Unlike URLs, there is no spec for parsing arguments. Much to my dismay, frankly. Living through argparse and docopt and click, it was like lash after lash against my poor CLI-loving flesh.
- getopt basis?
- Single- or no-argument flags only. No multi-argument flags
- Configurable behavior as to multiple appearances of the same flag
- error (default)
- additive - value will be an int for no-arg flags (as with --verbose and -vvv), and added to a list for single-argument flags
- Short flag support?
- strong subcommand support (compositionally similar to clastic?)
- store_true and store_false, or something better?
- single argument flags support space-based and 'x=y' style arguments
- transparent transformation between underscore and dash-based arguments (--enable-action and --enable_action are the same)
- single variadic argument list
- only valid for leaf subcommands
- support partial parsing (a la parse_known_args)
- support taking multiple flagfiles
- always the same argument name, like a builtin, then warn on conflict
- could be an argument type
- might need to take a flagfilereader argument for testin purposes
- No multi-level flag support. Flags push down under subcommands, conflicts raise errors early (at setup time). Flags can be masked out against being pushed under further subcommands (i.e., make the flag subcommand-local).
Big challenge: helpful error messages
/* TODO --key=val style arguments? */
By design, face supports command structure composed of five parts:
- The command
- The subcommand path
- Flags
- Positional arguments
- Passthrough arguments
cmd subcmd subsubcmd subsubsubcmd --flags -v --flag-with-arg arg posarg1 posarg2 -- passarg1 passarg2
command | subcommand path | flags | positional arguments | passthrough arguments
Note that only leaf subcommands support positional arguments.
"command" is just a display name, as no parsing is required for sys.argv[0]
Collapsing abbreviated flags is not supported
If there are subcommands, do zfs-style subcommand syntax, only showing required flags and pos args (by display name).
If at a leaf command, print full options listing for that path, with argparse-style help.
If at a non-leaf command, argparse-style options help at that level (and above) can go below the zfs-style subcommand summary.
Square [brackets] for optional. Angle for required.
Boltons dependency can do basic pluralization/singularization for help displays.
If a command has subcommands, then the automatic help should manifest as a subcommand. Otherwise, it should be a longform flag like --help. In a subcommand setting, the short "usage" message that pops up when an invalid command is issued should recommend typing "cmd help" for more options.
argparse is a pretty solid library, and despite many competitors over the years, the best argument parsing library available. Until now, of course. Here's an inventory of problems argparse did not solve, and in many ways, created.
- "Fuzzy" flag matching
- Inconvenient subcommand interface
- Flags at each level of the subcommand tree
- Positional arguments acceptable everywhere
- Bad help rendering (esp for subcommands)
- Inheritance-based API for extension with a lot of _*
At the end of the day, the real sin of argparse is that it enables the creation of bad CLIs, often at the expense of ease of making good UIs Despite this friction, argparse is far from infinitely powerful. As a library, it is still relatively opinionated, and can only model a somewhat-conventional UNIX-y CLI.
clastic calls your function for you, should this do that, too? is there an advantage to sticking to the argparse route of handing back a namespace? what would the signature of a CLI route be?
- Specifying the CLI
- Wiring up the routing/dispatch
- OR Using the programmatic result of the parse (the Result object)
- Formatting the help messages?
- Using the actual CLI
- Should we support arbitrary validators (schema?) or go the clastic route and only basic types:
- str
- int
- float
- bool (TODO: default to true/false, think store_true, store_false in argparse)
- list of the above
- (leaning toward just basic types)
- autosuggest on incorrect subcommand
- allow subcommand grouping
- hyphens and underscores equivalent for flags and subcommands
A command cannot have positional arguments and subcommands.
Need to be able to set display name for posargs
Which is the best default behavior for a flag? single flag where presence=True (e.g., --verbose) or flag which accepts single string arg (e.g., --path /a/b/c)
What to do if there appears to be flags after positional arguments? How to differentiate between a bad flag and a positional argument that starts with a dash?
"Face: the CLI framework that's friendly to your end-user."
