Re: [GSOC][PATCH] userdiff: add support for Scheme

Atharva Raykar [off-list ref] writes:

quoted

quoted

+         "(\\.|[^][)(\\}\\{ ])+"),

One or more "dot or anything other than SP or parentheses"?  But
a dot "." is neither a space or any {bra-ce} letter, so would the
above be equivalent to

	"[^][()\\{\\} \t]+"

I wonder...

A backslash is allowed in scheme identifiers, and I erroneously thought that
the first part handles the case for identifiers such as `component\new` or 
`\"id-with-quotes\"`. (I tested it with a regex engine that behaves differently
than the one git is using, my bad.)

Ah, perhaps you didn't have enough backslashes.  A half of the
doubled one before the dot is eaten by the C compiler, so the regexp
engine is seeing only a single backslash before the dot, which means
"literally a single dot".  If you meant "literally a single
backslash, followed by any single char", you probably would write 4
backslashes and a dot---half of the backslashes would be eaten by
the compiler, so you'd be passing two backslashes and a dot, which
is probably what you meant.

Having said that, two further points.

 - the "anything but whitespaces and various forms of parentheses"
   set would include backslash, so 'component\new' would be taken as
   a single word with "[^][()\\{\\} \t]+", wouldn't it?

 - how common is the use of backslashes in identifiers?  I am trying
   to see if the additional complexity needed to support them is
   worth the benefit.

But somehow, the regexp you suggested, ie:

	"[^][()\\{\\} \t]+"

does not handle the case of make\foo -> make\bar (it will only diff on foo).
I am not too sure why it treats backslashes as delimiters.

Perhaps because you have included two backslashes inside [] to say
"backslash is not a word character" in the original, and I blindly
copied that?  IOW, do you need to quote {} inside []?

Yes, this is exactly what I was trying to express. All words should be
delimited by either whitespace or a parenthesis, and all other special
characters should be accepted as part of the word.

That sentence after "All words should be..." would be a good comment
to replace what you wrote in the original, then ;-).

On 28-Mar-2021, at 23:36, Junio C Hamano [off-list ref] wrote:

Atharva Raykar [off-list ref] writes:

quoted

quoted

quoted

+         "(\\.|[^][)(\\}\\{ ])+"),

One or more "dot or anything other than SP or parentheses"?  But
a dot "." is neither a space or any {bra-ce} letter, so would the
above be equivalent to

	"[^][()\\{\\} \t]+"

I wonder...

A backslash is allowed in scheme identifiers, and I erroneously thought that
the first part handles the case for identifiers such as `component\new` or 
`\"id-with-quotes\"`. (I tested it with a regex engine that behaves differently
than the one git is using, my bad.)

Ah, perhaps you didn't have enough backslashes.  A half of the
doubled one before the dot is eaten by the C compiler, so the regexp
engine is seeing only a single backslash before the dot, which means
"literally a single dot".  If you meant "literally a single
backslash, followed by any single char", you probably would write 4
backslashes and a dot---half of the backslashes would be eaten by
the compiler, so you'd be passing two backslashes and a dot, which
is probably what you meant.

Having said that, two further points.

- the "anything but whitespaces and various forms of parentheses"
  set would include backslash, so 'component\new' would be taken as
  a single word with "[^][()\\{\\} \t]+", wouldn't it?

- how common is the use of backslashes in identifiers?  I am trying
  to see if the additional complexity needed to support them is
  worth the benefit.

I have refined the regex, and now it is much simpler and does all of what
I want it to:

	"([^][)(}{[:space:]])+"

I did not have to escape the various parentheses, so I avoided the need to
handle backslashes separately. The "\\t" was causing problems as well because
it took it as a '\' followed by a 't' (Thanks to j416 on #git-devel for
helping me out on this).

quoted

Yes, this is exactly what I was trying to express. All words should be
delimited by either whitespace or a parenthesis, and all other special
characters should be accepted as part of the word.

That sentence after "All words should be..." would be a good comment
to replace what you wrote in the original, then ;-).

Yes, that should make it a lot more clear.