This started from a real production crash trace:
TypeError: Cannot read properties of null (reading 'nextSibling')
Traced through a minified bundle back to siblingAfter() in
packages/core/src/hydration/node_lookup_utils.ts. It walks forward a
fixed number of DOM siblings during hydration, based on how many the
server rendered. Its only guard, validateSiblingNodeExists(), is
gated behind ngDevMode and stripped from production builds. If the
client DOM has fewer real siblings than the server-serialized data
expects — client/server render diverged, or something outside
Angular (a browser extension, an injected script) removed a node —
the loop ran fully unguarded in production: currentNode went null
partway through, and the next iteration's currentNode.nextSibling
threw a raw, uncoded TypeError instead of a coded, debuggable one.
Reproduced first, not just theorized: added a test that server-
renders a @for loop with 3 items, removes 2 of them before hydration
runs, and confirmed it actually throws that exact TypeError against
the original code before touching anything.
Fix: add a null check at the top of the loop, matching the pattern
already used for the existing NG0500/NG0502 hydration checks in
element.ts — the dev-mode check runs first as before (a no-op in
production), and the new check is a pure safety net that only fires
once that dev-mode check has already been compiled away. In dev mode
this is provably dead code, so nothing about dev behavior changes.
Coded as NG0501 (HYDRATION_MISSING_SIBLINGS, already existed).
While investigating, found and fixed two more call sites with the
exact same shape of bug — a dev-only check that leaves production
completely unguarded:
- navigateToNode() (same file): walks an explicit "firstChild /
nextSibling" navigation path recorded for nodes that can't rely on
simple sibling-walking (e.g. content right after an <ng-content>
slot). Its only guard was also ngDevMode-only. Added the same
production safety net, both mid-loop (the raw-crash case) and
post-loop (where it could previously return null silently despite
the function's return type promising a non-null RNode). New code:
NG0509 (HYDRATION_MISSING_NODE_ON_PATH).
- getParentRElement() (render3/node_manipulation.ts): typed its
tNode parameter as always non-null, but a real production trace
showed it can be null at runtime, crashing on tNode.parent with no
useful information. Widened the type to TNode | null and added a
guard that throws a coded error instead. New code: NG0510
(PARENT_NODE_NOT_FOUND).
Unlike the other two, this one isn't gated behind ngDevMode at all
in the original code — it reproduces unconditionally. Decoded the
actual production minified stack trace against this source
(matched every frame character-for-character) to find the real
cause instead of guessing: an @if/@switch branch's content is its
own embedded template with its own TView, built lazily the first
time that branch renders. If an error interrupts that first pass —
here, a hydration mismatch on the branch's second child, after the
first child's TNode was already created — TView.firstCreatePass
still gets flipped to false in render.ts's `catch` block before the
error propagates, permanently marking that TView as corrupted.
Unlike a component's TView (rebuilt from scratch next time via
getOrCreateComponentTView()'s incompleteFirstPass check), nothing
rebuilds an embedded view's TView. The next time that exact branch
is selected again, its instructions read straight from the
corrupted tView.data instead of creating a fresh TNode, and any
node past the interruption point is still null.
The real test added for this (full_app_hydration_spec.ts) exercises
that whole chain for real: a hydration mismatch on an @if branch's
second child, then re-entering the same branch. Confirmed it throws
the exact byte-for-byte production error message ("Cannot read
properties of null (reading 'parent')") without the fix, and the
coded NG0510 with it. This replaces an earlier synthetic unit test
that just cast a variable to null to bypass the type system rather
than reproducing the actual failure.
Note: a more thorough fix would rebuild the corrupted embedded TView
itself (mirroring getOrCreateComponentTView()), which does make the
crash disappear — but doing that surfaces a second, separate bug:
the aborted first attempt's partially-created LView/DOM is never
torn down, so the retried branch's content gets appended alongside
leftover orphaned nodes instead of replacing them, corrupting
content silently instead of crashing loudly. That's a materially
bigger fix (proper LView cleanup after a mid-creation exception) and
is intentionally out of scope here; this commit keeps the narrower,
safe fix (a clear coded error) rather than trading a loud crash for
silent data corruption.
Along the way, deduplicated describeDomNode(), which existed as two
near-identical private copies (one in this file's own NG0500 check,
one in platform-browser's dom_renderer.ts insertBefore check) and
moved it into core's hydration/error_handling.ts, shared via the
private ɵdescribeDomNode export.
That function was then removed from every production code path
entirely, per review feedback: computing a human-readable node
description is debug-oriented work that shouldn't ship unconditionally
in production bundles, regardless of how cheap it is — production
should get the bare coded error only, the same as everywhere else in
this file. All three fixes above follow that: ngDevMode && 'message'
in production, no computed description. Confirmed the removal
actually shrinks output, not just assumed it: regenerated all 8
affected bundling symbol goldens, and each one shows exactly one
symbol removed — "describeDomNode" — and nothing else.
locateOrCreateElementNodeImpl looks up the DOM node for an element
during hydration and immediately checks its nodeType. If the
client-rendered DOM has fewer nodes than the server-rendered HTML,
the lookup returns null, and in production that null flows straight
into the nodeType check and crashes with a raw, uncoded
"Cannot read properties of null (reading 'nodeType')" TypeError.
