forked from extern/nushell
f70c6d5d48
This commit extracts Tag, Span, Text, as well as source-related debug facilities into a new crate called nu_source. This change is much bigger than one might have expected because the previous code relied heavily on implementing inherent methods on `Tagged<T>` and `Spanned<T>`, which is no longer possible. As a result, this change creates more concrete types instead of using `Tagged<T>`. One notable example: Tagged<Value> became Value, and Value became UntaggedValue. This change clarifies the intent of the code in many places, but it does make it a big change.
54 lines
1.1 KiB
Rust
54 lines
1.1 KiB
Rust
use crate::commands::WholeStreamCommand;
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use crate::errors::ShellError;
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use crate::parser::CommandRegistry;
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use crate::prelude::*;
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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<u64>>,
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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(
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context.input.values.take(rows_desired),
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))
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}
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