Move 'nth' into 'select' (#4385)

crates/nu-command/src/core_commands/tutor.rs

@@ -176,10 +176,10 @@ using Nushell commands.
 
 To get the 3rd row in the table, you can use the `nth` command:
 ```
-ls | nth 2
+ls | select 2
 ```
-This will get the 3rd (note that `nth` is zero-based) row in the table created
+This will get the 3rd (note that `select` is zero-based) row in the table created
-by the `ls` command. You can use `nth` on any table created by other commands
+by the `ls` command. You can use `select` on any table created by other commands
 as well.
 
 You can also access the column of data in one of two ways. If you want
@@ -218,7 +218,7 @@ like lists and tables.
 To reach a cell of data from a table, you can combine a row operation and a
 column operation.
 ```
-ls | nth 4 | get name
+ls | select 4 | get name
 ```
 You can combine these operations into one step using a shortcut.
 ```

crates/nu-command/src/default_context.rs

@@ -84,7 +84,6 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
             Last,
             Length,
             Lines,
-            Nth,
             ParEach,
             ParEachGroup,
             Prepend,

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

@@ -35,7 +35,7 @@ impl Command for Columns {
                 result: None,
             },
             Example {
-                example: "[[name,age,grade]; [bill,20,a]] | columns | nth 1",
+                example: "[[name,age,grade]; [bill,20,a]] | columns | select 1",
                 description: "Get the second column from the table",
                 result: None,
             },

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

@@ -22,7 +22,6 @@ mod length;
 mod lines;
 mod merge;
 mod move_;
-mod nth;
 mod par_each;
 mod par_each_group;
 mod prepend;
@@ -69,7 +68,6 @@ pub use length::Length;
 pub use lines::Lines;
 pub use merge::Merge;
 pub use move_::Move;
-pub use nth::Nth;
 pub use par_each::ParEach;
 pub use par_each_group::ParEachGroup;
 pub use prepend::Prepend;

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

@@ -1,152 +0,0 @@
-use nu_engine::CallExt;
-use nu_protocol::ast::Call;
-use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{
-    Category, Example, IntoInterruptiblePipelineData, PipelineData, PipelineIterator, ShellError,
-    Signature, Span, SyntaxShape, Value,
-};
-
-#[derive(Clone)]
-pub struct Nth;
-
-impl Command for Nth {
-    fn name(&self) -> &str {
-        "nth"
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build("nth")
-            .rest("rest", SyntaxShape::Int, "the number of the row to return")
-            .switch("skip", "Skip the rows instead of selecting them", Some('s'))
-            .category(Category::Filters)
-    }
-
-    fn usage(&self) -> &str {
-        "Return or skip only the selected rows."
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![
-            Example {
-                example: "[sam,sarah,2,3,4,5] | nth 0 1 2",
-                description: "Get the first, second, and third row",
-                result: Some(Value::List {
-                    vals: vec![
-                        Value::test_string("sam"),
-                        Value::test_string("sarah"),
-                        Value::test_int(2),
-                    ],
-                    span: Span::test_data(),
-                }),
-            },
-            Example {
-                example: "[0,1,2,3,4,5] | nth 0 1 2",
-                description: "Get the first, second, and third row",
-                result: Some(Value::List {
-                    vals: vec![Value::test_int(0), Value::test_int(1), Value::test_int(2)],
-                    span: Span::test_data(),
-                }),
-            },
-            Example {
-                example: "[0,1,2,3,4,5] | nth -s 0 1 2",
-                description: "Skip the first, second, and third row",
