I’m on the process of making a filter based off evaluating a file’s signature obtained via a file’s buffer provided by Multer. I know Multer provides the MIME type, but I also have to check wether the file is actually of that MIME type via some other ways of validation.

Because of that, my steps are:

1. Temporarily store the request’s files in Multer’s memoryStorage() to get the buffer, then
2. Filter the valid files
3. Append those valid files and other information I need for a newly made FormData
4. Make a POST request to the other endpoint(“/upload”) with the new FormData
5. Store files in the cloud with Multer

PROBLEM IS: Once I force some error on the second endpoint, the process ends up on a loop. The error is detected, however I cannot return any HTTP code as a response to the first endpoint!

First endpoint:

/* NOTE: storeInMemory.array("files") stores in memory the files' buffer information, which 
/* are needed in order to work with validating the files! */
app.post("/filesUpload", storeInMemory.array("files"), async (req, res) => {
    const files = req.files;

    /* this array stores the items i have to upload */
    let uploadArray = [];

    /* filter only the items i actually need to upload */
    for (const item of files) {
        /*-- some filter logic --*/
        uploadArray.push(item);
    }

    /* create new FormData to store the actual files i have to upload -
    /* as multer works with http a new formdata has to be created, so i can make a call to another endpoint */
    let form = new FormData();
    form.append("someData", req.body["someData"]);

    /* append the files to the form i'll use to upload later */
    uploadArray.forEach((item) => {
        form.append("files", item.buffer, item.originalname);
    });

    try {
        const postUrl = process.env.MY_URL + "/upload";
        const myHeaders = { headers: { 'Content-Type': `multipart/form-data; boundary=${form._boundary}` } };
        /* Request to other endpoint */
        let uploadResult = await axios.post(postUrl, form, myHeaders);

        if (uploadResult.status == 200) return res.send(uploadResult).status(200);
        /* PROBLEM HERE: this is the point the program never gets to and i need it to */
        else {
            return res.send(uploadResult).status(500);
        }
    }
    catch (error) {
        console.error("Unpredicted error occurred: ", error);
        return res.send(error)
    }

});

Second endpoint:

app.post("/upload", async (req, res) => {
    try {
        await new Promise((resolve, reject) => {
            /* upload the files to cloud */
            uploadOnCloud.array("files")(req, res, (err) => {
                if (err) {
                    console.error("Error happened successfully!", err)
                    return reject(err);
                }
                else
                    return resolve();
            });
        });
        /* If no err detected, ends with 200 */
        res.sendStatus(200);
    }
    catch (error) {
        /* PROBLEM: can neither set status, nor anything else */
        res.status(500).send(error.message);
    }
});

What could be wrong here?