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The annotations emitted by chainlint to indicate detected problems are
overly terse, so much so that developers new to the project -- those who
should most benefit from the linting -- may find them baffling. For
instance, although the author of chainlint and seasoned Git developers
may understand that "?!AMP?!" is an abbreviation of "ampersand" and
indicates a break in the &&-chain, this may not be obvious to newcomers.
The "?!LOOP?!" case is particularly serious because that terse single
word does nothing to convey that the loop body should end with
"|| return 1" (or "|| exit 1" in a subshell) to ensure that a failing
command in the body aborts the loop immediately. Moreover, unlike
&&-chaining which is ubiquitous in Git tests, the "|| return 1" idiom is
relatively infrequent, thus may be harder for a newcomer to discover by
consulting nearby code.
Address these shortcomings by emitting human-readable messages which
both explain the problem and give a strong hint about how to correct it.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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>
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Now that chainlint.pl is functional, take advantage of the existing
chainlint self-tests to validate its operation. (While at it, stop
validating chainlint.sed against the self-tests since it will soon be
retired.)
Due to chainlint.sed implementation limitations leaking into the
self-test "expect" files, a few of them require minor adjustment to make
them compatible with chainlint.pl which does not share those
limitations.
First, because `sed` does not provide any sort of real recursion,
chainlint.sed only emulates recursion into subshells, and each level of
recursion leads to a multiplicative increase in complexity of the `sed`
rules. To avoid substantial complexity, chainlint.sed, therefore, only
emulates subshell recursion one level deep. Any subshell deeper than
that is passed through as-is, which means that &&-chains are not checked
in deeper subshells. chainlint.pl, on the other hand, employs a proper
recursive descent parser, thus checks subshells to any depth and
correctly flags broken &&-chains in deep subshells.
Second, due to sed's line-oriented nature, chainlint.sed, by necessity,
folds multi-line quoted strings into a single line. chainlint.pl, on the
other hand, employs a proper lexical analyzer which preserves quoted
strings as-is, including embedded newlines.
Furthermore, the output of chainlint.sed and chainlint.pl do not match
precisely in terms of whitespace. However, since the purpose of the
self-checks is to verify that the ?!AMP?! annotations are being
correctly added, minor whitespace differences are immaterial. For this
reason, rather than adjusting whitespace in all existing self-test
"expect" files to match the new linter's output, the `check-chainlint`
target ignores whitespace differences. Since `diff -w` is not POSIX,
`check-chainlint` attempts to employ `git diff -w`, and only falls back
to non-POSIX `diff -w` (and `-u`) if `git diff` is not available.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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>
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When chainlint.sed detects a broken &&-chain, it places an ?!AMP?!
annotation at the beginning of the line. However, this is an unusual
location for programmers accustomed to error messages (from compilers,
for instance) indicating the exact point of the problem. Therefore,
relocate the ?!AMP?! annotation to the end of the line in order to
better direct the programmer's attention to the source of the problem.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The chainlint self-test code snippets are supposed to represent the body
of a test_expect_success() or test_expect_failure(), yet the contents of
a few tests would have caused the shell to report syntax errors had they
been real test bodies due to the mix of single- and double-quotes.
Although chainlint.sed, with its simplistic heuristics, is blind to this
problem, a future more robust chainlint implementation might not have
such a limitation. Therefore, stop mixing quote types haphazardly in
those tests and unify quoting throughout. While at it, drop chunks of
tests which merely repeat what is already tested elsewhere but with
alternative quotes.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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chainlint.sed recognizes multi-line quoted strings within subshells:
echo "abc
def" >out &&
so it can avoid incorrectly classifying lines internal to the string as
breaking the &&-chain. To identify the first line of a multi-line
string, it checks if the line contains a single quote. However, this is
fragile and can be easily fooled by a line containing multiple strings:
echo "xyz" "abc
def" >out &&
Make detection more robust by checking for an odd number of quotes
rather than only a single one.
(Escaped quotes are not handled, but support may be added later.)
The original multi-line string recognizer rather cavalierly threw away
all but the final quote, whereas the new one is careful to retain all
quotes, so the "expected" output of a couple existing chainlint tests is
updated to account for this new behavior.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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>
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