Set auto expand to false if less pager is installed (#423)

* Set auto expand to false if less pager is installed
* Added tests and improved testability of code

Author: Elliot Boschwitz

mssqlcli/mssql_cli.py

@@ -44,6 +44,7 @@
 from mssqlcli.sqltoolsclient import SqlToolsClient
 from mssqlcli.packages import special
 from mssqlcli.mssqlbuffer import mssql_is_multiline
+from mssqlcli.util import is_command_valid
 import mssqlcli.localized_strings as localized
 
 # Query tuples are used for maintaining history
@@ -97,15 +98,18 @@ class MssqlCli(object):
     def set_default_pager(self, config):
         configured_pager = config['main'].get('pager')
         os_environ_pager = os.environ.get('PAGER')
+        is_less_installed = is_command_valid(['less', '--version'])
+        default_pager = configured_pager or os_environ_pager or \
+                        ('less -SRXF' if is_less_installed else False) or None
 
         if configured_pager:
             self.logger.info(
                 'Default pager found in config file: "%s"', configured_pager)
-            os.environ['PAGER'] = configured_pager
         elif os_environ_pager:
             self.logger.info('Default pager found in PAGER environment variable: "%s"',
                              os_environ_pager)
-            os.environ['PAGER'] = os_environ_pager
+        elif is_less_installed:
+            self.logger.info('Default pager set to Less')
         else:
             self.logger.info(
                 'No default pager found in environment. Using os default pager')
@@ -115,6 +119,9 @@ def set_default_pager(self, config):
         if not os.environ.get('LESS'):
             os.environ['LESS'] = '-SRXF'
 
+        os.environ['PAGER'] = default_pager
+        return default_pager
+
     def __init__(self, options):
 
         # Load config.
@@ -123,16 +130,13 @@ def __init__(self, options):
         self.initialize_logging()
         self.logger = logging.getLogger(u'mssqlcli.main')
 
-        self.set_default_pager(c)
         self.interactive_mode = options.interactive_mode
 
         self.table_format = c['main']['table_format']
         self.decimal_format = c['data_formats']['decimal']
         self.float_format = c['data_formats']['float']
         self.null_string = c['main'].get('null_string', '<null>')
         self.expanded_output = c['main']['expand'] == 'always'
-        self.auto_expand = options.auto_vertical_output or c['main']['expand'] == 'auto'
-        self.prompt_session = None
         self.integrated_auth = options.integrated_auth
         self.less_chatty = bool(
             options.less_chatty) or c['main'].as_bool('less_chatty') or self.interactive_mode
@@ -152,6 +156,12 @@ def __init__(self, options):
         }
 
         if self.interactive_mode:
+            pager = self.set_default_pager(c)
+            self.prompt_session = None
+
+            # set auto_expand to false if less is detected with auto expand
+            self.auto_expand = options.auto_vertical_output \
+                or (c['main']['expand'] == 'auto' and pager != 'less -SRXF')
             self.multiline = c['main'].as_bool('multi_line')
             self.multiline_mode = c['main'].get('multi_line_mode', 'tsql')
             self.vi_mode = c['main'].as_bool('vi')
@@ -559,7 +569,7 @@ def _evaluate_command(self, text):
                 all_success = False
                 continue
 
-            if self.auto_expand and self.prompt_session:
+            if self.interactive_mode and self.auto_expand and self.prompt_session:
                 max_width = self.prompt_session.output.get_size().columns
             else:
                 max_width = None

mssqlcli/util.py

@@ -1,3 +1,6 @@
+from os import devnull
+import subprocess
+
 def encode(s):
     try:
         return s.encode('utf-8')
@@ -14,3 +17,20 @@ def decode(s):
     except (AttributeError, SyntaxError, UnicodeEncodeError):
         pass
     return s
+
+def is_command_valid(command):
+    """
+    Checks if command is recognized on machine. Used to determine installations
+    of 'less' pager.
+    """
+    if not command:
+        return False
+
+    try:
+        # call command silentyly
+        with open(devnull, 'wb') as no_out:
+            subprocess.call(command, stdout=no_out, stderr=no_out)
+    except OSError:
+        return False
+    else:
+        return True

