Improve the shell command

poetry/console/commands/shell.py

@@ -36,5 +36,5 @@ def handle(self):
         # Setting this to avoid spawning unnecessary nested shells
         environ["POETRY_ACTIVE"] = "1"
         shell = Shell.get()
-        self.env.execute(shell.path)
+        shell.activate(self.env)
         environ.pop("POETRY_ACTIVE")

poetry/utils/shell.py

@@ -1,8 +1,16 @@
 import os
+import signal
+import sys
 
+import pexpect
+
+from clikit.utils.terminal import Terminal
 from shellingham import detect_shell
 from shellingham import ShellDetectionFailure
 
+from ._compat import WINDOWS
+from .env import VirtualEnv
+
 
 class Shell:
     """
@@ -40,5 +48,51 @@ def get(cls):  # type: () -> Shell
 
         return cls._shell
 
+    def activate(self, env):  # type: (VirtualEnv) -> None
+        if WINDOWS:
+            return env.execute(self.path)
+
+        terminal = Terminal()
+        with env.temp_environ():
+            c = pexpect.spawn(
+                self._path, ["-i"], dimensions=(terminal.height, terminal.width)
+            )
+
+        c.setecho(False)
+        activate_script = self._get_activate_script()
+        bin_dir = "Scripts" if WINDOWS else "bin"
+        activate_path = env.path / bin_dir / activate_script
+        c.sendline("{} {}".format(self._get_source_command(), activate_path))
+
+        def resize(sig, data):
+            terminal = Terminal()
+            c.setwinsize(terminal.height, terminal.width)
+
+        signal.signal(signal.SIGWINCH, resize)
+
+        # Interact with the new shell.
+        c.interact(escape_character=None)
+        c.close()
+
+        sys.exit(c.exitstatus)
+
+    def _get_activate_script(self):
+        if "fish" == self._name:
+            suffix = ".fish"
+        elif "csh" == self._name:
+            suffix = ".csh"
+        else:
+            suffix = ""
+
+        return "activate" + suffix
+
+    def _get_source_command(self):
+        if "fish" == self._name:
+            return "source"
+        elif "csh" == self._name:
+            return "source"
+
+        return "."
+
     def __repr__(self):  # type: () -> str
         return '{}("{}", "{}")'.format(self.__class__.__name__, self._name, self._path)

pyproject.toml

@@ -35,6 +35,7 @@ pkginfo = "^1.4"
 html5lib = "^1.0"
 shellingham = "^1.1"
 tomlkit = "^0.5.5"
+pexpect = "^4.7.0"
 
 # The typing module is not in the stdlib in Python 2.7 and 3.4
 typing = { version = "^3.6", python = "~2.7 || ~3.4" }