1 | export function observableToAsyncIterable(observable) {
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2 | const pullQueue = [];
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3 | const pushQueue = [];
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4 | let listening = true;
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5 | const pushValue = (value) => {
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6 | if (pullQueue.length !== 0) {
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7 |
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8 | pullQueue.shift()({ value, done: false });
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9 | }
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10 | else {
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11 | pushQueue.push({ value, done: false });
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12 | }
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13 | };
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14 | const pushError = (error) => {
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15 | if (pullQueue.length !== 0) {
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16 |
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17 | pullQueue.shift()({ value: { errors: [error] }, done: false });
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18 | }
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19 | else {
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20 | pushQueue.push({ value: { errors: [error] }, done: false });
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21 | }
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22 | };
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23 | const pushDone = () => {
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24 | if (pullQueue.length !== 0) {
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25 |
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26 | pullQueue.shift()({ done: true });
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27 | }
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28 | else {
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29 | pushQueue.push({ done: true });
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30 | }
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31 | };
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32 | const pullValue = () => new Promise(resolve => {
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33 | if (pushQueue.length !== 0) {
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34 | const element = pushQueue.shift();
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35 |
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36 | resolve(element);
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37 | }
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38 | else {
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39 | pullQueue.push(resolve);
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40 | }
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41 | });
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42 | const subscription = observable.subscribe({
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43 | next(value) {
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44 | pushValue(value);
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45 | },
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46 | error(err) {
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47 | pushError(err);
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48 | },
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49 | complete() {
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50 | pushDone();
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51 | },
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52 | });
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53 | const emptyQueue = () => {
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54 | if (listening) {
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55 | listening = false;
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56 | subscription.unsubscribe();
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57 | for (const resolve of pullQueue) {
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58 | resolve({ value: undefined, done: true });
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59 | }
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60 | pullQueue.length = 0;
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61 | pushQueue.length = 0;
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62 | }
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63 | };
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64 | return {
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65 | next() {
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66 |
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67 | return listening ? pullValue() : this.return();
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68 | },
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69 | return() {
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70 | emptyQueue();
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71 | return Promise.resolve({ value: undefined, done: true });
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72 | },
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73 | throw(error) {
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74 | emptyQueue();
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75 | return Promise.reject(error);
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76 | },
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77 | [Symbol.asyncIterator]() {
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78 | return this;
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79 | },
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80 | };
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81 | }
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