Can't Handle File and Non-File Field on multipart/form-data simultaneously

shibukazu commented 4 months ago

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I'm submitting a ...
- [x] bug report
- [ ] feature request
- [ ] support request
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- [x] used the search to make sure that a similar issue hasn't already been submit

Expected Behavior

The following code is an example of a post endpoint handler:

public async postHandler(
  @FormField("userId") userId: string,
  @UploadedFile("file1") file1: Express.Multer.File,
  @UploadedFile("file2") file2: Express.Multer.File
  ): Promise<Response> {}

The expected behavior is that this handler can handle multipart/form-data requests correctly.

Current Behavior

Currently, it outputs an error message like the following:

{
    "message": "Cannot read properties of undefined (reading 'length')"
}

Possible Solution

This issue seems to be caused by an incorrect implementation of the template engine, specifically expressTemplateService.ts line 84. The current implementation treats all fields in formData as files if any file is included in the multipart/form-data request. As a result, it fails to handle non-file fields correctly.

case 'formData': {
    const files = Object.values(args).filter(param => param.dataType === 'file');
    if (files.length > 0) {
        const requestFiles = request.files;
        const fileArgs = this.validationService.ValidateParam(param, requestFiles[name], name, fieldErrors, undefined, this.minimalSwaggerConfig);
        return fileArgs.length === 1 ? fileArgs[0] : fileArgs;
    }
    else if (param.dataType === 'array' && param.array && param.array.dataType === 'file') {
        return this.validationService.ValidateParam(param, request.files, name, fieldErrors, undefined, this.minimalSwaggerConfig);
    }
    else {
        return this.validationService.ValidateParam(param, request.body[name], name, fieldErrors, undefined, this.minimalSwaggerConfig);
    }
}

To address this issue, the code should be modified as follows:

case 'formData': {
    if (param.dataType === 'file') {
        const files = Object.values(args).filter(param => param.dataType === 'file');
        if (files.length > 0) {
            const requestFiles = request.files;
            const fileArgs = this.validationService.ValidateParam(param, requestFiles[name], name, fieldErrors, undefined, this.minimalSwaggerConfig);
            return fileArgs.length === 1 ? fileArgs[0] : fileArgs;
        }
    }
    else if (param.dataType === 'array' && param.array && param.array.dataType === 'file') {
        return this.validationService.ValidateParam(param, request.files, name, fieldErrors, undefined, this.minimalSwaggerConfig);
    }
    else {
        return this.validationService.ValidateParam(param, request.body[name], name, fieldErrors, undefined, this.minimalSwaggerConfig);
    }
}

May I publish pull request for this issue?