threads / discuss / 57816

Getting an odd diff

Subject: Getting an odd diff

## tl;dr

3 messages between Apr 29, 2022 and May 2, 2022.

replies: 2people: 2as markdown or json

Jack Adrian Zappa· Apr 29, 2022, 12:33 UTC · lore

So, I have a regex to select words so that I can focus on the actual changes. But then I noticed that it did something weird. It grouped some parenthesis with another word. I generated a minimal example for that line and it was reproducible.

Before: var result = ((res.State == ResultState.Succeeded) && string.IsNullOrEmpty(res.ErrorCode) )? (byte)0 : (byte)1;

After: var result = res.State == ResultState.Succeeded ? (byte)0 : (byte)1;

Diff: $ git diff2 --no-index b a warning: LF will be replaced by CRLF in b. The file will have its original line endings in your working directory warning: LF will be replaced by CRLF in a. The file will have its original line endings in your working directory

diff --git a/b b/a
index 4e3604a8e..619d21e4e 100644
--- a/b
+++ b/a
@@ -1 +1 @@
var result = [-((res-]{+res+}.State == ResultState.Succeeded[-) &&
string.IsNullOrEmpty(res.ErrorCode) )-] ? (byte)0 : (byte)1;

I tried to make a smaller example and it didn't cause the issue.

Before:
var abc = ((xyz.Stuff == other_stuff) && stuff.yay(question) ? yes : no;

After:
var abc = xyz.Stuff == other_stuff ? yes : no;

Diff:
$ git diff2 --no-index b a
warning: LF will be replaced by CRLF in b.
The file will have its original line endings in your working directory
warning: LF will be replaced by CRLF in a.
The file will have its original line endings in your working directory
diff --git a/b b/a
index df18ca34e..1024d6b68 100644
--- a/b
+++ b/a
@@ -1 +1 @@
var abc =[-((-] xyz.Stuff == other_stuff[-) && stuff.yay(question)-] ? yes : no;

So, my question is, what's going on here?

The alias is as follows:
     diff2 = diff --color=always --ignore-space-change
'--word-diff-regex=((\\r\\n?|\\n\\r?)[\\t
]*)?([a-zA-Z_][a-zA-Z_0-9]*|0([xX]([0-9][a-fA-F])+|[0-7]+|[bB][01]+)|[1-9][0-9]*(\\.[0-9]+)?([eE][0-9]+|[pP][0-9a-fA-F])?|\\S)(\\r\\n?|\\n\\r?)?'
-p

Thanks,


JAZ
JAZ

Johannes Sixt· Apr 30, 2022, 07:16 UTC · re: Jack Adrian Zappa · lore

Re: Getting an odd diff

Am 29.04.22 um 14:33 schrieb Jack Adrian Zappa:

Show 54 quoted lines

> So, I have a regex to select words so that I can focus on the actual
> changes.  But then I noticed that it did something weird.  It grouped
> some parenthesis with another word.  I generated a minimal example for
> that line and it was reproducible.
> 
> Before:
> var result = ((res.State == ResultState.Succeeded) &&
> string.IsNullOrEmpty(res.ErrorCode) )? (byte)0 : (byte)1;
> 
> After:
> var result = res.State == ResultState.Succeeded ? (byte)0 : (byte)1;
> 
> Diff:
> $ git diff2 --no-index b a
> warning: LF will be replaced by CRLF in b.
> The file will have its original line endings in your working directory
> warning: LF will be replaced by CRLF in a.
> The file will have its original line endings in your working directory
> diff --git a/b b/a
> index 4e3604a8e..619d21e4e 100644
> --- a/b
> +++ b/a
> @@ -1 +1 @@
> var result = [-((res-]{+res+}.State == ResultState.Succeeded[-) &&
> string.IsNullOrEmpty(res.ErrorCode) )-] ? (byte)0 : (byte)1;
> 
> I tried to make a smaller example and it didn't cause the issue.
> 
> Before:
> var abc = ((xyz.Stuff == other_stuff) && stuff.yay(question) ? yes : no;
> 
> After:
> var abc = xyz.Stuff == other_stuff ? yes : no;
> 
> Diff:
> $ git diff2 --no-index b a
> warning: LF will be replaced by CRLF in b.
> The file will have its original line endings in your working directory
> warning: LF will be replaced by CRLF in a.
> The file will have its original line endings in your working directory
> diff --git a/b b/a
> index df18ca34e..1024d6b68 100644
> --- a/b
> +++ b/a
> @@ -1 +1 @@
> var abc =[-((-] xyz.Stuff == other_stuff[-) && stuff.yay(question)-] ? yes : no;
> 
> So, my question is, what's going on here?
> 
> The alias is as follows:
>      diff2 = diff --color=always --ignore-space-change
> '--word-diff-regex=((\\r\\n?|\\n\\r?)[\\t
> ]*)?([a-zA-Z_][a-zA-Z_0-9]*|0([xX]([0-9][a-fA-F])+|[0-7]+|[bB][01]+)|[1-9][0-9]*(\\.[0-9]+)?([eE][0-9]+|[pP][0-9a-fA-F])?|\\S)(\\r\\n?|\\n\\r?)?'
> -p

I am a bit reluctant to diagnose what exactly is happening here because your word regex is outside the design space. It is definitely not a good idea to declare whitespace and even line breaks as part of a word. And in fact, when you remove the trailing (\\r\\n?|\\n\\r?)?, you get a more sensible word diff:

var result =[-((-] resx.State == ResultState.Succeeded[-) &&-] [-string.IsNullOrEmpty(res.ErrorCode) )-] ? (byte)0 : (byte)1;

But if I were you, I would remove all subexpressions that match any form of whitespace.

-- Hannes

Jack Adrian Zappa· May 2, 2022, 18:04 UTC · re: Johannes Sixt · lore

Re: Getting an odd diff

On Sat, Apr 30, 2022 at 3:16 AM Johannes Sixt <j6t@kdbg.org> wrote:

Show 11 quoted lines

> I am a bit reluctant to diagnose what exactly is happening here because
> your word regex is outside the design space. It is definitely not a good
> idea to declare whitespace and even line breaks as part of a word. And
> in fact, when you remove the trailing (\\r\\n?|\\n\\r?)?, you get a more
> sensible word diff:
>
> var result =[-((-] resx.State == ResultState.Succeeded[-) &&-]
> [-string.IsNullOrEmpty(res.ErrorCode) )-] ? (byte)0 : (byte)1;
>
> But if I were you, I would remove all subexpressions that match any form
> of whitespace.

Interesting... IIRC, the reason for the leading and trailing line breaks in the regex is to stop the diff from messing up the alignment of multiple edited lines. I don't remember the exact sequence I was seeing, but removing them doesn't appear to mess up the alignment so badly anymore. Still, I'm surprised that removing that trailing line break capture would have caused the issue seen here. For now, I'll remove the captures and if I see what I was seeing before, I'll report back to the group.

Thanks,

Jaz