Merge pull request #402 from ijt/add-last-command

Add `last` filter

src/cli.rs

@@ -168,6 +168,8 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
             whole_stream_command(SortBy),
             whole_stream_command(Tags),
             whole_stream_command(First),
+            whole_stream_command(Last),
+            whole_stream_command(FromArray),
             whole_stream_command(FromArray),
             whole_stream_command(FromCSV),
             whole_stream_command(FromINI),

src/commands.rs

@@ -22,6 +22,7 @@ crate mod from_toml;
 crate mod from_xml;
 crate mod from_yaml;
 crate mod get;
+crate mod last;
 crate mod lines;
 crate mod ls;
 crate mod mkdir;
@@ -76,6 +77,7 @@ crate use from_toml::FromTOML;
 crate use from_xml::FromXML;
 crate use from_yaml::FromYAML;
 crate use get::Get;
+crate use last::Last;
 crate use lines::Lines;
 crate use ls::LS;
 crate use mkdir::Mkdir;

src/commands/last.rs

@@ -0,0 +1,59 @@
+use crate::commands::WholeStreamCommand;
+use crate::errors::ShellError;
+use crate::parser::CommandRegistry;
+use crate::prelude::*;
+
+pub struct Last;
+
+impl WholeStreamCommand for Last {
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        last(args, registry)
+    }
+
+    fn name(&self) -> &str {
+        "last"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("last").required("amount", SyntaxType::Literal)
+    }
+}
+
+fn last(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let args = args.evaluate_once(registry)?;
+
+    let amount = args.expect_nth(0)?.as_i64();
+
+    let amount = match amount {
+        Ok(o) => o,
+        Err(_) => {
+            return Err(ShellError::labeled_error(
+                "Value is not a number",
+                "expected integer",
+                args.expect_nth(0)?.span(),
+            ))
+        }
+    };
+
+    if amount <= 0 {
+        return Err(ShellError::labeled_error(
+            "Value is too low",
+            "expected a positive integer",
+            args.expect_nth(0)?.span(),
+        ))
+    }
+
+    let stream = async_stream_block! {
+        let v: Vec<_> = args.input.into_vec().await;
+        let k = v.len() - (amount as usize);
+        for x in v[k..].iter() {
+            let y: Tagged<Value> = x.clone();
+            yield ReturnSuccess::value(y)
+        }
+    };
+    Ok(stream.to_output_stream())
+}

tests/filters_test.rs

@@ -100,3 +100,14 @@ fn can_filter_by_unit_size_comparison() {
 
     assert_eq!(output, "caco3_plastics.csv");
 }
+
+#[test]
+fn can_get_last() {
+    nu!(
+        output,
+        cwd("tests/fixtures/formats"),
+        "ls | sort-by name | last 1 | get name | trim | echo $it"
+    );
+
+    assert_eq!(output, "utf16.ini");
+}