Two-way bindings are meant to represent a property binding to an input and an event binding to an output, e.g. `[(ngModel)]="foo"` represents `[ngModel]="foo" (ngModelChange)="foo = $event"`. Previously due to a quirk in the template parser, we accidentally supported unassignable expressions in two-way bindings.
In #54154 the quirk was fixed, but we kept support or some common expression because of internal usages. Now the internal usages have been cleaned up so the backwards-compatibility code can be deleted.
Externally a migration was added in #54630 that will automatically fix any places that depended on the old behavior.
BREAKING CHANGE:
Angular only supports writable expressions inside of two-way bindings.
PR Close#55342
Based on some internal feedback, these changes add validations to prevent cases where the `@for` loop variable name is the same as one of the built-in context variables, or when one of the context variables is aliased to the same name as the item.
PR Close#55045
Currently when aliasing a `for` loop variable with `let`, we replace the variable's old name with the new one. Since users have found this to be confusing, these changes switch to a model where the variable is available both under the original name and the new one.
Fixes#52528.
PR Close#54942
`TemplateDefinitionBuilder` is the legacy template compiler, and was replaced by Template Pipeline as the default in v17.3.
This PR attempts to delete `TemplateDefinitionBuilder`, `ExpressionConverter`, and various helpers (i18n context, style builder, property visitors, etc).
Consider this a first pass: a lot of code has not yet been deleted (e.g. old TDB-specific test cases), and I'm sure I have missed additional helper code.
PR Close#54757
In one of the earlier commits, the logic that appends `=$event` before parsing two-way bindings was removed and some validation was added to prevent unassignable expressions from being used. This ended up being problematic, because previously the parser was incorrectly allowing some invalid expressions which users came to depend on. For example, it transformed `[(value)]="a && a.b"` to `a && (a.b = $event)`.
These changes add some special cases for the common breakages that came up during the TGP.
PR Close#54154
Currently the listener side two-way listeners are parsed by appending `=$event` to the raw expression. This is problematic, because:
1. It can interfere with other expressions (see #37809).
2. It can lead to confusing error messages because users will see code that they didn't write.
3. It doesn't allow us to further manipulate the expression.
These changes remove the logic that appends `=$event` to resolve the issue. There's also some new logic that checks the expression after it has been parsed to ensure that the result is an assignable expression.
Subsequent commits will update the code that emits the expression to add back the `$event` assignment where it's needed.
PR Close#54154
During the template parsing stage two-way bindings are split up into a property and event binding. All the downstream code treats these binding the same as their one-way equivalents. For some future work we'll have to distinguish between the two so these changes update the `BoundElementProperty.type` and `ParsedEvent.type` to include a `TwoWay` type. All existing call-sites have been updated to treat `TwoWay` the same as `Property`/`Regular`, but more specialized logic will be added in the future.
PR Close#54065
These changes expose the `ngContentSelectors` and `preserveWhitespaces` metadata to the TCB so they can be used in the next commit to implement a new diagnostic.
PR Close#53190
When blocks were initially implemented, they were represented as containers in the i18n AST. This is problematic, because block affect the structure of the message.
These changes introduce a new `BlockPlaceholder` AST node and integrate it into the i18n pipeline. With the new node blocks are represented with the `START_BLOCK_<name>` and `CLOSE_BLOCK_<name>` placeholders.
PR Close#52958
These changes expose the `ngContentSelectors` and `preserveWhitespaces` metadata to the TCB so they can be used in the next commit to implement a new diagnostic.
PR Close#52726
Fixes that our regex for parsing time values in defer blocks didn't allow for decimals. This isn't relevant for times in milliseconds, but it can be convenient to write something like `on timer(1.5s)`.
PR Close#52433
Adds some logic to skip over comments when resolving implicit `@defer` block triggers. This currently isn't a problem since we don't capture comments by default, but it may come up if we start capturing comments.
PR Close#52449
Updates the Ivy AST to allow for `@switch` blocks to capture nested blocks that are not `@case` and `@default`. These blocks will be used for autocompletion in the language service.
These changes also update the logic for `@switch` and `@if` blocks so that they produce an AST node even if there are errors. The errors will still be surfaced to users, but producing AST nodes allows us to recover parts of the expression later if necessary.
PR Close#52136
Two key refactors to enable deeper language service support for blocks:
(1) We now generate accurate source spans for the various block types. Additionally, all the top-level source spans for a block are now *inclusive* of all the connected or descending blocks. This helps the language service visit connected blocks.
(2) The language service's template visitor was previously skipping over the AST nodes corresponding to several block types. We are now careful to visit all such nodes.
PR Close#52038
Adds an `UnknownBlock` node to the Ivy AST to represent blocks that haven't been recognized by the compiler. This will make it easier to integrate blocks into the language service.
PR Close#52047
Enables the new `@` block syntax by default by removing the `enabledBlockTypes` flags. There are still some internal flags that allow special use cases to opt out of the block syntax, like during XML parsing and when compiling older libraries (see #51979).
PR Close#51994
Adds support for defining `viewport`, `interaction` and `hover` triggers with no parameters. If the framework encounters such a case, it resolves the trigger to the root element of the `@placeholder` block. Triggers with no parameters have the following restrictions:
1. They have to be placed on an `@defer` block that has an `@placeholder`.
2. The `@placeholder` can only have one root node.
3. The root placeholder node has to be an element.
PR Close#51922
Switches the syntax for blocks from `{#block}{/block}` to `@block {}` based on the feedback from the community.
