在从读取 stream 到写入 stream 的管道数据之后，从“完成”事件返回值

Question

I am trying to create a read stream and then pipe the contents of a word document XML file to a write stream and then read from that finished write stream. The problem I am running into is that on the first sequence of reading then writing and then reading I get a [Error: ENOENT: no such file or directory, open] error. However after this file was created from the first attempt the code runs smoothly and returns the pageCount value as expected. I have tried to read from the completed file and then return the pageCount value inside of the 'finish' event, but that just leaves me with an undefined returned value. As such, I am not sure what to do.

Any help would be appreciated for this struggling junior.

  console.log("unzipping");
  let pageCount = "";
  fs.createReadStream(data)
    .pipe(unzipper.Parse())
    .on("entry", function (entry) {
      const fileName = entry.path;
      const type = entry.type;
      const size = entry.vars.uncompressedSize;
      if (fileName === "docProps/app.xml") {
        // console.log(fileName);
        entry.pipe(fs.createWriteStream("./wordOutput")).on("finish", () => {
          console.log("finished writing the file");
        });
      } else {
        entry.autodrain();
      }
    });
  pageCount = await readWordFile("./wordOutput");
  if (pageCount === undefined) {
    console.log("PAGECOUNT IS UNDEFINED");
  }
  console.log("logging page count in unzip the file");
  console.log(pageCount);
  return pageCount;
};

const readWordFile = async (data) => {
  console.log("this is the data that readWordFile received");
  console.log(data);
  console.log("reading word file");
  const XMLData = await fsp.readFile(data, { encoding: "utf-8" });
  console.log(XMLData);
  const pageCount = XMLData.split("<Pages>")
    .join(",")
    .split("</Pages>")
    .join(",")
    .split(",")[1];
  console.log("getting page count from read word file");
  console.log(pageCount);
  return pageCount;
};

Answer 1

The error is coming from readWordFile , because it runs before the stream is done. You need to move reading to the finish part

Try this:

console.log("unzipping");
let pageCount = "";
fs.createReadStream(data)
    .pipe(unzipper.Parse())
    .on("entry", function(entry) {
        const fileName = entry.path;
        const type = entry.type;
        const size = entry.vars.uncompressedSize;
        if (fileName === "docProps/app.xml") {
            // console.log(fileName);
            entry.pipe(fs.createWriteStream("./wordOutput")).on("finish", async() => {
                console.log("finished writing the file");

                // finished writing, do everything here, and return
                pageCount = await readWordFile("./wordOutput");
                if (pageCount === undefined) {
                    console.log("PAGECOUNT IS UNDEFINED");
                }
                console.log("logging page count in unzip the file");
                console.log(pageCount);
                return pageCount;

            });
        } else {
            entry.autodrain();
        }
    });

};



const readWordFile = async(data) => {
    return new Promise(async(resolve, reject) => {

        console.log("this is the data that readWordFile received");
        console.log(data);
        console.log("reading word file");
        const XMLData = await fsp.readFile(data, {
            encoding: "utf-8"
        });
        console.log(XMLData);
        const pageCount = XMLData.split("<Pages>")
            .join(",")
            .split("</Pages>")
            .join(",")
            .split(",")[1];
        console.log("getting page count from read word file");
        console.log(pageCount);
        resolve(pageCount);
    });
};