This commit adds a base class that contains common logic for all ControlValueAccessors defined in Forms package. This allows to remove duplicated logic from all built-in ControlValueAccessor classes.
PR Close#41225
The other similar interfaces were renamed in https://github.com/angular/angular/pull/41119,
but this one was left since it had existed before Ivy. It looks like the interface was
never actually exposed on npm so it is safe to rename this one too.
PR Close#41316
Add new method `historyGo`, that will let
the user navigate to a specific page from session history identified by its
relative position to the current page.
We add some tests to `location_spec.ts` to validate the behavior of the
`historyGo` and `forward` methods.
Add more tests for `location_spec` to test `location.historyGo(0)`, `location.historyGo()`,
`location.historyGo(100)` and `location.historyGo(-100)`. We also add new tests for
`Integration` spec to validate the navigation when we using
`location#historyGo`.
Update the `historyGo` function docs
Note that this was made an optional function in the abstract classes to
avoid a breaking change. Because our location classes use `implements PlatformLocation`
rather than `extends PlatformLocation`, simply adding a default
implementation was not sufficient to make this a non-breaking change.
While we could fix the classes internal to Angular, this would still have been
a breaking change for any external developers who may have followed our
implementations as an example.
PR Close#38890
Introduces an **internal**, **experimental** `profiler` function, which
the runtime invokes around user code, including before and after:
- Running the template function of a component
- Executing a lifecycle hook
- Evaluating an output handler
The `profiler` function invokes a callback set with the global
`ng.ɵsetProfiler`. This API is **private** and **experimental** and
could be removed or changed at any time.
This implementation is cheap and available in production. It's cheap
because the `profiler` function is simple, which allows the JiT compiler
to inline it in the callsites. It also doesn't add up much to the
production bundle.
To listen for profiler events:
```ts
ng.ɵsetProfiler((event, ...args) => {
// monitor user code execution
});
```
PR Close#41255
The moved `XhrFactory` still needs to be available from `@angular/common/http`
for some libraries that were built prior to 12.0.0, otherwise they cannot be
used in applications built post-12.0.0.
This commit adds back the re-export of `XhrFactory` and deprecates it.
PR Close#41393
This instruction was created to work around a problem with injecting a
`ChangeDetectorRef` into a pipe. See #31438. This fix required special
metadata for when the thing being injected was a `ChangeDetectorRef`.
Now this is handled by adding a flag `InjectorFlags.ForPipe` to the
`ɵɵdirectiveInject()` call, which avoids the need to special test_cases
`ChangeDetectorRef` in the generated code.
PR Close#41231
With this change we move `XhrFactory` to the root entrypoint of `@angular/commmon`, this is needed so that we can configure `XhrFactory` DI token at a platform level, and not add a dependency between `@angular/platform-browser` and `@angular/common/http`.
Currently, when using `HttpClientModule` in a child module on the server, `ReferenceError: XMLHttpRequest is not defined` is being thrown because the child module has its own Injector and causes `XhrFactory` provider to be configured to use `BrowserXhr`.
Therefore, we should configure the `XhrFactory` at a platform level similar to other Browser specific providers.
BREAKING CHANGE:
`XhrFactory` has been moved from `@angular/common/http` to `@angular/common`.
**Before**
```ts
import {XhrFactory} from '@angular/common/http';
```
**After**
```ts
import {XhrFactory} from '@angular/common';
```
Closes#41311
PR Close#41313
The Ivy Language Service uses the compiler's template type-checking engine,
which honors the configuration in the user's tsconfig.json. We recommend
that users upgrade to `strictTemplates` mode in their projects to take
advantage of the best possible type inference, and thus to have the best
experience in Language Service.
If a project is not using `strictTemplates`, then the compiler will not
leverage certain type inference options it has. One case where this is very
noticeable is the inference of let- variables for structural directives that
provide a template context guard (such as NgFor). Without `strictTemplates`,
these guards will not be applied and such variables will be inferred as
'any', degrading the user experience within Language Service.
This is working as designed, since the Language Service _should_ reflect
types exactly as the compiler sees them. However, the View Engine Language
Service used its own type system that _would_ infer these types even when
the compiler did not. As a result, it's confusing to some users why the
Ivy Language Service has "worse" type inference.
