[core] Implement `--color` flag (#6904)

Authored by: Grub4K

5 files changed, 66 insertions, 12 deletions

diff --git a/README.md b/README.md
index d0eaba747..25ed3b844 100644
--- a/README.md
+++ b/README.md
@@ -425,8 +425,12 @@ If you fork the project on GitHub, you can run your fork's [build workflow](.git
     --no-wait-for-video             Do not wait for scheduled streams (default)
     --mark-watched                  Mark videos watched (even with --simulate)
     --no-mark-watched               Do not mark videos watched (default)
-    --no-colors                     Do not emit color codes in output (Alias:
-                                    --no-colours)
+    --color [STREAM:]POLICY         Whether to emit color codes in output,
+                                    optionally prefixed by the STREAM (stdout or
+                                    stderr) to apply the setting to. Can be one
+                                    of "always", "auto" (default), "never", or
+                                    "no_color" (use non color terminal
+                                    sequences). Can be used multiple times
     --compat-options OPTS           Options that can help keep compatibility
                                     with youtube-dl or youtube-dlc
                                     configurations by reverting some of the
@@ -2148,6 +2152,7 @@ While these options are redundant, they are still expected to be used due to the
     --playlist-end NUMBER            -I :NUMBER
     --playlist-reverse               -I ::-1
     --no-playlist-reverse            Default
+    --no-colors                      --color no_color
 
 
 #### Not recommended
diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index cd82b2772..e1e558836 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -415,7 +415,12 @@ class YoutubeDL:
                        - Raise utils.DownloadCancelled(msg) to abort remaining
                          downloads when a video is rejected.
                        match_filter_func in utils.py is one example for this.
-    no_color:          Do not emit color codes in output.
+    color:             A Dictionary with output stream names as keys
+                       and their respective color policy as values.
+                       Can also just be a single color policy,
+                       in which case it applies to all outputs.
+                       Valid stream names are 'stdout' and 'stderr'.
+                       Valid color policies are one of 'always', 'auto', 'no_color' or 'never'.
     geo_bypass:        Bypass geographic restriction via faking X-Forwarded-For
                        HTTP header
     geo_bypass_country:
@@ -537,6 +542,7 @@ class YoutubeDL:
                        data will be downloaded and processed by extractor.
                        You can reduce network I/O by disabling it if you don't
                        care about HLS. (only for youtube)
+    no_color:          Same as `color='no_color'`
     """
 
     _NUMERIC_FIELDS = {
@@ -603,9 +609,24 @@ class YoutubeDL:
         except Exception as e:
             self.write_debug(f'Failed to enable VT mode: {e}')
 
+        if self.params.get('no_color'):
+            if self.params.get('color') is not None:
+                self.report_warning('Overwriting params from "color" with "no_color"')
+            self.params['color'] = 'no_color'
+
+        term_allow_color = os.environ.get('TERM', '').lower() != 'dumb'
+
+        def process_color_policy(stream):
+            stream_name = {sys.stdout: 'stdout', sys.stderr: 'stderr'}[stream]
+            policy = traverse_obj(self.params, ('color', (stream_name, None), {str}), get_all=False)
+            if policy in ('auto', None):
+                return term_allow_color and supports_terminal_sequences(stream)
+            assert policy in ('always', 'never', 'no_color')
+            return {'always': True, 'never': False}.get(policy, policy)
+
         self._allow_colors = Namespace(**{
-            type_: not self.params.get('no_color') and supports_terminal_sequences(stream)
-            for type_, stream in self._out_files.items_ if type_ != 'console'
+            name: process_color_policy(stream)
+            for name, stream in self._out_files.items_ if name != 'console'
         })
 
         # The code is left like this to be reused for future deprecations
@@ -974,7 +995,7 @@ class YoutubeDL:
             text = text.encode(encoding, 'ignore').decode(encoding)
             if fallback is not None and text != original_text:
                 text = fallback
-        return format_text(text, f) if allow_colors else text if fallback is None else fallback
+        return format_text(text, f) if allow_colors is True else text if fallback is None else fallback
 
     def _format_out(self, *args, **kwargs):
         return self._format_text(self._out_files.out, self._allow_colors.out, *args, **kwargs)
@@ -3769,9 +3790,14 @@ class YoutubeDL:
 
