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c747ec75c9
# Description
When implementing a `Command`, one must also import all the types
present in the function signatures for `Command`. This makes it so that
we often import the same set of types in each command implementation
file. E.g., something like this:
```rust
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
ShellError, Signature, Span, Type, Value,
};
```
This PR adds the `nu_engine::command_prelude` module which contains the
necessary and commonly used types to implement a `Command`:
```rust
// command_prelude.rs
pub use crate::CallExt;
pub use nu_protocol::{
ast::{Call, CellPath},
engine::{Command, EngineState, Stack},
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};
```
This should reduce the boilerplate needed to implement a command and
also gives us a place to track the breadth of the `Command` API. I tried
to be conservative with what went into the prelude modules, since it
might be hard/annoying to remove items from the prelude in the future.
Let me know if something should be included or excluded.
82 lines
2.5 KiB
Rust
82 lines
2.5 KiB
Rust
use nu_engine::command_prelude::*;
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#[derive(Clone)]
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pub struct Print;
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impl Command for Print {
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fn name(&self) -> &str {
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"print"
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}
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fn signature(&self) -> Signature {
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Signature::build("print")
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.input_output_types(vec![
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(Type::Nothing, Type::Nothing),
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(Type::Any, Type::Nothing),
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])
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.allow_variants_without_examples(true)
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.rest("rest", SyntaxShape::Any, "the values to print")
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.switch(
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"no-newline",
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"print without inserting a newline for the line ending",
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Some('n'),
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)
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.switch("stderr", "print to stderr instead of stdout", Some('e'))
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.category(Category::Strings)
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}
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fn usage(&self) -> &str {
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"Print the given values to stdout."
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}
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fn extra_usage(&self) -> &str {
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r#"Unlike `echo`, this command does not return any value (`print | describe` will return "nothing").
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Since this command has no output, there is no point in piping it with other commands.
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`print` may be used inside blocks of code (e.g.: hooks) to display text during execution without interfering with the pipeline."#
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}
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fn search_terms(&self) -> Vec<&str> {
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vec!["display"]
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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 args: Vec<Value> = call.rest(engine_state, stack, 0)?;
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let no_newline = call.has_flag(engine_state, stack, "no-newline")?;
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let to_stderr = call.has_flag(engine_state, stack, "stderr")?;
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// This will allow for easy printing of pipelines as well
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if !args.is_empty() {
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for arg in args {
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arg.into_pipeline_data()
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.print(engine_state, stack, no_newline, to_stderr)?;
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}
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} else if !input.is_nothing() {
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input.print(engine_state, stack, no_newline, to_stderr)?;
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}
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Ok(PipelineData::empty())
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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: "Print 'hello world'",
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example: r#"print "hello world""#,
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result: None,
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},
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Example {
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description: "Print the sum of 2 and 3",
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example: r#"print (2 + 3)"#,
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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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