Break out liveQuery()

libs/dexie-live-query/.gitignore

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+**/bundle.js
+**/bundle.js.map
+dist

libs/dexie-live-query/package.json

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+{
+  "name": "dexie-live-query",
+  "version": "1.0.0",
+  "description": "Observe IndexedDB by turning Promise-returning functions into Observables.",
+  "main": "dist/dexie-live-query.js",
+  "module": "dist/dexie-live-query.mjs",
+  "scripts": {
+    "build": "just-build",
+    "test": "echo This package is tested in Dexie.js test suite"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/dfahlander/Dexie.js.git"
+  },
+  "keywords": [
+    "observables",
+    "reactive",
+    "indexeddb"
+  ],
+  "author": "david@dexie.org",
+  "license": "Apache-2.0",
+  "bugs": {
+    "url": "https://github.com/dfahlander/Dexie.js/issues"
+  },
+  "homepage": "https://github.com/dfahlander/Dexie.js#readme",
+  "dependencies": {
+    "dexie": "file:../..",
+    "rxjs": "^6.0.0"
+  },
+  "just-build": {
+    "default": [
+      "just-build dexie",
+      "rollup -c rollup.config.js",
+      "tsc --emitDeclarationOnly"
+    ],
+    "run-tests": [
+      "karma start test/karma.conf.js --single-run"
+    ],
+    "dexie": [
+      "cd ../..",
+      "npm run build"
+    ]
+  }
+}

libs/dexie-live-query/rollup.config.js

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+import commonjs from '@rollup/plugin-commonjs';
+import nodeResolve from '@rollup/plugin-node-resolve';
+import typescript from '@rollup/plugin-typescript';
+
+const ERRORS_TO_IGNORE = [
+  "THIS_IS_UNDEFINED",
+];
+
+export default {
+  input: './src/index.ts',
+  output: [{
+    file: 'dist/dexie-live-query.js',
+    format: 'umd',
+    globals: {dexie: "Dexie", rxjs: "Rx"},
+    name: 'liveQuery',
+    sourcemap: true
+  },{
+    file: 'dist/dexie-live-query.mjs',
+    format: 'es',
+    sourcemap: true
+  }],
+  external: ['dexie', 'rxjs'],
+  plugins: [
+    typescript(),
+    nodeResolve({
+      browser: true,
+      preferBuiltins: false
+    }),
+    commonjs(),
+  ],
+  onwarn ({loc, frame, code, message}) {
+    if (ERRORS_TO_IGNORE.includes(code)) return;
+    if ( loc ) {
+      console.warn( `${loc.file} (${loc.line}:${loc.column}) ${message}` );
+      if ( frame ) console.warn( frame );
+    } else {
+      console.warn(`${code} ${message}`);
+    }    
+  }
+};

libs/dexie-live-query/src/helpers.ts

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+import { ObservabilitySet, IntervalTree, mergeRanges } from "dexie";
+
+export const isAsyncFunction = typeof Symbol !== 'undefined'
+    ? (fn: Function) => fn[Symbol.toStringTag] === 'AsyncFunction'
+    : ()=>false;
+
+export function extendObservabilitySet(
+  target: ObservabilitySet,
+  newSet: ObservabilitySet
+): ObservabilitySet {
+  Object.keys(newSet).forEach(part => {
+    const rangeSet: IntervalTree = target[part] || (target[part] = {d: 0});
+    mergeRanges(rangeSet, newSet[part]);
+  });
+  return target;
+}

libs/dexie-live-query/src/index.ts

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+import { liveQuery } from "./liveQuery.js";