- Flag-first design that ensures flags stay consistent across all subcommands, for a more coherent API, less likely to surprise, more likely to delight.
(Note: need to do some research re: non-unicode flags to see how much non-US CLI users care about em.)
Case-sensitive flags are bad for business except for single-character flags (single-dash flags like -v vs -V).
TODO: normalizing subcommands
Should parse_as=List() with multi=extend give one long list or a list of lists?
Parser is unable to determine which subcommands are valid leaf commands, i.e., which ones can be handled as the last subcommand. The Command dispatcher will have to raise an error if a specific intermediary subcommand doesn't have a handler to dispatch to.
TODO: Duplicate arguments passed at the command line with the same value = ok?
- will need to disable and handle flagfiles separately if provenance is going to be retained?
- middleware seems unavoidable for setting up logs and generic teardowns/exit messages
- Might need an error map that maps various errors to exit codes for convenience. Neat idea, sort a list of classes by class hierarchy.
There are certain parse errors, such as the omission of a value that takes a string argument which can semi-silently pass. For instance:
copy --dest --verbose /a/b/c
In this terrible CLI, --verbose could be absorbed as --dest's value and now there's a file called --verbose on the filesystem. Here are a few ideas to improve the situation:
- Raise an exception for all flags' string arguments which start with a "-". Create a separate syntax for passing these args such as --flag=--dashedarg.
- Similar to the above, but only raise exceptions on known flags. This creates a bit of a moving API, as a new flag could cause old values to fail.
- Let particularly bad APIs like the above fail, but keep closer track of state to help identify missing arguments earlier in the line.
One big difference between Clastic and Face is that with Face, you typically know your first and only request at startup time. With Clastic, you create an Application and have to wait for some remote user to issue a request.
This translates to a different default behavior. With Clastic, all routes are checked for dependency satisfaction at Application creation. With Face, this check is performed on-demand, and only the single subcommand being executed is checked.
- iso8601 date/time/datetime
- duration
-
Clastic-like, but single function
-
Mark with a @middleware(provides=()) decorator for provides
-
Keywords (ParseResult members) end with _ (e.g., flags_), leaving injection namespace wide open for flags. With clastic, argument names are primarily internal, like a path parameter's name is not exposed to the user. With face, the flag names are part of the exposed API, and we don't want to reserve keywords or have excessively long prefixes.
-
add() supports @middleware decorated middleware
-
add_middleware() exists for non-decorated middleware functions, and just conveniently calls middleware decorator for you (decorator only necessary for provides)
Also Kurt says an easy way to access the subcommands to tweak them would be useful. I think it's better to build up from the leaves than to allow mutability that could trigger rechecks and failures across the whole subcommand tree. Better instead to make copies of subparsers/subcommands/flags and treat them as internal state.
- Different error message for when the command's handler function is unfulfilled vs middlewares.
- In addition to the existing function-as-first-arg interface, Command should take a list of add()-ables as the first argument. This allows easy composition from subcommands and common flags.
- DisplayOptions/DisplaySpec class? (display name and hidden)
- Should Commands have resources like clastic?
- name
- doc
- handler func
- list of middlewares
- parser (currently contains the following)
- flag map
- PosArgSpecs for posargs, post_posargs
- flagfile flag
- help flag (or help subcommand)
TODO: allow user to configure the message for CommandLineErrors TODO: should Command take resources? TODO: should version_ be a built-in/injectable?
Need to split up the checks. Basic verification of middleware structure OK. Can check for redefinitions of provides and conflicts. Need a final .check() method that checks that all subcommands have their requirements fulfilled. Technically a .run() only needs to run one specific subcommand, only thta one needs to get its middleware chain built. .check() would have to build/check them all.
- Command inherit from Parser
- Enable middleware flags
- Ensure top-level middleware flags like --verbose show up for subcommands
- Ensure "builtin" flags like --flagfile and --help show up for all commands
- Make help flag come from HelpHandler
- What to do when the top-level command doesn't have a help_handler, but a subcommand does? Maybe dispatch to the subcommand's help handler? Would deferring adding the HelpHandler's flag/subcmd help? Right now the help flag is parsed and ignored.