Read more about the decision-making process in our blog: https://blog.angular.io/meet-angulars-new-control-flow-a02c6eee7843
The existing block types changed in the following ways:
**Conditional blocks:**
```html
<!-- Before -->
{#if cond}
Main content
{:else if otherCond}
Else if content
{:else}
Else content
{/if}
<!-- After -->
@if (cond) {
Main content
} @else if (otherCond) {
Else if content
} @else {
Else content
}
```
**Deferred blocks**
```html
<!-- Before -->
{#defer when isLoaded}
Main content
{:loading} Loading...
{:placeholder} <icon>pending</icon>
{:error} Failed to load
{/defer}
<!-- After -->
@defer (when isLoaded) {
Main content
} @loading {
Loading...
} @placeholder {
<icon>pending</icon>
} @error {
Failed to load
}
```
**Switch blocks:**
```html
<!-- Before -->
{#switch value}
{:case 1}
One
{:case 2}
Two
{:default}
Default
{/switch}
<!-- After -->
@switch (value) {
@case (1) {
One
}
@case (2) {
Two
}
@default {
Default
}
}
```
**For loops**
```html
<!-- Before -->
{#for item of items; track item}
{{item.name}}
{:empty} No items
{/for}
<!-- After -->
@for (item of items; track item) {
{{item.name}}
} @empty {
No items
}
```
PR Close#51891
Adds support for template type checking inside `for` blocks. It is implemented by generating a JS `for...of` statement inside the TCB. The various loop variables (e.g. `$index`) are implemented by declaring a local number variable.
PR Close#51690
Adds support for template type checking inside `if` blocks. It is implemented by generating a JS `if` statement inside the TCB which allows us to do type narrowing of the expression. The `as` parameter is implemented by declaring a variable inside the `if` statement.
PR Close#51690
Adds a utility to the `BoundTarget` that helps with resolving which element a deferred block is pointing to. We need a separate method for this, because deferred blocks have some special logic for where the trigger can be located.
PR Close#51816
When the `TargetBinder` was written, the only embedded-view-based nodes were templates, but now we have `{#if}`, `{#switch}` and `{#defer}` which have similar semantics. These changes rework the binder to account for the new nodes.
PR Close#51816
When `preserveWhitespaces` is enabled, `switch` blocks can end up with content inside their main block due to the indentation that is usually used for the nested cases. This was tripping up the validation that doesn't allow content inside the main block of `switch`.
These changes update the validation to ignore empty text nodes.
PR Close#51570
Fixes that if a directive/pipe is used after a nested `defer` block, we weren't tracking it as lazy anymore. This was due to the fact that we were resetting the `isInDeferBlock` to false every time instead of the previous value.
PR Close#51262
Adds validations for the following invalid deferred block structures:
* Duplicated triggers.
* Multiple `minimum` parameters on `placeholder` and `loading` blocks.
* Multiple `after` parameters on `loading` blocks.
PR Close#51262
Stores the `deferred` block triggers as a map instead of an array, because triggers can't be duplicated and because having to search through an array will be inconvenient later on.
I've also added a `DeferredBlock.visitAll` method to deduplicate the logic from the various visitor implementations.
PR Close#51262
This commit updates the logic of the TemplateBinder and DirectiveBinder classes to recognize defer blocks. The logic is updated to prevent Directive and Pipe matching inside the defer block. Instead, the scope for those blocks would be calculated separately.
PR Close#51162
Change sourceSpan for Comment nodes to cover the whole comment
instead of just the opening token.
The primary motivation for this is the interaction between ESLint and
`@angular-eslint`. ESLint can detect unused `eslint-disable` directives
in comments and automatically remove them when running with `--fix`.
This is based on ranges computed from AST spans, and as a result
does not work inside Angular templates - right now all comments
claim to be 4 characters long so only the opening `<!--` is removed.
PR Close#50855
Adds the logic to create `defer`-specific AST nodes from the generic HTML `BlockGroup` and `Block`. The logic for parsing the triggers will be in the next commit.
PR Close#51050
Fixes that the compiler was matching directives based on `attr` bindings which doesn't correspond to the runtime behavior. This wasn't a problem until now because the matched directives would basically be a noop, but they can cause issues with required inputs.
PR Close#49713
Currently we are unsafely unquoting CSS values which in some cases causes valid values to become invalid and invalid values to become valid.
Example:
```html
<div style="width:"1px;""></div>
```
In the above case, `width` has an invalid value of `"1px"`, however the compiler will transform it to `1px` which makes it valid.
On the other hand, in the below case
```html
<div style="content:"foo""></div>
```
`content` has a valid value of `"foo"`, but since the compiler unwraps it to `foo` it becomes invalid. For correctness, we should not remove quotes.
```js
const div = document.createElement('div');
div.style.width='"1px"';
div.style.content='foo';
div.style.width; // ''
div.style.content; // ''
div.style.width='1px';
div.style.content='"foo"';
div.style.width; // '1px'
div.style.content; // '"foo"'
```
More information about values can be found https://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
PR Close#49460
Since we generate a `.mjs` file as entry-point for jasmine tests,
a couple of issues prevented the transitive dependencies from
bootstrap targets to be brought in (causing resolution errors):
1. The `_files` (previously `_esm2015`) targets are no longer needed,
and they also miss all the information on runfiles.
2. The aspect for computing linker mappings does not respect the
`bootstrap` attribute from the `spec_entrypoint` so we manually
add the extract ESM output targets (this rule works with the aspect
and forwards linker mappings).
PR Close#48521