To address this confusion, this commit implements a suggestion diagnostic
which is shown in the Language Service for variables which could have been
narrowed via a context guard, but the type checking configuration didn't
allow it. This should make the reason why variables receive the 'any' type
as well as the action needed to improve the typings much more obvious,
improving the Language Service experience.
Fixes angular/vscode-ng-language-service#1155
Closes#41042
PR Close#41072
ActivatedRoute.fragment was typed as Observable<string> but could emit
both null and undefined due to incorrect non-null assertion. These
non-null assertions have been removed and fragment has been retyped to
string | null.
BREAKING CHANGE:
Strict null checks will report on fragment potentially being null.
Migration path: add null check.
Fixes#23894, fixes#34197.
PR Close#37336
This commit makes the `RadioControlRegistry` class tree-shakable by adding the `providedIn` property to its
`@Injectable` decorator. Now if the radio buttons are not used in the app (thus no `RadioControlValueAccessor`
directive is initialized), the `RadioControlRegistry` should not be included into application's prod bundle.
PR Close#41126
A long-requested feature for HttpClient is the ability to store and retrieve
custom metadata for requests, especially in interceptors. This commit
implements this functionality via a new context object for requests.
Each outgoing HttpRequest now has an associated "context", an instance of
the HttpContext class. An HttpContext can be provided when making a request,
or if not then an empty context is created for the new request. This context
shares its lifecycle with the entire request, even across operations that
change the identity of the HttpRequest instance such as RxJS retries.
The HttpContext functions as an expando. Users can create typed tokens as instances of HttpContextToken, and
read/write a value for the key from any HttpContext object.
This commit implements the HttpContext functionality. A followup commit will
add angular.io documentation.
PR Close#25751
This commit updates Forms code to avoid direct references to all built-in ControlValueAccessor classes, which
prevents their tree-shaking from production builds. Instead, a new static property is added to all built-in
ControlValueAccessors, which is checked when we need to identify whether a given ControlValueAccessors is a
built-in one.
PR Close#41146
The custom elements spec is not compatible with ES5 style classes. This
means ES2015 code compiled to ES5 will not work with a native
implementation of Custom Elements. To support browsers that natively
support Custom Elements but not ES2015 modules, we load
`@webcomponents/custom-elements/src/native-shim.js`, which minimally
augments the native implementation to be compatible with ES5 code.
(See [here][1] for more details.)
Previously, the shim was included in `polyfills.ts`, which meant it was
loaded in all browsers (even those supporting ES2015 modules and thus
not needing the shim).
This commit moves the shim from `polyfills.ts` to a `nomodule` script
tag in `index.html`. This will ensure that it is only loaded in browsers
that do not support ES2015 modules and thus do not needed the shim.
NOTE:
This commit also reduces size of the polyfills bundle by ~400B
(52609B --> 52215B).
[1]: https://www.npmjs.com/package/@webcomponents/custom-elements#es5-vs-es2015
PR Close#41162
The `DomAdapter` is present in all Angular apps and its methods aren't tree shakeable.
These changes remove the methods that either aren't being used anymore or were only
used by our own tests. Note that these changes aren't breaking, because the adapter
is an internal API.
The following methods were removed:
* `getProperty` - only used within our own tests.
* `log` - Guaranteed to be defined on `console`.
* `logGroup` and `logGroupEnd` - Only used in one place. It was in the DomAdapter for built-in null checking.
* `logGroupEnd` - Only used in one place. It was placed in the DomAdapter for built in null checking.
* `performanceNow` - Only used in one place that has to be invoked through the browser console.
* `supportsCookies` - Unused.
* `getCookie` - Unused.
* `getLocation` and `getHistory` - Only used in one place which appears to have access to the DOM
already, because it had direct accesses to `window`. Furthermore, even if this was being used
in a non-browser context already, the `DominoAdapter` was set up to throw an error.
The following APIs were changed to be more compact:
* `supportsDOMEvents` - Changed to a readonly property.
* `remove` - No longer returns the removed node.
PR Close#41102
Previously, injector definitions contained a `factory` property that
was used to create a new instance of the associated NgModule class.
Now this factory has been moved to its own `ɵfac` static property on the
NgModule class itself. This is inline with how directives, components and
pipes are created.