The only fuzzy area is when to use prs.get_flag_map() vs prs._path_flag_map directly. Basically, when filtration-by-usage is desired, get_flag_map() (or get_flags()) should be used. Only Commands do this, so it looks a bit weird if you're only looking at the Parser, where this operation appears to do nothing. This only happens in 1-2 places so probably safe to just comment it for now.
Relatedly, there are some linting errors where it appears the private _path_flag_map is being accessed. I think these are ok, because these methods are operating on objects of the same type, so the members are still technically "protected", in the C++ OOP sense.
Should weak deps on builtins_ be treated differently than weak deps on flags? Should weak deps in handler functions be treated differently than that in the middleware (middleware implies more "passthrough")?
zpool help is probably handwritten (as evidenced by multiple instances of subcommands like "import" and spacing between groups like add/remove), but we can probably get pretty close to this.
$ zpool --help
usage: zpool command args ...
where 'command' is one of the following:
create [-fnd] [-o property=value] ...
[-O file-system-property=value] ...
[-m mountpoint] [-R root] <pool> <vdev> ...
destroy [-f] <pool>
add [-fgLnP] [-o property=value] <pool> <vdev> ...
remove <pool> <device> ...
labelclear [-f] <vdev>
list [-gHLPv] [-o property[,...]] [-T d|u] [pool] ... [interval [count]]
iostat [-gLPvy] [-T d|u] [pool] ... [interval [count]]
status [-gLPvxD] [-T d|u] [pool] ... [interval [count]]
online <pool> <device> ...
offline [-t] <pool> <device> ...
clear [-nF] <pool> [device]
reopen <pool>
attach [-f] [-o property=value] <pool> <device> <new-device>
detach <pool> <device>
replace [-f] [-o property=value] <pool> <device> [new-device]
split [-gLnP] [-R altroot] [-o mntopts]
[-o property=value] <pool> <newpool> [<device> ...]
scrub [-s] <pool> ...
import [-d dir] [-D]
import [-d dir | -c cachefile] [-F [-n]] <pool | id>
import [-o mntopts] [-o property=value] ...
[-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a
import [-o mntopts] [-o property=value] ...
[-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-F [-n]]
<pool | id> [newpool]
export [-af] <pool> ...
upgrade
upgrade -v
upgrade [-V version] <-a | pool ...>
reguid <pool>
history [-il] [<pool>] ...
events [-vHfc]
get [-pH] <"all" | property[,...]> <pool> ...
set <property=value> <pool>
argparse-based, lots of options
Usage: youtube-dl [OPTIONS] URL [URL...]
Options:
General Options:
-h, --help Print this help text and exit
--version Print program version and exit
-U, --update Update this program to latest version. Make sure that you have sufficient permissions (run with
sudo if needed)
-i, --ignore-errors Continue on download errors, for example to skip unavailable videos in a playlist
--abort-on-error Abort downloading of further videos (in the playlist or the command line) if an error occurs
--dump-user-agent Display the current browser identification
--list-extractors List all supported extractors
--extractor-descriptions Output descriptions of all supported extractors
--force-generic-extractor Force extraction to use the generic extractor
--default-search PREFIX Use this prefix for unqualified URLs. For example "gvsearch2:" downloads two videos from google
videos for youtube-dl "large apple". Use the value "auto" to let youtube-dl guess ("auto_warning"
to emit a warning when guessing). "error" just throws an error. The default value "fixup_error"
repairs broken URLs, but emits an error if this is not possible instead of searching.
--ignore-config Do not read configuration files. When given in the global configuration file /etc/youtube-dl.conf:
Do not read the user configuration in ~/.config/youtube-dl/config (%APPDATA%/youtube-dl/config.txt
on Windows)
--config-location PATH Location of the configuration file; either the path to the config or its containing directory.
--flat-playlist Do not extract the videos of a playlist, only list them.
