patchuserdiff: support Rust macros

From: Konrad Borowski <konrad@borowski.pw>

This adds a support for macro_rules! keyword which declares a macro. It also includes a test case.

Signed-off-by: Konrad Borowski <konrad@borowski.pw>
---
    userdiff: support Rust macros

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-865%2Fxfix%2Fuserdiff-macro-rules-rust-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-865/xfix/userdiff-macro-rules-rust-v1
Pull-Request: https://github.com/git/git/pull/865

 t/t4018/rust-macro-rules | 6 ++++++
 userdiff.c               | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/rust-macro-rules

Hi Konrad

Thanks for the patch, this would be a useful addition

On 06/10/2020 13:13, Konrad Borowski via GitGitGadget wrote:

I think you want the `!` before the `[\t ]`. We could probably get away with just adding `macro-rules!` as another alternative in the group starting with `struct`

Best Wishes

Phillip

[^;]*)$",

Am 06.10.20 um 14:13 schrieb Konrad Borowski via GitGitGadget:

We would write this sentence in imperative mood, i.e., give the codebase the order to become so. That a test case is included can be seen from the patch text and need not be mentioned.

In this case, if I were the only one to judge, I would accept this commit without a message if the commit summary were:

  userdiff: permit Rust's macro_rules! keyword in hunk headers

Technically, this looks fine. Originally I thought that the new keyword could just be thrown into the mix of struct|enum etc, but judging from the (existing) test cases, this new case looks fairly different (I am not a Rust expert, so I cannot really tell). Therefore, it is OK to put it in an alternative branch in the regexp.

Reviewed-by: Johannes Sixt <j6t@kdbg.org>

-- Hannes

From: Konrad Borowski <konrad@borowski.pw>

Changes since v1:
- Changed macro_rules! to be considered to use the same
  rule as rest of keywords to reduce the size of a change
  as suggested by Phillip Wood. This means that
  'pub macro_rules!` (a syntax error) is considered to be
  a hunk header.

- Written commit message in imperative mood as suggested by
  Johannes Sixt.

Signed-off-by: Konrad Borowski <konrad@borowski.pw>
---
    userdiff: support Rust macros

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-865%2Fxfix%2Fuserdiff-macro-rules-rust-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-865/xfix/userdiff-macro-rules-rust-v2
Pull-Request: https://github.com/git/git/pull/865

Range-diff vs v1:

 1:  9e071ddf63 ! 1:  a3fd67d84f userdiff: support Rust macros
     @@ Metadata
      Author: Konrad Borowski <konrad@borowski.pw>
      
       ## Commit message ##
     -    userdiff: support Rust macros
     +    userdiff: permit Rust's macro_rules! keyword in hunk headers
      
     -    This adds a support for macro_rules! keyword which declares
     -    a macro. It also includes a test case.
     +    Changes since v1:
     +    - Changed macro_rules! to be considered to use the same
     +      rule as rest of keywords to reduce the size of a change
     +      as suggested by Phillip Wood. This means that
     +      'pub macro_rules!` (a syntax error) is considered to be
     +      a hunk header.
     +
     +    - Written commit message in imperative mood as suggested by
     +      Johannes Sixt.
      
          Signed-off-by: Konrad Borowski <konrad@borowski.pw>
      
     @@ userdiff.c: PATTERNS("ruby", "^[ \t]*((class|module|def)[ \t].*)$",
       	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
       PATTERNS("rust",
      -	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl)[< \t]+[^;]*)$",
     -+	 "^[\t ]*(((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl)[< \t]+|macro_rules[\t ]*!)[^;]*)$",
     ++	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules[\t ]*!)[< \t]+[^;]*)$",
       	 /* -- */
       	 "[a-zA-Z_][a-zA-Z0-9_]*"
       	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"

 t/t4018/rust-macro-rules | 6 ++++++
 userdiff.c               | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/rust-macro-rules

"Konrad Borowski via GitGitGadget" <gitgitgadget@gmail.com> writes:

The above is where you write the proposed log message, not where you write the differences between v1 and v2 (which, if exists, would be below the three-dash line after your sign off). After all, people who are reading the final history of the project in "git log" will not even know or care that what they are reading is the second iteration and/or there was a first iteration that was different from the final version.

Somehow I find the "permit" a bit odd---it is not like we are disallowing Rust programs written in certain way.

     userdiff: recognize 'macro_rules!' as starting a Rust function block

or something?

As to the simplified rule that matches 'pub macro_rules!'.

We assume what is written by the end-user, in which these patterns are used to find function headers, is a syntactically correct program. This allows us to write a pattern that may match with a syntactic nonsense (i.e. false positive is perfectly fine). What we care about is to avoid false negatives---if our pattern does not recognize what users would consider a valid and common function header line, that is a problem.

So, from that point of view, you do not have to worry too much about 'pub macro_rules!' matching your pattern.

I notice that you still allow "macro_rules !" as Phillip pointed out. Is that intended?

Thanks.

From: Konrad Borowski <konrad@borowski.pw>

Signed-off-by: Konrad Borowski <konrad@borowski.pw>
---
    userdiff: support Rust macros
    
    Changes since v1:
    
     * Changed macro_rules! to be considered to use the same rule as rest of
       keywords to reduce the size of a change as suggested by Phillip Wood.
       This means that 'pub macro_rules!` (a syntax error) is considered to
       be a hunk header.
     * Written commit message in imperative mood as suggested by Johannes
       Sixt.
    
    Changes since v2:
    
     * Updated the commit message as suggested by Junio C Hamano.
     * Removed handling for 'macro_rules !' with a space in-between tokens.
       While it is allowed by the compiler to have a space between
       'macro_rules' and '!' it's pretty much never done.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-865%2Fxfix%2Fuserdiff-macro-rules-rust-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-865/xfix/userdiff-macro-rules-rust-v3
Pull-Request: https://github.com/git/git/pull/865

Range-diff vs v2:

 1:  a3fd67d84f ! 1:  0d8e6e06d4 userdiff: permit Rust's macro_rules! keyword in hunk headers
     @@ Metadata
      Author: Konrad Borowski <konrad@borowski.pw>
      
       ## Commit message ##
     -    userdiff: permit Rust's macro_rules! keyword in hunk headers
     -
     -    Changes since v1:
     -    - Changed macro_rules! to be considered to use the same
     -      rule as rest of keywords to reduce the size of a change
     -      as suggested by Phillip Wood. This means that
     -      'pub macro_rules!` (a syntax error) is considered to be
     -      a hunk header.
     -
     -    - Written commit message in imperative mood as suggested by
     -      Johannes Sixt.
     +    userdiff: recognize 'macro_rules!' as starting a Rust function block
      
          Signed-off-by: Konrad Borowski <konrad@borowski.pw>
      
     @@ userdiff.c: PATTERNS("ruby", "^[ \t]*((class|module|def)[ \t].*)$",
       	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
       PATTERNS("rust",
      -	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl)[< \t]+[^;]*)$",
     -+	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules[\t ]*!)[< \t]+[^;]*)$",
     ++	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules!)[< \t]+[^;]*)$",
       	 /* -- */
       	 "[a-zA-Z_][a-zA-Z0-9_]*"
       	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"

 t/t4018/rust-macro-rules | 6 ++++++
 userdiff.c               | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/rust-macro-rules