-                result: Some(Value::List {
-                    vals: vec![Value::test_int(3), Value::test_int(4), Value::test_int(5)],
-                    span: Span::test_data(),
-                }),
-            },
-            Example {
-                example: "[0,1,2,3,4,5] | nth 0 2 4",
-                description: "Get the first, third, and fifth row",
-                result: Some(Value::List {
-                    vals: vec![Value::test_int(0), Value::test_int(2), Value::test_int(4)],
-                    span: Span::test_data(),
-                }),
-            },
-            Example {
-                example: "[0,1,2,3,4,5] | nth 2 0 4",
-                description: "Get the first, third, and fifth row",
-                result: Some(Value::List {
-                    vals: vec![Value::test_int(0), Value::test_int(2), Value::test_int(4)],
-                    span: Span::test_data(),
-                }),
-            },
-        ]
-    }
-
-    fn run(
-        &self,
-        engine_state: &EngineState,
-        stack: &mut Stack,
-        call: &Call,
-        input: PipelineData,
-    ) -> Result<PipelineData, ShellError> {
-        let mut rows: Vec<usize> = call.rest(engine_state, stack, 0)?;
-        rows.sort_unstable();
-        let skip = call.has_flag("skip");
-        let pipeline_iter: PipelineIterator = input.into_iter();
-
-        Ok(NthIterator {
-            input: pipeline_iter,
-            rows,
-            skip,
-            current: 0,
-        }
-        .into_pipeline_data(engine_state.ctrlc.clone()))
-    }
-}
-
-struct NthIterator {
-    input: PipelineIterator,
-    rows: Vec<usize>,
-    skip: bool,
-    current: usize,
-}
-
-impl Iterator for NthIterator {
-    type Item = Value;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        loop {
-            if !self.skip {
-                if let Some(row) = self.rows.get(0) {
-                    if self.current == *row {
-                        self.rows.remove(0);
-                        self.current += 1;
-                        return self.input.next();
-                    } else {
-                        self.current += 1;
-                        let _ = self.input.next();
-                        continue;
-                    }
-                } else {
-                    return None;
-                }
-            } else if let Some(row) = self.rows.get(0) {
-                if self.current == *row {
-                    self.rows.remove(0);
-                    self.current += 1;
-                    let _ = self.input.next();
-                    continue;
-                } else {
-                    self.current += 1;
-                    return self.input.next();
-                }
-            } else {
-                return self.input.next();
-            }
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn test_examples() {
-        use crate::test_examples;
-
-        test_examples(Nth {})
-    }
-}

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

@@ -1,9 +1,9 @@
 use nu_engine::CallExt;
-use nu_protocol::ast::{Call, CellPath};
+use nu_protocol::ast::{Call, CellPath, PathMember};
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError,
+    Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
-    Signature, Span, SyntaxShape, Value,
+    PipelineIterator, ShellError, Signature, Span, SyntaxShape, Value,
 };
 
 #[derive(Clone)]
@@ -14,6 +14,7 @@ impl Command for Select {
         "select"
     }
 
+    // FIXME: also add support for --skip
     fn signature(&self) -> Signature {
         Signature::build("select")
             .rest(
@@ -63,9 +64,44 @@ fn select(
     columns: Vec<CellPath>,
     input: PipelineData,
 ) -> Result<PipelineData, ShellError> {
-    if columns.is_empty() {
+    let mut rows = vec![];
-        return Err(ShellError::CantFindColumn(span, span)); //FIXME?
