Auto-generate options in README from field attributes (#1015)

ruff_dev/src/generate_options.rs

@@ -0,0 +1,125 @@
+//! Generate a Markdown-compatible listing of configuration options.
+
+use std::fs;
+use std::fs::OpenOptions;
+use std::io::Write;
+use std::path::PathBuf;
+
+use anyhow::Result;
+use clap::Args;
+use itertools::Itertools;
+use ruff::settings::options::Options;
+use ruff::settings::options_base::{ConfigurationOptions, OptionEntry, OptionField};
+
+const BEGIN_PRAGMA: &str = "<!-- Begin auto-generated options sections. -->";
+const END_PRAGMA: &str = "<!-- End auto-generated options sections. -->";
+
+#[derive(Args)]
+pub struct Cli {
+    /// Write the generated table to stdout (rather than to `README.md`).
+    #[arg(long)]
+    dry_run: bool,
+}
+
+fn emit_field(output: &mut String, field: &OptionField, group_name: Option<&str>) {
+    output.push_str(&format!("#### [`{0}`](#{0})\n", field.name));
+    output.push('\n');
+    output.push_str(field.doc);
+    output.push_str("\n\n");
+    output.push_str(&format!("**Default value**: `{}`\n", field.default));
+    output.push('\n');
+    output.push_str(&format!("**Type**: `{}`\n", field.value_type));
+    output.push('\n');
+    output.push_str(&format!(
+        "**Example usage**:\n\n```toml\n[tool.ruff{}]\n{}\n```\n",
+        if group_name.is_some() {
+            format!(".{}", group_name.unwrap())
+        } else {
+            String::new()
+        },
+        field.example
+    ));
+    output.push('\n');
+}
+
+pub fn main(cli: &Cli) -> Result<()> {
+    let mut output = String::new();
+
+    // Generate all the top-level fields.
+    for field in Options::get_available_options()
+        .into_iter()
+        .filter_map(|entry| {
+            if let OptionEntry::Field(field) = entry {
+                Some(field)
+            } else {
+                None
+            }
+        })
+        .sorted_by_key(|field| field.name)
+    {
+        emit_field(&mut output, &field, None);
+        output.push_str("---\n\n");
+    }
+
+    // Generate all the sub-groups.
+    for group in Options::get_available_options()
+        .into_iter()
+        .filter_map(|entry| {
+            if let OptionEntry::Group(group) = entry {
+                Some(group)
+            } else {
+                None
+            }
+        })
+        .sorted_by_key(|group| group.name)
+    {
+        output.push_str(&format!("### `{}`\n", group.name));
+        output.push('\n');
+        for field in group
+            .fields
+            .iter()
+            .filter_map(|entry| {
+                if let OptionEntry::Field(field) = entry {
+                    Some(field)
+                } else {
+                    None
+                }
+            })
+            .sorted_by_key(|field| field.name)
+        {
+            emit_field(&mut output, field, Some(group.name));
+            output.push_str("---\n\n");
+        }
+    }
+
+    if cli.dry_run {
+        print!("{output}");
+    } else {
+        // Read the existing file.
+        let file = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .parent()
+            .expect("Failed to find root directory")
+            .join("README.md");
+        let existing = fs::read_to_string(&file)?;
+
+        // Extract the prefix.
+        let index = existing
+            .find(BEGIN_PRAGMA)
+            .expect("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");
+        let suffix = &existing[index..];
+
+        // Write the prefix, new contents, and suffix.
+        let mut f = OpenOptions::new().write(true).truncate(true).open(&file)?;
+        write!(f, "{prefix}\n\n")?;
+        write!(f, "{output}")?;
+        write!(f, "{suffix}")?;
+    }
+
+    Ok(())
+}