node.js Readable: can push(null) be called even if the last push returned false?

[Benjamin Pasero]

Hi,

I am looking into implementing my own Readable (by following https://nodejs.org/docs/v7.9.0/api/stream.html#stream_new_stream_readable_options). The documentation is a bit unclear to me in one point: if the EOS (end of stream) is reached, I should call this.push(null), however do I also have to check if the last call to push returned false and then not signal EOS?

My stream basically looks like this:

const readable = new Readable({

    read: function () {

        try {

            let chunk: string;

            let canPush = true;

            // Push all chunks as long as we can push and as long as

            // the underlying reader returns strings to us

            while (canPush && typeof (chunk = reader.read()) === 'string') {

                canPush = this.push(chunk);

            }

            // Signal EOS by pushing NULL

            if (typeof chunk !== 'string') {

                this.push(null);

            }

        } catch (error) {

            this.emit('error', error);

        }

    }

});

In this case I am happily calling this.push(null) even though maybe the last push signald I should wait?

Thanks for feedback,

Ben

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