid
+	do
+# LINT: "|| echo" signals failure in loop upstream of a pipe
+		path="$objdir/$(test_oid_to_path "$oid")" &&
+		printf "%s %d\n" "$oid" "$(test-tool chmtime --get "$path")" ||
+		echo "object list generation failed for $oid"
+	done |
+	sort -k1
+) >expect &&

-- 
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