fish-shell/doc_src/cmds/fish_opt.rst

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.. _cmd-fish_opt:
fish_opt - create an option spec for the argparse command
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Synopsis
--------
docs synopsis: add HTML highlighing and automate manpage markup Recent synopsis changes move from literal code blocks to [RST line blocks]. This does not translate well to HTML: it's not rendered in monospace, so aligment is lost. Additionally, we don't get syntax highlighting in HTML, which adds differences to our code samples which are highlighted. We hard-wrap synopsis lines (like code blocks). To align continuation lines in manpages we need [backslashes in weird places]. Combined with the **, *, and `` markup, it's a bit hard to get the alignment right. Fix these by moving synopsis sources back to code blocks and compute HTML syntax highlighting and manpage markup with a custom Sphinx extension. The new Pygments lexer can tokenize a synopsis and assign the various highlighting roles, which closely matches fish's syntax highlighing: - command/keyword (dark blue) - parameter (light blue) - operator like and/or/not/&&/|| (cyan) - grammar metacharacter (black) For manpage output, we don't project the fish syntax highlighting but follow the markup convention in GNU's man(1): bold text type exactly as shown. italic text replace with appropriate argument. To make it easy to separate these two automatically, formalize that (italic) placeholders must be uppercase; while all lowercase text is interpreted literally (so rendered bold). This makes manpages more consistent, see string-join(1) and and(1). Implementation notes: Since we want manpage formatting but Sphinx's Pygments highlighing plugin does not support manpage output, add our custom "synopsis" directive. This directive parses differently when manpage output is specified. This means that the HTML and manpage build processes must not share a cache, because the parsed doctrees are cached. Work around this by using separate cache locations for build targets "sphinx-docs" (which creates HTML) and "sphinx-manpages". A better solution would be to only override Sphinx's ManualPageBuilder but that would take a bit more code (ideally we could override ManualPageWriter but Sphinx 4.3.2 doesn't really support that). --- Alternative solution: stick with line blocks but use roles like :command: or :option: (or custom ones). While this would make it possible to produce HTML that is consistent with code blocks (by adding a bit of CSS), the source would look uglier and is harder to maintain. (Let's say we want to add custom formatting to the [|] metacharacters in HTML. This is much easier with the proposed patch.) --- [RST line blocks]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#line-blocks [backslashes in weird places]: https://github.com/fish-shell/fish-shell/pull/8626#discussion_r782837750
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.. synopsis::
fish_opt [--help]
fish_opt [(-slor | --multiple-vals=) OPTNAME]
Description
-----------
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This command provides a way to produce option specifications suitable for use with the :ref:`argparse <cmd-argparse>` command. You can, of course, write the option specs by hand without using this command. But you might prefer to use this for the clarity it provides.
The following ``argparse`` options are available:
- ``-s`` or ``--short`` takes a single letter that is used as the short flag in the option being defined. This option is mandatory.
- ``-l`` or ``--long`` takes a string that is used as the long flag in the option being defined. This option is optional and has no default. If no long flag is defined then only the short flag will be allowed when parsing arguments using the option spec.
- ``--long-only`` means the option spec being defined will only allow the long flag name to be used. The short flag name must still be defined (i.e., ``--short`` must be specified) but it cannot be used when parsing args using this option spec.
- ``-o`` or ``--optional-val`` means the option being defined can take a value but it is optional rather than required. If the option is seen more than once when parsing arguments only the last value seen is saved. This means the resulting flag variable created by ``argparse`` will zero elements if no value was given with the option else it will have exactly one element.
- ``-r`` or ``--required-val`` means the option being defined requires a value. If the option is seen more than once when parsing arguments only the last value seen is saved. This means the resulting flag variable created by ``argparse`` will have exactly one element.
- ``--multiple-vals`` means the option being defined requires a value each time it is seen. Each instance is stored. This means the resulting flag variable created by ``argparse`` will have one element for each instance of this option in the args.
- ``-h`` or ``--help`` displays help about using this command.
Examples
--------
Define a single option spec for the boolean help flag:
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::
set -l options (fish_opt -s h -l help)
argparse $options -- $argv
Same as above but with a second flag that requires a value:
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::
set -l options (fish_opt -s h -l help)
set options $options (fish_opt -s m -l max --required-val)
argparse $options -- $argv
Same as above but with a third flag that can be given multiple times saving the value of each instance seen and only the long flag name (``--token``) can be used:
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::
set -l options (fish_opt --short=h --long=help)
set options $options (fish_opt --short=m --long=max --required-val)
set options $options (fish_opt --short=t --long=token --multiple-vals --long-only)
argparse $options -- $argv