Dramatically changed the approach to this PR

Changes include:
- pager is no longer a settable parameter which can be changed by the end user at runtime
- The cmd2.Cmd class now has two different attributes:
    - pager
        - contains command-line command to use to display wrapped text using a pager
        - By default set to PAGER environment variable if it exists
            - 'more' on Windows or 'less -RXF' on POSIX
    - pager_chop
        - contains command-line command to use to display chopped (truncated) text using a pager
        - Set to same thing as pager unless pager starts with 'less', in which case  a ' -S' gets appended
- The cmd2.Cmd.ppaged() method now has an additional optional argument "chop" which defaults to False
    - If chop is True, then self.pager_chop gets used as the pager
    - If chop is False, then slef.pager gets used as the pager

I couldn't think of any single solution which would somehow magically make all stakeholders perfectly happy.  Hopefully this is a reasonable enough compromise that everyone feels that they can get what they need without too much pain ;-)

Author: tleonhardt

cmd2/cmd2.py

@@ -385,17 +385,6 @@ class Cmd(cmd.Cmd):
                     break
     feedback_to_output = False  # Do not include nonessentials in >, | output by default (things like timing)
     locals_in_py = False
-    pager = os.environ.get('PAGER')
-    if not pager:
-        if sys.platform.startswith('win'):
-            pager = 'more'
-        else:
-            # Here is the meaning of the various flags we are using with the less command:
-            # -S causes lines longer than the screen width to be chopped (truncated) rather than wrapped
-            # -R causes ANSI "color" escape sequences to be output in raw form (i.e. colors are displayed)
-            # -X disables sending the termcap initialization and deinitialization strings to the terminal
-            # -F causes less to automatically exit if the entire file can be displayed on the first screen
-            pager = 'less -SRXF'
     quiet = False  # Do not suppress nonessential output
     timing = False  # Prints elapsed time for each command
 
@@ -408,7 +397,6 @@ class Cmd(cmd.Cmd):
                 'editor': 'Program used by ``edit``',
                 'feedback_to_output': 'Include nonessentials in `|`, `>` results',
                 'locals_in_py': 'Allow access to your application in py via self',
-                'pager': 'Command used for displaying paged output',
                 'prompt': 'The prompt issued to solicit input',
                 'quiet': "Don't print nonessential feedback",
                 'timing': 'Report execution times'}
@@ -546,6 +534,24 @@ def __init__(self, completekey: str='tab', stdin=None, stdout=None, persistent_h
         # quote matches that are completed in a delimited fashion
         self.matches_delimited = False
 
+        # Set the pager(s) for use with the ppaged() method for displaying output using a pager
+        self.pager = os.environ.get('PAGER')
+        if not self.pager:
+            if sys.platform.startswith('win'):
+                self.pager = self.pager_chop = 'more'
+            else:
+                # Here is the meaning of the various flags we are using with the less command:
+                # -S causes lines longer than the screen width to be chopped (truncated) rather than wrapped
+                # -R causes ANSI "color" escape sequences to be output in raw form (i.e. colors are displayed)
+                # -X disables sending the termcap initialization and deinitialization strings to the terminal
+                # -F causes less to automatically exit if the entire file can be displayed on the first screen
+                self.pager = 'less -RXF'
+                self.pager_chop = 'less -SRXF'
+        else:
+            self.pager_chop = self.pager
+            if self.pager_chop.startswith('less'):
+                self.pager_chop += ' -S'
+
     # -----  Methods related to presenting output to the user -----
 
     @property
@@ -620,14 +626,18 @@ def pfeedback(self, msg: str) -> None:
             else:
                 sys.stderr.write("{}\n".format(msg))
 
-    def ppaged(self, msg: str, end: str='\n') -> None:
+    def ppaged(self, msg: str, end: str='\n', chop: bool=False) -> None:
         """Print output using a pager if it would go off screen and stdout isn't currently being redirected.
 
         Never uses a pager inside of a script (Python or text) or when output is being redirected or piped or when
         stdout or stdin are not a fully functional terminal.
 
-        :param msg: str - message to print to current stdout - anything convertible to a str with '{}'.format() is OK
-        :param end: str - string appended after the end of the message if not already present, default a newline
+        :param msg: message to print to current stdout - anything convertible to a str with '{}'.format() is OK
+        :param end: string appended after the end of the message if not already present, default a newline
+        :param chop: True  -> causes lines longer than the screen width to be chopped (truncated) rather than wrapped
+                              - truncated text is still accessible by scrolling with the right & left arrow keys
+                     False -> causes lines longer than the screen width to wrap to the next line
+                     WARNING: On Windows, the text always wraps regardless of what the chop argument is set to
         """
         import subprocess
         if msg is not None and msg != '':
@@ -647,7 +657,10 @@ def ppaged(self, msg: str, end: str='\n') -> None:
                 # Don't attempt to use a pager that can block if redirecting or running a script (either text or Python)
                 # Also only attempt to use a pager if actually running in a real fully functional terminal
                 if functional_terminal and not self.redirecting and not self._in_py and not self._script_dir:
-                    self.pipe_proc = subprocess.Popen(self.pager, shell=True, stdin=subprocess.PIPE)
+                    pager = self.pager
+                    if chop:
+                        pager = self.pager_chop
+                    self.pipe_proc = subprocess.Popen(pager, shell=True, stdin=subprocess.PIPE)
                     try:
                         self.pipe_proc.stdin.write(msg_str.encode('utf-8', 'replace'))
                         self.pipe_proc.stdin.close()

tests/conftest.py

@@ -80,10 +80,8 @@
 """
 
 expect_colors = True
-pager = 'less -SRXF'
 if sys.platform.startswith('win'):
     expect_colors = False
-    pager = 'more      '
 # Output from the show command with default settings
 SHOW_TXT = """colors: {}
 continuation_prompt: >
@@ -92,11 +90,10 @@
 editor: vim
 feedback_to_output: False
 locals_in_py: False
-pager: {}
 prompt: (Cmd)
 quiet: False
 timing: False
-""".format(expect_colors, pager)
+""".format(expect_colors)
 
 if expect_colors:
     color_str = 'True '
@@ -110,11 +107,10 @@
 editor: vim               # Program used by ``edit``
 feedback_to_output: False # Include nonessentials in `|`, `>` results
 locals_in_py: False       # Allow access to your application in py via self
-pager: {}         # Command used for displaying paged output
 prompt: (Cmd)             # The prompt issued to solicit input
 quiet: False              # Don't print nonessential feedback
 timing: False             # Report execution times
-""".format(color_str, pager)
+""".format(color_str)
 
 
 class StdOut(object):

tests/transcripts/regex_set.txt

@@ -12,7 +12,6 @@ editor: /.*/
 feedback_to_output: False
 locals_in_py: False
 maxrepeats: 3
-pager: /.*/
 prompt: (Cmd)/ /
 quiet: False
 timing: False