サンプル

clap 4.6.6: Define and test a clap 4 derive CLI across the #[clap] to #[command] and #[arg] attribute split, checking outcomes with try_parse_from and ErrorKind instead of a process

検証済みサンプル — cargo clap 4.6.6: Define and test a clap 4 derive CLI across the #[clap] to #[command] and #[arg] attribute split, checking outcomes with…

sha256:6e0aceb749a7c19cc2aa7a185f5f9cac427fedb08e50c9afc51b0c69de42d116

MIT-0

実行証拠

宣言された環境と署名済みの実行を分けてあります。このサンプルが何をどこで実行したかをそのまま確認できます。

宣言された環境 rust 1 linux x64 rust 1 rust cargo

環境	コントラクト	ステージ	実行日
rust 1 · linux alpine/x64 · docker ed25519:a2ec939a4c60e243	PASS	compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1	2026-08-14
rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9	PASS	compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1	2026-08-18

HOW

ゴール: Define and test a clap 4 derive CLI across the #[clap] to #[command] and #[arg] attribute split, checking outcomes with try_parse_from and ErrorKind instead of a process
パッケージ: clap 4.6.6
シンボル: Parser::try_parse_from
ArgAction::Count
Command::build
ErrorKind::UnknownArgument
ErrorKind::MissingRequiredArgument
ErrorKind::DisplayHelp
ValueEnum
CommandFactory::command
環境: rust 1
作成日: 2026-08-14T08:54:45Z

assert the command name comes from the attribute on the struct while every argument id comes from a field and its attribute
assert help and version are absent from the Command until Command::build injects them, and that parsing performs that build for you
assert the clap 3 #[clap(...)] spelling still compiles under clap 4, naming the command on the struct and declaring the argument on a field
assert a minimal invocation fills default_value_t and leaves an Option<T> option as None
assert dropping the program name from try_parse_from makes the first real argument the program name in the usage line and reports a missing required argument
assert -o value, --output value, --output=value and the attached -ovalue all set the same option
assert ArgAction::Count turns -vvv into 3 and -v -v into 2
assert -V is the version flag while -v stays the verbose counter
assert ValueEnum renders variants in kebab-case and that pretty_json, PrettyJson and JSON are ErrorKind::InvalidValue
assert an unknown flag is ErrorKind::UnknownArgument and that the rendered error carries the tip naming the real --output
assert a missing required positional is ErrorKind::MissingRequiredArgument
assert both real errors exit 2 and go to stderr
assert --help and -h are ErrorKind::DisplayHelp with exit code 0 on stdout, not a parse failure
assert the rendered help shows the default value and the possible values
assert --version is ErrorKind::DisplayVersion carrying the version from the command attribute