Improve docs re: proc macros (#1848)

Author: ianthetechie

docs/manual/src/proc_macro/index.md

@@ -23,7 +23,7 @@ true for all of UniFFI, so proceed with caution and the knowledge that things ma
 
 ## Build workflow
 
-Library mode is recommended when using UniFFI proc-macros (See the [Foreign language bindings docs](../tutorial/foreign_language_bindings.md) for more info).
+Be sure to use library mode when using UniFFI proc-macros (See the [Foreign language bindings docs](../tutorial/foreign_language_bindings.md) for more info).
 
 If your crate's API is declared using only proc-macros and not UDL files, call the `uniffi::setup_scaffolding` macro at the top of your source code:
 

docs/manual/src/tutorial/Rust_scaffolding.md

@@ -14,7 +14,12 @@ uniffi = "0.XX.0"
 uniffi = { version = "0.XX.0", features = ["build"] }
 ```
 
-Then create a `build.rs` file next to `Cargo.toml` that uses `uniffi` to generate the Rust scaffolding code.
+As noted in [Describing the interface](udl_file.md), UniFFI currently supports two methods of interface definitions: UDL files and proc macros.
+If you are using only proc macros, you can skip some boilerplate in your crate setup as well.
+
+### Setup for crates using UDL
+
+Crates using UDL need a `build.rs` file next to `Cargo.toml`. This uses `uniffi` to generate the Rust scaffolding code.
 
 ```rust
 fn main() {
@@ -30,7 +35,18 @@ uniffi::include_scaffolding!("math");
 
 **Note:** The file name is always `<namespace>.uniffi.rs`.
 
-Great! `add` is ready to see the outside world!
+### Setup for crates using only proc macros
+
+If you are only using proc macros, you can skip `build.rs` entirely!
+All you need to do is add this to the top of `lib.rs`
+NOTE: This function takes an optional parameter, the [`namespace`](../udl/namespace.md) used by the component.
+If not specified, the crate name will be used as the namespace.
+
+```rust
+uniffi::setup_scaffolding!();
+```
+
+**⚠ Warning ⚠** Do not call both `uniffi::setup_scaffolding!()` and `uniffi::include_scaffolding!!()` in the same crate.
 
 ### Libraries that depend on UniFFI components
 

docs/manual/src/tutorial/foreign_language_bindings.md

@@ -38,11 +38,11 @@ creating a binary for each crate that uses UniFFI.  You can avoid this by creati
 
 Then your can run `uniffi-bindgen` from any create in your project using `cargo run -p uniffi-bindgen [args]`
 
-## Running uniffi-bindgen using a library file
+## Running uniffi-bindgen using a library file (RECOMMENDED)
 
 Use `generate --library` to generate foreign bindings by using a cdylib file built for your library.
 This flag was added in UniFFI 0.24 and can be more convenient than specifying the UDL file -- especially when multiple UniFFI-ed crates are built together in one library.
-The plan is to make library mode the default in a future UniFFI version.
+The plan is to make library mode the default in a future UniFFI version, and it is highly recommended to specify the flag for now (because some features simply don't work otherwise).
 
 Taking `example/arithmetic` as an example, you can generate the bindings with:
 ```