Code block text formatting is broken if syntax highlighting is on

[jaywink]

Description

When "Enable automatic language detection for syntax highlighting" is on, certain types of code blocks get malformed. Included is an example:

Foo Foo Foo Foo: - Foo
===================================================
Foo  |  Foo  |  Foo                |  Foo  |  Foo     |  Foo  |  Foo                                    |  Foo  |  Foo        |  Foo  |  Foo  |  Foo  |  Foo  |  Foo  |  Foo                             |  Foo  |  Foo  |  Foo  |  Foo
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
5          |      |  Foo  |  Foo    |  Foo  |  Foo    |  Foo  |  x             |  Foo  |  ✓        |  ✓    |  ?           |  x    |  x      |  Foo  |            |  null        |  true     |  false   
5          |      |  Foo  |  Foo    |  Foo  |  Foo    |  Foo  |  x             |  Foo  |  ✓        |  ✓    |  ?           |  x    |  x      |  Foo  |            |  null        |  true     |  false   

Summary
=======
type                                  |  Foo  |  Foo
---------------------------------------------------------
Foo Foo                               |  0    |  0       
Foo Foo                               |  23   |  2       
Foo Foo                               |  23   |  2       
Foo Foo                               |  21   |  0       
Foo Foo                               |  2    |  2       
Foo Foo Foo                           |  5    |  -       
Foo Foo                               |  2    |  -       
Foo Foo Foo Foo                       |  9    |  -       

With syntax highlighting enabled (incorrect rendering):

With syntax highlight disabled (correct rendering):

Steps to reproduce

• Paste above snippet as code block.

Version information

• Platform: web and desktop
• Version: v1.7.34 and desktop nightly 2021080202

[SimonBrandner]

This look like a weird interaction between our CSS and highlight.js

[rootkea]

When Enable automatic language detection for syntax highlighting is off, the fenced code block prints extra lines at the end.

This is the markup I used:

```cpp
#include <bits/stdc++.h>
using namespace std;

void bubbleSort(int arr[], int n)
{
	int i, j;
	for (i = 0; i < n-1; i++)
	for (j = 0; j < n-i-1; j++)
		if (arr[j] > arr[j+1])
			swap(&arr[j], &arr[j+1]);
}

void bubbleSort(int arr[], int n)
{
	int i, j;
	for (i = 0; i < n-1; i++)
	for (j = 0; j < n-i-1; j++)
		if (arr[j] > arr[j+1])
			swap(&arr[j], &arr[j+1]);
}
```

And this is the o/p I got:

Notice the extra 2 blank lines at the end.

It seems the the total number of extra blank lines getting printed at the end are equal to the blank lines in the fenced code block. So if you add one another function separated by a blank line in above code block then there will be 3 blank lines at the end.

[rootkea]

It seems the the total number of extra blank lines getting printed at the end are equal to the blank lines in the fenced code block.

Ah, that seems to be incorrect. Just add one another function. Doesn't matter whether it's separated by a blank line or not. You'll see 3 blank lines at the end after rendering.

So the number of extra blank lines getting printed at the end seem to be related with no. of functions?