modo-upload-macros

Procedural macro crate for modo-upload. Provides the #[derive(FromMultipart)] macro that generates modo_upload::FromMultipart implementations for structs, enabling automatic parsing and validation of multipart/form-data requests.

This crate is an implementation detail of modo-upload. Add modo-upload to your dependencies — it re-exports FromMultipart and you interact with the macro through that crate.

Usage

Basic form with a required file

use modo_upload::{FromMultipart, UploadedFile};

#[derive(FromMultipart)]
struct ProfileForm {
    #[upload(max_size = "5mb", accept = "image/*")]
    avatar: UploadedFile,

    name: String,
    email: String,
}

Optional file and text fields

use modo_upload::{FromMultipart, UploadedFile};

#[derive(FromMultipart)]
struct UpdateForm {
    avatar: Option<UploadedFile>,
    bio: Option<String>,
}

Multiple files with count constraints

use modo_upload::{FromMultipart, UploadedFile};

#[derive(FromMultipart)]
struct GalleryForm {
    #[upload(min_count = 1, max_count = 10, max_size = "10mb", accept = "image/*")]
    images: Vec<UploadedFile>,

    title: String,
}

Renaming multipart fields

Use #[serde(rename = "...")] to map a Rust field to a differently named multipart field.

use modo_upload::{FromMultipart, UploadedFile};

#[derive(FromMultipart)]
struct UploadForm {
    #[serde(rename = "profile_picture")]
    avatar: UploadedFile,
}

Using FromStr fields

Any type that implements std::str::FromStr can be used as a text field.

use modo_upload::FromMultipart;

#[derive(FromMultipart)]
struct OrderForm {
    quantity: u32,
    price: f64,
    label: String,
}

Integration with MultipartForm extractor

In a modo handler, use MultipartForm<T> from modo_upload to extract and validate the form. MultipartForm<T> implements Deref<Target = T>, so struct fields are accessible directly.

use std::sync::Arc;
use modo::{Json, JsonResult, Service};
use modo_upload::{FileStorageDyn, FromMultipart, MultipartForm, UploadedFile};

#[derive(FromMultipart)]
struct ProfileForm {
    #[upload(max_size = "5mb", accept = "image/*")]
    avatar: UploadedFile,
    name: String,
}

#[modo::handler(POST, "/profile")]
async fn update_profile(
    storage: Service<Arc<dyn FileStorageDyn>>,
    form: MultipartForm<ProfileForm>,
) -> JsonResult<serde_json::Value> {
    let stored = storage.store("avatars", &form.avatar).await?;
    Ok(Json(serde_json::json!({
        "name": form.name,
        "avatar_path": stored.path,
    })))
}

Field attributes reference

#[upload(...)]

Applied to file fields (UploadedFile, Option<UploadedFile>, Vec<UploadedFile>, BufferedUpload). All sub-attributes are optional and can be combined.

#[serde(rename = "...")]

Overrides the multipart field name. By default the Rust field name is used.

Supported field types

Constraints

• Only structs with named fields are supported.
• At most one BufferedUpload field is allowed per struct.