QWeb Templates¶
QWeb is the primary templating engine used by Odoo2. It is an XML templating engine1 and used mostly to generate HTML fragments and pages.
Template directives are specified as XML attributes prefixed with t-
,
for instance t-if
for Conditionals, with elements
and other attributes being rendered directly.
To avoid element rendering, a placeholder element <t>
is also available,
which executes its directive but doesn’t generate any output in and of
itself:
<t t-if="condition">
<p>Test</p>
</t>
will result in:
<p>Test</p>
if condition
is true, but:
<div t-if="condition">
<p>Test</p>
</div>
will result in:
<div>
<p>Test</p>
</div>
Data output¶
QWeb’s output directive out
will automatically HTML-escape its input,
limiting XSS risks when displaying user-provided content.
out
takes an expression, evaluates it and injects the result in the document:
<p><t t-out="value"/></p>
rendered with the value value
set to 42
yields:
<p>42</p>
See Advanced Output for more advanced topics (e.g. injecting raw HTML, etc…).
Conditionals¶
QWeb has a conditional directive if
, which evaluates an expression given
as attribute value:
<div>
<t t-if="condition">
<p>ok</p>
</t>
</div>
The element is rendered if the condition is true:
<div>
<p>ok</p>
</div>
but if the condition is false it is removed from the result:
<div>
</div>
The conditional rendering applies to the bearer of the directive, which does
not have to be <t>
:
<div>
<p t-if="condition">ok</p>
</div>
will give the same results as the previous example.
Extra conditional branching directives t-elif
and t-else
are also
available:
<div>
<p t-if="user.birthday == today()">Happy birthday!</p>
<p t-elif="user.login == 'root'">Welcome master!</p>
<p t-else="">Welcome!</p>
</div>
Loops¶
QWeb has an iteration directive foreach
which take an expression returning
the collection to iterate on, and a second parameter t-as
providing the
name to use for the “current item” of the iteration:
<t t-foreach="[1, 2, 3]" t-as="i">
<p><t t-out="i"/></p>
</t>
will be rendered as:
<p>1</p>
<p>2</p>
<p>3</p>
Like conditions, foreach
applies to the element bearing the directive’s
attribute, and
<p t-foreach="[1, 2, 3]" t-as="i">
<t t-out="i"/>
</p>
is equivalent to the previous example.
foreach
can iterate on an array (the current item will be the current
value) or a mapping (the current item will be the current key). Iterating on an
integer (equivalent to iterating on an array between 0 inclusive and the
provided integer exclusive) is still supported but deprecated.
In addition to the name passed via t-as
, foreach
provides a few other
variables for various data points:
Warning
$as
will be replaced by the name passed to t-as
$as_all
(deprecated)the object being iterated over
Note
This variable is only available on JavaScript QWeb, not Python.
$as_value
the current iteration value, identical to
$as
for lists and integers, but for mappings it provides the value (where$as
provides the key)$as_index
the current iteration index (the first item of the iteration has index 0)
$as_size
the size of the collection if it is available
$as_first
whether the current item is the first of the iteration (equivalent to
$as_index == 0
)$as_last
whether the current item is the last of the iteration (equivalent to
$as_index + 1 == $as_size
), requires the iteratee’s size be available$as_parity
(deprecated)either
"even"
or"odd"
, the parity of the current iteration round$as_even
(deprecated)a boolean flag indicating that the current iteration round is on an even index
$as_odd
(deprecated)a boolean flag indicating that the current iteration round is on an odd index
These extra variables provided and all new variables created into the
foreach
are only available in the scope of the foreach
. If the
variable exists outside the context of the foreach
, the value is copied
at the end of the foreach into the global context.
