v4.5.58

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v4.5.57

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Fixes

• Regression from 4.5.55 where having an argument with .value_terminator("--") caused problems with an argument with .last(true)

v4.5.56

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Fixes

• On conflict error, don't show conflicting arguments in the usage

v4.5.55

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Fixes

• Fix inconsistency in precedence between positionals with a value_terminator("--") and escapes (--) where ./foo -- bar means the first arg is empty, rather than escaping future args

v4.5.54

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Fixes

• (help) Move [default] to its own paragraph when PossibleValue::help is present in --help

v4.5.53

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Features

• Add default_values_if, default_values_ifs

v4.5.52

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Fixes

• Don't panic when args_conflicts_with_subcommands conflicts with an ArgGroup

v4.5.51

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Fixes

• (help) Correctly calculate padding for short flags that take a value
• (help) Don't panic on short flags using ArgAction::Count

v4.5.50

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Features

• Accept Cow where String and &str are accepted

v4.5.49

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Fixes

• (help) Correctly wrap when ANSI escape codes are present

v4.5.48

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Documentation

• Add a new CLI Concepts document as another way of framing clap
• Expand the typed_derive cookbook entry

v4.5.47

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Features

• Added impl FromArgMatches for ()
• Added impl Args for ()
• Added impl Subcommand for ()
• Added impl FromArgMatches for Infallible
• Added impl Subcommand for Infallible

Fixes

• (derive) Update runtime error text to match clap

v4.5.46

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Features

• Expose StyledStr::push_str

v4.5.45

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Fixes

• (unstable-v5) ValueEnum variants now use the full doc comment, not summary, for PossibleValue::help

v4.5.44

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Features

• Add Command::mut_subcommands

v4.5.43

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Fixes

• (help) In long help, list Possible Values before defaults, rather than after, for a more consistent look

v4.5.42

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Fixes

• Include subcommand visible long aliases in --help

v4.5.41

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Features

• Add Styles::context and Styles::context_value to customize the styling of [default: value] like notes in the --help

v4.5.40

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Features

• Support quoted ids in arg!() macro (e.g. arg!("check-config": ...))

v4.5.39

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Fixes

• (help) Show short flag aliases before long
• (help) Merge the short and long flag alias lists

v4.5.38

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Fixes

• (help) When showing aliases, include leading -- or -

v4.5.37

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Features

• Added ArgMatches::try_clear_id()

v4.5.36

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Fixes

• (help) Revert 4.5.35's "Don't leave space for shorts if there are none" for now

v4.5.35

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Fixes

• (help) Align positionals and flags when put in the same help_heading
• (help) Don't leave space for shorts if there are none

v4.5.34

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Fixes

• (help) Don't add extra blank lines with flatten_help(true) and subcommands without arguments

v4.5.33

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Fixes

• (error) When showing the usage of a suggestion for an unknown argument, don't show the group

v4.5.32

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Features

• Add Error::remove

Documentation

• (cookbook) Switch from humantime to jiff
• (tutorial) Better cover required vs optional

Internal

• Update pulldown-cmark

v4.5.31

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Features

• Add ValueParserFactory for Saturating<T>

v4.5.30

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Fixes

• (assert) Allow num_args(0..=1) to be used with SetTrue
• (assert) Clean up rendering of takes_values assertions

v4.5.29

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Fixes

• Change ArgMatches::args_present so not-present flags are considered not-present (matching the documentation)

v4.5.28

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Features

• (derive) Unstable support for full markdown syntax for doc comments, enabled with unstable-markdown

v4.5.27

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Documentation

• Iterate on tutorials and reference based on feedback

v4.5.26

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Fixes

• (error) Reduce binary size with the suggestions feature

v4.5.25

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Fixes

• (help) Reduce binary size

v4.5.24

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Fixes

• (parser) Correctly handle defaults with ignore_errors(true) and when a suggestion is provided for an unknown argument

v4.5.23

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Fixes

• (parser) When check allow_negative_numbers, allow E again

v4.5.22

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Fixes

• (assert) Catch bugs with arguments requiring themself

v4.5.21

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Fixes

• (parser) Ensure defaults are filled in on error with ignore_errors(true)

