Cloning

Report definitions get elaborate, and the usual way to build the next one is to start from the last one. Table and Report therefore know how to copy themselves.

New in version 0.4.0

From the admin

Open a Table or a Report change form and press Clone in the object-tools bar (next to History). You land on the change form of the fresh copy, an entry is written to the admin history, and a success message names the new object.

The button posts to <pk>/clone/ under the model's admin URLs. It is a POST behind a CSRF token on purpose -- a GET link would let a foreign page create objects through an <img src="...">. Permissions: add on the model plus view on the source object (change on the source is deliberately not required, matching the built-in "Save as new").

The mixin providing all of this is flexible_reports.admin.CloneAdminMixin; it works with both the stock admin and grappelli.

From code

new_table = table.clone()
new_report = report.clone()

Both run in a transaction and return the newly created object. Neither modifies the source: after the call table.pk is unchanged and a later table.save() still updates the original.

What is copied

Table.clone()

The table itself, all of its Column rows, and all of its ColumnOrder rows -- with both foreign keys repointed, so the copy sorts by its own columns. Reports using the original table are left alone.

Report.clone()

The report itself and all of its ReportElement rows. The copy is shallow: cloned elements point at the very same Table and Datasource objects as the original. If you want an independent table, clone the table separately and repoint the element.

Element slugs are kept as they are. They cannot collide (uniqueness is per report) and the copied layout template addresses elements by slug, so renaming them would break it.

Datasource has no clone(). Duplicating one is a matter of copying its query into a new object.

Naming

The copy gets a (copy) suffix, and cloning a copy counts up rather than nesting:

"Books"            ->  "Books (copy)"
"Books (copy)"     ->  "Books (copy 2)"
"Books (copy 2)"   ->  "Books (copy 3)"

Slugs follow the same shape (library-report → library-report-copy), except that the stem is truncated to make room for the suffix, so a maximum length slug does not lose its suffix and collide with the source again.

The word "copy" is translatable (msgid "copy"), resolved against the language active at the time of the call: a Polish admin produces "Books (kopia)". If the translation slugifies to nothing (a language in a non-latin script), slugs fall back to the literal copy.

The helpers live in flexible_reports.models.cloning and are reusable: copy_word, strip_copy_suffix, make_copy_label, next_free_label, strip_slug_copy_suffix, make_copy_slug, next_free_slug.

Note

Finding the first free name is a scan, so two clones started at the very same moment can compute the same name. None of the fields involved is unique, so nothing breaks -- you simply end up with two identically named objects. Cloning is a manual administrative action, so this is accepted rather than locked against.