While working on chainlint.pl recently, we introduced some bugs that
showed incorrect line numbers in the output. But it was hard to notice,
since we sanitize the output by removing all of the line numbers! It
would be nice to retain these so we can catch any regressions.
The main reason we sanitize is for maintainability: we concatenate all
of the test snippets into a single file, so it's hard for each ".expect"
file to know at which offset its test input will be found. We can handle
that by storing the per-test line numbers in the ".expect" files, and
then dynamically offsetting them as we build the concatenated test and
expect files together.
The changes to the ".expect" files look like tedious boilerplate, but it
actually makes adding new tests easier. You can now just run:
perl chainlint.pl chainlint/foo.test |
tail -n +2 >chainlint/foo.expect
to save the output of the script minus the comment headers (after
checking that it is correct, of course). Whereas before you had to strip
the line numbers. The conversions here were done mechanically using
something like the script above, and then spot-checked manually.
It would be possible to do all of this in shell via the Makefile, but it
gets a bit complicated (and requires a lot of extra processes). Instead,
I've written a short perl script that generates the concatenated files
(we already depend on perl, since chainlint.pl uses it). Incidentally,
this improves a few other things:
- we incorrectly used $(CHAINLINTTMP_SQ) inside a double-quoted
string. So if your test directory required quoting, like:
make "TEST_OUTPUT_DIRECTORY=/tmp/h'orrible"
we'd fail the chainlint tests.
- the shell in the Makefile didn't handle &&-chaining correctly in its
loops (though in practice the "sed" and "cat" invocations are not
likely to fail).
- likewise, the sed invocation to strip numbers was hiding the exit
code of chainlint.pl itself. In practice this isn't a big deal;
since there are linter violations in the test files, we expect it to
exit non-zero. But we could later use exit codes to distinguish
serious errors from expected ones.
- we now use a constant number of processes, instead of scaling with
the number of test scripts. So it should be a little faster (on my
machine, "make check-chainlint" goes from 133ms to 73ms).
There are some alternatives to this approach, but I think this is still
a good intermediate step:
1. We could invoke chainlint.pl individually on each test file, and
compare it to the expected output (and possibly using "make" to
avoid repeating already-done checks). This is a much bigger change
(and we'd have to figure out what to do with the "# LINT" lines in
the inputs). But in this case we'd still want the "expect" files to
be annotated with line numbers. So most of what's in this patch
would be needed anyway.
2. Likewise, we could run a single chainlint.pl and feed it all of the
scripts (with "--jobs=1" to get deterministic output). But we'd
still need to annotate the scripts as we did here, and we'd still
need to either assemble the "expect" file, or break apart the
script output to compare to each individual ".expect" file.
So we may pursue those in the long run, but this patch gives us more
robust tests without too much extra work or moving in a useless
direction.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Because `sed` is line-oriented, for ease of implementation, when
chainlint.sed encounters an opening subshell in which the first command
is cuddled with the "(", it splits the line into two lines: one
containing only "(", and the other containing whatever follows "(".
This allows chainlint.sed to get by with a single set of regular
expressions for matching shell statements rather than having to
duplicate each expression (one set for matching non-cuddled statements,
and one set for matching cuddled statements).
However, although syntactically and semantically immaterial, this
transformation has no value to test authors and might even confuse them
into thinking that the linter is misbehaving by inserting (whitespace)
line-noise into the shell code it is validating. Moreover, it also
allows an implementation detail of chainlint.sed to seep into the
chainlint self-test "expect" files, which potentially makes it difficult
to reuse the self-tests should a more capable chainlint ever be
developed.
To address these concerns, stop splitting cuddled "(..." into two lines.
Note that, as an implementation artifact, due to sed's line-oriented
nature, this change inserts a blank line at output time just before the
"(..." line is emitted. It would be possible to suppress this blank line
but doing so would add a fair bit of complexity to chainlint.sed.
Therefore, rather than suppressing the extra blank line, the Makefile's
`check-chainlint` target which runs the chainlint self-tests is instead
modified to ignore blank lines when comparing chainlint output against
the self-test "expect" output. This is a reasonable compromise for two
reasons. First, the purpose of the chainlint self-tests is to verify
that the ?!AMP?! annotations are being correctly added; precise
whitespace is immaterial. Second, by necessity, chainlint.sed itself
already throws away all blank lines within subshells since, when
checking for a broken &&-chain, it needs to check the final _statement_
in a subshell, not the final _line_ (which might be blank), thus it has
never made any attempt to precisely reproduce blank lines in its output.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
chainlint.sed inserts a ">" annotation at the beginning of a line to
signal that its heuristics have identified an end-of-subshell. This was
useful as a debugging aid during development of the script, but it has
no value to test writers and might even confuse them into thinking that
the linter is misbehaving by inserting line-noise into the shell code it
is validating. Moreover, its presence also potentially makes it
difficult to reuse the chainlint self-test "expect" output should a more
capable linter ever be developed. Therefore, drop the ">" annotation.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The --chain-lint option uses heuristics and knowledge of shell syntax to
detect broken &&-chains in subshells by pure textual inspection. The
heuristics handle a range of stylistic variations in existing tests
(evolved over the years), however, they are still best-guesses. As such,
it is possible for future changes to accidentally break assumptions upon
which the heuristics are based. Protect against this possibility by
adding tests which check the linter itself for correctness.
In addition to protecting against regressions, these tests help document
(for humans) expected behavior, which is important since the linter's
implementation language ('sed') does not necessarily lend itself to easy
comprehension.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