--mark-watched Mark videos watched (YouTube only)
--no-mark-watched Do not mark videos watched (YouTube only)
--no-color Do not emit color codes in output
Network Options:
--proxy URL Use the specified HTTP/HTTPS/SOCKS proxy. To enable experimental SOCKS proxy, specify a proper
scheme. For example socks5://127.0.0.1:1080/. Pass in an empty string (--proxy "") for direct
connection
--socket-timeout SECONDS Time to wait before giving up, in seconds
--source-address IP Client-side IP address to bind to
-4, --force-ipv4 Make all connections via IPv4
-6, --force-ipv6 Make all connections via IPv6
Geo Restriction:
--geo-verification-proxy URL Use this proxy to verify the IP address for some geo-restricted sites. The default proxy specified
by --proxy (or none, if the options is not present) is used for the actual downloading.
--geo-bypass Bypass geographic restriction via faking X-Forwarded-For HTTP header (experimental)
--no-geo-bypass Do not bypass geographic restriction via faking X-Forwarded-For HTTP header (experimental)
--geo-bypass-country CODE Force bypass geographic restriction with explicitly provided two-letter ISO 3166-2 country code
(experimental)
Video Selection:
--playlist-start NUMBER Playlist video to start at (default is 1)
--playlist-end NUMBER Playlist video to end at (default is last)
--playlist-items ITEM_SPEC Playlist video items to download. Specify indices of the videos in the playlist separated by commas
like: "--playlist-items 1,2,5,8" if you want to download videos indexed 1, 2, 5, 8 in the playlist.
You can specify range: "--playlist-items 1-3,7,10-13", it will download the videos at index 1, 2,
3, 7, 10, 11, 12 and 13.
--match-title REGEX Download only matching titles (regex or caseless sub-string)
--reject-title REGEX Skip download for matching titles (regex or caseless sub-string)
--max-downloads NUMBER Abort after downloading NUMBER files
--min-filesize SIZE Do not download any videos smaller than SIZE (e.g. 50k or 44.6m)
--max-filesize SIZE Do not download any videos larger than SIZE (e.g. 50k or 44.6m)
--date DATE Download only videos uploaded in this date
--datebefore DATE Download only videos uploaded on or before this date (i.e. inclusive)
--dateafter DATE Download only videos uploaded on or after this date (i.e. inclusive)
--min-views COUNT Do not download any videos with less than COUNT views
--max-views COUNT Do not download any videos with more than COUNT views
--match-filter FILTER Generic video filter. Specify any key (see the "OUTPUT TEMPLATE" for a list of available keys) to
match if the key is present, !key to check if the key is not present, key > NUMBER (like
"comment_count > 12", also works with >=, <, <=, !=, =) to compare against a number, key =
'LITERAL' (like "uploader = 'Mike Smith'", also works with !=) to match against a string literal
and & to require multiple matches. Values which are not known are excluded unless you put a
question mark (?) after the operator. For example, to only match videos that have been liked more
than 100 times and disliked less than 50 times (or the dislike functionality is not available at
the given service), but who also have a description, use --match-filter "like_count > 100 &
dislike_count <? 50 & description" .
--no-playlist Download only the video, if the URL refers to a video and a playlist.
--yes-playlist Download the playlist, if the URL refers to a video and a playlist.
--age-limit YEARS Download only videos suitable for the given age
--download-archive FILE Download only videos not listed in the archive file. Record the IDs of all downloaded videos in it.
--include-ads Download advertisements as well (experimental)
Download Options:
-r, --limit-rate RATE Maximum download rate in bytes per second (e.g. 50K or 4.2M)
-R, --retries RETRIES Number of retries (default is 10), or "infinite".
--fragment-retries RETRIES Number of retries for a fragment (default is 10), or "infinite" (DASH, hlsnative and ISM)
--skip-unavailable-fragments Skip unavailable fragments (DASH, hlsnative and ISM)
--abort-on-unavailable-fragment Abort downloading when some fragment is not available
--keep-fragments Keep downloaded fragments on disk after downloading is finished; fragments are erased by default
--buffer-size SIZE Size of download buffer (e.g. 1024 or 16K) (default is 1024)
--no-resize-buffer Do not automatically adjust the buffer size. By default, the buffer size is automatically resized
from an initial value of SIZE.
