Add `--color` option and only color output to tty

README.mdwn

@@ -127,7 +127,7 @@ Output of the `./mjt.py --help`
 ```
 usage: mjt.py [-h] [--only_incorrect_tests] [--produce_no_reports]
               [--produce_all_reports] [--parallel]
-              [--output_no_incorrect_reports] [--no_color] [--ci_testing]
+              [--output_no_incorrect_reports] [--color] [--ci_testing]
               [--log_level LOG_LEVEL]
               {all,lexer,syntax,ast,semantic,exec} MJ_RUN
 
@@ -151,7 +151,8 @@ optional arguments:
   --parallel            Run the tests in parallel
   --output_no_incorrect_reports
                         Output the long report for every incorrect test case
-  --no_color            Output no color codes
+  --color               Output color output even if the output goes to into a
+                        file
   --ci_testing          In mode X the succeeding test cases of later
                         modes/phases should also succeed in this mode, and
                         failing test cases of prior modes/phases should also

mjtest/cli.py

@@ -48,8 +48,8 @@ if True:#__name__ == '__main__':
                         help="Run the tests in parallel")
     parser.add_argument("--output_no_incorrect_reports", action="store_true", default=False,
                         help="Output the long report for every incorrect test case")
-    parser.add_argument("--no_color", action="store_true", default=False,
-                        help="Output no color codes")
+    parser.add_argument("--color", action="store_true", default=False,
+                        help="Output color output even if the output goes to into a file")
     parser.add_argument("--ci_testing", action="store_true", default=False,
                         help="In mode X the succeeding test cases of later modes/phases should also succeed in "
                              "this mode, and failing test cases of prior modes/phases should also fail in this phase.")

mjtest/environment.py

@@ -6,7 +6,7 @@ import tempfile
 from datetime import datetime
 import time
 from mjtest.util.shell import execute
-from mjtest.util.utils import get_mjtest_basedir, disable_colored_output
+from mjtest.util.utils import get_mjtest_basedir, force_colored_output
 import mjtest.util.utils
 from typing import Tuple, List
 from preproc.preproc.preprocessor import PreProcessor, PreProcessorError, is_importable_file
@@ -46,9 +46,9 @@ class Environment:
                  timeout: int = 30, report_dir: str = "", log_level: str = "warn",
                  produce_no_reports: bool = True, output_no_incorrect_reports: bool = False,
                  produce_all_reports: bool = False, report_subdir: str = None,
-                 ci_testing: bool = False, no_color: bool = False):
-        if no_color:
-            disable_colored_output()
+                 ci_testing: bool = False, color: bool = False):
+        if color:
+            force_colored_output()
         self.mode = mode
         self.mj_run_cmd = os.path.realpath(mj_run)
 

mjtest/util/utils.py

@@ -3,17 +3,19 @@ from os import path
 import sys
 from typing import Tuple
 
-COLOR_OUTPUT_IF_POSSIBLE = True
+COLOR_OUTPUT_IF_POSSIBLE = False
 
-try:
-    import termcolor
-except ImportError:
-    COLOR_OUTPUT_IF_POSSIBLE = False
+if sys.stdout.isatty():
+    try:
+        import termcolor
+        COLOR_OUTPUT_IF_POSSIBLE = True
+    except ImportError:
+        COLOR_OUTPUT_IF_POSSIBLE = False
 
 
-def disable_colored_output():
+def force_colored_output():
     global COLOR_OUTPUT_IF_POSSIBLE
-    COLOR_OUTPUT_IF_POSSIBLE = False
+    COLOR_OUTPUT_IF_POSSIBLE = True
 
 
 def get_mjtest_basedir() -> str: