[GITHUB-10139][Fix] Generated Swift code not working for multipart/form-data video upload

[aman-v-singh]

Context

• In postman-app-support, Issue #10139 The user has described an issue they were facing with Swift code generated for Content-Type multipart/form-data.

Root-Cause-Analysis

• When the user was using the generated Swift code for uploading a .MOV video file, they were facing an issue on reaching this line:-
  let fileContent = String(data: fileData, encoding: .utf8)!

• On analysis, it is found that the error is arising because the generated code is trying to encode video data in UTF-8 format to be converted into String type, but we must realise every character in fileData would not be encodable in UTF-8 format.

Solution

• Instead of converting file data to String type, we will change the body variable from String to Data type. This way we don't have to convert the fileContent to String.

• For details refer to this answer.

Code Generated

import Foundation
#if canImport(FoundationNetworking)
import FoundationNetworking
#endif

let parameters = [
    [
        "key": "VideoFile",
        "src": "{VIDEO_FILE_PATH}",
        "type": "file"
    ]] as [[String: Any]]

let boundary = "Boundary-\(UUID().uuidString)"
var body = Data()
var error: Error? = nil
for param in parameters {
    if param["disabled"] != nil { continue }
    let paramName = param["key"]!
    body += Data("--\(boundary)\r\n".utf8)
    body += Data("Content-Disposition:form-data; name=\"\(paramName)\"".utf8)
    if param["contentType"] != nil {
        body += Data("\r\nContent-Type: \(param["contentType"] as! String)".utf8)
    }
    let paramType = param["type"] as! String
    if paramType == "text" {
        let paramValue = param["value"] as! String
        body += Data("\r\n\r\n\(paramValue)\r\n".utf8)
    } else {
        let paramSrc = param["src"] as! String
        let fileURL = URL(fileURLWithPath: paramSrc)
        if let fileContent = try? Data(contentsOf: fileURL) {
            body += Data("; filename=\"\(paramSrc)\"\r\n".utf8)
            body += Data("Content-Type: \"content-type header\"\r\n".utf8)
            body += Data("\r\n".utf8)
            body += fileContent
            body += Data("\r\n".utf8)
        }
    }
}
body += Data("--\(boundary)--\r\n".utf8);
let postData = body


var request = URLRequest(url: URL(string: "https://postman-echo.com/post")!,timeoutInterval: Double.infinity)
request.addValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")

request.httpMethod = "POST"
request.httpBody = postData

let task = URLSession.shared.dataTask(with: request) { data, response, error in 
    guard let data = data else {
        print(String(describing: error))
        exit(EXIT_SUCCESS)
    }
    print(String(data: data, encoding: .utf8)!)
    exit(EXIT_SUCCESS)
}

task.resume()
dispatchMain()

[VShingala]

@aman-v-singh Have we tested that this change doesn't affect existing flow. i.e. Other files which are in text format can sill be sent correctly in form-data body?

[VShingala]

@aman-v-singh Could you also attach updated snippet here in description once? Also let's communicate this latest snippet with the User that reported this issue and make sure it works for them to get their feedback.

[aman-v-singh]

@VShingala I have added the newly generated code above in the description and notified the user of the same.

@aman-v-singh Have we tested that this change doesn't affect existing flow. i.e. Other files which are in text format can sill be sent correctly in form-data body?

The Newman tests take care of these different possibilities.
eg:- Single/multiple file upload via form-data and Binary file upload via form-data check for different types of files.

• https://github.com/postmanlabs/postman-code-generators/blob/develop/test/codegen/newman/fixtures/formdataFileCollection.json
• Link to Unit test output:- https://github.com/postmanlabs/postman-code-generators/actions/runs/5475200225/jobs/9970978873?pr=714#step:7:23135

[VShingala]

@aman-v-singh There is a bit of catch with forma-data type of bodies and how files are stored in collection if selected. For example, the collection that you linked contains path to a file which is for the user that created this collection. This file doesn't exist in pipelines system or repository anywhere. As such actual data within files is not being sent with the request.

Which is why just wanted to make sure this is working correctly, could you give it a try manually and verify once?

[dhwaneetbhatt]

@aman-v-singh There is a bit of catch with forma-data type of bodies and how files are stored in collection if selected. For example, the collection that you linked contains path to a file which is for the user that created this collection. This file doesn't exist in pipelines system or repository anywhere. As such actual data within files is not being sent with the request.

Which is why just wanted to make sure this is working correctly, could you give it a try manually and verify once?

@VShingala these files and paths are generated on the fly when test case runs and this path gets updated locally. We usually don't commit the changes because it depends on the machine being run.

[VShingala]

@dhwaneetbhatt Thanks! Checked this out and Didn't know about this till now. This was a practice of habit for me while I was working on this as this file manipulation did not exist. 😅

For ref, below is code responsible for manipulation.

• postman-code-generators/npm/test.sh

  Line 16 in 989648d

  echo "Creating test files and adding paths to collection for testing form data file uploads"

• postman-code-generators/npm/addPathToFormdataFile.js

  Line 7 in 32e76dd

  formdata[0].src = path.resolve(__dirname, '../dummyFile1.txt');