Fix and document debug artifacts (#64)

Author: Joeoc2001

README.md

@@ -235,3 +235,7 @@ pub struct CommaSeparatedExprs {
 
 ### `Box<T>`
 Boxes are automatically constructed around the inner type when parsing, but Rust Sitter doesn't do anything extra beyond that.
+
+## Debugging
+
+To view the generated grammar, you can set the `RUST_SITTER_EMIT_ARTIFACTS` environment variable to `true`. This will cause the generated grammar to be written to wherever cargo sets `OUT_DIR` (usually `target/debug/build/<crate>-<hash>/out`).

tool/src/lib.rs

@@ -59,7 +59,9 @@ pub fn build_parsers(root_file: &Path) {
 
         let dir = if emit_artifacts {
             let grammar_dir = Path::new(out_dir.as_str()).join(format!("grammar_{grammar_name}",));
-            std::fs::remove_dir_all(&grammar_dir).expect("Couldn't clear old artifacts");
+            if grammar_dir.is_dir() {
+                std::fs::remove_dir_all(&grammar_dir).expect("Couldn't clear old artifacts");
+            }
             std::fs::DirBuilder::new()
                 .recursive(true)
                 .create(grammar_dir.clone())