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[IMP] compiler: add support for t-for directive

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This commit adds support for the `t-for` whose syntax and usage is
similar to the syntax of the for..of loop in JS (and in fact it compiles
to a for..of loop). This looping construct supports looping on arbitrary
iterables and destructuring assignments, which would be difficult to
support in a backward compatible manner on the existing t-foreach
directive.
This commit is contained in:
Samuel Degueldre
2023-07-20 13:17:57 +02:00
parent 9d99f8936b
commit fb97955729
10 changed files with 2172 additions and 23 deletions
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doc/reference/templates.md
+31 -20
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@@ -61,7 +61,7 @@ For reference, here is a list of all standard QWeb directives:
| `t-out` | [Outputting value, possibly without escaping](#outputting-data) |
| `t-set`, `t-value` | [Setting variables](#setting-variables) |
| `t-if`, `t-elif`, `t-else`, | [conditionally rendering](#conditionals) |
| `t-foreach`, `t-as` | [Loops](#loops) |
| `t-for/t-of`, `t-foreach/t-as` | [Loops](#loops) |
| `t-att`, `t-attf-*`, `t-att-*` | [Dynamic attributes](#dynamic-attributes) |
| `t-call` | [Rendering sub templates](#sub-templates) |
| `t-debug`, `t-log` | [Debugging](#debugging) |
@@ -372,6 +372,24 @@ Like conditions, `t-foreach` applies to the element bearing the directive’s at
is equivalent to the previous example.
Owl also has another pair of directives that can be used for looping that allow
destructuring the contents of the loop item: `t-for` and `t-of`, which behaves
much like `for..of` in javascript:
```xml
<t t-for="[left, right]" t-of="[['a', 1], ['b', 2], ['c', 3]]" t-key="left">
<p><t t-esc="left"/>: <t t-esc="right"/></p>
</t>
```
will be rendered as:
```xml
<p>a: 1</p>
<p>b: 2</p>
<p>c: 3</p>
```
An important difference should be made with the usual `QWeb` behaviour: Owl
requires the presence of a `t-key` directive, to be able to properly reconcile
renderings.
@@ -380,8 +398,9 @@ renderings.
and maps, it will expose the key of the current iteration as the contents of the
`t-as`, and the corresponding value with the same name and the suffix `_value`.
In addition to the name passed via t-as, `t-foreach` provides a few other useful
variables (note: `$as` will be replaced with the name passed to `t-as`):
In addition to the name passed via t-as, `t-foreach` (but not `t-for`) provides
a few other useful variables (note: `$as` will be replaced with the name passed
to `t-as`):
- `$as_value`: the current iteration value, identical to `$as` for arrays and
other iterables, but for objects and maps, it provides the value (where `$as`
@@ -393,10 +412,9 @@ variables (note: `$as` will be replaced with the name passed to `t-as`):
(equivalent to `$as_index + 1 == $as_size`), requires the iteratee’s size be
available
These extra variables provided and all new variables created into the `t-foreach`
are only available in the scope of the `t-foreach`. If the variable exists outside
the context of the `t-foreach`, the value is copied at the end of the foreach
into the global context.
These variables and all new variables created inside`t-foreach` and `t-for` are
only available inside of the loop. If a variable existed outside the context of
the loop, the assignment will affect the outer variable.
```xml
<t t-set="existing_variable" t-value="false"/>
@@ -408,7 +426,7 @@ into the global context.
<!-- existing_variable and new_variable now true -->
</p>
<!-- existing_variable always true -->
<!-- existing_variable still true -->
<!-- new_variable undefined -->
```
@@ -471,18 +489,11 @@ are all equivalent:
</t>
```
If there is no `t-key` directive, Owl will use the index as a default key.
Note: the `t-foreach` directive only accepts arrays (lists) or objects. It does
not work with other iterables, such as `Set`. However, it is only a matter of
using the `...` javascript operator. For example:
```xml
<t t-foreach="[...items]" t-as="item">...</t>
```
The `...` operator will convert the `Set` (or any other iterables) into a list,
which will work with Owl QWeb.
The `t-key` directive is mandatory, and as mentioned should represent the object's
identity. You may be tempted to use the loop index as a key, but keep in mind that
this is only correct if items in the loop cannot be reordered. If this is not the
case, using the index as the key can lead to bugs that are difficult to find, so
use the index as the key only if you are sure items cannot be reordered.
### Sub Templates