Initial changes for encapsulation of colorama usage within ansi.py

Changes include:
- ansi.py is now the only cmd2 code which depends on colorama
- cmd2 tests no longer rely on colorama
- Added new functions to ansi.py:
    - async_alert_str()
    - set_title_str
- Added unit test for set_title_str

TODO:
- Refactor async_alert_str so cursor position is passed in and import from rl_utils is no longer required
- Add unit test(s) for async_alert_str
- Refactor FG_COLORS and BG_COLORS in ansi.py to not use constants from colorama

2 files changed, 78 insertions, 54 deletions

diff --git a/cmd2/ansi.py b/cmd2/ansi.py
index 035991bb..59dcb43c 100644
--- a/cmd2/ansi.py
+++ b/cmd2/ansi.py
@@ -8,6 +8,9 @@ import colorama
 from colorama import Fore, Back, Style
 from wcwidth import wcswidth
 
+# On Windows, filter ANSI escape codes out of text sent to stdout/stderr, and replace them with equivalent Win32 calls
+colorama.init(strip=False)
+
 # Values for allow_ansi setting
 ANSI_NEVER = 'Never'
 ANSI_TERMINAL = 'Terminal'
@@ -65,6 +68,9 @@ FG_RESET = FG_COLORS['reset']
 BG_RESET = BG_COLORS['reset']
 RESET_ALL = Style.RESET_ALL
 
+BRIGHT = Style.BRIGHT
+NORMAL = Style.NORMAL
+
 # ANSI escape sequences not provided by colorama
 UNDERLINE_ENABLE = colorama.ansi.code_to_chars(4)
 UNDERLINE_DISABLE = colorama.ansi.code_to_chars(24)
@@ -180,3 +186,71 @@ def style(text: Any, *, fg: str = '', bg: str = '', bold: bool = False, underlin
 style_success = functools.partial(style, fg='green', bold=True)
 style_warning = functools.partial(style, fg='bright_yellow')
 style_error = functools.partial(style, fg='bright_red')
+
+
+def async_alert_str(*, prompt: str, line: str, alert_msg: str) -> str:
+    """Calculate the desired string, including ANSI escape codes, for displaying an asynchronous alert message.
+
+    :param prompt: prompt that is displayed on the current line
+    :param line: current contents of the Readline line buffer
+    :param alert_msg: the message to display to the user
+    :return: the correct string so that the alert message appears to the user to be printed above the current line.
+    """
+    import shutil
+    from colorama import Cursor
+
+    from .rl_utils import rl_get_point
+
+    # Get the size of the terminal
+    terminal_size = shutil.get_terminal_size()
+
+    # Split the prompt lines since it can contain newline characters.
+    prompt_lines = prompt.splitlines()
+
+    # Calculate how many terminal lines are taken up by all prompt lines except for the last one.
+    # That will be included in the input lines calculations since that is where the cursor is.
+    num_prompt_terminal_lines = 0
+    for line in prompt_lines[:-1]:
+        line_width = ansi_safe_wcswidth(line)
+        num_prompt_terminal_lines += int(line_width / terminal_size.columns) + 1
+
+    # Now calculate how many terminal lines are take up by the input
+    last_prompt_line = prompt_lines[-1]
+    last_prompt_line_width = ansi_safe_wcswidth(last_prompt_line)
+
+    input_width = last_prompt_line_width + ansi_safe_wcswidth(line)
+
+    num_input_terminal_lines = int(input_width / terminal_size.columns) + 1
+
+    # Get the cursor's offset from the beginning of the first input line
+    cursor_input_offset = last_prompt_line_width + rl_get_point()
+
+    # Calculate what input line the cursor is on
+    cursor_input_line = int(cursor_input_offset / terminal_size.columns) + 1
+
+    # Create a string that when printed will clear all input lines and display the alert
+    terminal_str = ''
+
+    # Move the cursor down to the last input line
+    if cursor_input_line != num_input_terminal_lines:
+        terminal_str += Cursor.DOWN(num_input_terminal_lines - cursor_input_line)
+
+    # Clear each line from the bottom up so that the cursor ends up on the first prompt line
+    total_lines = num_prompt_terminal_lines + num_input_terminal_lines
+    terminal_str += (colorama.ansi.clear_line() + Cursor.UP(1)) * (total_lines - 1)
+
+    # Clear the first prompt line
+    terminal_str += colorama.ansi.clear_line()
+
+    # Move the cursor to the beginning of the first prompt line and print the alert
+    terminal_str += '\r' + alert_msg
+    return terminal_str
+
+
+def set_title_str(title: str) -> str:
+    """Get the required string, including ANSI escape codes, for setting window title for the terminal.
+
+    :param title: new title for the window
+    :return string to write to sys.stderr in order to set the window title to the desired test
+    """
+    return colorama.ansi.set_title(title)
diff --git a/cmd2/cmd2.py b/cmd2/cmd2.py
index d41a631d..77af3910 100644
--- a/cmd2/cmd2.py
+++ b/cmd2/cmd2.py
@@ -42,8 +42,6 @@ from collections import namedtuple
 from contextlib import redirect_stdout
 from typing import Any, Callable, Dict, List, Mapping, Optional, Tuple, Type, Union
 
