The user should be able to define a custom field that has a set of possible values that are dynamically generated. An example would be:

• Versions
• Categories
• Developers
• Other calculated values
• Other values that depend on external databases.

This can be supported by allowing the user to define the possible values for a custom field as a "=functionname" where "enum" + "functionname" is a custom function. The "enum" is added for security reasons. This will allow the Mantis web users to only use custom functions that produce enums, and will not allow them to use other functions that were not intended for this purpose.

An example of a custom function is:

# --------------------

Construct an enumeration for all versions for the current project.
The enumeration will be empty if current project is ALL PROJECTS.
Enumerations format is: "abc|lmn|xyz"
To use this in a custom field type "=versions" in the possible values field.
function custom_function_default_enum_versions() {

$t_versions = version_get_all_rows( helper_get_current_project() );
$t_enum = array();
foreach( $t_versions as $t_version ) {
    $t_enum[] = $t_version['version'];
}

$t_possible_values = implode( '|', $t_enum );

return $t_possible_values;
}

To override custom functions or define new ones, see the following topic in the manual:

http://manual.mantisbt.org/manual.customizing.mantis.custom.functions.php

Since custom functions are implemented in PHP, it is possible to depend on the returned values on current user, current project, or any other criteria.