libs/dexie-live-query/src/liveQuery.ts

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+import { isAsyncFunction, extendObservabilitySet } from "./helpers";
+import Dexie, { ObservabilitySet, rangesOverlap, DexiePromiseConstructor } from "dexie";
+import {
+  Observable
+} from "rxjs";
+
+const DexiePromise = Dexie.Promise as DexiePromiseConstructor; // Reveals private properties of Dexie.Promise.
+const {iea, dea, newPSD, usePSD} = DexiePromise;
+
+export function liveQuery<T>(querier: () => T | Promise<T>): Observable<T> {
+  return new Observable<T>((observer) => {
+    const scopeFuncIsAsync = isAsyncFunction(querier);
+    function execute(subscr: ObservabilitySet) {
+      if (scopeFuncIsAsync) {
+        iea();
+      }
+      const exec = () => newPSD(querier, { subscr, trans: null });
+      const rv = DexiePromise.PSD.trans
+        ? // Ignore current transaction if active when calling subscribe().
+          usePSD(DexiePromise.PSD.transless, exec)
+        : exec();
+      if (scopeFuncIsAsync) {
+        (rv as Promise<any>).then(dea, dea);
+      }
+      return rv;
+    }
+
+    let closed = false;
+
+    let accumMuts: ObservabilitySet = {};
+    let currentObs: ObservabilitySet = {};
+
+    const subscription = {
+      get closed() {
+        return closed;
+      },
+      unsubscribe: () => {
+        closed = true;
+        Dexie.on.txcommitted.unsubscribe(mutationListener);
+      },
+    };
+
+    let querying = false,
+      startedListening = false;
+
+    function shouldNotify() {
+      return Object.keys(currentObs).some(
+        (key) =>
+          accumMuts[key] && rangesOverlap(accumMuts[key], currentObs[key])
+      );
+    }
+
+    const mutationListener = (parts: ObservabilitySet) => {
+      extendObservabilitySet(accumMuts, parts);
+      if (shouldNotify()) {
+        doQuery();
+      }
+    };
+
+    const doQuery = () => {
+      if (querying || closed) return;
+      accumMuts = {};
+      const subscr: ObservabilitySet = {};
+      const ret = execute(subscr);
+      if (!startedListening) {
+        Dexie.on("txcommitted", mutationListener);
+        startedListening = true;
+      }
+      querying = true;
+      Promise.resolve(ret).then(
+        (result) => {
+          querying = false;
+          if (closed) return;
+          if (shouldNotify()) {
+            // Mutations has happened while we were querying. Redo query.
+            doQuery();
+          } else {
+            accumMuts = {};
+            // Update what we are subscribing for based on this last run:
+            currentObs = subscr;
+            observer.next && observer.next(result);
+          }
+        },
+        (err) => {
+          querying = false;
+          observer.error && observer.error(err);
+          subscription.unsubscribe();
+        }
+      );
+    };
+
+    doQuery();
+    return subscription;
+  });
+}

libs/dexie-live-query/test/index.html

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+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>live-query unit tests</title>
+  <link rel="stylesheet" href="../../../node_modules/qunitjs/qunit/qunit.css">
+</head>
+<body>
+    <div id="qunit"></div>
+    <div id="qunit-fixture"></div>
+    <script src="../../../test/babel-polyfill/polyfill.min.js"></script>
+    <script src="../../../node_modules/qunitjs/qunit/qunit.js"></script>
+    <script src="../../../node_modules/rxjs/bundles/rxjs.umd.js"></script>
+    <script src="../../../dist/dexie.js"></script>
+    <script src="../dist/dexie-live-query.js"></script>
+    <script src="bundle.js"></script>
+</body>
+</html>

libs/dexie-live-query/test/index.js

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+import "./test-live-query.js";

libs/dexie-live-query/test/karma.conf.js

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+// Include common configuration
+const {karmaCommon, getKarmaConfig, defaultBrowserMatrix} = require('../../../test/karma.common');
+
+module.exports = function (config) {
+  const cfg = getKarmaConfig({
+    // Be fine with testing on local travis firefox
+    ci: [
+      "Firefox",
+      "bs_chrome_latest_supported",
+      "bs_safari_latest_supported"
+    ],
+    pre_npm_publish: [
+      "Firefox",
+      "bs_chrome_latest_supported",
+      "bs_safari_latest_supported"
+    ]
+  }, {
+    // Base path should point at the root 
+    basePath: '../../../',
+    files: karmaCommon.files.concat([
+      'node_modules/rxjs/bundles/rxjs.umd.js',
+      'dist/dexie.js',
+      'libs/dexie-live-query/dist/dexie-live-query.js',
+      'libs/dexie-live-query/test/bundle.js',
+      { pattern: 'libs/dexie-live-query/test/*.map', watched: false, included: false },
+      { pattern: 'libs/dexie-live-query/dist/*.map', watched: false, included: false }
+    ])
+  });
+
+  config.set(cfg);
+}