42 lines
1.3 KiB
JavaScript
42 lines
1.3 KiB
JavaScript
'use strict';
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const REGISTRATION_KEY = Symbol('@@any-observable/REGISTRATION');
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let registered = null;
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module.exports = (global, loadImplementation) => {
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return (implementation, opts) => {
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opts = opts || {};
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// global registration unless explicitly {global: false} in options (default true)
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const registerGlobal = opts.global !== false;
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// Load any previous global registration
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if (registerGlobal && !registered) {
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registered = global[REGISTRATION_KEY];
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}
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if (registered && implementation && registered.implementation !== implementation) {
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throw new Error(`any-observable already defined as "${registered.implementation}". You can only register an implementation before the first call to require('any-observable') and an implementation cannot be changed`);
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}
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if (!registered) {
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// Use provided implementation
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if (implementation && opts.Observable) {
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registered = {
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Observable: opts.Observable,
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implementation
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};
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} else {
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// Require implementation if implementation is specified but not provided
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registered = loadImplementation(implementation || null);
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}
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if (registerGlobal) {
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// Register preference globally in case multiple installations
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global[REGISTRATION_KEY] = registered;
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}
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}
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return registered;
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};
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};
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