@angular/core
Version:
Angular - the core framework
525 lines (518 loc) • 20 kB
JavaScript
/**
* @license Angular v20.0.3
* (c) 2010-2025 Google LLC. https://angular.io/
* License: MIT
*/
/**
* The default equality function used for `signal` and `computed`, which uses referential equality.
*/
function defaultEquals(a, b) {
return Object.is(a, b);
}
/**
* The currently active consumer `ReactiveNode`, if running code in a reactive context.
*
* Change this via `setActiveConsumer`.
*/
let activeConsumer = null;
let inNotificationPhase = false;
/**
* Global epoch counter. Incremented whenever a source signal is set.
*/
let epoch = 1;
/**
* If set, called after a producer `ReactiveNode` is created.
*/
let postProducerCreatedFn = null;
/**
* Symbol used to tell `Signal`s apart from other functions.
*
* This can be used to auto-unwrap signals in various cases, or to auto-wrap non-signal values.
*/
const SIGNAL = /* @__PURE__ */ Symbol('SIGNAL');
function setActiveConsumer(consumer) {
const prev = activeConsumer;
activeConsumer = consumer;
return prev;
}
function getActiveConsumer() {
return activeConsumer;
}
function isInNotificationPhase() {
return inNotificationPhase;
}
function isReactive(value) {
return value[SIGNAL] !== undefined;
}
const REACTIVE_NODE = {
version: 0,
lastCleanEpoch: 0,
dirty: false,
producerNode: undefined,
producerLastReadVersion: undefined,
producerIndexOfThis: undefined,
nextProducerIndex: 0,
liveConsumerNode: undefined,
liveConsumerIndexOfThis: undefined,
consumerAllowSignalWrites: false,
consumerIsAlwaysLive: false,
kind: 'unknown',
producerMustRecompute: () => false,
producerRecomputeValue: () => { },
consumerMarkedDirty: () => { },
consumerOnSignalRead: () => { },
};
/**
* Called by implementations when a producer's signal is read.
*/
function producerAccessed(node) {
if (inNotificationPhase) {
throw new Error(typeof ngDevMode !== 'undefined' && ngDevMode
? `Assertion error: signal read during notification phase`
: '');
}
if (activeConsumer === null) {
// Accessed outside of a reactive context, so nothing to record.
return;
}
activeConsumer.consumerOnSignalRead(node);
// This producer is the `idx`th dependency of `activeConsumer`.
const idx = activeConsumer.nextProducerIndex++;
assertConsumerNode(activeConsumer);
if (idx < activeConsumer.producerNode.length && activeConsumer.producerNode[idx] !== node) {
// There's been a change in producers since the last execution of `activeConsumer`.
// `activeConsumer.producerNode[idx]` holds a stale dependency which will be be removed and
// replaced with `this`.
//
// If `activeConsumer` isn't live, then this is a no-op, since we can replace the producer in
// `activeConsumer.producerNode` directly. However, if `activeConsumer` is live, then we need
// to remove it from the stale producer's `liveConsumer`s.
if (consumerIsLive(activeConsumer)) {
const staleProducer = activeConsumer.producerNode[idx];
producerRemoveLiveConsumerAtIndex(staleProducer, activeConsumer.producerIndexOfThis[idx]);
// At this point, the only record of `staleProducer` is the reference at
// `activeConsumer.producerNode[idx]` which will be overwritten below.
}
}
if (activeConsumer.producerNode[idx] !== node) {
// We're a new dependency of the consumer (at `idx`).
activeConsumer.producerNode[idx] = node;
// If the active consumer is live, then add it as a live consumer. If not, then use 0 as a
// placeholder value.
activeConsumer.producerIndexOfThis[idx] = consumerIsLive(activeConsumer)
? producerAddLiveConsumer(node, activeConsumer, idx)
: 0;
}
activeConsumer.producerLastReadVersion[idx] = node.version;
}
/**
* Increment the global epoch counter.
*
* Called by source producers (that is, not computeds) whenever their values change.
*/
function producerIncrementEpoch() {
epoch++;
}
/**
* Ensure this producer's `version` is up-to-date.