There is a small size increase to bundle sizes for each NgModule class,
because the `ɵfac` takes up a bit more space:
Before:
```js
let a = (() => {
class n {}
return n.\u0275mod = c.Cb({type: n}),
n.\u0275inj = c.Bb({factory: function(t) { return new (t || n) }, imports: [[e.a.forChild(s)], e.a]}),
n
})(),
```
After:
```js
let a = (() => {
class n {}
return n.\u0275fac = function(t) { return new (t || n) },
n.\u0275mod = c.Cb({type: n}),
n.\u0275inj = c.Bb({imports: [[r.a.forChild(s)], r.a]}),
n
})(),
```
In other words `n.\u0275fac = ` is longer than `factory: ` (by 5 characters)
and only because the tooling insists on encoding `ɵ` as `\u0275`.
This can be mitigated in a future PR by only generating the `ɵfac` property
if it is actually needed.
PR Close#41022
This commit adds a Forms-based test app into the `integration` folder to have an ability to measure and keep
track of payload size for the changes in Forms package.
PR Close#41045
In the new behavior Angular cleanups `popstate` and `hashchange` event listeners
when the root view gets destroyed, thus event handlers are not added twice
when the application is bootstrapped again.
BREAKING CHANGE:
Methods of the `PlatformLocation` class, namely `onPopState` and `onHashChange`,
used to return `void`. Now those methods return functions that can be called
to remove event handlers.
PR Close#31546
PR Close#40867
This commit updates the type of the `APP_INITIALIZER` injection token to
better document the expected types of values that Angular handles. Only
Promises and Observables are awaited and other types of values are ignored,
so the type of `APP_INITIALIZER` has been updated to
`Promise<unknown> | Observable<unknown> | void` to reflect this behavior.
BREAKING CHANGE:
The type of the `APP_INITIALIZER` token has been changed to more accurately
reflect the types of return values that are handled by Angular. Previously,
each initializer callback was typed to return `any`, this is now
`Promise<unknown> | Observable<unknown> | void`. In the unlikely event that
your application uses the `Injector.get` or `TestBed.inject` API to inject
the `APP_INITIALIZER` token, you may need to update the code to account for
the stricter type.
Additionally, TypeScript may report the TS2742 error if the `APP_INITIALIZER`
token is used in an expression of which its inferred type has to be emitted
into a .d.ts file. To workaround this, an explicit type annotation is needed,
which would typically be `Provider` or `Provider[]`.
Closes#40729
PR Close#40986
Before `unknown` was available, the `never` type was used to discourage
application developers from using "private" properties. The `unknown` type
is much better suited for this.
PR Close#41040
This commit updates the Angular framework, Angular CDK/Material and
Angular CLI to latest stable versions (11.2.3, 11.2.2 and 11.2.2
respectively).
This update also fixes a Lighthouse audit fail due to
`@angular/core@11.0.0` being identified as vulnerable to XSS:
https://snyk.io/vuln/SNYK-JS-ANGULARCORE-1070902
Regarding the payload size increases, they are mostly attributed to
Angular Material:
- Before this commit: 448461 B
- After framework update: 448554 B ( +93 B)
- After Material update: 449292 B (+738 B)
- After CLI update: 449310 B ( +18 B)
PR Close#40994
This change fixes an incompatibility between the old `@angular/http` package
and its successor (`@angular/common/http`) by re-introducing the types that were supported before.
It now allows to use number and boolean directly as HTTP params, instead of having to convert it to string first.
Before:
this.http.get('/api/config', { params: { page: `${page}` } });
After:
this.http.get('/api/config', { params: { page }});
`HttpParams` has also been updated to have most of its methods accept number or boolean values.
Fixes#23856
BREAKING CHANGE:
The methods of the `HttpParams` class now accept `string | number | boolean`
instead of `string` for the value of a parameter.
If you extended this class in your application,
you'll have to update the signatures of your methods to reflect these changes.
PR Close#40663
This commit adds more configurability to the `Router#isActive` method
and `RouterLinkActive#routerLinkActiveOptions`.
It allows tuning individual match options for query params and the url
tree, which were either both partial or both exact matches in the past.
Additionally, it also allows matching against the fragment and matrix
parameters.
fixes#13205
BREAKING CHANGE:
The type of the `RouterLinkActive.routerLinkActiveOptions` input was
expanded to allow more fine-tuned control. Code that previously read
this property may need to be updated to account for the new type.