-import colorama
-
 from . import ansi
 from . import constants
 from . import plugin
@@ -54,7 +52,7 @@ from .history import History, HistoryItem
 from .parsing import StatementParser, Statement, Macro, MacroArg, shlex_split
 
 # Set up readline
-from .rl_utils import rl_type, RlType, rl_get_point, rl_set_prompt, vt100_support, rl_make_safe_prompt
+from .rl_utils import rl_type, RlType, rl_set_prompt, vt100_support, rl_make_safe_prompt
 
 if rl_type == RlType.NONE:  # pragma: no cover
     rl_warning = "Readline features including tab completion have been disabled since no \n" \
@@ -359,9 +357,6 @@ class Cmd(cmd.Cmd):
             except AttributeError:
                 pass
 
-        # Override whether ansi codes should be stripped from the output since cmd2 has its own logic for doing this
-        colorama.init(strip=False)
-
         # initialize plugin system
         # needs to be done before we call __init__(0)
         self._initialize_plugin_system()
@@ -3782,9 +3777,6 @@ class Cmd(cmd.Cmd):
         if not (vt100_support and self.use_rawinput):
             return
 
-        import shutil
-        from colorama import Cursor
-
         # Sanity check that can't fail if self.terminal_lock was acquired before calling this function
         if self.terminal_lock.acquire(blocking=False):
 
@@ -3808,50 +3800,8 @@ class Cmd(cmd.Cmd):
                     update_terminal = True
 
             if update_terminal:
-                # Get the size of the terminal
-                terminal_size = shutil.get_terminal_size()
-
-                # Split the prompt lines since it can contain newline characters.
-                prompt_lines = current_prompt.splitlines()
-
-                # Calculate how many terminal lines are taken up by all prompt lines except for the last one.
-                # That will be included in the input lines calculations since that is where the cursor is.
-                num_prompt_terminal_lines = 0
-                for line in prompt_lines[:-1]:
-                    line_width = ansi.ansi_safe_wcswidth(line)
-                    num_prompt_terminal_lines += int(line_width / terminal_size.columns) + 1
-
-                # Now calculate how many terminal lines are take up by the input
-                last_prompt_line = prompt_lines[-1]
-                last_prompt_line_width = ansi.ansi_safe_wcswidth(last_prompt_line)
-
-                input_width = last_prompt_line_width + ansi.ansi_safe_wcswidth(readline.get_line_buffer())
-
-                num_input_terminal_lines = int(input_width / terminal_size.columns) + 1
-
-                # Get the cursor's offset from the beginning of the first input line
-                cursor_input_offset = last_prompt_line_width + rl_get_point()
-
-                # Calculate what input line the cursor is on
-                cursor_input_line = int(cursor_input_offset / terminal_size.columns) + 1
-
-                # Create a string that when printed will clear all input lines and display the alert
-                terminal_str = ''
-
-                # Move the cursor down to the last input line
-                if cursor_input_line != num_input_terminal_lines:
-                    terminal_str += Cursor.DOWN(num_input_terminal_lines - cursor_input_line)
-
-                # Clear each line from the bottom up so that the cursor ends up on the first prompt line
-                total_lines = num_prompt_terminal_lines + num_input_terminal_lines
-                terminal_str += (colorama.ansi.clear_line() + Cursor.UP(1)) * (total_lines - 1)
-
-                # Clear the first prompt line
-                terminal_str += colorama.ansi.clear_line()
-
-                # Move the cursor to the beginning of the first prompt line and print the alert
-                terminal_str += '\r' + alert_msg
-
+                terminal_str = ansi.async_alert_str(prompt=current_prompt, line=readline.get_line_buffer(),
+                                                    alert_msg=alert_msg)
                 if rl_type == RlType.GNU:
                     sys.stderr.write(terminal_str)
                 elif rl_type == RlType.PYREADLINE:
@@ -3904,7 +3854,7 @@ class Cmd(cmd.Cmd):
         # Sanity check that can't fail if self.terminal_lock was acquired before calling this function
         if self.terminal_lock.acquire(blocking=False):
             try:
-                sys.stderr.write(colorama.ansi.set_title(title))
+                sys.stderr.write(ansi.set_title_str(title))
             except AttributeError:
                 # Debugging in Pycharm has issues with setting terminal title
                 pass