1 files changed, 59 insertions, 0 deletions
diff --git a/third_party/rust/jsparagus/js_parser/try_it.py b/third_party/rust/jsparagus/js_parser/try_it.py
new file mode 100755
index 0000000000..d8cb89457a
--- /dev/null
+++ b/third_party/rust/jsparagus/js_parser/try_it.py
@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+
+"""js.py - Repl-like toy to explore parsing of lines of JS.
+
+See README.md for instructions.
+"""
+
+import argparse
+import traceback
+from .lexer import JSLexer
+from .parser import JSParser
+from jsparagus.lexer import SyntaxError
+
+
+def interactive_input(lexer, prompt="js> "):
+    while True:
+        line = input(prompt)
+        lexer.write(line + "\n")
+        if lexer.can_close():
+            return lexer.close()
+        prompt = "..> "
+
+
+def rpl():
+    """Read-print loop."""
+    while True:
+        parser = JSLexer(JSParser(), filename="<stdin>")
+        try:
+            result = interactive_input(parser)
+        except EOFError:
+            print()
+            break
+        except SyntaxError:
+            traceback.print_exc(limit=0)
+            continue
+        print(result)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Try out the JS parser.")
+    parser.add_argument('input_file', metavar='FILE', nargs='?',
+                        help=".js file to parse")
+    options = parser.parse_args()
+
+    if options.input_file is not None:
+        with open(options.input_file) as f:
+            source = f.readlines()
+        lexer = JSLexer(JSParser())
+        for line in source:
+            print(line.rstrip())
+            lexer.write(line)
+        ast = lexer.close()
+        print(ast)
+    else:
+        rpl()
+
+
+if __name__ == '__main__':
+    main()