1 files changed, 56 insertions, 0 deletions
diff --git a/src/prompt_toolkit/eventloop/dummy_contextvars.py b/src/prompt_toolkit/eventloop/dummy_contextvars.py
new file mode 100644
index 0000000..3fcd260
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/dummy_contextvars.py
@@ -0,0 +1,56 @@
+"""
+Dummy contextvars implementation, to make prompt_toolkit work on Python 3.6.
+
+As long as there is only one application running at a time, we don't need the
+real contextvars. So, stuff like the telnet-server and so on requires 3.7.
+"""
+from typing import TYPE_CHECKING, Any, Callable, Generic, Optional, TypeVar
+
+if TYPE_CHECKING:
+    from typing_extensions import ParamSpec
+
+
+def copy_context() -> "Context":
+    return Context()
+
+
+if TYPE_CHECKING:
+    _P = ParamSpec("_P")
+_T = TypeVar("_T")
+
+
+class Context:
+    def run(
+        self, callable: "Callable[_P, _T]", *args: "_P.args", **kwargs: "_P.kwargs"
+    ) -> _T:
+        return callable(*args, **kwargs)
+
+    def copy(self) -> "Context":
+        return self
+
+
+class Token(Generic[_T]):
+    pass
+
+
+class ContextVar(Generic[_T]):
+    def __init__(self, name: str, *, default: Optional[_T] = None) -> None:
+        self._name = name
+        self._value = default
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    def get(self, default: Optional[_T] = None) -> _T:
+        result = self._value or default
+        if result is None:
+            raise LookupError
+        return result
+
+    def set(self, value: _T) -> Token[_T]:
+        self._value = value
+        return Token()
+
+    def reset(self, token: Token[_T]) -> None:
+        pass