CLI: a splash of colour

[oliver-sanders]

Add colour support to the cli_function wrapper.

• Use the GNU-like colour argument for all Cylc sub-commands:
  • i.e. --color=(auto|always|never)
  • Default to auto which will use colour if displayed in a terminal.
• Use the ansimarkup library for easy colour control:
  • An xml-like pre-processor with basic ANSI style and 8-bit coluor support.
  • e.g. <red>Error</red>.
• Make important information prominent and unimportant information ambient.
  • CRITICAL - bold & red
  • ERROR - red
  • WARNING - yellow
  • DEBUG - grey
  • Success messages - green
  • Everything else - black
• Improve logger output when viewed from the terminal (log/suite/log file not effected).
  • Log entries formatted to width of terminal.
  • Critical, error and warning levels coloured.
• Colorise log/suite/log when viewed through cylc cat-log
• Convert some sys.exit to raise CylcError

Note: The cli_function wrapper may change with #2972, colour support is somewhat orthogonal to this.

Example

[hjoliver]

Some general comments first:

I definitely like colour output for the CLI

Colorama docs say: "ANSI escape character sequences have long been used to produce colored terminal text and cursor positioning on Unix and Macs. Colorama makes this work on Windows, too, by wrapping stdout, stripping ANSI sequences it finds (which would appear as gobbledygook in the output), and converting them into the appropriate win32 calls to modify the state of the terminal. On other platforms, Colorama does nothing."

i.e. "[on Linux] Colorama does nothing", and its main purpose is to translate ANSI color control codes to the MS Windows API (which we don't support).

Presumably in spite of the "it does nothing [on Linux]" statement, it is nicer to use than raw ANSI control codes.

There are high level libs built ontop of colorama including my fave ansimarkup.

Should we use ansimarkup then??

[oliver-sanders]

No objections so I've moved this along:

• Using ansimarkup to simplify output e.g. <red>red text</red>
• Pass the option parser to cli_function which populates the arguments of its decorated function

Colour support so far:

• cylc broadcast
• cylc validate
• cylc show

If no-one screams I'll complete the conversion, rename cli_function2 to cli_function and open to review.

@kinow I'm guessing you're not going to like my wrapping of the CLI methods as the wrapper populates the arguments. Happy to change, open to suggestions, trying not to write any solution into argparse.

[kinow]

Tested with a running suite, then validate and show, and show got some colours (validate was green, same colour as my terminal background, so maybe there was some colouring, but I couldn't notice).

Using ansimarkup to simplify output e.g. red text

Does it add/help a lot? Last commit in 2018, and few contributors - which could be fine, as the tool is simple, it could be feature-complete and only fix bugs (which it doesn't have any at the moment in github). But if it does add or simplify the code, and you think it's stable to be used in Cylc, all good 👍

@kinow I'm guessing you're not going to like my wrapping of the CLI methods as the wrapper populates the arguments. Happy to change, open to suggestions, trying not to write any solution into argparse.

No suggestion. I have never used anything like this before, so it looks quite alien for me, but not incorrect. I think it is OK to be added now and we can think in alternatives later if we find issues with the current approach, or if there are simpler alternatives.

(not reviewing as it's marked as discussion, so I think others will want to have a look and give their opinion too before we jump to reviewing/merging?)

[oliver-sanders]

validate was green, same colour as my terminal background

You have a green terminal background!

Not too sure what can be done about this one, it might be possible to detect the terminal background ANSI code, then pair the corresponding foreground code with a white background.

What do you see if you see with tools like diff?

ansimarkup - Does it add/help a lot?

It simplifies things somewhat making code more readable (cleaner syntax, no string formatting required), it also adds 8-bit colour support (where the terminal supports it) as used to turn the DEBUG messages grey (there is no grey ANSI code).

I think ansimarkup suffers from "being too simple" so it's not active as there aren't really any important changes to make.

looks quite alien for me, but not incorrect. I think it is OK

I'm not overjoyed by it as it causes linters to complain, but it's a perfectly valid Python pattern. Happy to change later for a nicer approach if we come up with one.

[kinow]

Oh sorry, actually green text color! Hahaa, would be pretty hard on my eyes a green background haha

[oliver-sanders]

Flaky tests/execution-time-limit/00-background.t keeps failing but all else passes.
All tests passing.

[wxtim]

• Sanity check code
• Try it out on desktop
  • With --color=[always|auto|never]
  • With my theme and a corner case "nasty" theme that I keep hanging around for this sort of thing. It looks no worse than the theme does anyway.
  • Used a color blindness simulator on the output. It's not as much of an improvement on the uncolored version, but it's not a degradation. :)

[hjoliver]

Codacy failure (2 new issues) because Pylint evidently doesn't understand when decorators alter a function signature:

Which is annoying.

[hjoliver]

Otherwise LGTM (not that the codacy problem is your fault; Pylint is just deficient).

[hjoliver]

Spurious test battery failure on Travis CI.

[oliver-sanders]

🌈