PR Close#40303
Currently the only way to disable animations is by providing the `NoopAnimationsModule`
which doesn't allow for it to be disabled based on runtime information. These changes
add support for disabling animations based on runtime information by using
`BrowserAnimationsModule.withConfig({disableAnimations: true})`.
PR Close#40731
Currently `NgTemplateOutlet` recreates its view if its template is swapped out or a context
object with a different shape is passed in. If an object with the same shape is passed in,
we preserve the old view and we mutate the previous object. This mutation of the original
object can be undesirable if two objects with the same shape are swapped between two
different template outlets.
The current behavior is a result of a limitation in `core` where the `context` of an embedded
view is read-only, however a previous commit made it writeable.
These changes resolve the context mutation issue and clean up a bunch of unnecessary
logic from `NgTemplateOutlet` by taking advantage of the earlier change.
Fixes#24515.
PR Close#40360
Currently `EmbeddedViewRef.context` is read-only which means that the only way to update
it is to mutate the object which can lead to some undesirable outcomes if the template
and the context are provided by an external consumer (see #24515).
These changes make the property writeable since there doesn't appear to be a specific
reason why it was readonly to begin with.
PR Close#40360
This PR formalizes, documents, and makes public the router outlet contract.
The set of `RouterOutlet` methods used by the `Router` has not changed
in over 4 years, since the introduction of route reuse strategies.
Creation of custom router outlets is already possible and is used by the
Ionic framework
(https://github.com/ionic-team/ionic-framework/blob/master/angular/src/directives/navigation/ion-router-outlet.ts).
There is a small "hack" that is needed to make this work, which is that
outlets must register with `ChildrenOutletContexts`, but it currently
only accepts our `RouterOutlet`.
By exposing the interface the `Router` uses to activate and deactivate
routes through outlets, we allow for developers to more easily and safely
extend the `Router` and have fine-tuned control over navigation and component
activation that fits project requirements.
PR Close#40827
This commit adds `ngDevMode` guard to show the warning only
in dev mode (similar to how things work in other parts of Ivy runtime code).
The `ngDevMode` flag helps to tree-shake the warning from production builds
(in dev mode everything will work as it works right now) to decrease production bundle size.
PR Close#40876
Our approach for handling cyclic imports results in code that is
not easy to tree-shake, so it is not suitable for publishing in a
library.
When compiling in partial compilation mode, we are targeting
such library publication, so we now create a fatal diagnostic
error instead of trying to handle the cyclic import situation.
Closes#40678
PR Close#40782
Fix router to ensure that a route module is only loaded once especially
in relation to the use of preload strategies with delayed or partial
loading.
Add test to check the interaction of PreloadingStrategy and normal
router navigation under differing scenarios.
Checking:
* Prevention of duplicate loading of modules.
related to #26557
* Prevention of duplicate RouteConfigLoad(Start|End) events
related to #22842
* Ensuring preload strategy remains active for submodules if needed
The selected preload strategy should still decide when to load submodules
* Possibility of memory leak with unfinished preload subscription
related to #26557
* Ensure that the stored loader promise is cleared so that subsequent
load will try the fetch again.
* Add error handle error from loadChildren
* Ensure we handle error from with NgModule create
Fixes#26557#22842#26557
PR Close#40389
This commit adds the `emitEvent` option to the following FormArray and FormGroup methods:
* FormGroup.addControl
* FormGroup.removeControl
* FormGroup.setControl
* FormArray.push
* FormArray.insert
* FormArray.removeAt
* FormArray.setControl
* FormArray.clear
This option can be used to prevent an event from being emitted when adding or removing controls.
BREAKING CHANGE:
The `emitEvent` option was added to the following `FormArray` and `FormGroup` methods:
* FormGroup.addControl
* FormGroup.removeControl
* FormGroup.setControl
* FormArray.push
* FormArray.insert
* FormArray.removeAt
* FormArray.setControl
* FormArray.clear
If your app has custom classes that extend `FormArray` or `FormGroup` classes and override the
above-mentioned methods, you may need to update your implementation to take the new options into
account and make sure that overrides are compatible from a types perspective.
Closes#29662.
PR Close#31031
`@angular/platform-server` provides the foundation for rendering an
Angular app on the server. In order to achieve that, it uses a
server-side DOM implementation (currently [domino][1]).
