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Dylan Hunn
f600f0fb27
Consider the following very quirky Angular template, which has both an i18n attribute binding and a property binding to `in`:
```
<cmp [in]="foo" in="bar" i18n-in />
```
What would you expect the above template to do? `TemplateDefinitionBuilder` will emit the following Ivy instructions:
```
// Element constant attributes
consts: () => {
__i18nMsg__('bar', [], {}, {})
return [["in", i18n_0, __AttributeMarker.I18n__, "in"]];
}
// ...
function MyComponent_Template(rf, ctx) {
if (rf & 1) {
// Create mode
i0.ɵɵelement(0, "cmp", 0);
}
}
```
This makes some sense -- we create a single element, and attach an i18n message to the `in` attribute. But is this actually correct? Notice that the property binding is completely missing!
Indeed, Template Pipeline actually produces this code:
```
// Element constant attributes
consts: () => {
__i18nMsg__('bar', [], {}, {})
return [["in", i18n_0, __AttributeMarker.I18n__, "in"]];
}
// ...
function MyComponent_Template(rf, ctx) {
if (rf & 1) {
// Create mode
i0.ɵɵelement(0, "cmp", 0);
} else if (rf & 2) {
// Update mode
i0.ɵɵproperty("in", ctx.foo);
}
}
```
Aha! There's the property binding! Arguably, this is a bug in `TemplateDefinitionBuilder`, but after some discussion on Slack, we have decided to ban this practice in a future Angular version.
For now, we allow Template Pipeline to have slightly different output, but print an error to warn the user of the issue.
PR Close #54063