v4.5.20

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Features

• (unstable) Add CommandExt

v4.5.19

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Internal

• Update dependencies

v4.5.18

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Features

• (builder) Expose Arg::get_display_order and Command::get_display_order

v4.5.17

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Fixes

• (help) Style required argument groups
• (derive) Improve error messages when unsupported fields are used

v4.5.16

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Fixes

• (derive) Improve error messages when derive feature is missing

v4.5.15

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Compatiblity

• (unstable-ext) Arg::remove changed return types

Fixes

• (unstable-ext) Make Arg::remove return the removed item

v4.5.14

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Features

• (unstable-ext) Added Arg::add for attaching arbitrary state, like completion hints, to Arg without Arg knowing about it

v4.5.13

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Fixes

• (derive) Improve error message when #[flatten]ing an optional #[group(skip)]
• (help) Properly wrap long subcommand descriptions in help

v4.5.12

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v4.5.11

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v4.5.10

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v4.5.9

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Fixes

• (error) When defining a custom help flag, be sure to suggest it like we do the built-in one

v4.5.8

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Fixes

• Reduce extra flushes

v4.5.7

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Fixes

• Clean up error message when too few arguments for num_args

v4.5.6

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v4.5.5

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Fixes

• (help) Move [default] to its own paragraph when PossibleValue::help is present in --help

v4.5.4

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Fixes

• (help) Correctly wrap when ANSI escape codes are present

v4.5.3

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Fixes

• (help) Show short flag aliases before long
• (help) Merge the short and long flag alias lists

v4.5.2

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Fixes

• Change ArgMatches::args_present so not-present flags are considered not-present (matching the documentation)

v4.5.1

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Internal

• Update dependencies

v4.5.0

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Compatibility

• Update MSRV to 1.74

v4.4.18

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Fixes

• (error) When lacking usage feature, ensure the list of required arguments is unique

v4.4.17

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Fixes

• Fix panic! when mixing args_conflicts_with_subcommands with ArgGroup (which is implicit with derive) introduced in 4.4.15

v4.4.16

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Fixes

• Ensure invalid escape sequences in user-defined strings are correctly stripped when terminal doesn't support color

v4.4.15

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Fixes

• Improve error for args_conflicts_with_subcommands
• Ensure we error for args_conflicts_with_subcommands when using subcommand short and long flags

v4.4.14

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Documentation

• Fix find cookbook entry to allow repeats of flags/options

Features

• Allow num_args(0) on options which allows making them emulate being a flag for position-tracking flags

v4.4.13

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Documentation

• Fix link to structopt migration guide

v4.4.12

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Performance

• Only ask TypedValueParser for possible values if needed

v4.4.11

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Features

• Add Command::mut_group

v4.4.10

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Documentation

• Link out to changelog
• Cross link derive's attribute reference to derive tutorial

v4.4.9

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Fixes

• (help) Show correct Command::about under flattened headings
• (help) Respect hide when flattening subcommands

v4.4.8

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Features

• Add Command::flatten_help to allow git stash -h like help for subcommands

v4.4.7

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Performance

• Reduced code size

v4.4.6

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Internal

• Upgrade anstream

v4.4.5

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Fixes

• (parser) When inferring subcommand name or long_flag, allow ambiguous-looking matches that unambiguously map back to the same command
• (parser) When inferring subcommand long_flag, don't panic
• (assert) Clarify what action is causing a positional that doesn't set values which is especially useful for derive users

v4.4.4

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Internal

• Update terminal_size to 0.3

v4.4.3

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Documentation

• (derive) Clarify use of attributes within the tutorial
• Split sections in the builder and derive tutorials into separate modules

v4.4.2

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Performance

• Improve build times by removing once_cell dependency

v4.4.1

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Fixes

• (error) When lacking usage feature, ensure the list of required arguments is unique

v4.4.0

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compatibility

• update msrv to 1.70.0

v4.3.24

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Fixes

• Ensure column padding is preserved in --help with custom templates

v4.3.23

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Fixes

• Fixed UnknownArgumentValueParser to not error on flag's absence

v4.3.22

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Features

• Add UnknownArgumentValueParser for injecting errors for improving the experience with errors

