Can we warn users if the first line of a code block is silently discarded if placed on the same line as ```?

Question

Here's an example. If a user types following into the question box:

```#include <iostream>
int main()
{
    std::cout << "Hello, world!\n";
}
```

It will look like this:

int main()
{
    std::cout << "Hello, world!\n";
}

The first line of code is silently discarded. It's probably interpreted as a language name for highlighting purposes, and since it's not a valid language, it's ignored.

I'm not sure if the old markdown renderer handled this differently from the new one, but I don't remember seeing this problem before the renderer was changed.

I've seen this cause unnecessary confusion in at least 3 questions so far. (recent example on ru.SO)

I think something should be done about it.

• We could display a warning/error if an invalid language is specified after ```.

• Or we could silently add a line break in those cases.

• Something else?

Answer 1

One solution would be to add an "Insert Code Block" button on the toolbar. Clicking it prompts you to select a supported language from a dropdown list. The user clicks 'OK' and it inserts a correctly-formatted code block at the current cursor position (newlines above or below as needed) and moves the cursor to the line after the backticks so that the user can just start typing/pasting code. An approach like this would:

• make this mistake less likely, since new users are more likely (I assume) to use buttons than write raw markup
• prevent the user from specifying an invalid/unsupported language
• consist of UI changes only, no changes to the parser (which I believe is a third-party component)

I know the toolbar currently has a "Code Sample" button, but it merely indents. It lacks the extra features of fenced code blocks.

Even better, though more work to implement: along with prompting for a language, the dialog could include a space to type/paste your code. Clicking "OK" would populate the generated code block with that code. This would be an opportunity for additional (optional) features that solve other problems, like fixing the sort of spacing/formatting problems that we commonly see when people copy/paste from an IDE.