java-diff-utils
Diffs recognizing less similarity since 4.10
Since version 4.10 of the library, diffs are recognizing less similarity between texts.
In the attached program, under version 4.9, the library correctly recognizes that there is only a 5-character difference between the texts (3 letters + 2 whitespace characters). Under version 4.10, the library reports that a large block of identical text has been deleted and then added.
4.9 output:
1 EQUAL apple1 apple1
2 EQUAL apple2 apple2
3 EQUAL apple3 apple3
4 CHANGE A man named Frankenstein==oldCHANGE==> abc <==old==to Switzerland for cookies! A man named Frankenstein
5 CHANGE ==newCHANGE==>xyz<==new==
6 CHANGE to Switzerland for cookies!
7 EQUAL banana1 banana1
8 EQUAL banana2 banana2
9 EQUAL banana3 banana3
4.10 output:
1 EQUAL apple1 apple1
2 EQUAL apple2 apple2
3 EQUAL apple3 apple3
4 CHANGE A man named Frankenstein==oldDELETE==> abc to Switzerland for cookies!<==old== A man named Frankenstein
5 INSERT ==newINSERT==>xyz<==new==
6 INSERT ==newINSERT==>to Switzerland for cookies!<==new==
7 EQUAL banana1 banana1
8 EQUAL banana2 banana2
9 EQUAL banana3 banana3
Admittedly, there are aspects of the 4.10 output that are improved over the 4.9 output. For example, the fact that line 6 of the 4.9 output is indicated as a CHANGE, but there is no oldLine text and no changes in the newLine text can be confusing. However, the sacrifice in accuracy in 4.10 is far less desirable. In 4.9, the line 6 difference is indeed a change, but it's almost like a new tag is needed to indicate a group (?) change to make it clear that the change is a continuation of the line 4 difference.
There was a change to somehow decompress the computed deltas that have different target and source sizes. That was needed to correct some issues with multi line diffs. But I will look into it. Maybe we could make this decompression skippable.
Could you check it? I added the possibility to skip the delta decompression. After it is switched off you get your old result.s
This does indeed appear to address my issue. Thank you very much for the quick turn-around (quicker than I've even checked back). I worry a little about yet-another-builder-option, but I defer to your understanding of the code.
Do you have some idea when the next release will be? In my production environment, due to security and network restrictions, I can only download published maven artifacts.
If you are curious, here is sample data for a test case that is closer to my real-world scenario:
issue129_1.txt
issue129_2.txt
My users are highly interested in seeing only substantive changes in text; in this data, nothing but white-space formatting has changed. With decompressDeltas(false), the text is recognized as a series of CHANGEs with small spacing differences; with decompressDeltas(true), the code outputs a series of CHANGEs and then an INSERT which would be counterproductive to my user base.
Thank you again!