Sieve Email Filtering: Include Extension

Sieve implementations that implement the "include", "return", "export" and "import" commands described below have an identifier of "include" for use with the capability mechanism. If any of the "include", "return", "export" or "import" commands are used in a script, the "include" capability MUST be listed in the "require" statement in that script. Sieve implementations must track the use of actions in included scripts so that implicit "keep" behavior can be properly determined based on whether any actions have executed in any script. Sieve implementations are allowed to limit the total number of nested included scripts, but MUST provide for a total of at least three levels of nested scripts including the top-level script. An error MUST be generated either when the script is uploaded to the Sieve repository, or when the script is executed, if any nesting limit is exceeded. If such an error is detected whilst processing a Sieve script, an implicit "keep" action MUST be executed to prevent loss of any messages. Sieve implementations MUST ensure that recursive includes are not possible. i.e. if script "A" includes script "B", and script "B" includes script "A" an error MUST be generated either when the script is uploaded to the Sieve repository, or when the script is executed. If such an error is detected whilst processing a Sieve script, an implicit "keep" action MUST be executed to prevent loss of any messages. Sieve implementations MUST handle missing scripts being referenced via an includes in an existing script. An error MUST be generated when a missing included script is discovered during execution. If such an error is detected an implicit "keep" action MUST be executed to prevent loss of any messages. If the Sieve "variables" extension is present, an issue arises with the "scope" of variables defined in scripts that may include each other. For example, if a script defines the variable "${status}" with one particular meaning or usage, and another defines "${status}" with a different meaning, then if one script includes the other there is an issue as to which "${status}" is being referenced. To solve this problem, Sieve implementations MUST follow the scoping rules defined in and support the "import" and "export" commands defined there.

] LOCATION = ":personal" / ":global" ]]> The "include" command includes an optional "location" parameter, and a single string argument representing the name of the script to include in the main script at that point. The "location" parameter defaults to ":personal" if not specified. The "location" has the following meanings: :personal Indicates that the named script is stored in the user's own personal (private) Sieve repository. :global Indicates that the named script is stored in a site-wide Sieve repository, accessible to all users of the Sieve system. CA The included script MUST be a valid Sieve script, including having necessary "require" statements for all optional capabilities used by the script. The scope of a "require" statement in an included script is for that script only, not the including script. e.g. if script "A" includes script "B", and script "B" uses the "fileinto" extension, script "B" must have a "require" statement for "fileinto", irrespective of whether script "A" has one. In addition, if script "A" does not have a "require" statement for "fileinto", "fileinto" cannot be used anywhere in script "A", even after inclusion of script "B". A "stop" command in an included script MUST stop all script processing, including the processing of the scripts that include the current one. The "return" command (described below) stops processing of the current script only, and allows the scripts that include it to continue. Examples: The user has four scripts stored in their personal repository: "default" This is the default active script that includes several others. "always_allow" This script special cases some correspondent email addresses and makes sure any message containing those addresses are always kept. "my_spam_tests" This script does some user-specific spam tests to catch spam messages not caught by the site-wide spam tests. "mailing_lists" This script looks for messages from different mailing lists and files each into a mailbox specific to the mailing list. There is one script stored in the global repository: "spam_tests" This script does some site-wide spam tests which any user at the site can include in their own scripts at a suitable point. The script content is kept up to date by the site administrator. The "include" command may appear anywhere in the script where a control structure is legal. Example:

The "return" command stops processing of the currently included script only and returns processing control to the script which includes it. If used in the main script (i.e. not in an included script), it has the same effect as the "stop" command, including the appropriate "keep" action if no other actions have been executed up to that point.

In order to avoid problems of variables in an included script "overwriting" those from the script that includes it, this specification requires that all variables defined in a script MUST be kept "private" to that script by default - i.e. they are not "visible" to other scripts. This ensures that two script authors cannot inadvertently cause problems by choosing the same name for a variable. However, sometimes there is a need to make a variable defined in one script available to others. This specification defines the new commands "export" and "import" to alter the default behavior of variable scoping to allow variables to be "seen" by other scripts. The "export" command takes a list of variable names defined in a script and makes those available to any script that explicitly wants to use them. The "import" command allows a script to gain access to variables that have been explicitly made available by other scripts. The explicit use of "export and "import", coupled with the default behavior of variables only having local scope, ensures that multiple scripts cannot inadvertently overwrite each others variables.

]]> The "import" command contains a string list argument that defines one or more names of variables exported by other scripts which should be made available to the current script. The "import" command, if present, MUST be used immediately after any "require" commands (at least one of which will be present listing the "include" extension). Multiple "import" commands are allowed. An error occurs if an "import" command appears after a command other than "require" or "import". Use of the "import" command makes the listed variables immediately available for use in the body of the script that uses it. If an "import" command lists a variable that has not been exported by any other script at that point during the Sieve execution process, then an error MUST occur. Example:

]]> The "export" command contains a string list argument that defines one or more names of variables defined in the current script which should be made available to any scripts that run during the current Sieve script execution process. The "export" command, if present, MUST be used immediately after any "require" or "import" commands. Multiple "export" commands are allowed. An error occurs if an "export" command appears after a command other than "require", "import" or "export". An error occurs if an "export" command lists a variable that is listed in an "import" command preceding it in the current script. Example: Example: