added codegen example

Author: iliabylich

examples/codegen.rs

@@ -0,0 +1,33 @@
+fn print_usage_and_exit() -> ! {
+    eprintln!("Usage: codegen --template <template.liquid> --write-to <outfile>");
+    std::process::exit(1);
+}
+
+fn main() {
+    let mut args = std::env::args().collect::<Vec<_>>();
+
+    let mut get_arg = |key: &str| {
+        let key_idx = args
+            .iter()
+            .enumerate()
+            .find(|&(_idx, e)| e == key)
+            .unwrap_or_else(|| {
+                eprintln!("Unable to get {} CLI argument", key);
+                print_usage_and_exit()
+            })
+            .0;
+        let _key = args.remove(key_idx);
+        if key_idx >= args.len() {
+            eprintln!("No {} CLI option given", key);
+            print_usage_and_exit();
+        }
+        let value = args.remove(key_idx);
+        value
+    };
+
+    let template_path = get_arg("--template");
+    let output_path = get_arg("--write-to");
+
+    let rendered = lib_ruby_parser_nodes::LiquidTemplate::new(template_path).render();
+    std::fs::write(output_path, rendered).unwrap();
+}