+
+    let mut new_columns = vec![];
+
+    for column in columns {
+        let CellPath { ref members } = column;
+        match members.get(0) {
+            Some(PathMember::Int { val, span }) => {
+                if members.len() > 1 {
+                    return Err(ShellError::SpannedLabeledError(
+                        "Select only allows row numbers for rows".into(),
+                        "extra after row number".into(),
+                        *span,
+                    ));
+                }
+
+                rows.push(*val);
+            }
+            _ => new_columns.push(column),
+        };
     }
+    let columns = new_columns;
+
+    let input = if !rows.is_empty() {
+        rows.sort_unstable();
+        // let skip = call.has_flag("skip");
+        let pipeline_iter: PipelineIterator = input.into_iter();
+
+        NthIterator {
+            input: pipeline_iter,
+            rows,
+            skip: false,
+            current: 0,
+        }
+        .into_pipeline_data(engine_state.ctrlc.clone())
+    } else {
+        input
+    };
 
     match input {
         PipelineData::Value(
@@ -78,17 +114,21 @@ fn select(
             let mut output = vec![];
 
             for input_val in input_vals {
-                let mut cols = vec![];
+                if !columns.is_empty() {
-                let mut vals = vec![];
+                    let mut cols = vec![];
-                for path in &columns {
+                    let mut vals = vec![];
-                    //FIXME: improve implementation to not clone
+                    for path in &columns {
-                    let fetcher = input_val.clone().follow_cell_path(&path.members)?;
+                        //FIXME: improve implementation to not clone
+                        let fetcher = input_val.clone().follow_cell_path(&path.members)?;
 
-                    cols.push(path.into_string());
+                        cols.push(path.into_string());
-                    vals.push(fetcher);
+                        vals.push(fetcher);
+                    }
+
+                    output.push(Value::Record { cols, vals, span })
+                } else {
+                    output.push(input_val)
                 }
-
-                output.push(Value::Record { cols, vals, span })
             }
 
             Ok(output
@@ -97,39 +137,89 @@ fn select(
         }
         PipelineData::ListStream(stream, ..) => Ok(stream
             .map(move |x| {
-                let mut cols = vec![];
+                if !columns.is_empty() {
-                let mut vals = vec![];
+                    let mut cols = vec![];
-                for path in &columns {
+                    let mut vals = vec![];
-                    //FIXME: improve implementation to not clone
+                    for path in &columns {
-                    match x.clone().follow_cell_path(&path.members) {
+                        //FIXME: improve implementation to not clone
-                        Ok(value) => {
+                        match x.clone().follow_cell_path(&path.members) {
-                            cols.push(path.into_string());
+                            Ok(value) => {
-                            vals.push(value);
+                                cols.push(path.into_string());
-                        }
+                                vals.push(value);
-                        Err(error) => {
+                            }
-                            cols.push(path.into_string());
+                            Err(error) => {
-                            vals.push(Value::Error { error });
+                                cols.push(path.into_string());
+                                vals.push(Value::Error { error });
+                            }
                         }
                     }
+                    Value::Record { cols, vals, span }
+                } else {
+                    x
                 }
-
-                Value::Record { cols, vals, span }
             })
             .into_pipeline_data(engine_state.ctrlc.clone())),
         PipelineData::Value(v, ..) => {
-            let mut cols = vec![];
+            if !columns.is_empty() {
-            let mut vals = vec![];
+                let mut cols = vec![];
+                let mut vals = vec![];
 
-            for cell_path in columns {
+                for cell_path in columns {
-                // FIXME: remove clone
+                    // FIXME: remove clone
-                let result = v.clone().follow_cell_path(&cell_path.members)?;
+                    let result = v.clone().follow_cell_path(&cell_path.members)?;
 
-                cols.push(cell_path.into_string());
+                    cols.push(cell_path.into_string());
-                vals.push(result);
+                    vals.push(result);