For rendering on the server to work as closely as possible to running
the app on the browser, we need to make DOM globals (such as `Element`,
`HTMLElement`, etc.), which are normally provided by the browser,
available as globals on the server as well.
Currently, `@angular/platform-server` achieves this by extending the
`global` object with the DOM implementation provided by `domino`. This
assignment happens in the [setDomTypes()][2] function, which is
[called in a `PLATFORM_INITIALIZER`][3]. While this works in most cases,
there are some scenarios where the DOM globals are needed sooner (i.e.
before initializing the platform). See, for example, #24551 and #39950
for more details on such issues.
This commit provides a way to solve this problem by exposing a
side-effect-ful entry-point (`@angular/platform-server/init`), that
shims the `global` object with DOM globals. People will be able to
import this entry-point in their server-rendered apps before
bootstrapping the app (for example, in their `main.server.ts` file).
(See also [#39950 (comment)][4].)
In a future update, the [`universal` schematics][5] will include such an
import by default in newly generated projects.
[1]: https://www.npmjs.com/package/domino
[2]: https://github.com/angular/angular/blob/0fc8466f1be392917e0c/packages/platform-server/src/domino_adapter.ts#L17-L21
[3]: https://github.com/angular/angular/blob/0fc8466f1be392917e0c/packages/platform-server/src/server.ts#L33
[4]: https://github.com/angular/angular/issues/39950#issuecomment-747598403
[5]: https://github.com/angular/angular-cli/blob/cc51432661eb4ab4b6a3/packages/schematics/angular/universal
PR Close#40559
Fix router to ensure that a route module is only loaded once especially
in relation to the use of preload strategies with delayed or partial
loading.
Add test to check the interaction of PreloadingStrategy and normal
router navigation under differing scenarios.
Checking:
* Prevention of duplicate loading of modules.
related to #26557
* Prevention of duplicate RouteConfigLoad(Start|End) events
related to #22842
* Ensuring preload strategy remains active for submodules if needed
The selected preload strategy should still decide when to load submodules
* Possibility of memory leak with unfinished preload subscription
related to #26557
* Ensure that the stored loader promise is cleared so that subsequent
load will try the fetch again.
* Add error handle error from loadChildren
* Ensure we handle error from with NgModule create
Fixes#26557#22842#26557
PR Close#40389
This commit adds support for Finnish full date formatting,
as well as `c/cc/ccc/cccc/ccccc/cccccc` date formats in the `DatePipe`.
Fixes#26922
PR Close#40766
Produces a diagnostic when we cannot resolve a component's external style sheet or external template.
The previous behavior was to throw an exception, which crashed the
Language Service.
fixes angular/vscode-ng-language-service#1079
PR Close#40660
This commit adds the missing `min` and `max` validators.
BREAKING CHANGE:
Previously `min` and `max` attributes defined on the `<input type="number">`
were ignored by Forms module. Now presence of these attributes would
trigger min/max validation logic (in case `formControl`, `formControlName`
or `ngModel` directives are also present on a given input) and
corresponding form control status would reflect that.
Fixes#16352
PR Close#39063
Two motivations behind this change:
1. We would like to expose the types of the Language Service to external
users (like the VSCode extension) via the npm package, on the top
level of the package
2. We would like the View Engine and Ivy LS to share a common interface
(notably after the inclusion of `getTcb`, the Ivy LS upholds a
strict superset of `ts.LanguageService`; previously both VE and Ivy
LS were aligned on `ts.LanguageService`.)
To this end, this commit refactors the exports on the toplevel of the
`language-service/` package to just be types common to both the VE and
Ivy language services. The VE and Ivy build targets then import and use
these types accordingly, and the expectation is that an external user
will just import the relevant typings from the toplevel package without
diving into either the VE or Ivy sources.
Follow up on #40607
PR Close#40621
The `AsyncPipe.transform<T>(emitter)` method must infer the `T`
type from the `emitter` parameter. Since we changed the `AsyncPipe`
to expect a `Subscribable<T>` rather than `Observable<T>` the
`EventEmitter.subscribe()` method needs to have a tighter signature.
Otherwise TypeScript struggles to infer the type and ends up making
it `unknown`.
Fixes#40637
PR Close#40644
They aim to improve code readability.
