'result' in FileReader has [object Object] instead of string after using upload method and reading file content

[marekdano]

Current behavior:

Desired behavior:

Thanks for creating this library. I like how clear is to use it to test upload file functionality.

I took the library to test uploading a JSON file, read the content in the file, set the state and display file content on the layout. I found while using this library, a JSON file uploads, FileReader executes, but the result returns [objectObject] instead of an expected string.

When I upload a file in the real app the FileReader result correctly contains a string which is a content of the uploaded file.

I'm not sure if there is a bug in the library or I missed something in my implementation which can be seen below.

Steps to reproduce: (app code and test code)

Please find the code that I use:

// implementation of file input

<input type="file" className="file-input" name="file" accept=".json" onChange={handleUploadFile}/>

// implementation of handleUploadFile

const handleUploadFile = (e: ChangeEvent<HTMLInputElement>) => {
    const file = e && ((e.target as HTMLInputElement).files as FileList)[0];
    if (file) {
      const fileReader = new FileReader();
      fileReader.onloadend = (e) => {
        const content = fileReader.result as string;
        
        console.log(content) // displays [object Object] instead of string
        setInput(JSON.parse(content));
        handleJSONChange(JSON.parse(content), null, 'input');
      }
      fileReader.readAsText(file);
    }
  }

// test

it.only('should upload a file', () => {
  const fileName = 'upload-file.json';
  const output = '{"sample": "json"}';

  cy.fixture(fileName)
      .then(fileContent => {
         cy.get('.file-input').upload({fileContent, fileName, mimeType: 'application/json'}, { subjectType: 'input', force: true })
       })
       .should(() => {
             cy.get('#input > .jsoneditor > .jsoneditor-outer > .ace_editor > textarea')
                 .should(($div) => {
                     const values = $div.map((i, el) => Cypress.$(el).text())
                     const result = values
                          .get()
                          .map(line => line.trimLeft())
                          .join('')

                     expect(result).to.eq(JSON.stringify(output))
                 });
         });
});

Versions

[justinlittman]

Just ran into this myself. The problem is that cy.fixture detects that the file is JSON and loads as such. This fixed the problem for me:

    cy.fixture(fileName).then(fileJson => {
      const fileContent = JSON.stringify(fileJson)
      cy.get('input[type="file"]').upload({ fileContent, fileName, mimeType: 'application/json' })
    })

[marekdano]

Thank you, @justinlittman! You'll fix it for me!
I'm closing the issue.

[abramenal]

Hi @marekdano!
Thanks for submitting the issue. I am really happy small community around the plugin now helps each other resolving such tricks.
This thing may be not obvious for other users as well so I intend to put this to README.md#Caveats section.

And shout out to @justinlittman for quick help!
@all-contributors add @justinlittman for question.

[allcontributors]

@abramenal

I've put up a pull request to add @justinlittman! 🎉