<t t-set="existing_variable" t-value="False"/>
<!-- existing_variable now False -->
<p t-foreach="[1, 2, 3]" t-as="i">
<t t-set="existing_variable" t-value="True"/>
<t t-set="new_variable" t-value="True"/>
<!-- existing_variable and new_variable now True -->
</p>
<!-- existing_variable always True -->
<!-- new_variable undefined -->
attributes¶
QWeb can compute attributes on-the-fly and set the result of the computation
on the output node. This is done via the t-att
(attribute) directive which
exists in 3 different forms:
t-att-$name
an attribute called
$name
is created, the attribute value is evaluated and the result is set as the attribute’s value:<div t-att-a="42"/>
will be rendered as:
<div a="42"></div>
t-attf-$name
same as previous, but the parameter is a format string instead of just an expression, often useful to mix literal and non-literal string (e.g. classes):
<t t-foreach="[1, 2, 3]" t-as="item"> <li t-attf-class="row {{ (item_index % 2 === 0) ? 'even' : 'odd' }}"> <t t-out="item"/> </li> </t>
will be rendered as:
<li class="row even">1</li> <li class="row odd">2</li> <li class="row even">3</li>
Tip
There are two equivalent syntaxes for format strings:
"plain_text {{code}}"
(aka jinja-style) and"plain_text #{code}"
(aka ruby-style).t-att=mapping
if the parameter is a mapping, each (key, value) pair generates a new attribute and its value:
<div t-att="{'a': 1, 'b': 2}"/>
will be rendered as:
<div a="1" b="2"></div>
t-att=pair
if the parameter is a pair (tuple or array of 2 element), the first item of the pair is the name of the attribute and the second item is the value:
<div t-att="['a', 'b']"/>
will be rendered as:
<div a="b"></div>
setting variables¶
QWeb allows creating variables from within the template, to memoize a computation (to use it multiple times), give a piece of data a clearer name, …
This is done via the set
directive, which takes the name of the variable
to create. The value to set can be provided in two ways:
a
t-value
attribute containing an expression, and the result of its evaluation will be set:<t t-set="foo" t-value="2 + 1"/> <t t-out="foo"/>
will print
3
if there is no
t-value
attribute, the node’s body is rendered and set as the variable’s value:<t t-set="foo"> <li>ok</li> </t> <t t-out="foo"/>
calling sub-templates¶
QWeb templates can be used for top-level rendering, but they can also be used
from within another template (to avoid duplication or give names to parts of
templates) using the t-call
directive:
<t t-call="other-template"/>
This calls the named template with the execution context of the parent, if
other_template
is defined as:
<p><t t-value="var"/></p>
the call above will be rendered as <p/>
(no content), but:
<t t-set="var" t-value="1"/>
<t t-call="other-template"/>
will be rendered as <p>1</p>
.
However, this has the problem of being visible from outside the t-call
.
Alternatively, content set in the body of the call
directive will be
evaluated before calling the sub-template, and can alter a local context:
<t t-call="other-template">
<t t-set="var" t-value="1"/>
</t>
<!-- "var" does not exist here -->
The body of the call
directive can be arbitrarily complex (not just
set
directives), and its rendered form will be available within the called
template as a magical 0
variable:
<div>
This template was called with content:
<t t-out="0"/>
</div>
being called thus:
<t t-call="other-template">
<em>content</em>
</t>
will result in:
<div>
This template was called with content:
<em>content</em>
</div>
Advanced Output¶
By default, out
should HTML-escape content which needs to be escaped,
protecting the system against XSS
Content which does not need to be escaped will instead be injected as-is in the document, and may become part of the document’s actual markup.
The only cross-platform “safe” content is the output of
t-call or a t-set
used with a “body” (as opposed to t-value
or t-valuef
).
Python¶
Usually you should not have to care too much: APIs for which it makes sense should generate “safe” content automatically, and things should work transparently.
For the cases where things need to be clearer though the following APIs output safe content which will by default not be (re-)escaped when injected into templates:
html_escape()
andmarkupsafe.escape()
(they are aliases, and have no risk of double-escaping).html_sanitize()
.markupsafe.Markup
.Warning
markupsafe.Markup
is an unsafe API, it’s an assertion that you want the content to be markup-safe but necessarily can not check that, it should be used with care.to_text()
does not mark the content as safe, but will not strip that information from safe content.
forcing double-escaping¶
If content is marked as safe but for some reason needs to be escaped anyway
(e.g. printing the markup of an HTML fields), it can just be converted back
to a normal string to “strip” the safety flag e.g. str(content)
in Python and
String(content)
in Javascript.
Note
Because Markup
is a much richer type than
Markup()
, some operations will strip the safety information from
a Markup()
but not a Markup
e.g. string
concatenation ('' + content
) in Python will result in a
Markup
with the other operand having been properly
escaped, while in Javascript will yield a String()
where the
other operand was not escaped before the concatenation.