--playlist-reverse Download playlist videos in reverse order
--playlist-random Download playlist videos in random order
--xattr-set-filesize Set file xattribute ytdl.filesize with expected file size (experimental)
--hls-prefer-native Use the native HLS downloader instead of ffmpeg
--hls-prefer-ffmpeg Use ffmpeg instead of the native HLS downloader
--hls-use-mpegts Use the mpegts container for HLS videos, allowing to play the video while downloading (some players
may not be able to play it)
--external-downloader COMMAND Use the specified external downloader. Currently supports
aria2c,avconv,axel,curl,ffmpeg,httpie,wget
--external-downloader-args ARGS Give these arguments to the external downloader
Filesystem Options:
-a, --batch-file FILE File containing URLs to download ('-' for stdin)
--id Use only video ID in file name
-o, --output TEMPLATE Output filename template, see the "OUTPUT TEMPLATE" for all the info
--autonumber-start NUMBER Specify the start value for %(autonumber)s (default is 1)
--restrict-filenames Restrict filenames to only ASCII characters, and avoid "&" and spaces in filenames
-w, --no-overwrites Do not overwrite files
-c, --continue Force resume of partially downloaded files. By default, youtube-dl will resume downloads if
possible.
--no-continue Do not resume partially downloaded files (restart from beginning)
--no-part Do not use .part files - write directly into output file
--no-mtime Do not use the Last-modified header to set the file modification time
--write-description Write video description to a .description file
--write-info-json Write video metadata to a .info.json file
--write-annotations Write video annotations to a .annotations.xml file
--load-info-json FILE JSON file containing the video information (created with the "--write-info-json" option)
--cookies FILE File to read cookies from and dump cookie jar in
--cache-dir DIR Location in the filesystem where youtube-dl can store some downloaded information permanently. By
default $XDG_CACHE_HOME/youtube-dl or ~/.cache/youtube-dl . At the moment, only YouTube player
files (for videos with obfuscated signatures) are cached, but that may change.
--no-cache-dir Disable filesystem caching
--rm-cache-dir Delete all filesystem cache files
Thumbnail images:
--write-thumbnail Write thumbnail image to disk
--write-all-thumbnails Write all thumbnail image formats to disk
--list-thumbnails Simulate and list all available thumbnail formats
Verbosity / Simulation Options:
-q, --quiet Activate quiet mode
--no-warnings Ignore warnings
-s, --simulate Do not download the video and do not write anything to disk
--skip-download Do not download the video
-g, --get-url Simulate, quiet but print URL
-e, --get-title Simulate, quiet but print title
--get-id Simulate, quiet but print id
--get-thumbnail Simulate, quiet but print thumbnail URL
--get-description Simulate, quiet but print video description
--get-duration Simulate, quiet but print video length
--get-filename Simulate, quiet but print output filename
--get-format Simulate, quiet but print output format
-j, --dump-json Simulate, quiet but print JSON information. See the "OUTPUT TEMPLATE" for a description of
available keys.
-J, --dump-single-json Simulate, quiet but print JSON information for each command-line argument. If the URL refers to a
playlist, dump the whole playlist information in a single line.
--print-json Be quiet and print the video information as JSON (video is still being downloaded).
--newline Output progress bar as new lines
--no-progress Do not print progress bar
--console-title Display progress in console titlebar
-v, --verbose Print various debugging information
--dump-pages Print downloaded pages encoded using base64 to debug problems (very verbose)
--write-pages Write downloaded intermediary pages to files in the current directory to debug problems
--print-traffic Display sent and read HTTP traffic
-C, --call-home Contact the youtube-dl server for debugging
--no-call-home Do NOT contact the youtube-dl server for debugging
Workarounds:
--encoding ENCODING Force the specified encoding (experimental)
--no-check-certificate Suppress HTTPS certificate validation
--prefer-insecure Use an unencrypted connection to retrieve information about the video. (Currently supported only
for YouTube)
--user-agent UA Specify a custom user agent
--referer URL Specify a custom referer, use if the video access is restricted to one domain
--add-header FIELD:VALUE Specify a custom HTTP header and its value, separated by a colon ':'. You can use this option
multiple times
--bidi-workaround Work around terminals that lack bidirectional text support. Requires bidiv or fribidi executable in
PATH
--sleep-interval SECONDS Number of seconds to sleep before each download when used alone or a lower bound of a range for
randomized sleep before each download (minimum possible number of seconds to sleep) when used along
with --max-sleep-interval.