The dev-mode check that would normally catch this (validateMatchingNode)
already handles a missing node, but it's compiled out of production
builds, so the crash only shows up outside of dev mode.
Add a null check ahead of the nodeType check that throws a coded
RuntimeError using the existing HYDRATION_MISSING_NODE (NG0502) code,
with a descriptive message in dev mode and a cheap fallback in
production. Also add a regression test that removes a server-rendered
element before hydration runs and asserts a coded RuntimeError is
thrown instead of a raw TypeError.
When hydration locates the DOM node for an ɵɵelementStart/ɵɵdomElementStart
instruction, locateOrCreateElementNodeImpl assumed the located node was
always an Element and called hasSkipHydrationAttrOnRElement(native), which
does native.hasAttribute(...). The check that would normally catch this
class of mismatch, validateMatchingNode, is gated behind `ngDevMode &&` and
is compiled out of production builds. So when a real SSR/hydration
structural mismatch located a Text or Comment node instead of the expected
Element, production builds hit .hasAttribute on a node type that doesn't
have it and crashed with a raw, uncoded TypeError instead of a coded
hydration-mismatch RuntimeError.
Add a cheap, always-on nodeType check ahead of that call. On mismatch it
throws RuntimeError(HYDRATION_NODE_MISMATCH, ngDevMode && '...'), the same
pattern used elsewhere in the codebase, so the descriptive message is only
built in dev mode and production keeps throwing just the bare NG0500 code
without pulling validateMatchingNode's DOM-printing machinery into the
production bundle (verified via the bundling/hydration golden-symbols test,
which is unchanged).
Fixes#69785
Add an Angular SSR integration test in platform-server verifying that null input values do not render string attributes like value="null" during server-side rendering, while normal non-empty string values like value="hello" are properly preserved.
When a component is created dynamically via ViewContainerRef.createComponent
and receives projectable nodes (e.g. raw DOM nodes or embedded view root nodes),
applying ngSkipHydration to its host element did not prevent NG0503 from being
thrown during SSR serialization.
The root cause is an asymmetry in the serialization pipeline. For inline child
components, serializeLView already guards the annotateHostElementForHydration
call with a ngSkipHydration attribute check, so the component's lView is never
serialized when hydration is opted out. For components hosted inside an
LContainer (created via ViewContainerRef.createComponent), serializeLContainer
called serializeLView unconditionally — bypassing that guard entirely. When
serializeLView then encountered a projection slot backed by a raw DOM node
array, it threw NG0503 regardless of the ngSkipHydration flag.
The fix adds the same guard inside serializeLContainer before calling
serializeLView: if the child lView belongs to a component whose host element
carries ngSkipHydration, the lView serialization is skipped. This matches the
existing behavior for inline components and allows the documented workaround to
actually work for dynamically created ones.
Fixes#67928
Improves error messages shown during hydration mismatches to better
surface cases where third-party scripts or browser extensions have
modified the DOM outside of Angular's control.
Fixed#59224
This commit updates provideClientHydration to automatically enable incremental hydration by default. It also introduces a new withNoIncrementalHydration feature for opting out, adds conflict safety checks, and includes a schematic migration.
The default change detection strategy is now OnPush.
BREAKING CHANGE: Component with undefined `changeDetection` property are now `OnPush` by default. Specify `changeDetection: ChangeDetectionStrategy.Eager` to keep the previous behavior.
The zoneless scheduler is always enabled, so if hydration works with zoneless, it works
for all Angular apps. There is no need for detection of custom zone implementations
PR Close#63847
This updates the enter and leave logic to use the stored LView data to dispatch the enter and leave animations at the right points in the lifecycle. This should fix issues with signals not being available yet, parallel animations, and also eliminate the need for the element registry.
fixes: #63391fixes: #63388fixes: #63369
PR Close#63450
This updates tests and examples only to prepare for zoneless by default.
These changes were identified and made as part of #63382. Anything that
failed gets `provideZoneChangeDetection` unless the fixes were easily
and quickly determined.
It also adds the zoneless provider to the `initTestEnvironment` calls
for tests in this repo to prevent regressions before #63382 is merged.
PR Close#63668
Projected nodes were missing ssrId information and were skipping annotating template information, which caused templates to be destroyed and recreated rather than hydrated.
fixes: #50543
PR Close#61989
This change renames the afterRender to afterEveryRender and marks the
renamed API as stable.
BREAKING CHANGE: afterRender was renamed to afterEveryRender.
