Columns can be renamed. (#1447)

src/cli.rs

@@ -318,6 +318,7 @@ pub fn create_default_context(
             whole_stream_command(Default),
             whole_stream_command(SkipWhile),
             whole_stream_command(Range),
+            whole_stream_command(Rename),
             whole_stream_command(Uniq),
             // Table manipulation
             whole_stream_command(Wrap),

src/commands.rs

@@ -69,6 +69,7 @@ pub(crate) mod range;
 #[allow(unused)]
 pub(crate) mod reduce_by;
 pub(crate) mod reject;
+pub(crate) mod rename;
 pub(crate) mod reverse;
 pub(crate) mod rm;
 pub(crate) mod save;
@@ -172,6 +173,7 @@ pub(crate) use range::Range;
 #[allow(unused_imports)]
 pub(crate) use reduce_by::ReduceBy;
 pub(crate) use reject::Reject;
+pub(crate) use rename::Rename;
 pub(crate) use reverse::Reverse;
 pub(crate) use rm::Remove;
 pub(crate) use save::Save;

src/commands/rename.rs

@@ -0,0 +1,97 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use indexmap::IndexMap;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_source::Tagged;
+
+pub struct Rename;
+
+#[derive(Deserialize)]
+pub struct Arguments {
+    column_name: Tagged<String>,
+    rest: Vec<Tagged<String>>,
+}
+
+impl WholeStreamCommand for Rename {
+    fn name(&self) -> &str {
+        "rename"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("rename")
+            .required(
+                "column_name",
+                SyntaxShape::String,
+                "the name of the column to rename for",
+            )
+            .rest(
+                SyntaxShape::Member,
+                "Additional column name(s) to rename for",
+            )
+    }
+
+    fn usage(&self) -> &str {
+        "Creates a new table with columns renamed."
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, rename)?.run()
+    }
+}
+
+pub fn rename(
+    Arguments { column_name, rest }: Arguments,
+    RunnableContext { input, name, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let mut new_column_names = vec![vec![column_name]];
+    new_column_names.push(rest);
+
+    let new_column_names = new_column_names.into_iter().flatten().collect::<Vec<_>>();
+
+    let stream = input
+        .values
+        .map(move |item| {
+            let mut result = VecDeque::new();
+
+            if let Value {
+                value: UntaggedValue::Row(row),
+                tag,
+            } = item
+            {
+                let mut renamed_row = IndexMap::new();
+
+                for (idx, (key, value)) in row.entries.iter().enumerate() {
+                    let key = if idx < new_column_names.len() {
+                        &new_column_names[idx].item
+                    } else {
+                        key
+                    };
+
+                    renamed_row.insert(key.clone(), value.clone());
+                }
+
+                let out = UntaggedValue::Row(renamed_row.into()).into_value(tag);
+
+                result.push_back(ReturnSuccess::value(out));
+            } else {
+                result.push_back(ReturnSuccess::value(
+                    UntaggedValue::Error(ShellError::labeled_error(
+                        "no column names available",
+                        "can't rename",
+                        &name,
+                    ))
+                    .into_untagged_value(),
+                ));
+            }
+
+            futures::stream::iter(result)
+        })
+        .flatten();
+
+    Ok(stream.to_output_stream())
+}