[IMP] base: remove t-cache directive from ir.qweb

closes #14639

See: odoo/odoo#224487
See: odoo/enterprise#93321
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

Author: Gorash

content/developer/reference/frontend/qweb.rst

@@ -445,228 +445,6 @@ Debugging
     The behaviour can be configured via :envvar:`PYTHONBREAKPOINT` or
     :func:`sys.breakpointhook`.
 
-Rendering cache:
-----------------
-
-``t-cache="key_cache"`` tags part of template to be cached at rendering time.
-Every sub-directives will be call only during the first rendering. It means
-that the sql queries excecuted during the rendering of those sub-directives
-are also done only once.
-
-``t-nocache="documentation"`` tags part of template to be render every time.
-The content can only use the root values.
-
-Why and when to use ``t-cache``?
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-This directive is used to speed up the rendering, by caching parts of the final
-document, which may save queries to the database.  However, it should be used
-sparingly, as ``t-cache`` will inevitably complicate templates (and their
-understanding of ``t-set`` for example).
-
-However, in order to actually save database queries, it might be necessary to
-render the template with values that are evaluated lazily.  If those lazy
-values are used in a cached part, they will not be evaluated if the part is
-available in cache.
-
-The ``t-cache`` directive is useful for template parts using values that depend
-on a limited amount of data.  We recommend to analyze the rendering of the
-template with the profiler (by activating the "**Add qweb directive context**"
-option).  Passing lazy values to the rendering in controllers allow you to
-display the directives using these values and triggering the queries.
-
-A concern of using such a cache are making it available to different users
-(different users should render the cached parts the same way).  Another
-potential issue is to invalidate its entries when necessary.  For the latter,
-the **key expression** should be chosen wisely.  Using the ``write_date`` of a
-recordset can make a cache key out-of-date without having to discard it
-explicitly from the cache, for instance.
-
-One should also pay attention to the fact that the values in ``t-cache`` parts
-are scoped. This implies that if there are ``t-set`` directives in this part of
-the template, the rendering of what comes after it could be different than if
-there was no ``t-cache`` directive.
-
-What if there is a ``t-cache`` inside a ``t-cache``?
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The parts are cached. Each containing only the string corresponding to its
-rendering. Thus, the ``t-cache`` inside will probably be read less often, its
-cache key will not necessarily be used. If this must be the case, then you may
-need to add a ``t-nocache`` (on the same node or a parent).
-
-What is ``t-nocache`` used for?
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-If you want to cache part of a template with ``t-cache`` but a small piece must
-remain dynamic and be evaluated at cache times. However, the part in
-``t-nocache`` will not have access to the ``t-set`` value of the template. Only
-the values ​​provided by the controller are accessible there.
-For example, the menu is cached because it's the same all the time and takes
-time to render (using the performance devtools with the qweb context lets you
-investigate). However, in the menu, we want the ecommerce cart to be always up
-to date. So there is a ``t-nocache`` to keep this part dynamic.
-
-The base of ``t-cache``
-~~~~~~~~~~~~~~~~~~~~~~~
-
-The ``t-cache`` directive allows you to store the rendered result of a template.
-The **key expression** (eg 42: ``t-cache="42"``) will be evaluated as a python
-expression. This will be used to generate the **cache key**. So there can be
-different **cache values** (cached render part) for the same template part. If
-the **key expression** is a tuple or a list, it will be searched when generating
-the **cache key**. If one or more recordsets are returned by the **key
-expression**, then the model, ids and their corresponding write_date will be
-used to generate the **cache key**. Special case: If the **key expression**
-returns a Falsy value, then the content will not be cached.
-
-Example::
-
-    <div t-cache="record,bool(condition)">
-        <span t-if="condition" t-field="record.partner_id.name">
-        <span t-else="" t-field="record.partner_id" t-options-widget="contact">
-    </div>
-
-In this case, there may be values ​​(string) in the cache corresponding to each
-record already returned with a true condition, as well as for the false
-condition. And if a module modifies the record, the write_date being modified,
-the cached value is discarded.
-
