* Fix handling empty values of NO_COLOR and FORCE_COLOR
Fix handling NO_COLOR and FORCE_COLOR environment variables to correctly
be ignored when they are set to an empty value, as defined
in the specification:
> Command-line software which adds ANSI color to its output by default
> should check for a NO_COLOR environment variable that, when present
> *and not an empty string* (regardless of its value), prevents
> the addition of ANSI color.
(emphasis mine, https://no-color.org/)
The same is true of FORCE_COLOR, https://force-color.org/.
* Streamline testing for FORCE_COLOR and NO_COLOR
Streamline the tests for FORCE_COLOR and NO_COLOR variables, and cover
all possible cases (unset, set to empty, set to "1"). Combine the two
assert functions into one taking boolean parameters. Mock file.isatty
in all circumstances to ensure that the environment variables take
precedence over the fallback value resulting from isatty check (or that
the fallback is actually used, in the case of both FORCE_COLOR
and NO_COLOR being unset).
* Put a 'reset' color in front of the highlighting
When doing the highlighting, some lexers will not set the initial color
explicitly, which may lead to the red from the errors being propagated
to the start of the expression
* Add syntactic highlighting to the error explanations
This updates the various error reporting to highlight python code when
displayed, to increase readability and make it easier to understand
This indicates at least for people using type checkers that these
classes are not designed for inheritance and we make no stability
guarantees regarding inheritance of them.
Currently this doesn't show up in the docs. Sphinx does actually support
`@final`, however it only works when imported directly from `typing`,
while we import from `_pytest.compat`.
In the future there might also be a `@sealed` decorator which would
cover some more cases.
`TerminalWriter`, imported recently from `py`, contains its own
incomplete wcwidth (`char_with`/`get_line_width`) implementation. The
`TerminalReporter` also needs this, but uses the external `wcwidth`
package.
This commit brings the `TerminalWriter` implementation up-to-par with
`wcwidth`, moves to implementation to a new file `_pytest._io.wcwidth`
which is used everywhere, and removes the dependency.
The differences compared to the `wcwidth` package are:
- Normalizes the string before counting.
- Uses Python's `unicodedata` instead of vendored Unicode tables. This
means the data corresponds to the Python's version Unicode version
instead of the `wcwidth`'s package version.
- Apply some optimizations.
Currently this property is computed eagerly, which means
get_line_width() is computed on everything written, but that is a slow
function.
Compute it lazily, so that get_line_width() only runs when needed.
Flushing on every write is somewhat expensive.
Rely on line buffering instead (if line buffering for stdout is
disabled, there must be some reason...), and add explicit flushes when
not outputting lines.
This is how regular `print()` e.g. work so should be familiar.