Add Python REPL mixin.

Fix some bugs.

elicit/fsm.py

@@ -44,7 +44,7 @@ def push(self, obj):
         self.stack.append(obj)
 
     def pop(self):
-        self.stack.pop()
+        return self.stack.pop()
 
     def add_default_transition(self, action, next_state):
         if action is None and next_state is None:

elicit/parser.py

@@ -147,7 +147,6 @@ def feed(self, text):
                 val = sys.exc_info()[1]
                 self.pop_controller(val.value)
             except exceptions.NewCommand as cmdex:
-
                 self.push_controller(controller.CommandController(cmdex.value))
         if self._fsm.current_state:  # non-zero, stuff left
             self._buf = text[i:]
@@ -207,7 +206,7 @@ def _endvar(self, c, fsm):
         else:
             fsm.push(c)
         try:
-            val = self._controller.environ.expand(fsm.varname)
+            val = self._controller.environ.expand(fsm.varname) or ""
         except:  # noqa
             ex, val, tb = sys.exc_info()
             self._controller._ui.error("Could not expand variable "

elicit/python.py

@@ -0,0 +1,50 @@
+# python3.7
+
+# Copyright Ouster, Inc.
+
+"""Python REPL mixin class for Command objects.
+"""
+
+from __future__ import annotations
+
+import sys
+import code
+import readline
+
+from elicit import completer
+
+
+class PythonMixin:
+
+    def _get_ns(self):
+        if hasattr(self, "_obj"):
+            try:
+                name = self._obj.__class__.__name__.split(".")[-1].lower()
+            except:  # noqa
+                name = "object"
+            return {name: self._obj, "environ": self._environ}
+        else:
+            return globals()
+
+    def python(self, arguments):
+        """Enter an interactive interpreter.
+
+        Usage:
+            python
+        """
+        ns = self._get_ns()
+        console = code.InteractiveConsole(ns)
+        console.raw_input = self._ui.user_input
+        try:
+            saveps1, saveps2 = sys.ps1, sys.ps2
+        except AttributeError:
+            saveps1, saveps2 = ">>> ", "... "
+        sys.ps1, sys.ps2 = "%GPython%N> ", "more> "
+        oc = readline.get_completer()
+        readline.set_completer(completer.Completer(ns).complete)
+        try:
+            console.interact(banner="You are now in Python. ^D exits.",
+                             exitmsg="Resuming command shell.")
+        finally:
+            readline.set_completer(oc)
+            sys.ps1, sys.ps2 = saveps1, saveps2

elicit/ui.py

@@ -60,10 +60,10 @@ def close(self):
 
     def set_theme(self, theme):
         self._theme = theme
-        self.environ.setdefault("PS1", self._theme.ps1)
-        self.environ.setdefault("PS2", self._theme.ps2)
-        self.environ.setdefault("PS3", self._theme.ps3)
-        self.environ.setdefault("PS4", self._theme.ps4)
+        self.environ["PS1"] = self._theme.ps1
+        self.environ["PS2"] = self._theme.ps2
+        self.environ["PS3"] = self._theme.ps3
+        self.environ["PS4"] = self._theme.ps4
 
     def clone(self, theme=None):
         return self.__class__(self._io, self.environ.copy(), theme or self._theme)