v4.3.21

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Features

• Expose TryMapValueParser so the type can be named

v4.3.20

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Features

• Command::mut_args for modifying all arguments en masse

v4.3.19

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Fixes

• (parse) Respect value_terminator even in the presence of later multiple-value positional arguments

v4.3.18

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Fixes

• (parse) Suggest -- in fewer places where it won't work

v4.3.17

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Fixes

• (help) Address a regression in wrapping PossibleValue descriptions in --help

v4.3.16

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Fixes

• Don't assert when stateful value parsers fail on defaults (e.g. checking if a path exists)

v4.3.15

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Features

• (unstable-styles) Re-export anstyle

Documentation

• (unstable-styles) Provide more examples

v4.3.14

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Features

• ArgAction::HelpShort and ArgAction::HelpLong for explicitly specifying which style of help to display

Fixes

• Skip [OPTIONS] in usage if a help or version ArgAction is used

v4.3.13

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v4.3.12

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Fixes

• (derive) Don't error on enum variant field attributes

v4.3.11

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Features

• (derive) Support fields wrapped in num::Wrapping, Box, or Arc
• (derive) Support Box<str>, Box<OsStr>, and Box<Path>

v4.3.10

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Performance

• Drop a dependency, reducing binary size by 1.3 KiB

v4.3.9

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Fixes

• Command::ignore_errors no longer masks help/version

v4.3.8

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Fixes

• Error on ambiguity with infer_long_arg, rather than arbitrarily picking one, matching the documentation and subcommand's behavior

v4.3.7

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Documentation

• Further clarify magic behavior in derive tutorial
• Further clarify derive API's relationship to builder within the tutorial

v4.3.6

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Documentation

• Suggest clio

v4.3.5

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• ColorChoice::possible_values is added to simplify things for builder users

Fixes

• ColorChoice::to_possible_value no longer includes descriptions, encouraging shorter help where possible

v4.3.4

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Features

• Add Error::exit_code

v4.3.3

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Features

• Command::defer for delayed initialization of subcommands to reduce startup times of large applications like deno

v4.3.2

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Fixes

• Ensure column padding is preserved in --help with custom templates

v4.3.1

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Fixes

• (parse) Respect value_terminator even in the presence of later multiple-value positional arguments

v4.3.0

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Fixes

• (assert) Allow multiple, value-terminated, positional arguments
• (assert) Clear up language on last assertion
• (parser) Correctly assign values to arguments when using multiple, value-termianted, positional arguments
• (parser) Ensure value_terminator has higher precedence than allow_hyphen_values
• (help) Only use next-line-help on subcommand list when explicitly specified, not just with --help
• (help) Correctly align possible values list
• (help) Don't waste code, vertical space in moving possible value descriptions to next line

v4.2.7

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Fixes

• Correctly track remaining length for iterators provided by ArgMatches

v4.2.6

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Features

• impl Eq<std::any::TypeId> for clap_builder::util::AnyValueId

v4.2.5

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Fixes

• Improve panic when a group requires a non-existent ID

v4.2.4

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Documentation

• Corrected docs for Command::style

v4.2.3

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Features

• Command::styles for theming help/errors (behind unstable-styles)

v4.2.2

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Internal

• Update dependencies

v4.2.1

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Fixes

• Don't highlight uninteresting parts of the error message

v4.2.0

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Compatibility

• Removed the languishing unstable-replace feature (open to discussion at #​2836)
• Removed the stablized unstable-grouped feature

Features

• Allow any StyledStr to accept text styled with ANSI escape codes
• Respect CLICOLOR, CLICOLOR_FORCE

Fixes

• Lighten the tone for "unexpected argument" errors (open to discussion at #​4638)

v4.1.14

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Features

• (derive) #[group] raw attribute support

Performance

• (derive) clap_builder was pulled out of clap so it could build in parallel to clap_derive
• os_str_bytes dependency was removed for faster builds and smaller binaries

v4.1.13

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Performance

• Reduce repeated alloc calls when building a Command
• Reduce duplicate dependencies for faster builds

v4.1.12

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Internal

• (derive) Update to syn v2

Performance

• (derive) Faster build times by dropping proc-macro-error dependency

v4.1.11

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Internal

• Update bitflags

v4.1.10

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Fixes

• (help) On Windows, avoid underlined text artifacts

v4.1.9

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Fixes

• (assert) Improve the assert when using the wrong action with get_count / get_flag

