Make ruff_cli binary a small wrapper around lib (#3398)

crates/ruff_dev/src/generate_cli_help.rs

@@ -1,13 +1,15 @@
 //! Generate CLI help.
-#![allow(clippy::print_stdout, clippy::print_stderr)]
+#![allow(clippy::print_stdout)]
 
 use std::path::PathBuf;
 use std::{fs, str};
 
-use anyhow::{bail, Result};
+use anyhow::{bail, Context, Result};
+use clap::CommandFactory;
 use pretty_assertions::StrComparison;
+use ruff_cli::args;
 
-use crate::generate_all::REGENERATE_ALL_COMMAND;
+use crate::generate_all::{Mode, REGENERATE_ALL_COMMAND};
 use crate::ROOT_DIR;
 
 const COMMAND_HELP_BEGIN_PRAGMA: &str = "<!-- Begin auto-generated command help. -->\n";
@@ -18,12 +20,8 @@ const SUBCOMMAND_HELP_END_PRAGMA: &str = "<!-- End auto-generated subcommand hel
 
 #[derive(clap::Args)]
 pub struct Args {
-    /// Write the generated help to stdout (rather than to `docs/configuration.md`).
-    #[arg(long)]
-    pub(crate) dry_run: bool,
-    /// Don't write to the file, check if the file is up-to-date and error if not
-    #[arg(long)]
-    pub(crate) check: bool,
+    #[arg(long, default_value_t, value_enum)]
+    pub(crate) mode: Mode,
 }
 
 fn trim_lines(s: &str) -> String {
@@ -36,59 +34,63 @@ fn replace_docs_section(
     section: &str,
     begin_pragma: &str,
     end_pragma: &str,
-) -> String {
+) -> Result<String> {
     // Extract the prefix.
     let index = existing
         .find(begin_pragma)
-        .expect("Unable to find begin pragma");
+        .with_context(|| "Unable to find begin pragma")?;
     let prefix = &existing[..index + begin_pragma.len()];
 
     // Extract the suffix.
     let index = existing
         .find(end_pragma)
-        .expect("Unable to find end pragma");
+        .with_context(|| "Unable to find end pragma")?;
     let suffix = &existing[index..];
 
-    format!("{prefix}\n{section}{suffix}")
+    Ok(format!("{prefix}\n{section}{suffix}"))
 }
 
-pub fn main(args: &Args) -> Result<()> {
+pub(super) fn main(args: &Args) -> Result<()> {
     // Generate `ruff help`.
-    let command_help = trim_lines(ruff_cli::command_help().trim());
+    let command_help = trim_lines(&help_text());
 
     // Generate `ruff help check`.
-    let subcommand_help = trim_lines(ruff_cli::subcommand_help().trim());
+    let subcommand_help = trim_lines(&check_help_text());
 
-    if args.dry_run {
+    if args.mode.is_dry_run() {
         print!("{command_help}");
         print!("{subcommand_help}");
-    } else {
-        // Read the existing file.
-        let filename = "docs/configuration.md";
-        let file = PathBuf::from(ROOT_DIR).join(filename);
-        let existing = fs::read_to_string(&file)?;
+        return Ok(());
+    }
 
-        let new = replace_docs_section(
-            &existing,
-            &format!("```text\n{command_help}\n```\n\n"),
-            COMMAND_HELP_BEGIN_PRAGMA,
-            COMMAND_HELP_END_PRAGMA,
-        );
-        let new = replace_docs_section(
-            &new,
-            &format!("```text\n{subcommand_help}\n```\n\n"),
-            SUBCOMMAND_HELP_BEGIN_PRAGMA,
-            SUBCOMMAND_HELP_END_PRAGMA,
-        );
+    // Read the existing file.
+    let filename = "docs/configuration.md";
+    let file = PathBuf::from(ROOT_DIR).join(filename);
+    let existing = fs::read_to_string(&file)?;
 
-        if args.check {
+    let new = replace_docs_section(
+        &existing,
+        &format!("```text\n{command_help}\n```\n\n"),
+        COMMAND_HELP_BEGIN_PRAGMA,
+        COMMAND_HELP_END_PRAGMA,
+    )?;
+    let new = replace_docs_section(
+        &new,
+        &format!("```text\n{subcommand_help}\n```\n\n"),
+        SUBCOMMAND_HELP_BEGIN_PRAGMA,
+        SUBCOMMAND_HELP_END_PRAGMA,
+    )?;
+
+    match args.mode {
+        Mode::Check => {
             if existing == new {
                 println!("up-to-date: {filename}");
             } else {
                 let comparison = StrComparison::new(&existing, &new);
                 bail!("{filename} changed, please run `{REGENERATE_ALL_COMMAND}`:\n{comparison}");
             }
-        } else {
+        }
+        _ => {
             fs::write(file, &new)?;
         }
     }
@@ -96,16 +98,33 @@ pub fn main(args: &Args) -> Result<()> {
     Ok(())
 }
 
+/// Returns the output of `ruff help`.
+fn help_text() -> String {
+    args::Args::command().render_help().to_string()
+}
+
+/// Returns the output of `ruff help check`.
+fn check_help_text() -> String {
+    let mut cmd = args::Args::command();
+
+    // The build call is necessary for the help output to contain `Usage: ruff
+    // check` instead of `Usage: check` see https://github.com/clap-rs/clap/issues/4685
+    cmd.build();
+
+    cmd.find_subcommand_mut("check")
+        .expect("`check` subcommand not found")
+        .render_help()
+        .to_string()
+}
+
 #[cfg(test)]
 mod test {
     use super::{main, Args};
+    use crate::generate_all::Mode;
     use anyhow::Result;
 
     #[test]
     fn test_generate_json_schema() -> Result<()> {
-        main(&Args {
-            dry_run: false,
-            check: true,
-        })
+        main(&Args { mode: Mode::Check })
     }
 }