Add cargo dev generate-all --check and catch outdated docs in cargo test (#3320)

crates/ruff_dev/src/generate_json_schema.rs

@@ -3,7 +3,9 @@
 use std::fs;
 use std::path::PathBuf;
 
-use anyhow::Result;
+use crate::generate_all::REGENERATE_ALL_COMMAND;
+use anyhow::{bail, Result};
+use pretty_assertions::StrComparison;
 use ruff::settings::options::Options;
 use schemars::schema_for;
 
@@ -14,17 +16,44 @@ pub struct Args {
     /// Write the generated table to stdout (rather than to `ruff.schema.json`).
     #[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,
 }
 
 pub fn main(args: &Args) -> Result<()> {
     let schema = schema_for!(Options);
     let schema_string = serde_json::to_string_pretty(&schema).unwrap();
+    let filename = "ruff.schema.json";
+    let schema_path = PathBuf::from(ROOT_DIR).join(filename);
 
     if args.dry_run {
         println!("{schema_string}");
+    } else if args.check {
+        let current = fs::read_to_string(schema_path)?;
+        if current == schema_string {
+            println!("up-to-date: {filename}");
+        } else {
+            let comparison = StrComparison::new(&current, &schema_string);
+            bail!("{filename} changed, please run `{REGENERATE_ALL_COMMAND}`:\n{comparison}");
+        }
     } else {
-        let file = PathBuf::from(ROOT_DIR).join("ruff.schema.json");
+        let file = schema_path;
         fs::write(file, schema_string.as_bytes())?;
     }
     Ok(())
 }
+
+#[cfg(test)]
+mod test {
+    use super::{main, Args};
+    use anyhow::Result;
+
+    #[test]
+    fn test_generate_json_schema() -> Result<()> {
+        main(&Args {
+            dry_run: false,
+            check: true,
+        })
+    }
+}