v4.1.8

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Fixes

• (derive) Don't deny lints on the users behalf

v4.1.7

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Fixes

• (derive) Hide some nightly clippy warnings

v4.1.6

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Fixes

• (help) Don't show long help for --help just because hidden possible values include a description

v4.1.5

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Fixes

• (help) Don't show long help for --help just because a hidden arg has a possible value with a description

v4.1.4

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Fixes

• (help) Respect disable_colored_help when using arg_required_else_help

Performance

• Speed up compiling arg! macro

v4.1.3

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Fixes

• (error) Improve suggested flag/value/subcommand when two share a long preifx
• (error) When suggesting one of several subcommands, use the plural subcommands, rather than subcommand

v4.1.2

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Fixes

• In documentation, refer to get_flag, rather than get_one::<bool>

v4.1.1

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Features

• (derive) #[group] raw attribute support

Performance

• (derive) clap_builder was pulled out of clap so it could build in parallel to clap_derive
• os_str_bytes dependency was removed for faster builds and smaller binaries

v4.1.0

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Compatibility

MSRV changed to 1.64.0

For apps with custom --help and --version flags:

• Descriptions for --help and --version changed

When apps have errors imitating clap's error style:

• Error message style was changed, including
  • Moving away from "did you mean" to tips
  • Leading letter is lower case
  • "For more" added some punctuation

Features

• ArgMatches::get_occurrences support for argument values to be grouped by their occurrence

Fixes

• (derive) Allow upgrade_from when arguments / subcommands are explicitly marked as required
• (help) Try be more clearer and succinct with --help and --version (also helps with overflow)
• (error) Try to be more clearer and succinct with error messages
• (error) Officially adopt an error style guide

v4.0.32

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Fixes

• (parser) When overriding required(true), consider args that conflict with its group

v4.0.31

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Performance

• Speed up parsing when a lot of different flags are present (100 unique flags)

v4.0.30

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Fixes

• (error) Improve error for args_conflicts_with_subcommand

v4.0.29

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v4.0.28

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Fixes

• Fix wasm support which was broken in 4.0.27

v4.0.27

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Features

• Have Arg::value_parser accept Vec<impl Into<PossibleValue>>
• Implement Display and FromStr for ColorChoice

Fixes

• Remove soundness issue by switching from atty to is-terminal

v4.0.26

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Fixes

• (error) Fix typos in ContextKind::as_str

v4.0.25

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Features

• (error) Report available subcommands when required subcommand is missing

v4.0.24

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Fixes

• Avoid panic when printing an argument that isn't built

v4.0.23

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Fixes

• Don't panic on reporting invalid-long errors when followed by invalid UTF8
• (help) Clarified argument to help subcommand

v4.0.22

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Fixes

• (help) Don't overflow into next-line-help early due to stale (pre-v4) padding calculations

v4.0.21

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Features

• (derive) long_about and long_help attributes, without a value, force using doc comment (before it wouldn't be set if there wasn't anything different than the short help)

v4.0.20

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Fixes

• (derive) Allow defaulted value parser for '()' fields

v4.0.19

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Features

• ColorChoice now implements ValueEnum

v4.0.18

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Fixes

• (derive) Allow #[command(skip)] to also work with enum variants with a value

v4.0.17

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Fixes

• Allow using Arg::last(true) with Arg::value_hint(ValueHint::CommandWithArguments)

v4.0.16

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Fixes

• Arg::exclusive(true) should not be exclusive with the argument's own ArgGroup

v4.0.15

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Fixes

• (error) Don't suggest -- when it doesn't help
• (error) Be more consistent in quoting, punctuation, and indentation in errors

v4.0.14

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Fixes

• Only put ArgGroup in ArgMatches when explicitly specified, fixing derives handling of option-flattened fields (#​4375)

v4.0.13

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Features

• (derive) Allow () for fields to mean "don't read" (#​4371)

v4.0.12

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Features

• Added TypedValueParser::try_map for when adapting an existing TypedValueParser can fail
• (error) Create errors like clap with Error::new, Error::with_cmd, and Error::insert

v4.0.11

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Fixes

• (help) Fix wrapping calculations with ANSI escape codes

v4.0.10

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Features

• (derive) Support #[arg(flatten)] on Option types (#​4211, #​4350)

v4.0.9

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Fixes

• (derive) Process doc comments for #[command(subcommand)] like in clap v3

v4.0.8

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Fixes

• (derive) Remove a low-value assert preventing defaulting Help and Version actions

v4.0.7

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Features

• (derive) Populate implicit ArgGroup (#​3165)

