feat(basics): add iter::toString (#4489) & perf(logging): reduce pe…

…ak memory usage in CDF export (#4490)

docs/exercises/01-iteration/06-json.exercise.ts

@@ -140,7 +140,5 @@ function extractNamesFromContactsSolutionInner(): AsyncGenerator<string> {
 // in a real application you would want to use the AsyncGenerator directly. Otherwise
 // you would be building up a huge string in memory.
 async function extractNamesFromContactsSolution(): Promise<string> {
-  return (await iter(extractNamesFromContactsSolutionInner()).toArray()).join(
-    ''
-  );
+  return await iter(extractNamesFromContactsSolutionInner()).toString();
 }

libs/auth/src/cast_vote_record_hashes.test.ts

@@ -89,15 +89,15 @@ const expectedCastVoteRecordRootHash =
 test('readableFileFromData', async () => {
   const readableFile = readableFileFromData('1', 'a');
   expect(readableFile.fileName).toEqual('1');
-  expect((await iter(readableFile.open()).toArray()).join('')).toEqual('a');
+  expect(await iter(readableFile.open()).toString()).toEqual('a');
   expect(await readableFile.computeSha256Hash()).toEqual(sha256('a'));
 });
 
 test('readableFileFromDisk', async () => {
   fs.writeFileSync(path.join(tempDirectoryPath, '1'), 'a');
   const readableFile = readableFileFromDisk(path.join(tempDirectoryPath, '1'));
   expect(readableFile.fileName).toEqual('1');
-  expect((await iter(readableFile.open()).toArray()).join('')).toEqual('a');
+  expect(await iter(readableFile.open()).toString()).toEqual('a');
   expect(await readableFile.computeSha256Hash()).toEqual(sha256('a'));
 });
 

libs/basics/src/iterators/async_iterator_plus.test.ts

@@ -321,11 +321,6 @@ test('toMap property', async () => {
   );
 });
 
-test('toSet', async () => {
-  expect(await iter([]).async().toSet()).toEqual(new Set());
-  expect(await iter([1, 2, 3]).async().toSet()).toEqual(new Set([1, 2, 3]));
-});
-
 test('toMap from iterable', async () => {
   expect(
     await iter(integers({ from: 1, through: 10 }))
@@ -339,6 +334,22 @@ test('toMap from iterable', async () => {
   );
 });
 
+test('toSet', async () => {
+  expect(await iter([]).async().toSet()).toEqual(new Set());
+  expect(await iter([1, 2, 3]).async().toSet()).toEqual(new Set([1, 2, 3]));
+});
+
+test('toString', async () => {
+  expect(await iter([]).async().toString()).toEqual('');
+  expect(await iter([1, 2, 3]).async().toString()).toEqual('123');
+  expect(await iter([1, 2, 3]).async().toString(' ')).toEqual('1 2 3');
+  expect(
+    await iter([{ toString: (): string => 'hello' }, 'world'])
+      .async()
+      .toString(', ')
+  ).toEqual('hello, world');
+});
+
 test('first', async () => {
   expect(await iter([]).async().first()).toEqual(undefined);
   expect(await iter([1]).async().first()).toEqual(1);

libs/basics/src/iterators/async_iterator_plus.ts

@@ -391,6 +391,10 @@ export class AsyncIteratorPlusImpl<T> implements AsyncIteratorPlus<T> {
     return set;
   }
 
+  async toString(separator = ''): Promise<string> {
+    return (await this.toArray()).join(separator);
+  }
+
   windows(groupSize: 0): never;
   windows(groupSize: 1): AsyncIteratorPlus<[T]>;
   windows(groupSize: 2): AsyncIteratorPlus<[T, T]>;

libs/basics/src/iterators/iterator_plus.test.ts

@@ -240,11 +240,6 @@ test('toMap property', () => {
   );
 });
 
-test('toSet', () => {
-  expect(iter([]).toSet()).toEqual(new Set());
-  expect(iter([1, 2, 3]).toSet()).toEqual(new Set([1, 2, 3]));
-});
-
 test('toMap from iterable', () => {
   expect(iter(integers({ from: 1, through: 10 })).toMap((a) => a % 2)).toEqual(
     new Map([
@@ -254,6 +249,20 @@ test('toMap from iterable', () => {
   );
 });
 
+test('toSet', () => {
+  expect(iter([]).toSet()).toEqual(new Set());
+  expect(iter([1, 2, 3]).toSet()).toEqual(new Set([1, 2, 3]));
+});
+
+test('toString', () => {
+  expect(iter([]).toString()).toEqual('');
+  expect(iter([1, 2, 3]).toString()).toEqual('123');
+  expect(iter([1, 2, 3]).toString(' ')).toEqual('1 2 3');
+  expect(
+    iter([{ toString: (): string => 'hello' }, 'world']).toString(', ')
+  ).toEqual('hello, world');
+});
+
 test('first', () => {
   expect(iter([]).first()).toEqual(undefined);
   expect(iter([1]).first()).toEqual(1);

libs/basics/src/iterators/iterator_plus.ts

@@ -379,6 +379,10 @@ export class IteratorPlusImpl<T> implements IteratorPlus<T>, AsyncIterable<T> {
     return new Set(this.iterable);
   }
 
+  toString(separator = ''): string {
+    return this.toArray().join(separator);
+  }
+
   windows(groupSize: 0): never;
   windows(groupSize: 1): IteratorPlus<[T]>;
   windows(groupSize: 2): IteratorPlus<[T, T]>;

libs/basics/src/iterators/lines.test.ts

@@ -112,7 +112,7 @@ test('lines (async)', async () => {
   ).toEqual(['abc', 'de']);
 
   const input = createReadStream(__filename);
-  expect((await lines(input).toArray()).join('\n')).toEqual(
+  expect(await lines(input).toString('\n')).toEqual(
     await readFile(__filename, 'utf8')
   );
 

libs/basics/src/iterators/types.ts

@@ -496,6 +496,12 @@ export interface IteratorPlus<T> extends Iterable<T> {
    */
   toSet(): Set<T>;
 
+  /**
+   * Returns a string representation of `this` by joining elements with
+   * `separator`. Consumes the entire contained iterable.
+   */
+  toString(separator?: string): string;
+
   /**
    * Throws an error because `groupSize` must be greater than 0.
    */
@@ -1121,6 +1127,12 @@ export interface AsyncIteratorPlus<T> extends AsyncIterable<T> {
    */
   toSet(): Promise<Set<T>>;
 
+  /**
+   * Returns a string representation of `this` by joining elements with
+   * `separator`. Consumes the entire contained iterable.
+   */
+  toString(separator?: string): Promise<string>;
+
   /**
    * Throws an error because `groupSize` must be greater than 0.
    */