PR Close#60999
BREAKING CHANGE:
This commit deprecates `ng-reflect-*` attributes and updates the runtime to stop producing them by default. Please refactor application and test code to avoid relying on `ng-reflect-*` attributes.
To enable a more seamless upgrade to v20, we've added the `provideNgReflectAttributes()` function (can be imported from the `@angular/core` package), which enables the mode in which Angular would be producing those attribites (in dev mode only). You can add the `provideNgReflectAttributes()` function to the list of providers within the bootstrap call.
PR Close#60973
This commit moves zoneless from experimental to developer preview.
* Update tag on provider API
* Remove "experimental" from provider name
* Move documentation from "experimental features" to "Best practives ->
Performance" (at least temporarily until there is a better place)
BREAKING CHANGE: `provideExperimentalZonelessChangeDetection` is
renamed to `provideZonelessChangeDetection` as it is now "Developer
Preview" rather than "Experimental".
PR Close#60748
In this commit, we unsubscribe the `hasPendingTasks` subject to remove all active observers and enable granular garbage collection, as users may forget to unsubscribe manually when subscribing to `isStable`.
PR Close#59723
This properly cleans up stale control flow branches in the case
that branches change between server and client at the same
timing as NgIf / NgSwitch.
fixes: #58670fixes: #60218
PR Close#60425
In this commit, we check whether the application is destroyed before printing hydration stats. The application may be destroyed before it becomes stable, so when the `whenStableWithTimeout` resolves, the injector might already be in a destroyed state. As a result, calling `injector.get` would throw an error indicating that the injector has already been destroyed.
PR Close#59716
For `afterRender`/`afterNextRender` calls associated with a particular
view, ensure that they are not registered until after the first time the
view is rendered.
Co-authored-by: Alex Rickabaugh <alxhub@users.noreply.github.com>
PR Close#58250
This commit updates defer block logic to avoid triggering `on idle` and `on timer` on the server for regular SSR mode (when incremental hydration is not enabled). Triggering the mentioned condition resulted in invoking `setTimeout` calls, which delayed serialization on the server during SSR (the process was waiting for the timeouts to clear).
PR Close#59177
This commit removes a custom `whenStable` util in favor of standard `ApplicationRef.whenStable` API.
There is also an important different between the custom `whenStable` function and `ApplicationRef.whenStable` implementation: the `whenStable` was caching the "stable" promise on per-ApplicationRef basis, which resulted in unexpected behavior with zoneless, when some code ended up getting a stale resolved promise, when an application was not stable yet, this causing order of operations issues. This commit also has an extra test that covers that case.
PR Close#58834
Fixes an edge case where a control flow node that has non-projectable nodes followed by an element node at the end would cause the entire control flow node to be project. For example if we have a projection target of `Main: <ng-content/> Slot: <ng-content select="[foo]"/>`, inserting a node of `@if (true) {Hello <span foo>world</span>}` would project the entire `Hello world` into the `[foo]` slot.
In the process of working on the issue, I also found that `@let` declarations at the root of the control flow node would prevent content projection as well.
PR Close#58607
This commit addresses a problem with tests that use the `fit` function to focus on individual test cases. While these tests run successfully in the full suite, they fail when focused individually using `fit`.
The issue lies in the behavior of `withEventReply` and other hydration-related functions (i.e., `provideX`, `withX`). These functions return platform-specific providers based on the `ngServerMode` setting, causing inconsistencies between server and browser environments. As a result, provider instances cannot be reused across server and browser applications.
**Example of problematic code:**
```ts
const hydrationFeatures = [withEventReply()];
const html = await ssr(SimpleComponent, { hydrationFeatures });
// Expected behavior ...
const appRef = await prepareEnvironmentAndHydrate(doc, html, SimpleComponent, {
hydrationFeatures,
});
// Expected behavior ...
```
**Solution:**
To address this, we define `hydrationFeatures` as a function instead of a static array. This ensures that a new instance of `withEventReply` is created separately for each environment, eliminating platform-specific mismatches between server and browser contexts:
```typescript
const hydrationFeatures = () => [withEventReply()]; // Define as a function
const html = await ssr(SimpleComponent, { hydrationFeatures: hydrationFeatures() });
// Expected behavior ...
const appRef = await prepareEnvironmentAndHydrate(doc, html, SimpleComponent, {
hydrationFeatures: hydrationFeatures(),
});
// Expected behavior ...
```
PR Close#58538
This commit adds the `ngServerMode` as global, which allows for the tree-shaking of server-only code from the bundles. When this flag is unset at runtime, server-specific code will be excluded by Closure, optimizing bundle size.
**Internal Angular Flag:** This is an internal Angular flag (not a public API), avoid relying on it in application code.
PR Close#58386
This re-organizes the hydration tests to make it easier to add new tests. Incremental hydration can have tests in a separate file after this groundwork is landed.
PR Close#58196
Matthieu Riegler