I can make a simple translation string like this:
<?php _e('Hello world','text-domain'); ?>
But how to make a translation string if there is a markup in it? For example this:
<?php _e('<span>Hello</span> world','text-domain'); ?>
Is the above correct?
Localizing a string with html markup inside the string can be a very opinionated story as you can see from one of my questions when I started out.
I would not say you are right, neither would I say that you are wrong, but I would say that your method is not prefered.
If you have a look at I18n for WordPress Developers, you'll see that you should use printf() and placeholders when you have variables inside a string, well, the same applies for markup. My emphasis, you should never translate html tags, always use html tags outside of your string.
An example, with what I've just covered, should render a string like this
printf(__( '%s Hello %s world', 'textdomain' ), '<span>', '</span>' );
It works.
echo '<span>' . esc_html__( 'Hello world', 'textdomain' ) . '</span>';
