<FileInput> doesn't work

[ss-dev]

I have a simple form for editing emails:

<Edit {...props} undoable={false}>
    <SimpleForm>
        <TextField source="id" />
        <TextInput source="name" />
        <TextInput source="subject" />
        <RichTextInput source="body" />
        <FileInput source="attachment">
            <FileField source="src" title="title" />
        </FileInput>
    </SimpleForm>
</Edit>

When I save it without any files, it's okay.
But if I add some file, and click "Save" button, I have next error:

sanitizeEmptyValues.js:16 Uncaught TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)
    at sanitizeEmptyValues (sanitizeEmptyValues.js:16)
    at sanitizeEmptyValues.js:18
    at Array.reduce (<anonymous>)
    at sanitizeEmptyValues (sanitizeEmptyValues.js:16)
    at submit (SimpleForm.js:60)
    at Object.submit (final-form.es.js:1291)
    at handleSubmit (react-final-form.es.js:263)
    at SimpleForm.js:118
    at handleMouseDown (SaveButton.js:115)
    at ButtonBase.js:145
    at useEventCallback.js:15
    at HTMLUnknownElement.callCallback (react-dom.development.js:337)
    at Object.invokeGuardedCallbackDev (react-dom.development.js:386)
    at invokeGuardedCallback (react-dom.development.js:439)
    at invokeGuardedCallbackAndCatchFirstError (react-dom.development.js:454)
    at executeDispatch (react-dom.development.js:585)
    at executeDispatchesInOrder (react-dom.development.js:610)
    at executeDispatchesAndRelease (react-dom.development.js:713)
    at executeDispatchesAndReleaseTopLevel (react-dom.development.js:722)
    at forEachAccumulated (react-dom.development.js:694)
    at runEventsInBatch (react-dom.development.js:739)
    at runExtractedPluginEventsInBatch (react-dom.development.js:881)
    at handleTopLevel (react-dom.development.js:5832)
    at batchedEventUpdates$1 (react-dom.development.js:24387)
    at batchedEventUpdates (react-dom.development.js:1414)
    at dispatchEventForPluginEventSystem (react-dom.development.js:5928)
    at attemptToDispatchEvent (react-dom.development.js:6045)
    at dispatchEvent (react-dom.development.js:5948)
    at unstable_runWithPriority (scheduler.development.js:704)
    at runWithPriority$2 (react-dom.development.js:12232)
    at discreteUpdates$1 (react-dom.development.js:24404)
    at discreteUpdates (react-dom.development.js:1439)
    at dispatchDiscreteEvent (react-dom.development.js:5915)

dependencies:

    "@material-ui/core": "^4.6.1",
    "body-parser": "^1.19.0",
    "connected-react-router": "^6.6.0",
    "create-react-app": "^3.2.0",
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "express-basic-auth": "^1.2.0",
    "express-handlebars": "^3.1.0",
    "express-interceptor": "^1.2.0",
    "material-ui": "^0.20.2",
    "prop-types": "^15.7.2",
    "ra-core": "^3.0.0",
    "ra-data-json-server": "^3.0.0",
    "ra-input-rich-text": "^3.0.0",
    "ra-ui-materialui": "^3.0.0",
    "react": "^16.12.0",
    "react-admin": "^3.0.0",
    "react-dom": "^16.12.0",
    "react-final-form": "^6.3.3",
    "react-scripts": "^3.2.0",
    "react-split-pane": "^0.1.89"

[fzaninotto]

I can't reproduce the issue on the simple example. Can you please provide a CodeSandbox demonstrating the issue?

[ss-dev]

@fzaninotto https://codesandbox.io/s/react-admin-file-upload-issue-m7v4o

Just try to edit an existing record. Add some attachment and click "Save".

[bicstone]

it might be related to #4035 and #3087 (comment)

works below:
https://codesandbox.io/s/react-admin-file-upload-issue-qcrxn?hidenavigation=1&module=%2Fsrc%2Fdata.js

data.js:9

- attachment: null
+ attachment: ""

[ss-dev]

@bicstone yeah, it works. thanks!

[fzaninotto]

Reproduced and confirmed, thanks.

[fzaninotto]

Fixed by #4082