Deprecate support for Python 3.6 and remove dependency on attrs (#1257)

* Start deprecation of Python 3.6

* Removed dependency on attrs and replaced with dataclasses

* Fix typing

* Added comments to assist with dropping support of Python versions in the future.

---------

Co-authored-by: Kevin Van Brunt <kmvanbrunt@gmail.com>

Author: tleonhardt

.github/CONTRIBUTING.md

@@ -46,9 +46,8 @@ The tables below list all prerequisites along with the minimum required version
 #### Prerequisites to run cmd2 applications
 
 | Prerequisite                                        | Minimum Version |
-| --------------------------------------------------- | --------------- |
-| [python](https://www.python.org/downloads/)         | `3.6`           |
-| [attrs](https://github.com/python-attrs/attrs)      | `16.3`          |
+| --------------------------------------------------- |-----------------|
+| [python](https://www.python.org/downloads/)         | `3.7`           |
 | [pyperclip](https://github.com/asweigart/pyperclip) | `1.6`           |
 | [setuptools](https://pypi.org/project/setuptools/)  | `34.4`          |
 | [wcwidth](https://pypi.python.org/pypi/wcwidth)     | `0.1.7`         |

.github/workflows/doc.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10"]
+        python-version: ["3.11"]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:

.github/workflows/format.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10"]
+        python-version: ["3.11"]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:

.github/workflows/lint.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10"]
+        python-version: ["3.11"]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:

.github/workflows/mypy.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.10"]
+        python-version: ["3.11"]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:

.gitignore

@@ -39,4 +39,7 @@ Pipfile.lock
 .venv
 
 # Commitizen configuration
-.cz.toml
+.cz.toml
+
+# pyenv version file
+.python-version

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 2.5.0 (TBD)
+* Breaking Change
+  * `cmd2` 2.5 supports Python 3.7+ (removed support for Python 3.6)
+* Enhancements
+  * Removed dependency on `attrs` and replaced with [dataclasses](https://docs.python.org/3/library/dataclasses.html)
+
 ## 2.4.3 (January 27, 2023)
 * Bug Fixes
   * Fixed ValueError caused when passing `Cmd.columnize()` strings wider than `display_width`.

Pipfile

@@ -4,7 +4,6 @@ url = "https://pypi.org/simple"
 verify_ssl = true
 
 [packages]
-attrs = ">=16.3.0"
 pyperclip = ">=1.6"
 setuptools = ">=34.4"
 wcwidth = ">=0.1.7"

README.md

@@ -78,7 +78,7 @@ On all operating systems, the latest stable version of `cmd2` can be installed u
 pip install -U cmd2
 ```
 
-cmd2 works with Python 3.6+ on Windows, macOS, and Linux. It is pure Python code with few 3rd-party dependencies.
+cmd2 works with Python 3.7+ on Windows, macOS, and Linux. It is pure Python code with few 3rd-party dependencies.
 
 For information on other installation options, see
 [Installation Instructions](https://cmd2.readthedocs.io/en/latest/overview/installation.html) in the cmd2

cmd2/argparse_completer.py

@@ -273,10 +273,8 @@ def update_mutex_groups(arg_action: argparse.Action) -> None:
             # Check if this action is in a mutually exclusive group
             for group in self._parser._mutually_exclusive_groups:
                 if arg_action in group._group_actions:
-
                     # Check if the group this action belongs to has already been completed
                     if group in completed_mutex_groups:
-
                         # If this is the action that completed the group, then there is no error
                         # since it's allowed to appear on the command line more than once.
                         completer_action = completed_mutex_groups[group]
@@ -307,7 +305,6 @@ def update_mutex_groups(arg_action: argparse.Action) -> None:
         # Parse all but the last token
         #############################################################################################
         for token_index, token in enumerate(tokens[:-1]):
-
             # If we're in a positional REMAINDER arg, force all future tokens to go to that
             if pos_arg_state is not None and pos_arg_state.is_remainder:
                 consume_argument(pos_arg_state)
@@ -339,7 +336,6 @@ def update_mutex_groups(arg_action: argparse.Action) -> None:
 
             # Check the format of the current token to see if it can be an argument's value
             if _looks_like_flag(token, self._parser) and not skip_remaining_flags:
-
                 # Check if there is an unfinished flag
                 if (
                     flag_arg_state is not None
@@ -484,7 +480,6 @@ def update_mutex_groups(arg_action: argparse.Action) -> None:
 
         # Otherwise check if we have a positional to complete
         elif pos_arg_state is not None or remaining_positionals:
-
             # If we aren't current tracking a positional, then get the next positional arg to handle this token
             if pos_arg_state is None:
                 action = remaining_positionals.popleft()