Pre-save transforms (PST) are transformations which are applied to the content before it is even saved. They are implemented in the function preSaveTransform() of the appropriate Content subclass.

Wikitext

For {{ll|Manual:WikitextContent.php|Wikitext content}}, the {{ll|Manual:Parser.php|parser}}’s preSaveTransform() applies the following transformations, in order:

Null characters

Null characters are removed.

Trailing whitespace

Whitespace (according to PHP's rtrim()) at the end of the text is removed.

Line endings

Line endings \r\n as well as \r are normalized to \n.

Substitutions

{{subst: template name| template parameters}}

Signatures

~~~, ~~~~ and ~~~~~ − Note that this order has the nontrivial effect of not allowing template substitutions within a signature.

Pipe trick

[[phabricator:T1|]] becomes [[phabricator:T1|T1]]
[[title (topic)|]] becomes [[title (topic)|title]]

JSON

JsonContent::preSaveTransform() applies the following transformations, in order:

Beautify JSON

standardizes the formatting (“pretty”, i. e. split across lines and indented)

Line endings

Line endings \r\n as well as \r are normalized to \n.