Deprecated output directives¶
esc
An alias for
out
, would originally HTML-escape its input. Not yet formally deprecated as the only difference betweenout
andesc
is that the latter is a bit unclear / incorrect.raw
A version of
out
which never escapes its content. Content is emitted as-is, whether it’s safe or not.Deprecated since version 15.0: Use
out
with amarkupsafe.Markup
value instead.t-raw
was deprecated because as the code producting the content evolves it can be hard to track that it’s going to be used for markup, leading to more complicated reviews and more dangerous lapses.
Python¶
Exclusive directives¶
Asset bundles¶
“smart records” fields formatting¶
The t-field
directive can only be used when performing field access
(a.b
) on a “smart” record (result of the browse
method). It is able
to automatically format based on field type, and is integrated in the
website’s rich text editing.
t-options
can be used to customize fields, the most common option
is widget
, other options are field- or widget-dependent.
Debugging¶
t-debug
with an empty value, invokes the
breakpoint()
builtin function, which usually invokes a debugger (pdb
by default).The behaviour can be configured via
PYTHONBREAKPOINT
orsys.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¶
Request-based¶
Most Python-side uses of QWeb are in controllers (and during HTTP requests),
in which case templates stored in the database (as
views) can be trivially rendered by calling
odoo.http.HttpRequest.render()
:
response = http.request.render('my-template', {
'context_value': 42
})
This automatically creates a Response
object which can
be returned from the controller (or further customized to suit).
View-based¶
At a deeper level than the previous helper is the _render
method on
ir.qweb
(use the datable) and the public module method render
(don’t use the database):
- _render(id[, values])¶
Renders a QWeb view/template by database id or external id. Templates are automatically loaded from
ir.qweb
records._prepare_environment
method sets up a number of default values in the rendering context. Thehttp_routing
andwebsite
addons, also default values they need. You can useminimal_qcontext=False
option to avoid this default value like the public methodrender
:request
the current
Request
object, if anydebug
whether the current request (if any) is in
debug
modequote_plus
url-encoding utility function
json
the corresponding standard library module
time
the corresponding standard library module
datetime
the corresponding standard library module
- relativedelta
see module
keep_query
the
keep_query
helper function
- Parameters
values – context values to pass to QWeb for rendering
engine (str) – name of the Odoo model to use for rendering, can be used to expand or customize QWeb locally (by creating a “new” qweb based on
ir.qweb
with alterations)
- render(template_name, values, load, **options)¶
load(ref)()
returns etree object, ref
Javascript¶
Exclusive directives¶
Defining templates¶
The t-name
directive can only be placed at the top-level of a template
file (direct children to the document root):
<templates>
<t t-name="template-name">
<!-- template code -->
</t>
</templates>
It takes no other parameter, but can be used with a <t>
element or any
other. With a <t>
element, the <t>
should have a single child.
The template name is an arbitrary string, although when multiple templates are related (e.g. called sub-templates) it is customary to use dot-separated names to indicate hierarchical relationships.
Template inheritance¶
- Template inheritance is used to either:
Alter existing templates in-place, e.g. to add information to templates
- created by other modules.
Create a new template from a given parent template
- Template inheritance is performed via the use of two directives:
t-inherit
which is the name of the template to inherit from,t-inherit-mode
which is the behaviour of the inheritance: it can either be set toprimary
to create a new child template from the parented one or toextension
to alter the parent template in place.
An optional t-name
directive can also be specified. It will be the name of
the newly created template if used in primary mode, else it will be added as a
comment on the transformed template to help retrace inheritances.
For the inheritance itself, the changes are done using xpaths directives. See the XPATH documentation for the complete set of available instructions.
Primary inheritance (child template):
<t t-name="child.template" t-inherit="base.template" t-inherit-mode="primary">
<xpath expr="//ul" position="inside">
<li>new element</li>
</xpath>
</t>
Extension inheritance (in-place transformation):
<t t-inherit="base.template" t-inherit-mode="extension">
<xpath expr="//tr[1]" position="after">
<tr><td>new cell</td></tr>
</xpath>
</t>
Old inheritance mechanism (deprecated)¶
Template inheritance is performed via the t-extend
directive which takes
the name of the template to alter as parameter.
