Simplify empty?, improve default

crates/nu-command/src/filters/default.rs

@@ -1,7 +1,7 @@
 use nu_engine::CallExt;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, Signature, Spanned, SyntaxShape, Value};
+use nu_protocol::{Category, Example, PipelineData, Signature, Span, Spanned, SyntaxShape, Value};
 
 #[derive(Clone)]
 pub struct Default;
@@ -13,12 +13,12 @@ impl Command for Default {
 
  fn signature(&self) -> Signature {
  Signature::build("default")
- .required("column name", SyntaxShape::String, "the name of the column")
  .required(
- "column value",
+ "default value",
  SyntaxShape::Any,
- "the value of the column to default",
+ "the value to use as a default",
  )
+ .optional("column name", SyntaxShape::String, "the name of the column")
  .category(Category::Filters)
  }
 
@@ -37,11 +37,26 @@ impl Command for Default {
  }
 
  fn examples(&self) -> Vec<Example> {
- vec![Example {
- description: "Give a default 'target' to all file entries",
- example: "ls -la | default target 'nothing'",
- result: None,
- }]
+ vec![
+ Example {
+ description: "Give a default 'target' column to all file entries",
+ example: "ls -la | default 'nothing' target ",
+ result: None,
+ },
+ Example {
+ description: "Default the `$nothing` value in a list",
+ example: "[1, 2, $nothing, 4] | default 3",
+ result: Some(Value::List {
+ vals: vec![
+ Value::test_int(1),
+ Value::test_int(2),
+ Value::test_int(3),
+ Value::test_int(4),
+ ],
+ span: Span::test_data(),
+ }),
+ },
+ ]
  }
 }
 
@@ -51,42 +66,52 @@ fn default(
  call: &Call,
  input: PipelineData,
 ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
- let column: Spanned<String> = call.req(engine_state, stack, 0)?;
- let value: Value = call.req(engine_state, stack, 1)?;
+ let value: Value = call.req(engine_state, stack, 0)?;
+ let column: Option<Spanned<String>> = call.opt(engine_state, stack, 1)?;
 
  let ctrlc = engine_state.ctrlc.clone();
 
- input.map(
- move |item| match item {
- Value::Record {
- mut cols,
- mut vals,
- span,
- } => {
- let mut idx = 0;
- let mut found = false;
+ if let Some(column) = column {
+ input.map(
+ move |item| match item {
+ Value::Record {
+ mut cols,
+ mut vals,
+ span,
+ } => {
+ let mut idx = 0;
+ let mut found = false;
 
- while idx < cols.len() {
- if cols[idx] == column.item {
- found = true;
- if matches!(vals[idx], Value::Nothing { .. }) {
- vals[idx] = value.clone();
+ while idx < cols.len() {
+ if cols[idx] == column.item {
+ found = true;
+ if matches!(vals[idx], Value::Nothing { .. }) {
+ vals[idx] = value.clone();
+ }
  }
+ idx += 1;
  }
- idx += 1;
- }
 
- if !found {
- cols.push(column.item.clone());
- vals.push(value.clone());
- }
+  if !found {
+  cols.push(column.item.clone());
+  vals.push(value.clone());
+  }
 
- Value::Record { cols, vals, span }
- }
- _ => item,
- },
- ctrlc,
- )
+ Value::Record { cols, vals, span }
+ }
+ _ => item,
+ },
+ ctrlc,
+ )
+ } else {
+ input.map(
+ move |item| match item {
+ Value::Nothing { .. } => value.clone(),
+ x => x,
+ },
+ ctrlc,
+ )
+ }
 }
 
 #[cfg(test)]