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https://github.com/nushell/nushell
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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.
80 lines
2.2 KiB
Rust
80 lines
2.2 KiB
Rust
use crate::math::{
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reducers::{reducer_for, Reduce},
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utils::run_with_function,
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};
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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 product"
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}
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fn signature(&self) -> Signature {
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Signature::build("math product")
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.input_output_types(vec![
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(Type::List(Box::new(Type::Number)), Type::Number),
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(Type::Range, Type::Number),
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(Type::Table(vec![]), Type::Record(vec![])),
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(Type::Record(vec![]), Type::Record(vec![])),
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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 product of a list of numbers or the products of each column of a table."
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}
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fn search_terms(&self) -> Vec<&str> {
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vec!["times", "multiply", "x", "*"]
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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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run_with_function(call, input, product)
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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: "Compute the product of a list of numbers",
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example: "[2 3 3 4] | math product",
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result: Some(Value::test_int(72)),
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},
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Example {
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description: "Compute the product of each column in a table",
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example: "[[a b]; [1 2] [3 4]] | math product",
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result: Some(Value::test_record(record! {
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"a" => Value::test_int(3),
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"b" => Value::test_int(8),
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})),
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},
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]
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}
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}
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/// Calculate product of given values
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pub fn product(values: &[Value], span: Span, head: Span) -> Result<Value, ShellError> {
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let product_func = reducer_for(Reduce::Product);
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product_func(Value::nothing(head), values.to_vec(), span, head)
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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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