-``t-cache`` and scoped values (``t-set``, ``t-foreach``...)
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Values in ``t-cache`` are scoped, this involves a change in behavior between
-having or not having ``t-cache`` on one of the parent nodes. Don't forget to
-take into account that Odoo uses a lot of templates, ``t-call`` and view
-inheritance. Adding a ``t-cache`` can therefore modify the rendering of a
-template that you do not see when editing.
-(``t-foreach`` it's like a ``t-set`` for each iteration)
-
-Example::
-
-        <div>
-            <t t-set="a" t-value="1"/>
-            <inside>
-                <t t-set="a" t-value="2"/>
-                <t t-out="a"/>
-            </inside>
-            <outside t-out="a"/>
-
-            <t t-set="b" t-value="1"/>
-            <inside t-cache="True">
-                <t t-set="b" t-value="2"/>
-                <t t-out="b"/>
-            </inside>
-            <outside t-out="b"/>
-        </div>
-
-Will render::
-
-        <div>
-            <inside>2</inside>
-            <outside>2</inside>
-
-            <inside>2</inside>
-            <outside>1</inside>
-        </div>
-
-
-The base of ``t-nocache``
-~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The template part contained in a node with a ``t-nocache`` attribute is not
-cached. This content is therefore **dynamic** and is rendered systematically.
-However the available values are those provided by the controller (when
-calling the ``_render`` method).
-
-Example::
-
-        <section>
-            <article t-cache="record">
-                <title><t t-out="record.name"/> <i t-nocache="">(views: <t t-out="counter"/>)</i></titlle>
-                <content t-out="record.description"/>
-            </article>
-        </section>
-
-Will render (counter = 1)::
-
-        <section>
-            <article>
-                <title>The record name <i>(views: 1)</i></titlle>
-                <content>Record description</content>
-            </article>
-        </section>
-
-Here the ``<i>`` tag that contains the container will always be rendered. While
-the rest is as a single string in the cache.
-
-``t-nocache`` and scoped root values (``t-set``, ``t-foreach``...)
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The contents of the ``t-nocache`` tag can be used for documentation and to
-explain why the directive is added.
-The values are scoped into ``t-nocache``, these values are root values only
-(values provided by the controller and/or when calling the ``_render`` method
-of ``ir.qweb``). ``t-set`` can be done in the template part, but will not be
-available elsewhere.
-
-Example::
-
-        <section>
-            <t t-set="counter" t-value="counter * 10"/>
-            <header t-nocache="">
-                <t t-set="counter" t-value="counter + 5"/>
-                (views: <t t-out="counter"/>)
-            </header>
-            <article t-cache="record">
-                <title><t t-out="record.name"/> <i t-nocache="">(views: <t t-out="counter"/>)</i></titlle>
-                <content t-out="record.description"/>
-            </article>
-            <footer>(views: <t t-out="counter"/>)</footer>
-        </section>
-
-Will render (counter = 1)::
-
-        <section>
-            <header>
-                (views: 6)
-            </header>
-            <article>
-                <title>The record name <i>(views: 1)</i></titlle>
-                <content>Record description</content>
-            </article>
-            <footer>(views: 10)</footer>
-        </section>
-
-Here the ``<i>`` tag that contains the container will always be rendered. While
-the rest is as a single string in the cache. The counter is not updated by the
-``t-set`` out of the ``t-nocache``
-
-``t-nocache-*`` add some primitive values in the cache
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-In order to be able to use values generated in the template, it is possible to
-cache them. The directive is used as ``t-nocache-*="expr"`` where ``*`` is the
-name of the chosen value and ``expr`` the python expression so the result will
-be cached. The cached value must be primitive type.
-
-Example::
-
-        <section t-cache="records">
-            <article t-foreach="records" t-as="record">
-                <header>
-                    <title t-field="record.get_method_title()"/>
-                </header>
-                <footer t-nocache="This part has a dynamic counter and must be rendered all the time."
-                        t-nocache-cached_value="record.get_base_counter()">
-                    <span t-out="counter + cached_value"/>
-                </footer>
-            </article>
-        </section>
-
-The value ``cached_value`` is cached with the cached template part of
-``t-cache="records"`` and add to the scoped root values each time.
-
 Helpers
 -------