Hi,

here is a proposal for a fix:

// config_defaults_inc.php

/**
 * Bug Linking
 * if a number follows this tag it will create a link to a bug.
 * for a list of tags, use the pipe character '|' as delimiter
 * eg. for # a link would be #45
 * eg. for bug: a link would be bug:98
 * eg. for #|MANTIS- a link would be #45 and/or MANTIS-125
 * @global string $g_bug_link_tag
 */
$g_bug_link_tag = '#';

// string_api.php

function string_process_bug_link( $p_string, ... ) {
    ...
    $t_tag = config_get( 'bug_link_tag' );
    $t_tags = array_map('trim', explode('|', $t_tag)); // **NEW**
    ...
    foreach($t_tags as $tag) { // **NEW**
        $p_string = preg_replace_callback(
            '/(^|[^\w&])' . preg_quote( $tag, '/' ) . '(\d+)\b/', // **MODIFIED**
            $s_bug_link_callback[$p_include_anchor][$p_detail_info][$p_fqdn],
            $p_string
        );
    } // **NEW**
}

// config_inc.php

$g_bug_link_tag = '#|MANTIS-';

it seems like the parameters does not accept these characters '|' and '-' even though it seems to be parsed as a regular expression

This is because we use preg_quote() to ensure that whatever character(s) are used in $g_bug_link_tag are taken literally and not as part of the regex.

To achieve the desired feature, I think it would be better to define the config for multiple tags as an array, instead of splitting a string by | (what if someone wants to use that as a delimiter ?). Then you can avoid the explode statement, and build the regexp with something along the lines of $t_bug_pattern = implode( '|', array_map( 'preg_quote', $t_tag ) ); and use the same code as before instead of introducing a foreach loop.

EDIT: probably a callback function is needed for array_map, so preg_quote can be called with '/' as second parameter.

That being said, I'm a bit concerned about performance. PCRE and callback functions are slow, so pages with many bug links could have degraded response times (but I did not actually benchmark this).

Finally, for consistency I think the same change should be applied to bugnote tags.

Let me know your thoughts.

Damien your solution seems reasonably good to me, though I don’t have anything to say about perf issues (But the current implementation already uses pcre and callbacks as it seems).

I thought about proposing a change of that prop into an array as well, but that would mean a breaking change! Or introducing a new config prop but it would then mean deal with @deprecated config otherwise.

In any case, I don’t really mind the final solution to choose :-)
For now I modified manually the core files of Mantis in my installation as there is no custom function neither available to change that behaviour.

About performance: on second thoughts, the preprocessing overhead necessary to handle multiple tags based on an array (whether it's based on a foreach loop or a more complex regex) will most likely be negligible compared to the cost of having preg_replace_callback() execute the closure for each pattern match. I'll try to run some benchmark as time allows, but

I thought about proposing a change of that prop into an array as well, but that would mean a breaking change! Or introducing a new config prop but it would then mean deal with @deprecated config otherwise.

I don't think deprecating the config is necessary - backwards-compatibility can easily be achieved with if( is_array( $t_tag ) { ... }