Add edit capabilities to Python repl

This is meant to emulate the `:e` command in ghci.

1 files changed, 23 insertions, 0 deletions

diff --git a/Biz/Repl.py b/Biz/Repl.py
index cb9dfe7..2f71c33 100644
--- a/Biz/Repl.py
+++ b/Biz/Repl.py
@@ -18,6 +18,7 @@ import importlib
 import importlib.util
 import logging
 import os
+import subprocess
 import sys
 
 import mypy.api
@@ -59,13 +60,31 @@ def typecheck(path: str) -> None:
     sys.stderr.flush()
 
 
+def edit_file(ns: str, path: str, editor: str) -> None:
+    """
+    Edit and reload the given namespace and path.
+
+    It is assumed ns and path go together. If `editor` returns something other
+    than 0, this function will not reload the ns.
+    """
+    try:
+        proc = subprocess.run([editor, path], check=False)
+    except FileNotFoundError:
+        Log.fail("editor '%s' not found", editor)
+    if proc.returncode == 0:
+        use(ns, path)
+        typecheck(path)
+
+
 if __name__ == "__main__":
     Log.setup()
     NS = sys.argv[1]
     PATH = sys.argv[2]
+    EDITOR = os.environ.get("EDITOR", "$EDITOR")
     use(NS, PATH)
     typecheck(PATH)
 
+    logging.info("use edit() to open %s in %s", NS, EDITOR)
     logging.info("use reload() after making changes")
     sys.ps1 = f"{NS}> "
     sys.ps2 = f"{NS}| "
@@ -74,3 +93,7 @@ if __name__ == "__main__":
         """Reload the namespace."""
         use(NS, PATH)
         typecheck(PATH)
+
+    def edit() -> None:
+        """Edit the current namespace."""
+        edit_file(NS, PATH, EDITOR)