*/
function producerUpdateValueVersion(node) {
if (consumerIsLive(node) && !node.dirty) {
// A live consumer will be marked dirty by producers, so a clean state means that its version
// is guaranteed to be up-to-date.
return;
}
if (!node.dirty && node.lastCleanEpoch === epoch) {
// Even non-live consumers can skip polling if they previously found themselves to be clean at
// the current epoch, since their dependencies could not possibly have changed (such a change
// would've increased the epoch).
return;
}
if (!node.producerMustRecompute(node) && !consumerPollProducersForChange(node)) {
// None of our producers report a change since the last time they were read, so no
// recomputation of our value is necessary, and we can consider ourselves clean.
producerMarkClean(node);
return;
}
node.producerRecomputeValue(node);
// After recomputing the value, we're no longer dirty.
producerMarkClean(node);
}
/**
* Propagate a dirty notification to live consumers of this producer.
*/
function producerNotifyConsumers(node) {
if (node.liveConsumerNode === undefined) {
return;
}
// Prevent signal reads when we're updating the graph
const prev = inNotificationPhase;
inNotificationPhase = true;
try {
for (const consumer of node.liveConsumerNode) {
if (!consumer.dirty) {
consumerMarkDirty(consumer);
}
}
}
finally {
inNotificationPhase = prev;
}
}
/**
* Whether this `ReactiveNode` in its producer capacity is currently allowed to initiate updates,
* based on the current consumer context.
*/
function producerUpdatesAllowed() {
return activeConsumer?.consumerAllowSignalWrites !== false;
}
function consumerMarkDirty(node) {
node.dirty = true;
producerNotifyConsumers(node);
node.consumerMarkedDirty?.(node);
}
function producerMarkClean(node) {
node.dirty = false;
node.lastCleanEpoch = epoch;
}
/**
* Prepare this consumer to run a computation in its reactive context.
*
* Must be called by subclasses which represent reactive computations, before those computations
* begin.
*/
function consumerBeforeComputation(node) {
node && (node.nextProducerIndex = 0);
return setActiveConsumer(node);
}
/**
* Finalize this consumer's state after a reactive computation has run.
*
* Must be called by subclasses which represent reactive computations, after those computations
* have finished.
*/
function consumerAfterComputation(node, prevConsumer) {
setActiveConsumer(prevConsumer);
if (!node ||
node.producerNode === undefined ||
node.producerIndexOfThis === undefined ||
node.producerLastReadVersion === undefined) {
return;
}
if (consumerIsLive(node)) {
// For live consumers, we need to remove the producer -> consumer edge for any stale producers
// which weren't dependencies after the recomputation.
for (let i = node.nextProducerIndex; i < node.producerNode.length; i++) {
producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
}
}
// Truncate the producer tracking arrays.
// Perf note: this is essentially truncating the length to `node.nextProducerIndex`, but
// benchmarking has shown that individual pop operations are faster.
while (node.producerNode.length > node.nextProducerIndex) {
node.producerNode.pop();
node.producerLastReadVersion.pop();
node.producerIndexOfThis.pop();
}
}
/**
* Determine whether this consumer has any dependencies which have changed since the last time
* they were read.
*/
function consumerPollProducersForChange(node) {
assertConsumerNode(node);
// Poll producers for change.
for (let i = 0; i < node.producerNode.length; i++) {
const producer = node.producerNode[i];
const seenVersion = node.producerLastReadVersion[i];
// First check the versions. A mismatch means that the producer's value is known to have
// changed since the last time we read it.
if (seenVersion !== producer.version) {
return true;
}
// The producer's version is the same as the last time we read it, but it might itself be
// stale. Force the producer to recompute its version (calculating a new value if necessary).
producerUpdateValueVersion(producer);
// Now when we do this check, `producer.version` is guaranteed to be up to date, so if the
// versions still match then it has not changed since the last time we read it.
if (seenVersion !== producer.version) {
return true;
}
}
return false;
}
/**
* Disconnect this consumer from the graph.
*/
function consumerDestroy(node) {
assertConsumerNode(node);
if (consumerIsLive(node)) {
// Drop all connections from the graph to this node.
for (let i = 0; i < node.producerNode.length; i++) {
producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
}
}
// Truncate all the arrays to drop all connection from this node to the graph.
node.producerNode.length =
node.producerLastReadVersion.length =
node.producerIndexOfThis.length =
0;
if (node.liveConsumerNode) {
node.liveConsumerNode.length = node.liveConsumerIndexOfThis.length = 0;
}
}
/**
* Add `consumer` as a live consumer of this node.
*
* Note that this operation is potentially transitive. If this node becomes live, then it becomes
* a live consumer of all of its current producers.
