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>
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>
>From inception, when chainlint.sed encountered a line using semicolon to
separate commands rather than `&&`, it would insert a ?!SEMI?!
annotation at the beginning of the line rather ?!AMP?! even though the
&&-chain is also broken by the semicolon. Given a line such as:
?!SEMI?! cmd1; cmd2 &&
the ?!SEMI?! annotation makes it easier to see what the problem is than
if the output had been:
?!AMP?! cmd1; cmd2 &&
which might confuse the test author into thinking that the linter is
broken (since the line clearly ends with `&&`).
However, now that the ?!AMP?! an ?!SEMI?! annotations are inserted at
the point of breakage rather than at the beginning of the line, and
taking into account that both represent a broken &&-chain, there is
little reason to distinguish between the two. Using ?!AMP?! alone is
sufficient to point the test author at the problem. For instance, in:
cmd1; ?!AMP?! cmd2 &&
cmd3
it is clear that the &&-chain is broken between `cmd1` and `cmd2`.
Likewise, in:
cmd1 && cmd2 ?!AMP?!
cmd3
it is clear that the &&-chain is broken between `cmd2` and `cmd3`.
Finally, in:
cmd1; ?!AMP?! cmd2 ?!AMP?!
cmd3
it is clear that the &&-chain is broken between each command.
Hence, there is no longer a good reason to make a distinction between a
broken &&-chain due to a semicolon and a broken chain due to a missing
`&&` at end-of-line. Therefore, drop the ?!SEMI?! annotation and use
?!AMP?! exclusively.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When chainlint.sed detects commands separated by a semicolon rather than
by `&&`, it places a ?!SEMI?! 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 ?!SEMI?! annotation to the location
of the semicolon 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>
The purpose of chainlint.sed is to detect &&-chain breakage only within
subshells (one level deep); it doesn't bother checking for top-level
&&-chain breakage since the &&-chain checker built into t/test-lib.sh
should detect broken &&-chains outside of subshells by making them
magically exit with code 117.
Unfortunately, one of the chainlint.sed self-tests has overly intimate
knowledge of this particular division of responsibilities and only cares
about what chainlint.sed itself will produce, while ignoring the fact
that a more all-encompassing linter would complain about a broken
&&-chain outside the subshell. This makes it difficult to re-use the
test with a more capable chainlint implementation should one ever be
developed. Therefore, adjust the test and its "expected" output to
avoid being specific to the tunnel-vision of this one implementation.
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>
