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41 lines
1.3 KiB
41 lines
1.3 KiB
'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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