Re: [PATCH v8 11/11] convert: add filter.<driver>.process option

On 29 Sep 2016, at 01:14, Jakub Narębski [off-list ref] wrote:

Part third (and last) of the review of v8 11/11.

W dniu 20.09.2016 o 21:02, larsxschneider@gmail.com napisał:

quoted

@@ -31,7 +31,10 @@ test_expect_success setup '

	cat test >test.i &&
	git add test test.t test.i &&
	rm -f test test.t test.i &&
-	git checkout -- test test.t test.i
+	git checkout -- test test.t test.i &&
+
+	echo "content-test2" >test2.o &&
+	echo "content-test3 - subdir" >"test3 - subdir.o"

I see that you prepare here a few uncommitted files, but both
their names and their contents leave much to be desired - you
don't know from the name and contents what they are for.

And the '"subdir"' file which is not in subdirectory is
especially egregious.

These are 3 files with somewhat random test content. I renamed
"subdir" to "spaces".

quoted

+check_filter () {
+	rm -f rot13-filter.log actual.log &&
+	"$@" 2> git_stderr.log &&
+	test_must_be_empty git_stderr.log &&
+	cat >expected.log &&

This is too clever by half.  Having a function that both tests
the behavior and prepares 'expected' file is too much.

In my opinion preparation of 'expected.log' file should be moved
to another function or functions.

Also, if we are running sort on output, I think we should also
run sort on 'expected.log', so that what we write doesn't need to
be created sorted (so we don't have to sort expected lines by hand).
Or maybe we should run the same transformation on rot13-filter.log
and on the contents of expected.log.

Agreed. Very good suggestion!

quoted

+check_filter_ignore_clean () {
+	rm -f rot13-filter.log actual.log &&
+	"$@" &&

Why we don't check for stderr here?

Because this function is used by "git checkout" which writes all
kinds of stuff to stderr. I added "--quiet --no-progress" to
disable this behavior. 

quoted

+check_rot13 () {
+	test_cmp "$1" "$2" &&
+	./../rot13.sh <"$1" >expected &&

Why there is .. in this invocation?

Because this script is located in the root of the current test directory.

quoted

+	git cat-file blob :"$2" >actual &&
+	test_cmp expected actual
+}
+
+test_expect_success PERL 'required process filter should filter data' '
+	test_config_global filter.protocol.process "$TEST_DIRECTORY/t0021/rot13-filter.pl clean smudge" &&
+	test_config_global filter.protocol.required true &&
+	rm -rf repo &&
+	mkdir repo &&
+	(
+		cd repo &&
+		git init &&

Don't you think that creating a fresh test repository for each
separate test is a bit too much?  I guess that you want for
each and every test to be completely independent, but this setup
and teardown is a bit excessive.

Other tests in the same file (should we reuse the test, or use
new test file) do not use this method.

I see your point. However, I am always annoyed if Git tests are
entangled because it makes working with them way way harder.
This test test runs in 4.5s on a slow Travis CI machine. I think
that is OK considering that we have tests running 3.5min (t3404).

quoted

+		echo "*.r filter=protocol" >.gitattributes &&
+		git add . &&
+		git commit . -m "test commit" &&
+		git branch empty &&

Err... I think it would be better to name it 'empty-branch'
(or 'almost-empty-branch', as it does include .gitattributes file).
See my mistake below (marked <del>...</del>).

"empty-branch". OK

quoted

+
+		cp ../test.o test.r &&
+		cp ../test2.o test2.r &&

What does this test2.o / test2.r file tests, that test.o / test.r
doesn't?  The name doesn't tell us.

This just tests multiple files with different content.

Why it is test.r, but test2.r?  Why it isn't test1.r?

test.r already existed (created in setup test).

quoted

+		mkdir testsubdir &&
+		cp "../test3 - subdir.o" "testsubdir/test3 - subdir.r" &&

Why it needs to have different contents?

To check that the filer does the right thing with multiple files
and contents.

quoted

+		>test4-empty.r &&

You test ordinary file, file in subdirectory, file with filename
containing spaces, and an empty file.

Other tests of single file `clean`/`smudge` filters use filename
that requires mangling; maybe we should use similar file?

       special="name  with '\''sq'\'' and \$x" &&
       echo some test text >"$special" &&

OK.

