How to import serde's custom derive macors properly?

TL;DR Follow the official documentation

A little bit of history:

• Before Rust 2018, you do:

extern crate serde;
#[macro_use] extern crate serde_derive; // Imports the procedural macros

#[derive(Serialize, Deserialize)]
struct Foo;

• But Rust 2018 introduced new way of doing this:

use serde_derive::{Serialize, Deserialize}; // Imports the procedural macros

#[derive(Serialize, Deserialize)]
struct Foo;

• However, the serde crate re-exports the serde_derive::{Serialize, Deserialize} macros, hidden behind the feature flag derive. So if you enable the derive feature you can get both the Serialize/Deserialize traits and procedural macros (i.e., the custom derive) from the serde crate by one single use:

// Cargo.toml
[dependencies]
serde = { version = "1.0", features = ["derive"] }

// src/main.rs or lib.rs
use serde::{Serialize, Deserialize}; // Imports both the traits and procedural macros

#[derive(Serialize, Deserialize)]
struct Foo;

• You can choose not to use the derive feature. But you’ll run into this issue if any of your dependencies enables the derive feature. You can either:
  • Just enable derive (recommended).
  • Use serde::ser::Serialize and serde::de::Deserialize to get the trait and keep using serde_derive::{Serialize, Deserialize} to get the procedural macros.