The directive t-extend
will act as a primary inheritance when combined with
t-name
and as an extension one when used alone.
In both cases the alteration is then performed with any number of t-jquery
sub-directives:
<t t-extend="base.template">
<t t-jquery="ul" t-operation="append">
<li>new element</li>
</t>
</t>
The t-jquery
directives takes a CSS selector. This selector is used
on the extended template to select context nodes to which the specified
t-operation
is applied:
append
the node’s body is appended at the end of the context node (after the context node’s last child)
prepend
the node’s body is prepended to the context node (inserted before the context node’s first child)
before
the node’s body is inserted right before the context node
after
the node’s body is inserted right after the context node
inner
the node’s body replaces the context node’s children
replace
the node’s body is used to replace the context node itself
attributes
the nodes’s body should be any number of
attribute
elements, each with aname
attribute and some textual content, the named attribute of the context node will be set to the specified value (either replaced if it already existed or added if not)- No operation
if no
t-operation
is specified, the template body is interpreted as javascript code and executed with the context node asthis
Warning
while much more powerful than other operations, this mode is also much harder to debug and maintain, it is recommended to avoid it
debugging¶
The javascript QWeb implementation provides a few debugging hooks:
t-log
takes an expression parameter, evaluates the expression during rendering and logs its result with
console.log
:<t t-set="foo" t-value="42"/> <t t-log="foo"/>
will print
42
to the consolet-debug
triggers a debugger breakpoint during template rendering:
<t t-if="a_test"> <t t-debug=""/> </t>
will stop execution if debugging is active (exact condition depend on the browser and its development tools)
t-js
the node’s body is javascript code executed during template rendering. Takes a
context
parameter, which is the name under which the rendering context will be available in thet-js
’s body:<t t-set="foo" t-value="42"/> <t t-js="ctx"> console.log("Foo is", ctx.foo); </t>
Helpers¶
- core.qweb¶
(core is the
web.core
module) An instance ofQWeb2.Engine()
with all module-defined template files loaded, and references to standard helper objects_
(underscore),_t
(translation function) and JSON.core.qweb.render
can be used to easily render basic module templates
API¶
- class QWeb2.Engine()¶
The QWeb “renderer”, handles most of QWeb’s logic (loading, parsing, compiling and rendering templates).
Odoo Web instantiates one for the user in the core module, and exports it to
core.qweb
. It also loads all the template files of the various modules into that QWeb instance.A
QWeb2.Engine()
also serves as a “template namespace”.- QWeb2.Engine.QWeb2.Engine.render(template[, context])¶
Renders a previously loaded template to a String, using
context
(if provided) to find the variables accessed during template rendering (e.g. strings to display).- Arguments
template (
String()
) – the name of the template to rendercontext (
Object()
) – the basic namespace to use for template rendering
- Returns
String
The engine exposes an other method which may be useful in some cases (e.g. if you need a separate template namespace with, in Odoo Web, Kanban views get their own
QWeb2.Engine()
instance so their templates don’t collide with more general “module” templates):- QWeb2.Engine.QWeb2.Engine.add_template(templates)¶
Loads a template file (a collection of templates) in the QWeb instance. The templates can be specified as:
- An XML string
QWeb will attempt to parse it to an XML document then load it.
- A URL
QWeb will attempt to download the URL content, then load the resulting XML string.
- A
Document
orNode
QWeb will traverse the first level of the document (the child nodes of the provided root) and load any named template or template override.
A
QWeb2.Engine()
also exposes various attributes for behavior customization:- QWeb2.Engine.QWeb2.Engine.prefix¶
Prefix used to recognize directives during parsing. A string. By default,
t
.
- QWeb2.Engine.QWeb2.Engine.debug¶
Boolean flag putting the engine in “debug mode”. Normally, QWeb intercepts any error raised during template execution. In debug mode, it leaves all exceptions go through without intercepting them.
- QWeb2.Engine.QWeb2.Engine.jQuery¶
The jQuery instance used during template inheritance processing. Defaults to
window.jQuery
.
- QWeb2.Engine.QWeb2.Engine.preprocess_node¶
A
Function
. If present, called before compiling each DOM node to template code. In Odoo Web, this is used to automatically translate text content and some attributes in templates. Defaults tonull
.