Clean up terminal width handling (#9143)

* Remove fixed_terminal_width from utils.colorize docstring

This was added by 91adf61, yet colorize()
doesn't actually have a fixed_terminal_width argument.

* Move MYPY_FORCE_TERMINAL_WIDTH handling into get_terminal_width()

Those two callers are the only two, and both check MYPY_FORCE_TERMINAL_WIDTH
before calling get_terminal_width().

* Use shutil.get_terminal_size()

The documentation for Python's os.get_terminal_size() says:

    shutil.get_terminal_size() is the high-level function which should normally
    be used, os.get_terminal_size is the low-level implementation.

https://docs.python.org/3/library/os.html#os.get_terminal_size

shutil.get_terminal_size() already takes care of various corner cases such as:

- Providing a fallback (to 80 columns, like the current DEFAULT_COLUMNS)
- Returning that fallback if os.get_terminal_size() raises OSError
- Doing the same if it returns a size of 0

In addition to that:

- It takes care of some more corner cases ("stdout is None, closed, detached, or
  not a terminal, or os.get_terminal_size() is unsupported")
- It adds support for the COLUMNS environment variable (rather than the
  non-standard MYPY_FORCE_TERMINAL_WIDTH)

https://github.com/python/cpython/blob/v3.8.3/Lib/shutil.py#L1298-L1341

mypy/dmypy/client.py

@@ -475,8 +475,7 @@ def request(status_file: str, command: str, *, timeout: Optional[int] = None,
     # Tell the server whether this request was initiated from a human-facing terminal,
     # so that it can format the type checking output accordingly.
     args['is_tty'] = sys.stdout.isatty() or int(os.getenv('MYPY_FORCE_COLOR', '0')) > 0
-    args['terminal_width'] = (int(os.getenv('MYPY_FORCE_TERMINAL_WIDTH', '0')) or
-                              get_terminal_width())
+    args['terminal_width'] = get_terminal_width()
     bdata = json.dumps(args).encode('utf8')
     _, name = get_status(status_file)
     try:

mypy/util.py

@@ -7,6 +7,7 @@
 import sys
 import hashlib
 import io
+import shutil
 
 from typing import (
     TypeVar, List, Tuple, Optional, Dict, Sequence, Iterable, Container, IO, Callable
@@ -34,7 +35,6 @@
 PLAIN_ANSI_DIM = '\x1b[2m'  # type: Final
 
 DEFAULT_SOURCE_OFFSET = 4  # type: Final
-DEFAULT_COLUMNS = 80   # type: Final
 
 # At least this number of columns will be shown on each side of
 # error location when printing source code snippet.
@@ -424,14 +424,7 @@ def split_words(msg: str) -> List[str]:
 
 def get_terminal_width() -> int:
     """Get current terminal width if possible, otherwise return the default one."""
-    try:
-        cols, _ = os.get_terminal_size()
-    except OSError:
-        return DEFAULT_COLUMNS
-    else:
-        if cols == 0:
-            return DEFAULT_COLUMNS
-        return cols
+    return int(os.getenv('MYPY_FORCE_TERMINAL_WIDTH', '0')) or shutil.get_terminal_size().columns
 
 
 def soft_wrap(msg: str, max_len: int, first_offset: int,
@@ -594,8 +587,7 @@ def style(self, text: str, color: Literal['red', 'green', 'blue', 'yellow', 'non
     def fit_in_terminal(self, messages: List[str],
                         fixed_terminal_width: Optional[int] = None) -> List[str]:
         """Improve readability by wrapping error messages and trimming source code."""
-        width = (fixed_terminal_width or int(os.getenv('MYPY_FORCE_TERMINAL_WIDTH', '0')) or
-                 get_terminal_width())
+        width = fixed_terminal_width or get_terminal_width()
         new_messages = messages.copy()
         for i, error in enumerate(messages):
             if ': error:' in error:
@@ -619,11 +611,7 @@ def fit_in_terminal(self, messages: List[str],
         return new_messages
 
     def colorize(self, error: str) -> str:
-        """Colorize an output line by highlighting the status and error code.
-
-        If fixed_terminal_width is given, use it instead of calling get_terminal_width()
-        (used by the daemon).
-        """
+        """Colorize an output line by highlighting the status and error code."""
         if ': error:' in error:
             loc, msg = error.split('error:', maxsplit=1)
             if not self.show_error_codes: