DioxusLabs/dioxus · error · syn::Error

keyword argument repeated: `input_derive`

Error message

keyword argument repeated: `input_derive`

What it means

`input_derive = ...` adds `#[derive(...)]` attributes to the generated input wrapper type for a `#[server]` function; like every keyword here it may be set only once (packages/fullstack-macro/src/lib.rs:1602-1608).

Source

Thrown at packages/fullstack-macro/src/lib.rs:1604

                        }
                        fn_path = Some(stream.parse()?);
                    } else if key == "input" {
                        if encoding.is_some() {
                            return Err(syn::Error::new(
                                key.span(),
                                "`encoding` and `input` should not both be \
                                 specified",
                            ));
                        } else if input.is_some() {
                            return Err(syn::Error::new(
                                key.span(),
                                "keyword argument repeated: `input`",
                            ));
                        }
                        input = Some(stream.parse()?);
                    } else if key == "input_derive" {
                        if input_derive.is_some() {
                            return Err(syn::Error::new(
                                key.span(),
                                "keyword argument repeated: `input_derive`",
                            ));
                        }
                        input_derive = Some(stream.parse()?);
                    } else if key == "output" {
                        if encoding.is_some() {
                            return Err(syn::Error::new(
                                key.span(),
                                "`encoding` and `output` should not both be \
                                 specified",
                            ));
                        } else if output.is_some() {
                            return Err(syn::Error::new(
                                key.span(),
                                "keyword argument repeated: `output`",
                            ));
                        }

View on GitHub (pinned to 393d190a80)

Solutions

1. Combine all derives into a single `input_derive(Clone, Debug, Deserialize)` list.
2. Delete the duplicated `input_derive` entry.
3. Check `output_derive` for the same duplication pattern while you are there.

Example fix

// before
#[server(input_derive(Clone), input_derive(Deserialize))]
async fn run(task: Task) { ... }

// after
#[server(input_derive(Clone, Deserialize))]
async fn run(task: Task) { ... }

# Reuse the duplicate-key checker from index 93; input_derive is in its key list.

When it happens

Trigger: `#[server(input_derive(Deserialize), input_derive(Clone))]`; adding a second derive while migrating from `encoding` (where derives came bundled) to explicit keys; merge conflicts leaving two `input_derive` entries.

Common situations: Not realizing multiple derives go in ONE `input_derive(...)` list; copy-paste of an example that already had `input_derive`; version upgrades moving derives from `encoding` sugar to the explicit key.

Related errors

• keyword argument repeated: `name`
• keyword argument repeated: `prefix`
• keyword argument repeated: `encoding`
• keyword argument repeated: `endpoint`
• `encoding` and `input` should not both be specified

AI-assisted analysis of DioxusLabs/dioxus@393d190a80 (2026-08-16). Data as JSON: /api/errors/9c411110f864c8e6. Report an issue: GitHub.