Add -V and -p flags/options (#202)

src/input.rs

@@ -232,6 +232,7 @@ impl CrateCode {
 
 	pub fn read_expansion<P>(
 		manifest_path: Option<P>,
+		package: Option<String>,
 		target: &Target,
 		features: Option<String>,
 		no_default_features: bool,
@@ -245,6 +246,9 @@ impl CrateCode {
 		if let Some(manifest_path) = manifest_path {
 			cmd.arg("--manifest-path").arg(manifest_path.as_ref());
 		}
+		if let Some(package) = package.as_deref() {
+			cmd.arg("-p").arg(package);
+		}
 		if let Some(features) = features {
 			cmd.arg("--features").arg(features);
 		}

src/lib.rs

@@ -26,12 +26,14 @@ use diagnostic::Diagnostic;
 use input::{CrateCode, InputFile, TargetType};
 
 #[doc(hidden)]
-/// Read input. The manifest path, if present, will be passed to `cargo metadata`. If you set
-/// expand_macros to true, the input will be passed to the rust compiler to expand macros. This
-/// will only work on a nightly compiler. The template doesn't have to exist, a default will
-/// be used if it does not exist.
+#[allow(clippy::too_many_arguments)] // TODO
+/// Read input. The manifest path options, if present, will be passed to
+/// `cargo metadata`. If you set expand_macros to true, the input will be passed to the
+/// rust compiler to expand macros. This will only work on a nightly compiler. The
+/// template doesn't have to exist, a default will be used if it does not exist.
 pub fn read_input(
 	manifest_path: Option<PathBuf>,
+	package: Option<String>,
 	prefer_bin: bool,
 	expand_macros: bool,
 	template: PathBuf,
@@ -109,10 +111,19 @@ pub fn read_input(
 		cmd.manifest_path(path);
 	}
 	let metadata = unwrap!(cmd.exec(), "Failed to get cargo metadata");
-	let pkg = unwrap!(
-		metadata.root_package(),
-		"Missing package. Please make sure there is a package here, workspace roots don't contain any documentation."
-	);
+	let pkg = match package.as_deref() {
+		Some(package) => unwrap!(
+			metadata.packages.iter().find(|pkg| pkg.name == package),
+			"Cannot find requested package"
+		),
+		None => unwrap!(
+			metadata.root_package(),
+			// TODO this could be a real "help" message from ariadne
+			r#"Missing package. Please make sure there is a package here, workspace roots don't contain any documentation.
+
+Help: You can use --manifest-path and/or -p to specify the package to use."#
+		)
+	};
 
 	// find the target whose rustdoc comment we'll use.
 	// this uses a library target if exists, otherwise a binary target with the same name as the
@@ -171,6 +182,7 @@ pub fn read_input(
 		unwrap!(
 			CrateCode::read_expansion(
 				manifest_path.as_ref(),
+				package,
 				target,
 				features,
 				no_default_features,

src/main.rs

@@ -96,55 +96,60 @@ enum Subcommand {
 }
 
 #[derive(Parser)]
+#[command(about, version)]
 struct Args {
 	/// Path to Cargo.toml.
-	#[clap(long)]
+	#[arg(long)]
 	manifest_path: Option<PathBuf>,
 
+	/// Package to read.
+	#[arg(short, long)]
+	package: Option<String>,
+
 	/// Output File.
-	#[clap(short, long, default_value = "README.md")]
+	#[arg(short, long, default_value = "README.md")]
 	out: PathBuf,
 
 	/// Template File. This is processed by minijinja. Look at the source code for
 	/// cargo-doc2readme for an example.
-	#[clap(short, long, default_value = "README.j2")]
+	#[arg(short, long, default_value = "README.j2")]
 	template: PathBuf,
 
 	/// Use nightly rustc to expand macros prior to reading the source. This is necessary
 	/// if you use function-like macros in doc attributes, as introduced in Rust 1.54.
-	#[clap(long)]
+	#[arg(long)]
 	expand_macros: bool,
 
 	/// Space or comma separated list of features to activate. This will be ignored unless
 	/// `--expand-macros` is enabled, in which case it is being passed to cargo.
-	#[clap(short = 'F', long)]
+	#[arg(short = 'F', long)]
 	features: Option<String>,
 
 	/// Activate all available features. This will be ignored unless `--expand-macros` is
 	/// enabled, in which case it is being passed to cargo.
-	#[clap(long)]
+	#[arg(long)]
 	all_features: bool,
 
 	/// Do not activate the `default` feature. This will be ignored unless
 	/// `--expand-macros` is enabled, in which case it is being passed to cargo.
-	#[clap(long)]
+	#[arg(long)]
 	no_default_features: bool,
 
 	/// Prefer binary targets over library targets for rustdoc source.
-	#[clap(long, conflicts_with = "lib")]
+	#[arg(long, conflicts_with = "lib")]
 	bin: bool,
 
 	/// Prefer library targets over binary targets for rustdoc source. This is the default.
-	#[clap(long, conflicts_with = "bin")]
+	#[arg(long, conflicts_with = "bin")]
 	lib: bool,
 
 	/// Verify that the output file is (reasonably) up to date, and fail
 	/// if it needs updating. The output file will not be changed.
-	#[clap(long)]
+	#[arg(long)]
 	check: bool,
 
 	/// Enable verbose output.
-	#[clap(short, long)]
+	#[arg(short, long)]
 	verbose: bool
 }
 
@@ -194,6 +199,7 @@ fn main() -> ExitCode {
 
 	let (input_file, template, diagnostics) = read_input(
 		args.manifest_path,
+		args.package,
 		args.bin,
 		args.expand_macros,
 		args.template,
@@ -245,3 +251,14 @@ fn main() -> ExitCode {
 		ExitCode::SUCCESS
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn verify_cli() {
+		use clap::CommandFactory;
+		Args::command().debug_assert()
+	}
+}

tests/fail/workspace-root/stderr.log

@@ -1 +1,3 @@
 Error: Missing package. Please make sure there is a package here, workspace roots don't contain any documentation.
+
+Help: You can use --manifest-path and/or -p to specify the package to use.

tests/tests.rs

@@ -65,6 +65,7 @@ fn run_test(data: &TestData) -> Result<(), Failed> {
 
 	let (input_file, template, diagnostic) = read_input(
 		Some(manifest_path),
+		None,
 		false,
 		data.config.expand_macros,
 		template_path,