+                }
+
+                Ok(Value::Record { cols, vals, span }.into_pipeline_data())
+            } else {
+                Ok(v.into_pipeline_data())
             }
-
-            Ok(Value::Record { cols, vals, span }.into_pipeline_data())
         }
         _ => Ok(PipelineData::new(span)),
     }
 }
+
+struct NthIterator {
+    input: PipelineIterator,
+    rows: Vec<usize>,
+    skip: bool,
+    current: usize,
+}
+
+impl Iterator for NthIterator {
+    type Item = Value;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if !self.skip {
+                if let Some(row) = self.rows.get(0) {
+                    if self.current == *row {
+                        self.rows.remove(0);
+                        self.current += 1;
+                        return self.input.next();
+                    } else {
+                        self.current += 1;
+                        let _ = self.input.next();
+                        continue;
+                    }
+                } else {
+                    return None;
+                }
+            } else if let Some(row) = self.rows.get(0) {
+                if self.current == *row {
+                    self.rows.remove(0);
+                    self.current += 1;
+                    let _ = self.input.next();
+                    continue;
+                } else {
+                    self.current += 1;
+                    return self.input.next();
+                }
+            } else {
+                return self.input.next();
+            }
+        }
+    }
+}

crates/nu-command/tests/commands/get.rs

@@ -108,7 +108,7 @@ fn fetches_more_than_one_column_path() {
                 arepas = 1
 
                 [[fortune_tellers]]
-                name = "Jonathan Turner"
+                name = "JT"
                 arepas = 1
 
                 [[fortune_tellers]]
@@ -126,7 +126,7 @@ fn fetches_more_than_one_column_path() {
             "#
         ));
 
-        assert_eq!(actual.out, "Jonathan Turner");
+        assert_eq!(actual.out, "JT");
     })
 }
 

crates/nu-command/tests/commands/mod.rs

@@ -34,7 +34,6 @@ mod math;
 mod merge;
 mod mkdir;
 mod move_;
-mod nth;
 mod open;
 mod parse;
 mod path;

crates/nu-command/tests/commands/move_/column.rs

@@ -133,7 +133,7 @@ fn moves_columns_after() {
                 open sample.csv
                 | move letters and_more --after column1
                 | get
-                | nth 1 2
+                | select 1 2
                 | str collect
             "#
         ));

crates/nu-command/tests/commands/nth.rs

@@ -1,41 +0,0 @@
-use nu_test_support::fs::Stub::EmptyFile;
-use nu_test_support::playground::Playground;
-use nu_test_support::{nu, pipeline};
-
-#[test]
-fn selects_a_row() {
-    Playground::setup("nth_test_1", |dirs, sandbox| {
-        sandbox.with_files(vec![EmptyFile("notes.txt"), EmptyFile("arepas.txt")]);
-
-        let actual = nu!(
-            cwd: dirs.test(), pipeline(
-            r#"
-                ls
-                | sort-by name
-                | nth 0
-                | get name.0
-            "#
-        ));
-
-        assert_eq!(actual.out, "arepas.txt");
-    });
-}
-
-#[test]
-fn selects_many_rows() {
-    Playground::setup("nth_test_2", |dirs, sandbox| {
-        sandbox.with_files(vec![EmptyFile("notes.txt"), EmptyFile("arepas.txt")]);
-
-        let actual = nu!(
-            cwd: dirs.test(), pipeline(
-            r#"
-                ls
-                | get name
-                | nth 1 0
-                | length
-            "#
-        ));
-
-        assert_eq!(actual.out, "2");
-    });
-}

crates/nu-command/tests/commands/open.rs

@@ -59,7 +59,7 @@ fn parses_csv() {
 fn parses_bson() {
     let actual = nu!(
         cwd: "tests/fixtures/formats",
-        "open sample.bson | get root | nth 0 | get b"
+        "open sample.bson | get root | select 0 | get b"
     );
 
     assert_eq!(actual.out, "hello");
@@ -73,7 +73,7 @@ fn parses_more_bson_complexity() {
         r#"
             open sample.bson
             | get root
-            | nth 6
+            | select 6
             | get b
             | get '$binary_subtype'
         "#
@@ -120,7 +120,7 @@ fn parses_more_bson_complexity() {
 // `ints` has just `z`, and `floats` has only the column `f`. This means, in general, when working
 // with sqlite, one will want to select a single table, e.g.:
 //
-// open sample.db | nth 1 | get table_values
+// open sample.db | select 1 | get table_values
 // ━━━┯━━━━━━
 //  # │ z
 // ───┼──────
@@ -139,7 +139,7 @@ fn parses_sqlite() {
         r#"
             open sample.db
             | get table_values
-            | nth 2
+            | select 2
             | get x
         "#
     ));

crates/nu-command/tests/commands/parse.rs

@@ -25,7 +25,7 @@ mod simple {
