Added some docs on around how to debug expanded derive marcos.

Author: qhua948

.github/workflows/rust.yml

@@ -16,4 +16,6 @@ jobs:
     - name: Run tests
       run: cargo test --verbose
     - name: Run clippy
-      run: cargo clippy -- -D warnings
+      run: cargo clippy --version && cargo clippy -- -D warnings
+    - name: Run cargo expand
+      run: (rustup default nightly && cd argh && cargo install cargo-expand && cargo expand --example simple_example.rs)

README.md

@@ -175,3 +175,16 @@ struct SubCommandTwo {
 ```
 
 NOTE: This is not an officially supported Google product.
+
+
+## How to debug the expanded derive marco for `argh`
+
+The `argh::FromArgs` derive marco can be debugged with the [cargo-expand](https://crates.io/crates/cargo-expand) crate.
+
+### Expand the derive marco in `examples/simple_example.rs`
+
+See [argh/examples/simple_example.rs](./argh/examples/simple_example.rs) for the example struct we wish to expand.
+
+First, install `cargo-expand` by running `cargo install cargo-expand`. Note this requires the nightly build of Rust.
+
+Once installed, run `cargo expand` with in the `argh` package and you can see the expanded code.

argh/examples/simple_example.rs

@@ -0,0 +1,39 @@
+// Copyright (c) 2022 Google LLC All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+use {argh::FromArgs, std::fmt::Debug};
+
+#[derive(FromArgs, PartialEq, Debug)]
+/// Top-level command.
+struct TopLevel {
+    #[argh(subcommand)]
+    nested: MySubCommandEnum,
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand)]
+enum MySubCommandEnum {
+    One(SubCommandOne),
+    Two(SubCommandTwo),
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+/// First subcommand.
+#[argh(subcommand, name = "one")]
+struct SubCommandOne {
+    #[argh(option)]
+    /// how many x
+    x: usize,
+}
+
+#[derive(FromArgs, PartialEq, Debug)]
+/// Second subcommand.
+#[argh(subcommand, name = "two")]
+struct SubCommandTwo {
+    #[argh(switch)]
+    /// whether to fooey
+    fooey: bool,
+}
+
+fn main() {}

argh_derive/src/help.rs

@@ -26,6 +26,7 @@ pub(crate) fn help(
     fields: &[StructField<'_>],
     subcommand: Option<&StructField<'_>>,
 ) -> TokenStream {
+    #![allow(clippy::format_push_string)]
     let mut format_lit = "Usage: {command_name}".to_string();
 
     let positional = fields.iter().filter(|f| f.kind == FieldKind::Positional);
@@ -225,7 +226,7 @@ fn positional_description(out: &mut String, field: &StructField<'_>) {
 }
 
 fn positional_description_format(out: &mut String, name: &str, description: &str) {
-    let info = argh_shared::CommandInfo { name: &*name, description };
+    let info = argh_shared::CommandInfo { name, description };
     argh_shared::write_description(out, &info);
 }
 
@@ -255,6 +256,6 @@ fn option_description_format(
     }
     name.push_str(long_with_leading_dashes);
 
-    let info = argh_shared::CommandInfo { name: &*name, description };
+    let info = argh_shared::CommandInfo { name: &name, description };
     argh_shared::write_description(out, &info);
 }