feat: add Symbol.asyncInterator to Query.stream()

[schmidt-sebastian]

This PR removes the dependency on bun, which exposed an old Stream interface that did not expose Symbol.asyncInterator.

A lot of the code churn in this PR is combining readStream and readWriteStream, which were almost identical before (readStream sent request to the GAPIC method directly, whereas readWriteStream sent it to the stream). The new method handles all Stream callbacks uniformly and combines both stream modes.

A disclaimer: I don't really understand Node streams, but we have semi-good test coverage for most error cases.

Fixes #789

[codecov]

Codecov Report

Merging #843 into master will decrease coverage by 0.13%.
The diff coverage is 85.29%.

@@            Coverage Diff             @@
##           master     #843      +/-   ##
==========================================
- Coverage   88.83%   88.69%   -0.14%     
==========================================
  Files          27       27              
  Lines       16769    16681      -88     
  Branches     1156     1151       -5     
==========================================
- Hits        14896    14796     -100     
- Misses       1868     1880      +12     
  Partials        5        5

Impacted Files	Coverage Δ
dev/src/external-modules.d.ts	0% <0%> (ø)	⬆️
dev/src/index.ts	98.78% <100%> (+0.04%)	⬆️
dev/src/watch.ts	98.45% <100%> (ø)	⬆️
dev/src/reference.ts	99.07% <100%> (ø)	⬆️

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[schmidt-sebastian]

@bcoe It looks like the coverage decrease in this PR is because of the license comment I had to add to external-modules.d.ts.

[alexander-fenster]

Is it a breaking change?

[schmidt-sebastian]

This is not part of of our public API (we define our own types). I can use an underscore prefix here, but in general the client is pretty inconsistent here.

[alexander-fenster]

OK. Since it's TypeScript, we might as well make those methods private.

[schmidt-sebastian]

Unfortunately, these are "module private" and used in other internal classes.

[alexander-fenster]

if it's an externally visible function, I would vote for an enum (but up to you)

[schmidt-sebastian]

This should be private.

[alexander-fenster]

Does TypeScript compile it into something that older versions of Node.js can understand? Async iterators only appeared in Node 10, right?

[schmidt-sebastian]

I am a little surprised too, but it seems to work. I stole this test from googleapis/nodejs-storage#799

[schmidt-sebastian]

Typescript transpiles it away:

  it('stream() supports readable[Symbol.asyncIterator]()', async () => {
        var e_1, _a;
        let received = 0;
        await randomCol.doc().set({ foo: 'bar' });
        await randomCol.doc().set({ foo: 'bar' });
        const stream = randomCol.stream();
        try {
            for (var stream_1 = __asyncValues(stream), stream_1_1; stream_1_1 = await stream_1.next(), !stream_1_1.done;) {
                const chunk = stream_1_1.value;
                ++received;
            }
        }
        catch (e_1_1) { e_1 = { error: e_1_1 }; }
        finally {
            try {
                if (stream_1_1 && !stream_1_1.done && (_a = stream_1.return)) await _a.call(stream_1);
            }
            finally { if (e_1) throw e_1.error; }
        }
        chai_1.expect(received).to.equal(2);
    });

[schmidt-sebastian]

Also verifies that the test does indeed work with Symbol.asyncIterator by changing the target level to ES2019.