Fixes

• (derive) Support #[group(skip)] on Parser derive
• (derive) Tell users about implicit arg groups when running into group name conflicts
• (error) Don't report unrelated groups in conflict or requires errors

v4.0.6

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Features

• (derive) Support #[group(skip)] (#​4279, #​4301)

v4.0.5

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v4.0.4

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Fixes

• (error) Specialize the self-conflict error to look like clap v3

v4.0.3

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Fixes

• (parser) When overriding required(true), consider args that conflict with its group

v4.0.2

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v4.0.1

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Features

• ColorChoice now implements ValueEnum

v4.0.0

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Highlights

Arg::num_args(range)

Clap has had several ways for controlling how many values will be captured without always being clear on how they interacted, including

• Arg::multiple_values(true)
• Arg::number_of_values(4)
• Arg::min_values(2)
• Arg::max_values(20)
• Arg::takes_value(true)

These have now all been collapsed into Arg::num_args which accepts both
single values and ranges of values. num_args controls how many raw arguments
on the command line will be captured as values per occurrence and independent
of value delimiters.

See Issue 2688 for more background.

Polishing Help

Clap strives to give a polished CLI experience out of the box with little
ceremony. With some feedback that has accumulated over time, we took this
release as an opportunity to re-evaluate our --help output to make sure it is
meeting that goal.

In doing this evaluation, we wanted to keep in mind:

• Whether other CLIs had ideas that make sense to apply
• Providing an experience that fits within the rest of applications and works across all shells

Before:

git
A fictional versioning CLI
USAGE:
 git <SUBCOMMAND>
OPTIONS:
 -h, --help Print help information
SUBCOMMANDS:
 add adds things
 clone Clones repos
 help Print this message or the help of the given subcommand(s)
 push pushes things
 stash

After:

A fictional versioning CLI
Usage: git <COMMAND>
Commands:
 clone Clones repos
 push pushes things
 add adds things
 stash
 help Print this message or the help of the given subcommand(s)
Options:
 -h, --help Print help information

• name/version header was removed because we couldn't justify the space it occupied when
  • Usage already includes the name
  • --version is available for showing the same thing (if the program has a version set)
• Usage was dropped to one line to save space
• Focus is put on the subcommands
• Headings are now Title case
• The more general term "command" is used rather than being explicit about being "subcommands"
• The output is more dense with the expectation that it won't affect legibility but will allow more content
• We've moved to a more neutral palette for highlighting elements (not highlighted above)

In talking to users, we found some that liked clap's man-like experience.
When deviating from this, we are making the assumption that those are more
power users and that the majority of users wouldn't look as favorably on being
consistent with man.

See Issue 4132 for more background.

More Dynamicism

Clap's API has focused on &str for performance but this can make
dealing with owned data difficult, like #[arg(default_value_t)] generating a
String from the default value.

Additionally, to avoid ArgMatches from borrowing (and for some features we
decided to forgo), clap took the &str argument IDs and hashed them. This
prevented us from providing a usable API for iterating over existing arguments.

Now clap has switched to a string newtype that gives us the flexibility to
decide whether to use &'static str, Cow<'static, str> for fast dynamic behavior, or
Box<str> for dynamic behavior with small binary size.

As an extension of that work, you can now call ArgMatches::ids to iterate
over the arguments and groups that were found when parsing. The newtype Id
was used to prevent some classes of bugs and to make it easier to understand
when opaque Ids are used vs user-visible strings.