         def get_encoding(stream):
             ret = str(getattr(stream, 'encoding', 'missing (%s)' % type(stream).__name__))
+            additional_info = []
+            if os.environ.get('TERM', '').lower() == 'dumb':
+                additional_info.append('dumb')
             if not supports_terminal_sequences(stream):
                 from .utils import WINDOWS_VT_MODE  # Must be imported locally
-                ret += ' (No VT)' if WINDOWS_VT_MODE is False else ' (No ANSI)'
+                additional_info.append('No VT' if WINDOWS_VT_MODE is False else 'No ANSI')
+            if additional_info:
+                ret = f'{ret} ({",".join(additional_info)})'
             return ret
 
         encoding_str = 'Encodings: locale %s, fs %s, pref %s, %s' % (
diff --git a/yt_dlp/__init__.py b/yt_dlp/__init__.py
index 9563d784a..137c9503f 100644
--- a/yt_dlp/__init__.py
+++ b/yt_dlp/__init__.py
@@ -436,6 +436,10 @@ def validate_options(opts):
         elif ed and proto == 'default':
             default_downloader = ed.get_basename()
 
+    for policy in opts.color.values():
+        if policy not in ('always', 'auto', 'no_color', 'never'):
+            raise ValueError(f'"{policy}" is not a valid color policy')
+
     warnings, deprecation_warnings = [], []
 
     # Common mistake: -f best
@@ -894,7 +898,7 @@ def parse_options(argv=None):
         'playlist_items': opts.playlist_items,
         'xattr_set_filesize': opts.xattr_set_filesize,
         'match_filter': opts.match_filter,
-        'no_color': opts.no_color,
+        'color': opts.color,
         'ffmpeg_location': opts.ffmpeg_location,
         'hls_prefer_native': opts.hls_prefer_native,
         'hls_use_mpegts': opts.hls_use_mpegts,
diff --git a/yt_dlp/downloader/common.py b/yt_dlp/downloader/common.py
index c48a2ff8a..477ec3c8a 100644
--- a/yt_dlp/downloader/common.py
+++ b/yt_dlp/downloader/common.py
@@ -296,7 +296,8 @@ class FileDownloader:
             self._multiline = BreaklineStatusPrinter(self.ydl._out_files.out, lines)
         else:
             self._multiline = MultilinePrinter(self.ydl._out_files.out, lines, not self.params.get('quiet'))
-        self._multiline.allow_colors = self._multiline._HAVE_FULLCAP and not self.params.get('no_color')
+        self._multiline.allow_colors = self.ydl._allow_colors.out and self.ydl._allow_colors.out != 'no_color'
+        self._multiline._HAVE_FULLCAP = self.ydl._allow_colors.out
 
     def _finish_multiline_status(self):
         self._multiline.end()
diff --git a/yt_dlp/options.py b/yt_dlp/options.py
index 838d79fcb..fecc27403 100644
--- a/yt_dlp/options.py
+++ b/yt_dlp/options.py
@@ -34,6 +34,7 @@ from .utils import (
     join_nonempty,
     orderedSet_from_options,
     remove_end,
+    variadic,
     write_string,
 )
 from .version import CHANNEL, __version__
@@ -250,7 +251,7 @@ def create_parser():
             if multiple_args:
                 val = [val, *value[1:]]
         elif default_key is not None:
-            keys, val = [default_key], value
+            keys, val = variadic(default_key), value
         else:
             raise optparse.OptionValueError(
                 f'wrong {opt_str} formatting; it should be {option.metavar}, not "{value}"')
@@ -440,8 +441,25 @@ def create_parser():
         help='Do not mark videos watched (default)')
     general.add_option(
         '--no-colors', '--no-colours',
-        action='store_true', dest='no_color', default=False,
-        help='Do not emit color codes in output (Alias: --no-colours)')
+        action='store_const', dest='color', const={
+            'stdout': 'no_color',
+            'stderr': 'no_color',
+        },
+        help=optparse.SUPPRESS_HELP)
+    general.add_option(
+        '--color',
+        dest='color', metavar='[STREAM:]POLICY', default={}, type='str',
+        action='callback', callback=_dict_from_options_callback,
+        callback_kwargs={
+            'allowed_keys': 'stdout|stderr',
+            'default_key': ['stdout', 'stderr'],
+            'process': str.strip,
+        }, help=(
+            'Whether to emit color codes in output, optionally prefixed by '
+            'the STREAM (stdout or stderr) to apply the setting to. '
+            'Can be one of "always", "auto" (default), "never", or '
+            '"no_color" (use non color terminal sequences). '
+            'Can be used multiple times'))
     general.add_option(
         '--compat-options',
         metavar='OPTS', dest='compat_opts', default=set(), type='str',