tests/mssqltestutils.py

@@ -5,6 +5,7 @@
 import mssqlcli.sqltoolsclient as sqltoolsclient
 import mssqlcli.mssqlcliclient as mssqlcliclient
 from mssqlcli.mssql_cli import MssqlCli
+from mssqlcli.config import get_config
 from mssqlcli.mssqlclioptionsparser import create_parser
 from utility import random_str
 
@@ -70,6 +71,14 @@ def create_mssql_cli_options(**nondefault_options):
 
     return default_mssql_cli_options
 
+def create_mssql_cli_config(options=None):
+    """
+    Create config from options.
+    """
+    if not options:
+        options = create_mssql_cli_options()
+    return get_config(options.mssqlclirc_file)
+
 def shutdown(connection):
     connection.shutdown()
 

tests/test_interactive_mode.py

@@ -1,13 +1,21 @@
+import os
+import sys
 import pytest
+import utility
+from mssqlcli.util import is_command_valid
 from mssqltestutils import (
     create_mssql_cli,
+    create_mssql_cli_config,
     shutdown,
     test_queries,
     get_file_contents,
     get_io_paths
 )
 
-class TestInteractiveModeQueries:
+class TestInteractiveMode:
+    """
+    Fixture used at class-level.
+    """
     @staticmethod
     @pytest.fixture(scope='class')
     def mssqlcli():
@@ -19,6 +27,7 @@ def mssqlcli():
         yield mssqlcli
         shutdown(mssqlcli)
 
+class TestInteractiveModeQueries(TestInteractiveMode):
     @staticmethod
     @pytest.mark.parametrize("query_str, test_file", test_queries)
     @pytest.mark.timeout(60)
@@ -73,3 +82,59 @@ def invalid_run(**options):
         finally:
             if mssqlcli is not None:
                 shutdown(mssqlcli)
+
+class TestInteractiveModePager(TestInteractiveMode):
+    """
+    Test default pager setting.
+    """
+
+    @staticmethod
+    @pytest.mark.timeout(60)
+    def test_pager_environ(mssqlcli):
+        """
+        Defaults to environment variable with no config value for pager
+        """
+        os.environ['PAGER'] = 'testing environ value'
+
+        config = create_mssql_cli_config()
+
+        # remove config pager value if exists
+        if 'pager' in config['main'].keys():
+            config['main'].pop('pager')
+
+        assert mssqlcli.set_default_pager(config) == 'testing environ value'
+
+        os.environ['PAGER'] = 'less -SRXF'
+        assert mssqlcli.set_default_pager(config) == 'less -SRXF'
+
+    @staticmethod
+    @pytest.mark.timeout(60)
+    def test_pager_config(mssqlcli):
+        """
+        Defaults to config value over environment variable
+        """
+        os.environ['PAGER'] = 'less -SRXF'
+        config_value = 'testing config value'
+
+        config = create_mssql_cli_config()
+        config['main']['pager'] = config_value
+        assert mssqlcli.set_default_pager(config) == config_value
+
+    @staticmethod
+    @pytest.mark.timeout(60)
+    def test_valid_command():
+        """
+        Checks valid command by running mssql-cli executable in repo
+        """
+        if sys.platform == 'win32':
+            exe_name = 'mssql-cli.bat'
+        else:
+            exe_name = 'mssql-cli'
+
+        assert is_command_valid([os.path.join(utility.ROOT_DIR, exe_name), '--version'])
+
+    @staticmethod
+    @pytest.mark.timeout(60)
+    def test_invalid_command():
+        assert not is_command_valid(None)
+        assert not is_command_valid('')