522a828687
* Refactor InputStream and affected commands. First, making `values` private and leaning on the `Stream` implementation makes consumes of `InputStream` less likely to have to change in the future, if we change what an `InputStream` is internally. Second, we're dropping `Option<InputStream>` as the input to pipelines, internals, and externals. Instead, `InputStream.is_empty` can be used to check for "emptiness". Empty streams are typically only ever used as the first input to a pipeline. * Add run_external internal command. We want to push external commands closer to internal commands, eventually eliminating the concept of "external" completely. This means we can consolidate a couple of things: - Variable evaluation (for example, `$it`, `$nu`, alias vars) - Behaviour of whole stream vs per-item external execution It should also make it easier for us to start introducing argument signatures for external commands, * Update run_external.rs * Update run_external.rs * Update run_external.rs * Update run_external.rs Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>
53 lines
1.1 KiB
Rust
53 lines
1.1 KiB
Rust
use crate::commands::WholeStreamCommand;
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use crate::context::CommandRegistry;
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use crate::prelude::*;
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use nu_errors::ShellError;
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use nu_protocol::{Signature, SyntaxShape};
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use nu_source::Tagged;
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pub struct First;
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#[derive(Deserialize)]
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pub struct FirstArgs {
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rows: Option<Tagged<usize>>,
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}
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impl WholeStreamCommand for First {
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fn name(&self) -> &str {
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"first"
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}
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fn signature(&self) -> Signature {
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Signature::build("first").optional(
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"rows",
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SyntaxShape::Int,
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"starting from the front, the number of rows to return",
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)
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}
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fn usage(&self) -> &str {
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"Show only the first number of rows."
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}
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fn run(
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&self,
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args: CommandArgs,
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registry: &CommandRegistry,
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) -> Result<OutputStream, ShellError> {
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args.process(registry, first)?.run()
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}
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}
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fn first(
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FirstArgs { rows }: FirstArgs,
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context: RunnableContext,
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) -> Result<OutputStream, ShellError> {
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let rows_desired = if let Some(quantity) = rows {
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*quantity
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} else {
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1
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};
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Ok(OutputStream::from_input(context.input.take(rows_desired)))
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}
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