Numerous needless hashes are wrapping the snapshot string

[nyurik]

What happened?

If a string contains an character that requires escaping in a non-raw literal, the number of hashes is incorrect. This is especially noticeable when validating markdown generation.

Reproduction steps

// No newlines, a single `\` (escaped)
let value = "abc \\######### xyz";
assert_snapshot!(value, @r##########"abc \######### xyz"##########);

// Same number of hashes, only this time there is no escapable symbols
let value = "abc ######### xyz";
assert_snapshot!(value, @"abc ######### xyz");

// A single newline
let value = "abc \n######### xyz";
assert_snapshot!(value, @r##########"
abc 
######### xyz
"##########);

// Copy of the previous test - note that newline is inserted before and after, plus indentation. I assume this is by design?
let value = "
abc
######### xyz
";
assert_snapshot!(value, @r##########"

    abc
    ######### xyz
    
"##########);

Insta Version

1.40.0

rustc Version

1.81.0

What did you expect?

There should be as many hash characters as really needed.

[max-sixty]

Re:

// Copy of the previous test - note that newline is inserted before and after, plus indentation. I assume this is by design?

...this should be solved by #581 (and tested / supplemented by #563). These didn't get a review before the most recent release.

---

Re the hashes: we previously always used ###, this was recently changed to base off the number of hashes in the string. There was a preference to always use raw strings (#561 (comment)) — but we can rethink how we decide the number of hashes.

What rule would you propose?

[nyurik]

thx for the quick and thorough reply!

I think we should base it off of the definition of the raw string itself -- it ends when it sees a "#### - so we just need to find the longest double quote+hashes string, and add one more hash to use as the string declaration.

regex dependency is currently optional, but could be made required, in which case something like this:

    let text = "foo ### bar";
    let re = Regex::new("\"#*").unwrap();

    let number_of_hashes_to_use = re
        .find_iter(text)
        .map(|m| m.as_str().len())
        .max()
        .unwrap_or(0);

[max-sixty]

Yes I think that could work quite well!

We are really vigilant about dependencies but could do something similar without regex.

No pressure but if you wanted to do a PR that would be great; otherwise I'll try and get to it soom.