Merge pull request #1045 from sebastian-xyz/range

add range command

src/cli.rs

@@ -309,6 +309,7 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
             whole_stream_command(What),
             whole_stream_command(Which),
             whole_stream_command(Debug),
+            whole_stream_command(Range),
         ]);
 
         cfg_if::cfg_if! {

src/commands.rs

@@ -60,6 +60,7 @@ pub(crate) mod post;
 pub(crate) mod prepend;
 pub(crate) mod prev;
 pub(crate) mod pwd;
+pub(crate) mod range;
 #[allow(unused)]
 pub(crate) mod reduce_by;
 pub(crate) mod reject;
@@ -149,6 +150,7 @@ pub(crate) use post::Post;
 pub(crate) use prepend::Prepend;
 pub(crate) use prev::Previous;
 pub(crate) use pwd::PWD;
+pub(crate) use range::Range;
 #[allow(unused)]
 pub(crate) use reduce_by::ReduceBy;
 pub(crate) use reject::Reject;

src/commands/range.rs

@@ -0,0 +1,88 @@
+use crate::commands::WholeStreamCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape};
+use nu_source::Tagged;
+
+#[derive(Deserialize)]
+struct RangeArgs {
+    area: Tagged<String>,
+}
+
+pub struct Range;
+
+impl WholeStreamCommand for Range {
+    fn name(&self) -> &str {
+        "range"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("range").required(
+            "rows ",
+            SyntaxShape::Any,
+            "range of rows to return: Eg) 4..7 (=> from 4 to 7)",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Return only the selected rows"
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, range)?.run()
+    }
+}
+
+fn range(
+    RangeArgs { area: rows }: RangeArgs,
+    RunnableContext { input, name, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    match rows.item.find(".") {
+        Some(value) => {
+            let (first, last) = rows.item.split_at(value);
+            let first = match first.parse::<u64>() {
+                Ok(postion) => postion,
+                Err(_) => {
+                    if first == "" {
+                        0
+                    } else {
+                        return Err(ShellError::labeled_error(
+                            "no correct start of range",
+                            "'from' needs to be an Integer or empty",
+                            name,
+                        ));
+                    }
+                }
+            };
+            let last = match last.trim_start_matches(".").parse::<u64>() {
+                Ok(postion) => postion,
+                Err(_) => {
+                    if last == ".." {
+                        std::u64::MAX - 1
+                    } else {
+                        return Err(ShellError::labeled_error(
+                            "no correct end of range",
+                            "'to' needs to be an Integer or empty",
+                            name,
+                        ));
+                    }
+                }
+            };
+            return Ok(OutputStream::from_input(
+                input.values.skip(first).take(last - first + 1),
+            ));
+        }
+        None => {
+            return Err(ShellError::labeled_error(
+                "No correct formatted range found",
+                "format: <from>..<to>",
+                name,
+            ));
+        }
+    }
+}

tests/commands_test.rs

@@ -204,6 +204,74 @@ fn group_by_errors_if_unknown_column_name() {
     })
 }
 
+#[test]
+fn range_selects_a_row() {
+    Playground::setup("range_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![EmptyFile("notes.txt"), EmptyFile("tests.txt")]);
+
+        let actual = nu!(
+            cwd: dirs.test(), h::pipeline(
+            r#"
+                ls
+                | sort-by name
+                | range 0..0
+                | get name
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "notes.txt");
+    });
+}
+
+#[test]
+fn range_selects_some_rows() {
+    Playground::setup("range_test_2", |dirs, sandbox| {
+        sandbox.with_files(vec![
+            EmptyFile("notes.txt"),
+            EmptyFile("tests.txt"),
+            EmptyFile("persons.txt"),
+        ]);
+
+        let actual = nu!(
+            cwd: dirs.test(), h::pipeline(
+            r#"
+                ls
+                | get name
+                | range 1..2
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "2");
+    });
+}
+
+#[test]
+fn range_selects_all_rows() {
+    Playground::setup("range_test_3", |dirs, sandbox| {
+        sandbox.with_files(vec![
+            EmptyFile("notes.txt"),
+            EmptyFile("tests.txt"),
+            EmptyFile("persons.txt"),
+        ]);
+
+        let actual = nu!(
+            cwd: dirs.test(), h::pipeline(
+            r#"
+                ls
+                | get name
+                | range ..
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "3");
+    });
+}
+
 #[test]
 fn split_by() {
     Playground::setup("split_by_test_1", |dirs, sandbox| {