Syntax highlight in the diff output

[vlsi]

It would be nice if there was syntax highlighting in the diff output, so the code structure is easier to understand.

Sample PL/SQL diff:

git version 2.33.0

difftastic 0.8

delta 0.8.3

---

PL/SQL diff where the diff is within string literals (the indentation at line 256 looks odd, and I did not notice it before I took the screenshots).
The code is "PL/SQL code generator written in PL/SQL", and I do not expect that PL/SQL code within string literals to be highlighted as PL/SQL :) However, it would be nice if string literals were highlighted differently from the regular code.

git version 2.33.0

difftastic 0.8

delta 0.8.3

---

Re "string literals vs code" there's a semi-standard extension from IntelliJ: https://www.jetbrains.com/help/idea/using-language-injections.html#use-language-injection-comments

For instance, the following bit in Groovy code (Jenkins Job DSL code) is highlighted as XML in IntelliJ IDEA:

// $/ ... /$ is a multi-line string in Groovy
//  language=xml comment triggers "inject XML into the following literal" in IDEA
+ echo('> config/config.xml', /* language=xml */ $/
<root>
  <profile>
    <datasources>
    </datasources>
  </profile>
</root>
/$) +

[Wilfred]

Yeah, I think syntax highlighting would be very worthwhile. It's not something I plan to work on until I've got the diffing logic solid, so it's not a high priority for me.

For your specific example, I'm afraid difftastic doesn't support .sql files. There isn't an mature tree-sitter parser for SQL that I'm aware of.

[robinmoussu]

I would also love to get more syntax highlight. The minimal version that you did (dimmed comments and bold keywords) is already great. Thanks a lot for the hard work.

[vlsi]

I've upgraded to 0.11.0, and I like word-level diffs:

[Wilfred]

See also #311.

[nh2]

I do not understand whether the commit that closed this issue should fix the following:

I inserted 2 lines into a Nix multi-line string, and difftastic shows the whole string as changed, making it difficult to see which lines are actually changed in git diff:

difftastic:

delta:

This is on Difftastic 0.34.0, which has commit a5de97a in -- should it look different?

[Wilfred]

@nh2 currently difftastic treats strings atomically, even when they're big multiline literals. See #178, it would be nice to do something better.

[nh2]

I inserted 2 lines into a Nix multi-line string

@Wilfred Should #409 (comment) help with this?

E.g. would one need to write code similar to the one added in 9133918 ?

[Wilfred]

@nh2 I don't think sublanguages help here. In a generic string literal, there's no way for difftastic to know what the language in the string is.

Better handling of multiline comments/string is what will really help here I think.

[nh2]

@Wilfred It's shell script in ~95% of the cases. There are also some hints, e.g. the variable name that the string is assigned to.

Separate question though: VSCode auto-detects languages based on heuristics; if it looks like shell or Python, it guesses it. Such thing would certainly help here. Does difftastic have a such functionality one could turn on / do the libraries it uses provide such features?