Since they are defined by `const enum` they have zero runtime performance impact
over just using constant literals.
Fixes#23543
PR Close#23548
This PR adds a way for the language server to retrieve compiler options
diagnostics via `languageService.getCompilerOptionsDiagnostics()`.
This will be used by the language server to show a prompt in the editor if
users don't have `strict` or `fullTemplateTypeCheck` turned on.
Ref https://github.com/angular/vscode-ng-language-service/issues/1053
PR Close#40423
Adds an `appendAll()` method to `HttpParams` that can construct the HTTP
request/response body from an object of parameters and values.
This avoids calling `append()` multiple times when multiple parameters
need to be added.
Fixes#20798
PR Close#20930
The injector system uses a bloom filter to determine if a token is
possibly defined in the node injector tree, which is stored across
multiple bloom buckets that each represent 32 bits of the full 256-bit
wide bloom hash. This means that a computation is required to determine
the exact bloom bucket which is responsible for storing any given 32-bit
interval, which was previously computed using three bitmask operations
and three branches to derive the bloom bucket offset.
This commit exploits the observation that all bits beyond the low 5 bits
of the bloom hash are an accurate representation for the bucket offset,
if shifted right such that those bits become the least significant bits.
This reduces the three bitmask operations and three branches with a
single shift operation, while additionally offering a code size
improvement.
PR Close#40489
Previous implementation would fire changes `QueryList.changes.subscribe`
whenever the `QueryList` was recomputed. This resulted in artificially
high number of change notifications, as it is possible that recomputing
`QueryList` results in the same list. When the `QueryList` gets recomputed
is an implementation detail and it should not be the thing which determines
how often change event should fire.
This change introduces a new `emitDistinctChangesOnly` option for
`ContentChildren` and `ViewChildren`.
```
export class QueryCompWithStrictChangeEmitParent {
@ContentChildren('foo', {
// This option will become the default in the future
emitDistinctChangesOnly: true,
})
foos!: QueryList<any>;
}
```
PR Close#40091
This commit updates the logic that calculates `useFactory` function arguments to avoid relying on `instanceof`
checks (thus always retaining symbols) and relies on flags that DI decorators contain (as a monkey-patched property).
Another perf benefit is having less megamorphic reads while calculating args for the `useFactory` call: we used to
check whether a token has `ngMetadataName` property 4 times (in worst case), now we have just 1 megamorphic read in
all cases.
Closes#40143.
PR Close#40145
When we attach a `ViewRef` to a `ViewContainerRef`, we save a reference to the container
onto the `ViewRef` so that we can remove it when the ref is destroyed. The problem is
that if the container's `hostView` is destroyed first, the `ViewRef` has no way of knowing
that it should stop referencing the container.
These changes remove the leak by not saving a reference at all. Instead, when a `ViewRef`
is destroyed, we clean it up through the `LContainer` directly. We don't need to worry
about the case where the container is destroyed before the view, because containers
automatically clean up all of their views upon destruction.
Fixes#38648.
PR Close#40219
There are two parts to this commit:
1. Revert the changes from #38379. This change had an incomplete view of
how things worked and also diverged the implementations of
`applyRedirects` and `recognize` even more.
2. Apply the fixes from the `recognize` algorithm to ensure that named
outlets with empty path parents can be matched. This change also passes
all the tests that were added in #38379 with the added benefit of being
a more complete fix that stays in-line with the `recognize` algorithm.
This was made possible by using the same approach for `split` by
always creating segments for empty path matches (previously, this was
only done in `applyRedirects` if there was a `redirectTo` value). At the
end of the expansions, we need to squash all empty segments so that
serializing the final `UrlTree` returns the same result as before.
Fixes#39952Fixes#10726Closes#30410
PR Close#40029
Andrew Kushnir
Pete Bacon Darwin
Ahmed Ayed
mgechev
Alan Agius
Alex Rickabaugh
Matthias Kunnen
FDIM
George Kalpakas
Kristiyan Kostadinov
Sagar Pandita
arturovt
abarghoud
twerske
cexbrayat
Andrew Scott
Paul Gammans
Michael Jerred
Joey Perrott
kirjs
Zach Arend
Sonu Kapoor
ayazhafiz
Quentin Focheux
Keen Yee Liau
Harun Urhan
JoostK
Misko Hevery
Martin Sikora