[Toybox] patch and fuzz

[enh]

oh, i see you silently fixed this. i gave it a spin and AOSP seems
fine with the new version, so we can switch the build over to toybox
patch.

thanks!

On Fri, Jul 17, 2020 at 5:21 PM enh <enh at google.com> wrote:
>
> (sorry, been ooo.)
>
> On Sun, Jun 28, 2020 at 11:21 PM Rob Landley <rob at landley.net> wrote:
>>
>> On 6/26/20 2:35 PM, enh via Toybox wrote:
>> > toybox patch fails to apply the patch
>> > https://android.googlesource.com/platform/external/snakeyaml/+/refs/heads/master/src/patches/android/Representer.patch
>>
>> That's html, I clicked the ".txt" link at the bottom and it downloaded a block
>> of "Zy95YW1sL3NuYWtleWFtbC9yZXByZXNlbnRlci9SZXByZXNlbnRlci5qYXZhCkBAIC0xNSw3"
>> which I don't recognize the encoding of?
>>
>>   $ file Representer.txt
>>   Representer.txt: ASCII text, with very long lines, with no line terminators
>>
>> The debian file command is editorializing, but not helpful.
>>
>> > to the file https://android.googlesource.com/platform/external/snakeyaml/+/refs/heads/master/src/main/java/org/yaml/snakeyaml/representer/Representer.java.
>>
>> Could you send me the two files?
>
>
> attached.
>
> note that when you're finding gittiles unhelpful (which, let's face it, it usually is), you can just chop the first part off the URL and `git clone`. so here, for example, `git clone https://android.googlesource.com/platform/external/snakeyaml/` will check out this single git project, which isn't very large.
>
>>
>> > the worst part is that it _thinks_ it succeeds :-(
>> >
>> > the interesting bit happens when we come to apply this hunk:
>> >
>> > @@ -15,7 +15,6 @@
>> > */
>> >  package org.yaml.snakeyaml.representer;
>> >
>> > -import java.beans.IntrospectionException;
>> >  import java.util.ArrayList;
>> >  import java.util.Arrays;
>> >  import java.util.Iterator;
>> >
>> > here:
>> >
>> > package org.yaml.snakeyaml.representer;
>> >
>> > import java.beans.IntrospectionException;
>> > import java.util.ArrayList;
>> > import java.util.Arrays;
>> > import java.util.Collections;
>> > import java.util.Iterator;
>> > import java.util.List;
>> >
>> > the eagle-eyed human will notice that there's an extra "Collections"
>> > in the actual file that isn't in the patch, because the patch was
>> > actually against an older version of the source.
>>
>> Didn't commit 333a10f9ef59 fix this back in February? (It was supposed to...)
>>
>> > the bug is that toybox drops that new line in its output.
>> >
>> > it reads it:
>> >
>> > MAYBE:
>> > IN: import java.beans.IntrospectionException;
>> > MAYBE: -import java.beans.IntrospectionException;
>> > IN: import java.util.ArrayList;
>> > MAYBE:  import java.util.ArrayList;
>> > IN: import java.util.Arrays;
>> > MAYBE:  import java.util.Arrays;
>> > IN: import java.util.Collections;
>> > FUZZED: 21  import java.util.Iterator;
>> >
>> > but then it does a `goto fuzzed` and explicitly drops that line it
>> > just read. which is clearly wrong here, but the code comment
>> > explicitly calls out this behavior:
>> >
>> >     // If match failed, flush first line of buffered data and
>> >     // recheck buffered data for a new match until we find one or run
>> >     // out of buffer.
>>
>> That's leading data. The idea was if you're matching
>>
>> @@
>>   abc
>> - def
>>   ghi
>>
>> And the data says:
>>
>>  abc
>>  abc
>>  def
>>  ghi
>>
>> It shouldn't see the first abc, read in the second abc and go "nope, that's not
>> def" and then discard _both_ before checking again. (It has to advance _one_
>> line and try again, thus checking at every possible offset, including rechecking
>> the data it's already buffered  because it thought it might be a later part of
>> the hunk under consideration. The actual _start_ of the hunk might be in that
>> mismatched later part it's already read in.)
>>
>> > so i'm not quite sure i understand the intended logic here. when would
>> > you ever want to drop an input line that doesn't have a '-' or '+'
>> > line in the hunk?
>>
>> Can you send me the test files? (I can try to put together a test from what
>> you've sent me, but I'd rather have the real one.)
>>
>> Thanks,
>>
>> Rob