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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.
115 lines
3.0 KiB
Rust
115 lines
3.0 KiB
Rust
use nu_engine::command_prelude::*;
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#[derive(Clone)]
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pub struct SubCommand;
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impl Command for SubCommand {
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fn name(&self) -> &str {
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"math sqrt"
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}
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fn signature(&self) -> Signature {
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Signature::build("math sqrt")
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.input_output_types(vec![
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(Type::Number, Type::Float),
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(
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Type::List(Box::new(Type::Number)),
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Type::List(Box::new(Type::Float)),
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),
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])
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.allow_variants_without_examples(true)
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.category(Category::Math)
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}
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fn usage(&self) -> &str {
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"Returns the square root of the input number."
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}
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fn search_terms(&self) -> Vec<&str> {
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vec!["square", "root"]
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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 head = call.head;
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// This doesn't match explicit nulls
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if matches!(input, PipelineData::Empty) {
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return Err(ShellError::PipelineEmpty { dst_span: head });
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}
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input.map(
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move |value| operate(value, head),
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engine_state.ctrlc.clone(),
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)
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Compute the square root of each number in a list",
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example: "[9 16] | math sqrt",
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result: Some(Value::list(
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vec![Value::test_float(3.0), Value::test_float(4.0)],
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Span::test_data(),
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)),
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}]
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}
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}
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fn operate(value: Value, head: Span) -> Value {
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let span = value.span();
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match value {
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Value::Int { val, .. } => {
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let squared = (val as f64).sqrt();
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if squared.is_nan() {
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return error_negative_sqrt(head, span);
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}
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Value::float(squared, span)
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}
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Value::Float { val, .. } => {
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let squared = val.sqrt();
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if squared.is_nan() {
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return error_negative_sqrt(head, span);
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}
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Value::float(squared, span)
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}
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Value::Error { .. } => value,
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other => Value::error(
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ShellError::OnlySupportsThisInputType {
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exp_input_type: "numeric".into(),
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wrong_type: other.get_type().to_string(),
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dst_span: head,
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src_span: other.span(),
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},
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head,
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),
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}
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}
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fn error_negative_sqrt(head: Span, span: Span) -> Value {
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Value::error(
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ShellError::UnsupportedInput {
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msg: String::from("Can't square root a negative number"),
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input: "value originates from here".into(),
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msg_span: head,
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input_span: span,
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},
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span,
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)
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_examples() {
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use crate::test_examples;
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test_examples(SubCommand {})
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}
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}
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