Comments (2)
I found a fairly simple way to accomplish the same:
data Opts = Opts
{ inputDb :: String
, optKeywords :: Maybe String -- Maybe here means this is optional
}
options :: Parser Opts
options = Opts
<$> strOption (long "input-db"
& metavar "FILE"
& help "Input database file")
<*> option (long "keywords"
& value Nothing
& reader Just
& help "Comma-delimited list of bug keywords")
I still maintain that it would be useful to have an example that demonstrates how to do this.
from optparse-applicative.
You can do this more directly using optional
in Control.Applicative
:
optional (option (long "keywords"))
But you're right that this should be stated more explicitly in the documentation. You're not the first one to ask this question. I'll leave this issue open as a reminder to improve the docs.
from optparse-applicative.
Related Issues (20)
- Support for parsing RawFilePath HOT 1
- Showing help on empty with inline subcommands HOT 6
- Listification (like `some1`) does not change the `metavar` to plural HOT 2
- Add ability to group aliases in --help HOT 2
- Offer a positional parser HOT 2
- Parse in interactive program HOT 2
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- Options shown in Global section can include unreachable alternatives. HOT 4
- Add Semigroup/Monoid to Parser HOT 7
- Ignore unused flags HOT 2
- Parser HOT 1
- (Question) Is there value in storing CLI output in a text file and using it as a golden test? HOT 1
- Is it possible to automatically show in help which values are valid for an option? HOT 3
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- Ansi annotations aren't being rendered.
- How do I print help info with colored command names? HOT 14
- v0.18: `text` no longer exported from `Options.Applicative.Help.Pretty` HOT 4
- Default command and command alias
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