In case of `process` filter, a special filename could look like
this:

       process_special="name=with equals and\nembedded newlines\n" &&
       echo some test text >"$process_special" &&

I think this test would create trouble on Windows. I'll stick to
the special characters used in the single shot filter.

quoted

+				<<-\EOF &&
+					1 IN: clean test.r 57 [OK] -- OUT: 57 . [OK]
+					1 IN: clean test2.r 14 [OK] -- OUT: 14 . [OK]
+					1 IN: clean test4-empty.r 0 [OK] -- OUT: 0  [OK]
+					1 IN: clean testsubdir/test3 - subdir.r 23 [OK] -- OUT: 23 . [OK]
+					1 START
+					1 STOP
+					1 wrote filter header
+				EOF

First, this indentation level confirms that the check_filter
function is too clever by half, and that preparing expected.log
file should be a separate step.

Agreed.

Second, if we run "sort" on contents to be in expected.log, we
can write it in more natural, and less fragile way:

Agreed.

Third, why the filter even writes output size? It is no longer
part of `process` filter driver protocol, and it makes test more
fragile.

I would prefer to leave that in. I think it is good for the test to
check that we are transmitting the amount of content that what we 
think we transmit.

If we are to keep sizes, then to make test less fragile with
respect to changes in contents of tested files, we should use
variables containing file size:

  		test_r_size=$(wc -c test.r)
  		...
  		sort >expected.log <<-EOF &&
  		...
  			1 IN: clean test.r $test_r_size [OK] -- OUT: $test_r_size . [OK]

Agreed.

quoted

+		rm -f test?.r "testsubdir/test3 - subdir.r" &&

Why 'test?.r' when we are removing only 'test2.r'; why not be explicit?

True!

quoted

+				<<-\EOF &&
+					START
+					wrote filter header
+					STOP
+				EOF

Why is even filter process invoked?  If this is not expected, perhaps
simply ignore what checking out almost empty branch (one without any
files marked for filtering) does.

Shouldn't we test_expect_failure no-call?

Because a clean operation could happen. I added a clean operation to
the expected log in order to make this visible (expected log is stripped
of clean operations in the same way as the actual log per your suggestion
above).

quoted

+
+		check_filter_ignore_clean \
+			git checkout master \

Does this checks different code path than 'git checkout .'? For
example, does this test increase code coverage (e.g. as measured
by gcov)?  If not, then this test could be safely dropped.

We checked out the "empty-branch" before. That's why we check here
that the smudge filter runs for all files (smudge filter did not run
for all files with `git checkout .`).

quoted

+				<<-\EOF &&
+					START
+					wrote filter header
+					IN: smudge test.r 57 [OK] -- OUT: 57 . [OK]
+					IN: smudge test2.r 14 [OK] -- OUT: 14 . [OK]
+					IN: smudge test4-empty.r 0 [OK] -- OUT: 0  [OK]
+					IN: smudge testsubdir/test3 - subdir.r 23 [OK] -- OUT: 23 . [OK]

Can we assume that Git would pass files to filter in alphabetical
order?  This assumption might make the test unnecessary fragile.

I have never experienced another behavior. If we see fragility we could
sort the result...

quoted

+test_expect_success PERL 'required process filter should clean only and take precedence' '

Trying to describe it better results in overly long description,
which probably means that this test should be split into few
smaller ones:

- `process` filter takes precedence over `clean` and/or `smudge`
  filters, regardless if it supports relevant ("clean" or "smudge")
  capability or not

- `process` filter that includes only "clean" capability should
  clean only (be used only for 'clean' operation)

Agreed!

In my opinion all functions should be placed at beginning,
or even in separate file (if they are used in more than
one test).

OK

quoted

+generate_test_data () {

The name is not good, it doesn't describe what kind of data
we want to generate.

"generate_random_characters" ok?!

quoted

+		perl -pe "s/./chr((ord($&) % 26) + 97)/sge" >../$NAME.file &&

Those constants (26 and 97) are a bit cryptic; magical constants.
I guess this is

 +		perl -pe "s/./chr((ord($&) % (ord('z') - ord('a') + 1) + ord('a'))/sge" >../$NAME.file &&

or

 +		perl -pe "s/./chr((ord($&) % 26 + ord('a'))/sge" >../$NAME.file &&

OK!

Do we re-generate this file each time?

quoted

+	./../rot13.sh <../$NAME.file >../$NAME.file.rot13

Anyway, I wonder if taking the last two lines out of the function
(as they are not about _generating_ a file) would make it more
readable or not.

