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.
69 lines
1.8 KiB
Rust
69 lines
1.8 KiB
Rust
use crate::dataframe::values::NuExpression;
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use nu_engine::command_prelude::*;
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use polars::prelude::col;
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#[derive(Clone)]
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pub struct ExprCol;
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impl Command for ExprCol {
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fn name(&self) -> &str {
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"dfr col"
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}
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fn usage(&self) -> &str {
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"Creates a named column expression."
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}
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fn signature(&self) -> Signature {
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Signature::build(self.name())
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.required(
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"column name",
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SyntaxShape::String,
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"Name of column to be used",
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)
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.input_output_type(Type::Any, Type::Custom("expression".into()))
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.category(Category::Custom("expression".into()))
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Creates a named column expression and converts it to a nu object",
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example: "dfr col a | dfr into-nu",
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result: Some(Value::test_record(record! {
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"expr" => Value::test_string("column"),
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"value" => Value::test_string("a"),
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})),
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}]
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}
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fn search_terms(&self) -> Vec<&str> {
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vec!["create"]
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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 name: String = call.req(engine_state, stack, 0)?;
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let expr: NuExpression = col(name.as_str()).into();
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Ok(PipelineData::Value(expr.into_value(call.head), None))
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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::super::super::test_dataframe::test_dataframe;
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use super::*;
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use crate::dataframe::eager::ToNu;
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#[test]
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fn test_examples() {
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test_dataframe(vec![Box::new(ExprCol {}), Box::new(ToNu {})])
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}
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}
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