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# Description
The meaning of the word usage is specific to describing how a command
function is *used* and not a synonym for general description. Usage can
be used to describe the SYNOPSIS or EXAMPLES sections of a man page
where the permitted argument combinations are shown or example *uses*
are given.
Let's not confuse people and call it what it is a description.
Our `help` command already creates its own *Usage* section based on the
available arguments and doesn't refer to the description with usage.
# User-Facing Changes
`help commands` and `scope commands` will now use `description` or
`extra_description`
`usage`-> `description`
`extra_usage` -> `extra_description`
Breaking change in the plugin protocol:
In the signature record communicated with the engine.
`usage`-> `description`
`extra_usage` -> `extra_description`
The same rename also takes place for the methods on
`SimplePluginCommand` and `PluginCommand`
# Tests + Formatting
- Updated plugin protocol specific changes
# After Submitting
- [ ] update plugin protocol doc
75 lines
2.2 KiB
Rust
75 lines
2.2 KiB
Rust
use nu_engine::command_prelude::*;
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#[derive(Clone)]
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pub struct Echo;
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impl Command for Echo {
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fn name(&self) -> &str {
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"echo"
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}
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fn description(&self) -> &str {
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"Returns its arguments, ignoring the piped-in value."
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}
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fn signature(&self) -> Signature {
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Signature::build("echo")
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.input_output_types(vec![(Type::Nothing, Type::Any)])
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.rest("rest", SyntaxShape::Any, "The values to echo.")
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.category(Category::Core)
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}
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fn extra_description(&self) -> &str {
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r#"Unlike `print`, which prints unstructured text to stdout, `echo` is like an
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identity function and simply returns its arguments. When given no arguments,
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it returns an empty string. When given one argument, it returns it as a
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nushell value. Otherwise, it returns a list of the arguments. There is usually
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little reason to use this over just writing the values as-is."#
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}
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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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_input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let mut args = call.rest(engine_state, stack, 0)?;
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let value = match args.len() {
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0 => Value::string("", call.head),
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1 => args.pop().expect("one element"),
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_ => Value::list(args, call.head),
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};
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Ok(value.into_pipeline_data())
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}
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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description: "Put a list of numbers in the pipeline. This is the same as [1 2 3].",
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example: "echo 1 2 3",
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result: Some(Value::list(
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vec![Value::test_int(1), Value::test_int(2), Value::test_int(3)],
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Span::test_data(),
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)),
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},
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Example {
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description:
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"Returns the piped-in value, by using the special $in variable to obtain it.",
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example: "echo $in",
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result: None,
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},
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]
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}
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}
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#[cfg(test)]
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mod test {
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#[test]
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fn test_examples() {
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use super::Echo;
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use crate::test_examples;
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test_examples(Echo {})
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}
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}
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