                     open key_value_separated_arepa_ingredients.txt
                     | lines
                     | each { echo $it | parse "{Name}={Value}" }
-                    | nth 1
+                    | select 1
                     | get Value
                 "#
             ));

crates/nu-command/tests/commands/select.rs

@@ -1,4 +1,4 @@
-use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
+use nu_test_support::fs::Stub::{EmptyFile, FileWithContentToBeTrimmed};
 use nu_test_support::playground::Playground;
 use nu_test_support::{nu, pipeline};
 
@@ -126,3 +126,41 @@ fn ignores_duplicate_columns_selected() {
 
     assert_eq!(actual.out, "first name last name");
 }
+
+#[test]
+fn selects_a_row() {
+    Playground::setup("select_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![EmptyFile("notes.txt"), EmptyFile("arepas.txt")]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                ls
+                | sort-by name
+                | select 0
+                | get name.0
+            "#
+        ));
+
+        assert_eq!(actual.out, "arepas.txt");
+    });
+}
+
+#[test]
+fn selects_many_rows() {
+    Playground::setup("select_test_2", |dirs, sandbox| {
+        sandbox.with_files(vec![EmptyFile("notes.txt"), EmptyFile("arepas.txt")]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                ls
+                | get name
+                | select 1 0
+                | length
+            "#
+        ));
+
+        assert_eq!(actual.out, "2");
+    });
+}

crates/nu-command/tests/format_conversions/sqlite.rs

@@ -11,7 +11,7 @@ fn table_to_sqlite_and_back_into_table() {
             | to sqlite
             | from sqlite
             | get table_values
-            | nth 2
+            | select 2
             | get x
         "#
     ));

crates/nu-command/tests/format_conversions/tsv.rs

@@ -43,7 +43,7 @@ fn table_to_tsv_text() {
                 | last 1
                 | to tsv
                 | lines
-                | nth 1
+                | select 1
             "#
         ));
 

crates/nu-protocol/src/value/mod.rs

@@ -564,7 +564,7 @@ impl Value {
         Value::Nothing { span }
     }
 
-    /// Follow a given column path into the value: for example accessing nth elements in a stream or list
+    /// Follow a given column path into the value: for example accessing select elements in a stream or list
     pub fn follow_cell_path(self, cell_path: &[PathMember]) -> Result<Value, ShellError> {
         let mut current = self;
         for member in cell_path {
@@ -575,7 +575,7 @@ impl Value {
                     val: count,
                     span: origin_span,
                 } => {
-                    // Treat a numeric path member as `nth <val>`
+                    // Treat a numeric path member as `select <val>`
                     match &mut current {
                         Value::List { vals: val, .. } => {
                             if let Some(item) = val.get(*count) {
@@ -671,7 +671,7 @@ impl Value {
         Ok(current)
     }
 
-    /// Follow a given column path into the value: for example accessing nth elements in a stream or list
+    /// Follow a given column path into the value: for example accessing select elements in a stream or list
     pub fn update_cell_path(
         &mut self,
         cell_path: &[PathMember],

docs/commands/lines.md

@@ -26,7 +26,7 @@ Basic usage:
 One useful application is piping the contents of file into `lines`. This example extracts a certain line from a given file.
 
 ```shell
-> cat lines.md | lines | nth 6
+> cat lines.md | lines | select 6
 ## Examples
 ```
 

docs/commands/nth.md

@@ -1,12 +1,12 @@
 # nth
 
-This command returns the nth row of a table, starting from 0.
+This command returns the select row of a table, starting from 0.
 If the number given is less than 0 or more than the number of rows, nothing is returned.
 
 ## Usage
 
 ```shell
-> [input-command] | nth <row number>  ...args
+> [input-command] | select <row number>  ...args
 ```
 
 ## Parameters
@@ -45,7 +45,7 @@ If the number given is less than 0 or more than the number of rows, nothing is r
 ```
 
 ```shell
-> ls | nth 0
+> ls | select 0
 ──────────┬────────────────────
  name     │ CODE_OF_CONDUCT.md
  type     │ File
@@ -55,7 +55,7 @@ If the number given is less than 0 or more than the number of rows, nothing is r
 ```
 
 ```shell
-> ls | nth 0 2
+> ls | select 0 2
 ───┬────────────────────┬──────┬──────────┬─────────────
  # │ name               │ type │ size     │ modified
 ───┼────────────────────┼──────┼──────────┼─────────────
@@ -65,7 +65,7 @@ If the number given is less than 0 or more than the number of rows, nothing is r
 ```
 
 ```shell
-> ls | nth 5
+> ls | select 5
 ──────────┬───────────────
  name     │ Makefile.toml
  type     │ File