Document the macro system architecture

unshell-macros/ABOUT.md

@@ -0,0 +1,90 @@
+# UnShell Macros
+
+This crate owns the compile-time declaration layer for UnShell application-facing
+leaves.
+
+## Purpose
+
+The protocol crate intentionally stays generic: it knows how to route packets,
+validate framing, and deliver local events, but it should not need handwritten
+registration code for every leaf.
+
+The macro layer exists to move as much of that registration work as possible to
+compile time.
+
+In practical terms, the macro system is responsible for:
+
+- deriving canonical leaf identities
+- deriving canonical procedure identifiers
+- generating compile-time procedure inventories for leaves
+- binding one leaf declaration to separate endpoint and TUI host structs without
+  repeating the metadata on each host
+- generating dispatch glue for simple call-driven leaves
+
+## Model
+
+There are three layers in the intended design.
+
+### 1. Leaf declaration
+
+One declaration is the source of truth for one protocol leaf.
+
+The declaration answers:
+
+- what is this leaf called on the wire?
+- which procedure suffixes belong to it?
+- which host structs implement its endpoint and TUI roles?
+
+The goal is that this information is written once and reused everywhere.
+
+### 2. Host structs
+
+One leaf can have multiple host structs with different responsibilities.
+
+- the endpoint host owns runtime state and protocol-side behavior
+- the TUI host owns user-interface state and interpretation behavior
+
+Those hosts should not each have to repeat the leaf name or procedure inventory.
+They bind to the declaration instead.
+
+### 3. Procedure and method metadata
+
+Procedures and future typed remote methods need stable canonical identifiers.
+
+The macro layer generates those identifiers from the leaf declaration and the
+local suffix for each procedure or method. That lets the runtime consume a
+compile-time inventory instead of handwritten lists.
+
+## Current direction
+
+The current migration keeps the older derive-based APIs working while adding a
+new declaration-first API.
+
+That migration is intentionally incremental:
+
+1. keep `#[derive(Leaf)]`, `#[derive(Procedure)]`, and `#[procedures]` working
+2. introduce one declaration macro for compile-time leaf metadata
+3. let endpoint and TUI structs bind to the declaration instead of duplicating
+   metadata
+4. remove leaf-owned endpoint-construction boilerplate by generating leaf specs
+   from the declaration
+5. add typed remote-method metadata on top of the same declaration model
+
+## Design constraints
+
+The system is optimized for a few constraints that matter to this repository.
+
+- compile-time declaration should replace handwritten runtime registration where
+  possible
+- protocol-visible names should remain deterministic and canonical
+- generated code should stay explicit enough to debug
+- endpoint and TUI roles should share metadata but not be forced into the same
+  runtime trait when their behavior differs
+- migration should be low-breakage for the existing examples and tests
+
+## Non-goals
+
+This crate does not own transport, connection management, or packet execution.
+Those remain in `unshell-protocol` and higher application layers.
+
+The macro crate should generate metadata and glue, not hide the runtime model.

unshell-macros/src/lib.rs

@@ -8,6 +8,25 @@ mod utils;
 use proc_macro::TokenStream;
 use syn::{DeriveInput, ItemImpl, parse_macro_input};
 
+/// Derives canonical protocol-leaf identity helpers for one host type.
+///
+/// What it is: a derive macro that implements `ProtocolLeaf` and generates the
+/// `protocol_leaf_name()` convenience method.
+///
+/// Why it exists: simple leaves and compatibility paths still need a lightweight
+/// way to say "this host type exposes this canonical wire name" without writing
+/// the trait implementation by hand.
+///
+/// # Example
+/// ```ignore
+/// use unshell::Leaf;
+///
+/// #[derive(Leaf)]
+/// #[leaf(leaf_name = "echo")]
+/// struct EchoLeaf;
+///
+/// assert!(EchoLeaf::protocol_leaf_name().contains("echo"));
+/// ```
 #[proc_macro_derive(Leaf, attributes(leaf))]
 pub fn derive_leaf(input: TokenStream) -> TokenStream {
     match leaf::expand_leaf(parse_macro_input!(input as DeriveInput)) {
@@ -16,6 +35,28 @@ pub fn derive_leaf(input: TokenStream) -> TokenStream {
     }
 }
 
+/// Derives canonical stateful-procedure metadata for one procedure type.
+///
+/// What it is: a derive macro that records one procedure suffix and generates
+/// the canonical `protocol_procedure_id()` helper for that procedure.
+///
+/// Why it exists: hook-backed procedures need one stable `procedure_id`, but the
+/// runtime should not require each procedure to handwrite the identifier logic.
+///
+/// # Example
+/// ```ignore
+/// use unshell::{Leaf, Procedure};
+///
+/// #[derive(Leaf)]
+/// #[leaf(leaf_name = "shell")]
+/// struct ShellLeaf;
+///
+/// #[derive(Procedure)]
+/// #[procedure(leaf = ShellLeaf, name = "open")]
+/// struct OpenSession;
+///
+/// assert!(OpenSession::protocol_procedure_id().ends_with(".open"));
+/// ```
 #[proc_macro_derive(Procedure, attributes(procedure))]
 pub fn derive_procedure(input: TokenStream) -> TokenStream {
     match procedure::expand_procedure(parse_macro_input!(input as DeriveInput)) {
@@ -24,6 +65,33 @@ pub fn derive_procedure(input: TokenStream) -> TokenStream {
     }
 }
 
+/// Generates dispatch glue for a simple call-driven leaf impl block.
+///
+/// What it is: an attribute macro placed on one `impl` block whose `#[call]`
+/// methods define the callable surface for that leaf.
+///
+/// Why it exists: one-shot leaves should be able to declare a small RPC-like API
+/// on ordinary Rust methods while still producing the canonical procedure list
+/// and dispatch logic expected by the protocol runtime.
+///
+/// # Example
+/// ```ignore
+/// use unshell::{Leaf, procedures};
+///
+/// #[derive(Leaf)]
+/// #[leaf(id = "org.example.v1.echo")]
+/// struct EchoLeaf;
+///
+/// #[procedures(error = core::convert::Infallible)]
+/// impl EchoLeaf {
+///     #[call]
+///     fn echo(&mut self, input: String) -> String {
+///         input
+///     }
+/// }
+///
+/// assert!(EchoLeaf::protocol_procedure_id("echo").is_some());
+/// ```
 #[proc_macro_attribute]
 pub fn procedures(attr: TokenStream, item: TokenStream) -> TokenStream {
     match procedures::expand_procedures(