Now that the `$localize` translations are `MessageId` based the
compiler must render `MessageId`s in its generated `$localize` code.
This is because the `MessageId` used by the compiler is computed
from information that does not get passed through to the `$localize`
tagged string.
For example, the generated code for the following template
```html
<div id="static" i18n-title="m|d" title="introduction"></div>
```
will contain these localization statements
```ts
if (ngI18nClosureMode) {
/**
* @desc d
* @meaning m
*/
const MSG_EXTERNAL_8809028065680254561$$APP_SPEC_TS_1 = goog.getMsg("introduction");
I18N_1 = MSG_EXTERNAL_8809028065680254561$$APP_SPEC_TS_1;
}
else {
I18N_1 = $localize \`:m|d@@8809028065680254561:introduction\`;
}
```
Since `$localize` is not able to accurately regenerate the source-message
(and so the `MessageId`) from the generated code, it must rely upon the
`MessageId` being provided explicitly in the generated code.
The compiler now prepends all localized messages with a "metadata block"
containing the id (and the meaning and description if defined).
Note that this metadata block will also allow translation file extraction
from the compiled code - rather than relying on the legacy ViewEngine
extraction code. (This will be implemented post-v9).
Although these metadata blocks add to the initial code size, compile-time
inlining will completely remove these strings and so will not impact on
production bundle size.
PR Close#32594
b741a1c3e7