Clearing Out Deprecations

Instead of doing all development on clap 4.0.0, we implemented a lot of new features during clap 3's development, deprecating the old API while introducing the new API, including:

• Replacing the implicit behavior for args when parsing them with ArgAction
• Replacing various one-off forms of value validation with the ValueParser API
  • Allowing derives to automatically do the right thing for PathBuf (allowing invalid UTF-8)
• Replacing AppSettings and ArgSettings enums with getters/setters
• Clarifying terms and making them more consistent

Migrating

Steps:

0. Upgrade to v3 if you haven't already
1. Add CLI tests (including example below), -h and --help output at a minimum (recommendation: trycmd for snapshot testing)
2. If using Builder API: Explicitly set the arg.action(ArgAction::...) on each argument (StoreValue for options and IncOccurrences for flags)
3. Run cargo check --features clap/deprecated and resolve all deprecation warnings
4. Upgrade to v4
5. Update feature flags

• If default-features = false, run cargo add clap -F help,usage,error-context
• Run cargo add clap -F wrap_help unless you want to hard code line wraps

6. Resolve compiler errors
7. Resolve behavior changes (see "subtle changes" under BREAKING CHANGES)
8. At your leisure: resolve new deprecation notices

Example test (derive):

#[derive(clap::Parser)]
struct Cli {
 ...
}
#[test]
fn verify_cli() {
 use clap::CommandFactory;
 Cli::command().debug_assert()
}

Example test (builder):

fn cli() -> clap::Command {
 ...
}
#[test]
fn verify_cli() {
 cli().debug_assert();
}

Note: the idiomatic / recommended way of specifying different types of args in the Builder API has changed:

Before

.arg(Arg::new("flag").long("flag")) # --flag
.arg(Arg::new("option").long("option").takes_value(true)) # --option <option>

After:

.arg(Arg::new("flag").long("flag").action(ArgAction::SetTrue)) # --flag
.arg(Arg::new("option").long("option")) # --option <option>

In particular, num_args (the replacement for takes_value) will default appropriately
from the ArgAction and generally only needs to be set explicitly for the
other num_args use cases.

Breaking Changes

Subtle changes (i.e. compiler won't catch):

• arg! now sets one of (#​3795):
  • ArgAction::SetTrue, requiring ArgMatches::get_flag instead of ArgMatches::is_present
  • ArgAction::Count, requiring ArgMatches::get_count instead of ArgMatches::occurrences_of
  • ArgAction::Set, requiring ArgMatches::get_one instead of ArgMatches::value_of
  • ArgAction::Append, requiring ArgMatches::get_many instead of ArgMatches::values_of
• ArgAction::Set, ArgAction::SetTrue, and Arg::Action::SetFalse now
  conflict by default to be like ArgAction::StoreValue and
  ArgAction::IncOccurrences, requiring cmd.args_override_self(true) to override instead (#​4261)
• By default, an Args default action is ArgAction::Set, rather than ArgAction::IncOccurrence to reduce confusing magic through consistency (#​2687, #​4032, see also #​3977)
• mut_arg can no longer be used to customize help and version arguments, instead disable them (Command::disable_help_flag, Command::disable_version_flag) and provide your own (#​4056)
• Removed lifetimes from Command, Arg, ArgGroup, and PossibleValue, assuming 'static. string feature flag will enable support for Strings (#​1041, #​2150, #​4223)
• arg!(--flag <value>) is now optional, instead of required. Add .required(true) at the end to restore the original behavior (#​4206)
• Added default feature flags, help, usage and error-context, requiring adding them back in if default-features = false (#​4236)
• (parser) Always fill in "" argument for external subcommands to make it easier to distinguish them from built-in commands (#​3263)
• (parser) Short flags now have higher precedence than hyphen values with Arg::allow_hyphen_values, to be consistent with Command::allow_hyphen_values (#​4187)
• (parser) Arg::value_terminator must be its own argument on the CLI rather than being in a delimited list (#​4025)
• (help) Line wrapping of help is now behind the existing wrap_help feature flag, either enable it or hard code your wraps (#​4258)
• (help) Make DeriveDisplayOrder the default and removed the setting. To sort help, set next_display_order(None) (#​2808)
• (help) Subcommand display order respects Command::next_display_order instead of DeriveDisplayOrder and using its own initial display order value ([#​2808](https://redirect.github.com/clap-rs/clap/issues/2808