--max-sleep-interval SECONDS Upper bound of a range for randomized sleep before each download (maximum possible number of
seconds to sleep). Must only be used along with --min-sleep-interval.
Video Format Options:
-f, --format FORMAT Video format code, see the "FORMAT SELECTION" for all the info
--all-formats Download all available video formats
--prefer-free-formats Prefer free video formats unless a specific one is requested
-F, --list-formats List all available formats of requested videos
--youtube-skip-dash-manifest Do not download the DASH manifests and related data on YouTube videos
--merge-output-format FORMAT If a merge is required (e.g. bestvideo+bestaudio), output to given container format. One of mkv,
mp4, ogg, webm, flv. Ignored if no merge is required
Subtitle Options:
--write-sub Write subtitle file
--write-auto-sub Write automatically generated subtitle file (YouTube only)
--all-subs Download all the available subtitles of the video
--list-subs List all available subtitles for the video
--sub-format FORMAT Subtitle format, accepts formats preference, for example: "srt" or "ass/srt/best"
--sub-lang LANGS Languages of the subtitles to download (optional) separated by commas, use --list-subs for
available language tags
Authentication Options:
-u, --username USERNAME Login with this account ID
-p, --password PASSWORD Account password. If this option is left out, youtube-dl will ask interactively.
-2, --twofactor TWOFACTOR Two-factor authentication code
-n, --netrc Use .netrc authentication data
--video-password PASSWORD Video password (vimeo, smotri, youku)
Adobe Pass Options:
--ap-mso MSO Adobe Pass multiple-system operator (TV provider) identifier, use --ap-list-mso for a list of
available MSOs
--ap-username USERNAME Multiple-system operator account login
--ap-password PASSWORD Multiple-system operator account password. If this option is left out, youtube-dl will ask
interactively.
--ap-list-mso List all supported multiple-system operators
Post-processing Options:
-x, --extract-audio Convert video files to audio-only files (requires ffmpeg or avconv and ffprobe or avprobe)
--audio-format FORMAT Specify audio format: "best", "aac", "flac", "mp3", "m4a", "opus", "vorbis", or "wav"; "best" by
default; No effect without -x
--audio-quality QUALITY Specify ffmpeg/avconv audio quality, insert a value between 0 (better) and 9 (worse) for VBR or a
specific bitrate like 128K (default 5)
--recode-video FORMAT Encode the video to another format if necessary (currently supported: mp4|flv|ogg|webm|mkv|avi)
--postprocessor-args ARGS Give these arguments to the postprocessor
-k, --keep-video Keep the video file on disk after the post-processing; the video is erased by default
--no-post-overwrites Do not overwrite post-processed files; the post-processed files are overwritten by default
--embed-subs Embed subtitles in the video (only for mp4, webm and mkv videos)
--embed-thumbnail Embed thumbnail in the audio as cover art
--add-metadata Write metadata to the video file
--metadata-from-title FORMAT Parse additional metadata like song title / artist from the video title. The format syntax is the
same as --output. Regular expression with named capture groups may also be used. The parsed
parameters replace existing values. Example: --metadata-from-title "%(artist)s - %(title)s" matches
a title like "Coldplay - Paradise". Example (regex): --metadata-from-title "(?P<artist>.+?) -
(?P<title>.+)"
--xattrs Write metadata to the video file's xattrs (using dublin core and xdg standards)
--fixup POLICY Automatically correct known faults of the file. One of never (do nothing), warn (only emit a
warning), detect_or_warn (the default; fix file if we can, warn otherwise)
--prefer-avconv Prefer avconv over ffmpeg for running the postprocessors (default)
--prefer-ffmpeg Prefer ffmpeg over avconv for running the postprocessors
--ffmpeg-location PATH Location of the ffmpeg/avconv binary; either the path to the binary or its containing directory.
