@angular/core
Version:
Angular - the core framework
92 lines • 12.4 kB
JavaScript
/**
* @license
* Copyright Google LLC All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import { defaultEquals } from './equality';
import { consumerAfterComputation, consumerBeforeComputation, producerAccessed, producerUpdateValueVersion, REACTIVE_NODE, SIGNAL } from './graph';
/**
* Create a computed signal which derives a reactive value from an expression.
*/
export function createComputed(computation) {
const node = Object.create(COMPUTED_NODE);
node.computation = computation;
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;
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,
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('Detected cycle in computations.');
}
const oldValue = node.value;
node.value = COMPUTING;
const prevConsumer = consumerBeforeComputation(node);
let newValue;
try {
newValue = node.computation();
}
catch (err) {
newValue = ERRORED;
node.error = err;
}
finally {
consumerAfterComputation(node, prevConsumer);
}
if (oldValue !== UNSET && oldValue !== ERRORED && newValue !== ERRORED &&
node.equal(oldValue, newValue)) {
// No change to `valueVersion` - old and new values are
// semantically equivalent.
node.value = oldValue;
return;
}
node.value = newValue;
node.version++;
},
};
})();
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Used to detect cycles in computation chains.\n * Explicitly typed as `any` so we can use it as signal's value.\n */\nconst COMPUTING: any = /* @__PURE__ */ Symbol('COMPUTING');\n\n/**\n * A dedicated symbol used in place of a computed signal value to indicate that a given computation\n * failed. The thrown error is cached until the computation gets dirty again.\n * Explicitly typed as `any` so we can use it as signal's value.\n */\nconst ERRORED: any = /* @__PURE__ */ Symbol('ERRORED');\n\n// Note: Using an IIFE here to ensure that the spread assignment is not considered\n// a side-effect, ending up preserving `COMPUTED_NODE` and `REACTIVE_NODE`.\n// TODO: remove when https://github.com/evanw/esbuild/issues/3392 is resolved.\nconst COMPUTED_NODE = /* @__PURE__ */ (() => {\n  return {\n    ...REACTIVE_NODE,\n    value: UNSET,\n    dirty: true,\n    error: null,\n    equal: defaultEquals,\n\n    producerMustRecompute(node: ComputedNode<unknown>): boolean {\n      // Force a recomputation if there's no current value, or if the current value is in the\n      // process of being calculated (which should throw an error).\n      return node.value === UNSET || node.value === COMPUTING;\n    },\n\n    producerRecomputeValue(node: ComputedNode<unknown>): void {\n      if (node.value === COMPUTING) {\n        // Our computation somehow led to a cyclic read of itself.\n        throw new Error('Detected cycle in computations.');\n      }\n\n      const oldValue = node.value;\n      node.value = COMPUTING;\n\n      const prevConsumer = consumerBeforeComputation(node);\n      let newValue: unknown;\n      try {\n        newValue = node.computation();\n      } catch (err) {\n        newValue = ERRORED;\n        node.error = err;\n      } finally {\n        consumerAfterComputation(node, prevConsumer);\n      }\n\n      if (oldValue !== UNSET && oldValue !== ERRORED && newValue !== ERRORED &&\n          node.equal(oldValue, newValue)) {\n        // No change to `valueVersion` - old and new values are\n        // semantically equivalent.\n        node.value = oldValue;\n        return;\n      }\n\n      node.value = newValue;\n      node.version++;\n    },\n  };\n})();\n"]}