Clean up iterable utilities

ts/sql/cleanDataForIpc.ts

@@ -3,7 +3,7 @@
 
 import { isPlainObject } from 'lodash';
 
-import { isIterable } from '../util/isIterable';
+import { isIterable } from '../util/iterables';
 
 /**
  * IPC arguments are serialized with the [structured clone algorithm][0], but we can only

ts/test-both/util/isIterable_test.ts

@@ -1,50 +0,0 @@
-// Copyright 2021 Signal Messenger, LLC
-// SPDX-License-Identifier: AGPL-3.0-only
-
-import { assert } from 'chai';
-
-import { isIterable } from '../../util/isIterable';
-
-describe('isIterable', () => {
-  it('returns false for non-iterables', () => {
-    assert.isFalse(isIterable(undefined));
-    assert.isFalse(isIterable(null));
-    assert.isFalse(isIterable(123));
-    assert.isFalse(isIterable({ foo: 'bar' }));
-    assert.isFalse(
-      isIterable({
-        length: 2,
-        '0': 'fake',
-        '1': 'array',
-      })
-    );
-  });
-
-  it('returns true for iterables', () => {
-    assert.isTrue(isIterable('strings are iterable'));
-    assert.isTrue(isIterable(['arrays too']));
-    assert.isTrue(isIterable(new Set('and sets')));
-    assert.isTrue(isIterable(new Map([['and', 'maps']])));
-    assert.isTrue(
-      isIterable({
-        [Symbol.iterator]() {
-          return {
-            next() {
-              return {
-                value: 'endless iterable',
-                done: false,
-              };
-            },
-          };
-        },
-      })
-    );
-    assert.isTrue(
-      isIterable(
-        (function* generators() {
-          yield 123;
-        })()
-      )
-    );
-  });
-});

ts/test-both/util/iterables_test.ts

@@ -4,9 +4,84 @@
 import { assert } from 'chai';
 import * as sinon from 'sinon';
 
-import { map, take } from '../../util/iterables';
+import { isIterable, size, map, take } from '../../util/iterables';
 
 describe('iterable utilities', () => {
+  describe('isIterable', () => {
+    it('returns false for non-iterables', () => {
+      assert.isFalse(isIterable(undefined));
+      assert.isFalse(isIterable(null));
+      assert.isFalse(isIterable(123));
+      assert.isFalse(isIterable({ foo: 'bar' }));
+      assert.isFalse(
+        isIterable({
+          length: 2,
+          '0': 'fake',
+          '1': 'array',
+        })
+      );
+    });
+
+    it('returns true for iterables', () => {
+      assert.isTrue(isIterable('strings are iterable'));
+      assert.isTrue(isIterable(['arrays too']));
+      assert.isTrue(isIterable(new Set('and sets')));
+      assert.isTrue(isIterable(new Map([['and', 'maps']])));
+      assert.isTrue(
+        isIterable({
+          [Symbol.iterator]() {
+            return {
+              next() {
+                return {
+                  value: 'endless iterable',
+                  done: false,
+                };
+              },
+            };
+          },
+        })
+      );
+      assert.isTrue(
+        isIterable(
+          (function* generators() {
+            yield 123;
+          })()
+        )
+      );
+    });
+  });
+
+  describe('size', () => {
+    it('returns the length of a string', () => {
+      assert.strictEqual(size(''), 0);
+      assert.strictEqual(size('hello world'), 11);
+    });
+
+    it('returns the length of an array', () => {
+      assert.strictEqual(size([]), 0);
+      assert.strictEqual(size(['hello', 'world']), 2);
+    });
+
+    it('returns the size of a set', () => {
+      assert.strictEqual(size(new Set()), 0);
+      assert.strictEqual(size(new Set([1, 2, 3])), 3);
+    });
+
+    it('returns the length (not byte length) of typed arrays', () => {
+      assert.strictEqual(size(new Uint8Array(3)), 3);
+      assert.strictEqual(size(new Uint32Array(3)), 3);
+    });
+
+    it('returns the size of arbitrary iterables', () => {
+      function* someNumbers() {
+        yield 3;
+        yield 6;
+        yield 9;
+      }
+      assert.strictEqual(size(someNumbers()), 3);
+    });
+  });
+
   describe('map', () => {
     it('returns an empty iterable when passed an empty iterable', () => {
       const fn = sinon.fake();

ts/util/grapheme.ts

@@ -1,13 +1,9 @@
 // Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
+import { size } from './iterables';
+
 export function count(str: string): number {
   const segments = new Intl.Segmenter().segment(str);
-  const iterator = segments[Symbol.iterator]();
-
-  let result = -1;
-  for (let done = false; !done; result += 1) {
-    done = Boolean(iterator.next().done);
-  }
-  return result;
+  return size(segments);
 }

ts/util/isIterable.ts

@@ -1,9 +0,0 @@
-// Copyright 2021 Signal Messenger, LLC
-// SPDX-License-Identifier: AGPL-3.0-only
-
-export function isIterable(value: unknown): value is Iterable<unknown> {
-  return (
-    (typeof value === 'object' && value !== null && Symbol.iterator in value) ||
-    typeof value === 'string'
-  );
-}

ts/util/iterables.ts

@@ -3,6 +3,31 @@
 
 /* eslint-disable max-classes-per-file */
 
+export function isIterable(value: unknown): value is Iterable<unknown> {
+  return (
+    (typeof value === 'object' && value !== null && Symbol.iterator in value) ||
+    typeof value === 'string'
+  );
+}
+
+export function size(iterable: Iterable<unknown>): number {
+  // We check for common types as an optimization.
+  if (typeof iterable === 'string' || Array.isArray(iterable)) {
+    return iterable.length;
+  }
+  if (iterable instanceof Set || iterable instanceof Map) {
+    return iterable.size;
+  }
+
+  const iterator = iterable[Symbol.iterator]();
+
+  let result = -1;
+  for (let done = false; !done; result += 1) {
+    done = Boolean(iterator.next().done);
+  }
+  return result;
+}
+
 export function map<T, ResultT>(
   iterable: Iterable<T>,
   fn: (value: T) => ResultT