--exec CMD Execute a command on the file after downloading, similar to find's -exec syntax. Example: --exec
'adb push {} /sdcard/Music/ && rm {}'
--convert-subs FORMAT Convert the subtitles to other format (currently supported: srt|ass|vtt|lrc)
modified argparse
$ pprotect --help
usage: pprotect [COMMANDS]
Commands:
add-domain add a new domain to the protected
add-key-custodian add a new key custodian to the protected
add-owner add a key custodian as owner of a domain
add-secret add a secret to a specified domain
decrypt-domain decrypt and display JSON-formatted cleartext for a
domain
init create a new pocket-protected file
list-all-secrets display all secrets, with a list of domains the key is
present in
list-audit-log display a chronological list of audit log entries
representing file activity
list-domain-secrets display a list of secrets under a specific domain
list-domains display a list of available domains
list-user-secrets similar to list-all-secrets, but filtered by a given
user
rm-domain remove a domain from the protected
rm-owner remove an owner's privileges on a specified domain
rm-secret remove a secret from a specified domain
rotate-domain-keys rotate the internal keys for a particular domain (must
be owner)
set-key-custodian-passphrase
change a key custodian passphrase
update-secret update an existing secret in a specified domain
Options:
-h, --help show this help message and exit
$ git lol
git: 'lol' is not a git command. See 'git --help'.
Did you mean this?
log
Pretty nice, draws attention to itself by being bigger, recommends help. The "did you mean" should include the command itself, i.e., "git log" instead of just "log" for easy copy and pastability.
Face is designed to scale to a wide variety of command-line applications. As such, there are multiple levels of integration, each providing more control.
- A single "autocommand" convenience function that automatically generates a command-line interface.
- A more explicit object-oriented Command construction interface, with a polymorphic .add() method to add subcommands, flags, and middlewares.
- Same as #2, but with explicit Command construction and direct usage of the explicit methods used to add subcommands and flags.
All these options also come with the .run() method, which is used to dispatch to the developer's logic, much like how a web framework dispatches a client request to a endpoint function (sometimes called a "view" or "controller"). By default, the program automatically handles any --help / -h flags, prints the help output, and exits.
For certain advanced use cases, there is an additional API option, the Parser itself.
Face's Parser is configured almost identically to the Command, except that it does not take callables, and has no .run() method to dispatch to application code. Instead, integrators call .parse() to parse and validate flags and arguments, and handle flow control themselves. The Parser, much like the Command, has a default HelpHandler, which can render help, but only if explicitly called by the integrator. Parse errors can be caught like any other kind of Python exception. Again, the integrator has full control of program flow.
Thanks to their prevalence in our workflow, we developers underestimate the variety and configurability of CLIs. As mentioned above, Face's APIs intentionally use polymorphism to better serve the evolving needs of a growing CLI.
A common pattern for Face arguments:
- Unset. Most arguments to Face APIs are optional. Everything has defaults designed to minimize surprise.
- Boolean. Pass True to enable a behavior (or show an element), or False to disable it (or hide it).
- Integer or string. Enable/show, and use this limit/label.
- dict. Complex configurables are represented by objects. This dictionary is a mapping of keyword arguments that will be passed straight through to the configuration object constructor. Mostly used to minimize imports and memorization of class names.
- A configuration object, manually imported and constructed by the user. Like most data objects, stateless and reusable. The most explicit option.
For an example of this, look no further than the "posargs" argument to Parser/Command and the PosArgSpec configuration object that it expects or expects to be able to create.
In my experience, the worst part about argparse and other UI libraries is constantly referencing the docs. When the API is too big, and there are too many methods and signatures to memorize, I find myself spending too much time in the docs (and often still not finding the feature I want/need). Face aims to be the library that changes that for CLIs. As few imports, methods, and arguments as is responsible.