Fixes #27605: inline math blocks can't be preceeded/followed by alphanumerical characters

[jmlt2002]

• Inline math blocks couldn't be preceeded or succeeded by alphanumerical characters due to changes introduced in PR Fix slight bug in katex #21171. Removed the condition that caused this (precedingCharacter condition) and added a new exit condition of the for-loop that checks if a specific '$' was escaped using '' so that the math expression can be rendered as intended.
• Additionally this PR fixes another bug where math blocks of the type '$xyz$abc$' where the dollar sign was not escaped by the user, generated an error (shown in the screenshots below)
• Altered the tests to accomodate for the changes

Former behaviour (from try.gitea.io):

Fixed behaviour (from my local build):

(Edit) Source code for the README.md file:

$x$ -$x$ $x$-

a$xa$ $xa$a 1$xb$ $xb$1

$a a$b b$

a$b $a a$b b$

$a a\$b b$

[silverwind]

I tested what GitHub renders for your example and only the first one works. Would you say those are bugs in GitHub's implementation?

[silverwind]

Also, could you add a few more test cases, instead of only modifying the existing ones.

[jmlt2002]

I tested what GitHub renders for your example and only the first one works. Would you say those are bugs in GitHub's implementation?

I think so since I don't see a particular reason why it wouldn't be allowed for characters to come directly before or after the math expressions.

[silverwind]

Seems like GitLab rendering does agree with your solution, so 👍 from me on the rendering part.

[jmlt2002]

Seems like GitLab rendering does agree with your solution, so 👍 from me on the rendering part.

We missed it but it seems that GitLab does not agree with my solution after all, the last expression of the second line is not rendered, and the rendering in the fourth line does not match

[wxiaoguang]

TBH, I still have question about why it needs this change.

Why it needs to handle $a a$b b$ / a$x$ that way? Why "inline math blocks should be preceeded/followed by alphanumerical characters"?

By reading #27605, I didn't get the answer, and I haven't seen a real world example yet ....

Could you elaborate the use cases by real examples?

[jmlt2002]

For the a$x$ expression you could have for example something of the type a$x²$ where 'a' is a constant. If 'a' was inside the math expression it would have the same formatting as 'x²' making it less readable.

As for the $a a$b b$, it's an extra, it's a side effect of changing the render as mentioned above. Before, this expression would generate an error, as shown in the first comment of the conversation, and now it no longer does that.

[wxiaoguang]

For the a$x$ expression you could have for example something of the type a$x²$ where 'a' is a constant. If 'a' was inside the math expression it would have the same formatting as 'x²' making it less readable.

Why people would write such expr a$x²$? I think it is still an over-abstracted example, but not a real world example. I used some examples above like The price is between $1 and $10, because people really write that way. But for a$x²$ , could you show some real world documents/comments that why it is written?

As for the $a a$b b$, it's an extra, it's a side effect of changing the render as mentioned above. Before, this expression would generate an error, as shown in the first comment of the conversation, and now it no longer does that.

Yup, I agree that it is just a side-effect of this change. The root question is still the first one.

[jmlt2002]

But for a$x²$ , could you show some real world documents/comments that why it is written?

I looked at some websites and math research papers and it seems that the math expressions are never directly preceeded by a character, they are either a whole mathematical block or have a space in between like a $x$.

I will change the code to not allow either preceeding or suceeding characters, and solely fix the bug that was fixed by as a side-effect.

[jmlt2002]

Should the math expressions not allowed to be followed by alphanumerical characters or also not allowed to be followed by any character besides ' ' or a newline?

[wxiaoguang]

IMO following by a punctuation or newline is fine, because that's also how a sentence is written. GitHub:

• It is $1$, or maybe $2$. => It is $1$, or maybe $2$.

[wxiaoguang]

Could there be a case for something like:

• $a a\\$b b$ => $a a\$b b$

?

In case the users would like to escape and use $

I have this question because I guess the old code might work with $a a\\$b b$ (although it reports errors for $a a$b b$, it is still acceptable)

So I'd like to confirm the new code's behavior.

[jmlt2002]

The old code does what you described with $a a\$b b$, with only one backslash. With two, or any even number of backslashes it would generate an error.

With the current code, the expression $a a\\$b b$ generates the expression below.

If the user wanted to get the output that you described he would need to use the following expression
$a a \$ b b$

[silverwind]

Guess 1.22 backport is enough. Edit: Nevermind, GiteaBot was faster.