*/
function producerAddLiveConsumer(node, consumer, indexOfThis) {
assertProducerNode(node);
if (node.liveConsumerNode.length === 0 && isConsumerNode(node)) {
// When going from 0 to 1 live consumers, we become a live consumer to our producers.
for (let i = 0; i < node.producerNode.length; i++) {
node.producerIndexOfThis[i] = producerAddLiveConsumer(node.producerNode[i], node, i);
}
}
node.liveConsumerIndexOfThis.push(indexOfThis);
return node.liveConsumerNode.push(consumer) - 1;
}
/**
* Remove the live consumer at `idx`.
*/
function producerRemoveLiveConsumerAtIndex(node, idx) {
assertProducerNode(node);
if (typeof ngDevMode !== 'undefined' && ngDevMode && idx >= node.liveConsumerNode.length) {
throw new Error(`Assertion error: active consumer index ${idx} is out of bounds of ${node.liveConsumerNode.length} consumers)`);
}
if (node.liveConsumerNode.length === 1 && isConsumerNode(node)) {
// When removing the last live consumer, we will no longer be live. We need to remove
// ourselves from our producers' tracking (which may cause consumer-producers to lose
// liveness as well).
for (let i = 0; i < node.producerNode.length; i++) {
producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
}
}
// Move the last value of `liveConsumers` into `idx`. Note that if there's only a single
// live consumer, this is a no-op.
const lastIdx = node.liveConsumerNode.length - 1;
node.liveConsumerNode[idx] = node.liveConsumerNode[lastIdx];
node.liveConsumerIndexOfThis[idx] = node.liveConsumerIndexOfThis[lastIdx];
// Truncate the array.
node.liveConsumerNode.length--;
node.liveConsumerIndexOfThis.length--;
// If the index is still valid, then we need to fix the index pointer from the producer to this
// consumer, and update it from `lastIdx` to `idx` (accounting for the move above).
if (idx < node.liveConsumerNode.length) {
const idxProducer = node.liveConsumerIndexOfThis[idx];
const consumer = node.liveConsumerNode[idx];
assertConsumerNode(consumer);
consumer.producerIndexOfThis[idxProducer] = idx;
}
}
function consumerIsLive(node) {
return node.consumerIsAlwaysLive || (node?.liveConsumerNode?.length ?? 0) > 0;
}
function assertConsumerNode(node) {
node.producerNode ??= [];
node.producerIndexOfThis ??= [];
node.producerLastReadVersion ??= [];
}
function assertProducerNode(node) {
node.liveConsumerNode ??= [];
node.liveConsumerIndexOfThis ??= [];
}
function isConsumerNode(node) {
return node.producerNode !== undefined;
}
function runPostProducerCreatedFn(node) {
postProducerCreatedFn?.(node);
}
function setPostProducerCreatedFn(fn) {
const prev = postProducerCreatedFn;
postProducerCreatedFn = fn;
return prev;
}
/**
* Create a computed signal which derives a reactive value from an expression.
*/
function createComputed(computation, equal) {
const node = Object.create(COMPUTED_NODE);
node.computation = computation;
if (equal !== undefined) {
node.equal = equal;
}
const computed = () => {
// Check if the value needs updating before returning it.
producerUpdateValueVersion(node);
// Record that someone looked at this signal.
producerAccessed(node);
if (node.value === ERRORED) {
throw node.error;
}
return node.value;
};
computed[SIGNAL] = node;
if (typeof ngDevMode !== 'undefined' && ngDevMode) {
const debugName = node.debugName ? ' (' + node.debugName + ')' : '';
computed.toString = () => `[Computed${debugName}: ${node.value}]`;
}
runPostProducerCreatedFn(node);
return computed;
}
/**
* A dedicated symbol used before a computed value has been calculated for the first time.
* Explicitly typed as `any` so we can use it as signal's value.
*/
const UNSET = /* @__PURE__ */ Symbol('UNSET');
/**
* A dedicated symbol used in place of a computed signal value to indicate that a given computation
* is in progress. Used to detect cycles in computation chains.
* Explicitly typed as `any` so we can use it as signal's value.
*/
const COMPUTING = /* @__PURE__ */ Symbol('COMPUTING');
/**
* A dedicated symbol used in place of a computed signal value to indicate that a given computation
* failed. The thrown error is cached until the computation gets dirty again.
* Explicitly typed as `any` so we can use it as signal's value.
*/
const ERRORED = /* @__PURE__ */ Symbol('ERRORED');
// Note: Using an IIFE here to ensure that the spread assignment is not considered
// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.
// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.
const COMPUTED_NODE = /* @__PURE__ */ (() => {
return {
...REACTIVE_NODE,
value: UNSET,
dirty: true,
error: null,
equal: defaultEquals,
kind: 'computed',
producerMustRecompute(node) {
// Force a recomputation if there's no current value, or if the current value is in the
// process of being calculated (which should throw an error).
return node.value === UNSET || node.value === COMPUTING;
},
producerRecomputeValue(node) {
if (node.value === COMPUTING) {
// Our computation somehow led to a cyclic read of itself.
throw new Error(typeof ngDevMode !== 'undefined' && ngDevMode ? 'Detected cycle in computations.' : '');
}
const oldValue = node.value;
node.value = COMPUTING;
const prevConsumer = consumerBeforeComputation(node);
let newValue;
let wasEqual = false;
try {
newValue = node.computation();
// We want to mark this node as errored if calling `equal` throws; however, we don't want
// to track any reactive reads inside `equal`.
setActiveConsumer(null);
wasEqual =
oldValue !== UNSET &&
oldValue !== ERRORED &&
newValue !== ERRORED &&
node.equal(oldValue, newValue);
}
catch (err) {
newValue = ERRORED;
node.error = err;
}
finally {
consumerAfterComputation(node, prevConsumer);
}
if (wasEqual) {
// No change to `valueVersion` - old and new values are
// semantically equivalent.
node.value = oldValue;
return;
}
node.value = newValue;
node.version++;
},
};
})();
function defaultThrowError() {
throw new Error();
}
let throwInvalidWriteToSignalErrorFn = defaultThrowError;
function throwInvalidWriteToSignalError(node) {
throwInvalidWriteToSignalErrorFn(node);
}
function setThrowInvalidWriteToSignalError(fn) {
throwInvalidWriteToSignalErrorFn = fn;
}
/**
* If set, called after `WritableSignal`s are updated.
*
* This hook can be used to achieve various effects, such as running effects synchronously as part
* of setting a signal.
*/
let postSignalSetFn = null;
/**
* Creates a `Signal` getter, setter, and updater function.
*/
function createSignal(initialValue, equal) {
const node = Object.create(SIGNAL_NODE);
node.value = initialValue;
if (equal !== undefined) {
node.equal = equal;
}
const getter = (() => signalGetFn(node));
getter[SIGNAL] = node;
if (typeof ngDevMode !== 'undefined' && ngDevMode) {
const debugName = node.debugName ? ' (' + node.debugName + ')' : '';
getter.toString = () => `[Signal${debugName}: ${node.value}]`;
}
runPostProducerCreatedFn(node);
const set = (newValue) => signalSetFn(node, newValue);
const update = (updateFn) => signalUpdateFn(node, updateFn);
return [getter, set, update];
}
function setPostSignalSetFn(fn) {
const prev = postSignalSetFn;
postSignalSetFn = fn;
return prev;
}
function signalGetFn(node) {
producerAccessed(node);
return node.value;
}
function signalSetFn(node, newValue) {
if (!producerUpdatesAllowed()) {
throwInvalidWriteToSignalError(node);
}
if (!node.equal(node.value, newValue)) {
node.value = newValue;
signalValueChanged(node);
}
}
function signalUpdateFn(node, updater) {
if (!producerUpdatesAllowed()) {
throwInvalidWriteToSignalError(node);
}
signalSetFn(node, updater(node.value));
}
function runPostSignalSetFn(node) {
postSignalSetFn?.(node);
}
// Note: Using an IIFE here to ensure that the spread assignment is not considered
// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.
// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.
const SIGNAL_NODE = /* @__PURE__ */ (() => {
return {
...REACTIVE_NODE,
equal: defaultEquals,
value: undefined,
kind: 'signal',
};
})();
function signalValueChanged(node) {
node.version++;
producerIncrementEpoch();
producerNotifyConsumers(node);
postSignalSetFn?.(node);
}
export { COMPUTING, ERRORED, REACTIVE_NODE, SIGNAL, SIGNAL_NODE, UNSET, consumerAfterComputation, consumerBeforeComputation, consumerDestroy, consumerMarkDirty, consumerPollProducersForChange, createComputed, createSignal, defaultEquals, getActiveConsumer, isInNotificationPhase, isReactive, producerAccessed, producerIncrementEpoch, producerMarkClean, producerNotifyConsumers, producerUpdateValueVersion, producerUpdatesAllowed, runPostProducerCreatedFn, runPostSignalSetFn, setActiveConsumer, setPostProducerCreatedFn, setPostSignalSetFn, setThrowInvalidWriteToSignalError, signalGetFn, signalSetFn, signalUpdateFn };
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