Agreed.

quoted

+
+		echo "*.file filter=protocol" >.gitattributes &&
+		check_filter \
+			git add *.file .gitattributes \

Should it be shell expansion, or git expansion, that is

  			git add '*.file' .gitattributes

Both have the same output. Would the difference matter?

quoted

+					1 START
+					1 STOP
+					1 wrote filter header
+				EOF
+		git commit . -m "test commit" &&

Is this needed / necessary?

Yes, to test the smudge afterwards!

quoted

+
+		rm -f *.file &&
+		git checkout -- *.file &&

Is this necessary?  I guess this checks that it doesn't crash, but
we do not check that smudge operation works correctly, as we did
for clean.

Good point. Smudge check added!

quoted

+		for f in *.file
+		do
+			git cat-file blob :$f >actual &&
+			test_cmp ../$f.rot13 actual
+		done

Wasn't there helper function for this?

True :-)

quoted

+test_expect_success PERL 'required process filter should with clean error should fail' '

                                                    ^^^^^^                  ^^^^^^

Errr... what?  You have 'should' twice here.

Fixed

Also, does it matter that the error is during clean operation?
We don't test that error during smudge operation is handled in
the same way, do we?

Clean and smudge should hit the same code paths here. Therefore I think
it is sufficient to test clean only.

quoted

+	test_config_global filter.protocol.process "$TEST_DIRECTORY/t0021/rot13-filter.pl clean smudge" &&

Do we need to pass 'clean smudge', or does it provide both by
default?

We need to pass them. Default is empty.

quoted

+		git add . &&
+		git commit . -m "test commit" &&

You don't need to commit for 'git checkout <path>' (e.g. for .)
or 'git cat-file -p :<file>' to work.

True!

quoted

+	)
+'
+
+test_expect_success PERL 'process filter should not restart in case of an error' '

Errr... what? This description is not clear.  Did you mean
that filter should not be restarted if it *signals* an error
with file (either before sending anything, or after sending
partial contents)?

OK renamed to "process filter should not be restarted if it signals an error"

quoted

+test_expect_success PERL 'process filter should be able to signal an error for all future files' '

Did you mean here that filter can abort processing of
all future files?

"process filter signals abort once to abort processing of all future files", better?

quoted

+
+		cp ../test.o test.r &&
+		test_must_fail git add . 2> git_stderr.log &&
+		grep "not support long running filter protocol" git_stderr.log

Shouldn't this use gettext poison (or rather C locale)?
This error message could be translated in the future.

I would prefer to adjust that when we translate it.

quoted

+    $str =~ y/A-Za-z/N-ZA-Mn-za-m/;

Why not use tr/// version of this quote-like operation?
Or do you follow prior art here?

I am not Perl expert. That worked for me :-)

quoted

+sub packet_bin_read {
+    my $buffer;
+    my $bytes_read = read STDIN, $buffer, 4;
+    if ( $bytes_read == 0 ) {
+
+        # EOF - Git stopped talking to us!
+        print $debug "STOP\n";
+        exit();
+    }
+    elsif ( $bytes_read != 4 ) {
+        die "invalid packet size '$bytes_read' field";

Errr, $bytes_read is not packet size field.  It is $buffer.
Also, error message looks strange

  		invalid packet size '004' field

Shouldn't it be at end?

True. Fixed!

quoted

+        }
+        return ( 0, $buffer );
+    }
+    else {
+        die "invalid packet size";

Is keep-alive packet valid ("0004")?

No.

quoted

+packet_flush();
+print $debug "wrote filter header\n";

Or perhaps "handshake end"?

"init handshake complete", ok?

quoted

+    print $debug " $pathname";

No " pathname=$pathname" ?

Yes, otherwise it gets too verbose in the tests.

quoted

+        while ( length($output) > 0 ) {
+            my $packet = substr( $output, 0, $MAX_PACKET_CONTENT_SIZE );
+            packet_bin_write($packet);
+            print $debug ".";

All right, so number of dots is the number of packets.  This is
surprisingly opaque.

I added a comment.

quoted

+            if ( length($output) > $MAX_PACKET_CONTENT_SIZE ) {
+                $output = substr( $output, $MAX_PACKET_CONTENT_SIZE );
+            }
+            else {
+                $output = "";
+            }
+        }
+        packet_flush();
+        print $debug " [OK]\n";
+        $debug->flush();
+        packet_flush();

Should we test partial contents case?  Or failure during printing?
What happens then - is file cleared by Git, or left partially converted?

Git will clear the file on any error (it doesn't matter when the error happens).

---

I am astonished how many valuable suggestion you were able to make
even though I am working with this code for months now.

Thanks a lot for taking the time to review my code that thoroughly.

- Lars