Try out tree-sitter

examples/parse_python.rs

@@ -0,0 +1,130 @@
+use anyhow::Result;
+use tree_sitter::{Parser, Query, QueryCursor};
+
+enum Action {
+    Up,
+    Down,
+    Right,
+}
+
+fn main() -> Result<()> {
+    let src = r#"
+def double(x):
+    # Return a double.
+    return x * 2
+
+x = double(1)
+y = (f"{x}" "b")
+"#;
+    let mut parser = Parser::new();
+    parser
+        .set_language(tree_sitter_python::language())
+        .expect("Error loading Python grammar");
+    let parse_tree = parser.parse(src, None);
+
+    if let Some(parse_tree) = &parse_tree {
+        // Check for comments.
+        let query = Query::new(tree_sitter_python::language(), "(comment) @capture")?;
+        let mut query_cursor = QueryCursor::new();
+        let all_matches = query_cursor.matches(&query, parse_tree.root_node(), src.as_bytes());
+
+        for each_match in all_matches {
+            for capture in each_match.captures.iter() {
+                let range = capture.node.range();
+                let text = &src[range.start_byte..range.end_byte];
+                let line = range.start_point.row;
+                let col = range.start_point.column;
+                println!(
+                    "[Line: {}, Col: {}] Offending source code: `{}`",
+                    line, col, text
+                );
+            }
+        }
+
+        // Check for string concatenations.
+        let query = Query::new(
+            tree_sitter_python::language(),
+            "(concatenated_string) @capture",
+        )?;
+        let mut query_cursor = QueryCursor::new();
+        let all_matches = query_cursor.matches(&query, parse_tree.root_node(), src.as_bytes());
+
+        for each_match in all_matches {
+            for capture in each_match.captures.iter() {
+                let range = capture.node.range();
+                let text = &src[range.start_byte..range.end_byte];
+                let line = range.start_point.row;
+                let col = range.start_point.column;
+                println!(
+                    "[Line: {}, Col: {}] Offending source code: `{}`",
+                    line, col, text
+                );
+            }
+        }
+
+        // Walk the tree.
+        let mut cursor = parse_tree.walk();
+        let mut action = Action::Down;
+        loop {
+            match action {
+                Action::Up => {
+                    if cursor.goto_next_sibling() {
+                        action = Action::Right;
+                    } else if cursor.goto_parent() {
+                        action = Action::Up;
+                    } else {
+                        break;
+                    }
+                }
+                Action::Down => {
+                    let range = cursor.node().range();
+                    let text = &src[range.start_byte..range.end_byte];
+                    let line = range.start_point.row;
+                    let col = range.start_point.column;
+                    println!(
+                        "[Line: {}, Col: {}] {}: `{}`",
+                        line,
+                        col,
+                        cursor.node().kind(),
+                        text
+                    );
+
+                    if cursor.goto_first_child() {
+                        action = Action::Down;
+                    } else if cursor.goto_next_sibling() {
+                        action = Action::Right;
+                    } else if cursor.goto_parent() {
+                        action = Action::Up;
+                    } else {
+                        break;
+                    }
+                }
+                Action::Right => {
+                    let range = cursor.node().range();
+                    let text = &src[range.start_byte..range.end_byte];
+                    let line = range.start_point.row;
+                    let col = range.start_point.column;
+                    println!(
+                        "[Line: {}, Col: {}] {}: `{}`",
+                        line,
+                        col,
+                        cursor.node().kind(),
+                        text
+                    );
+
+                    if cursor.goto_first_child() {
+                        action = Action::Down;
+                    } else if cursor.goto_next_sibling() {
+                        action = Action::Right;
+                    } else if cursor.goto_parent() {
+                        action = Action::Up;
+                    } else {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    Ok(())
+}