Add prepend and append commands

src/cli.rs

@@ -264,6 +264,8 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
             whole_stream_command(Lines),
             whole_stream_command(Reject),
             whole_stream_command(Reverse),
+            whole_stream_command(Append),
+            whole_stream_command(Prepend),
             whole_stream_command(Trim),
             whole_stream_command(ToBSON),
             whole_stream_command(ToCSV),

src/commands.rs

@@ -1,6 +1,7 @@
 #[macro_use]
 pub(crate) mod macros;
 
+pub(crate) mod append;
 pub(crate) mod args;
 pub(crate) mod autoview;
 pub(crate) mod cd;
@@ -45,6 +46,7 @@ pub(crate) mod pick;
 pub(crate) mod pivot;
 pub(crate) mod plugin;
 pub(crate) mod post;
+pub(crate) mod prepend;
 pub(crate) mod prev;
 pub(crate) mod pwd;
 pub(crate) mod reject;
@@ -79,6 +81,7 @@ pub(crate) use command::{
     UnevaluatedCallInfo, WholeStreamCommand,
 };
 
+pub(crate) use append::Append;
 pub(crate) use classified::ClassifiedCommand;
 pub(crate) use config::Config;
 pub(crate) use count::Count;
@@ -119,6 +122,7 @@ pub(crate) use open::Open;
 pub(crate) use pick::Pick;
 pub(crate) use pivot::Pivot;
 pub(crate) use post::Post;
+pub(crate) use prepend::Prepend;
 pub(crate) use prev::Previous;
 pub(crate) use pwd::PWD;
 pub(crate) use reject::Reject;

src/commands/append.rs

@@ -0,0 +1,49 @@
+use crate::commands::WholeStreamCommand;
+use crate::errors::ShellError;
+use crate::parser::CommandRegistry;
+use crate::prelude::*;
+
+#[derive(Deserialize)]
+struct AppendArgs {
+    row: Tagged<Value>,
+}
+
+pub struct Append;
+
+impl WholeStreamCommand for Append {
+    fn name(&self) -> &str {
+        "append"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("append").required(
+            "row value",
+            SyntaxShape::Any,
+            "the value of the row to append to the table",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Append the given row to the table"
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, append)?.run()
+    }
+}
+
+fn append(
+    AppendArgs { row }: AppendArgs,
+    RunnableContext { input, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let mut after: VecDeque<Tagged<Value>> = VecDeque::new();
+    after.push_back(row);
+
+    Ok(OutputStream::from_input(
+        input.values.chain(after),
+    ))
+}

src/commands/prepend.rs

@@ -0,0 +1,49 @@
+use crate::commands::WholeStreamCommand;
+use crate::errors::ShellError;
+use crate::parser::CommandRegistry;
+use crate::prelude::*;
+
+#[derive(Deserialize)]
+struct PrependArgs {
+    row: Tagged<Value>,
+}
+
+pub struct Prepend;
+
+impl WholeStreamCommand for Prepend {
+    fn name(&self) -> &str {
+        "prepend"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("prepend").required(
+            "row value",
+            SyntaxShape::Any,
+            "the value of the row to prepend to the table",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Prepend the given row to the front of the table"
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, prepend)?.run()
+    }
+}
+
+fn prepend(
+    PrependArgs { row }: PrependArgs,
+    RunnableContext { input, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let mut prepend: VecDeque<Tagged<Value>> = VecDeque::new();
+    prepend.push_back(row);
+
+    Ok(OutputStream::from_input(
+        prepend.chain(input.values),
+    ))
+}

tests/tests.rs

@@ -72,6 +72,38 @@ fn read_plugin() {
     assert_eq!(actual, "StupidLongName");
 }
 
+#[test]
+fn prepend_plugin() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", h::pipeline(
+        r#"
+            open fileA.txt
+            | lines
+            | prepend "testme"
+            | nth 0
+            | echo $it
+        "#
+    ));
+
+    assert_eq!(actual, "testme");
+}
+
+#[test]
+fn append_plugin() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", h::pipeline(
+        r#"
+            open fileA.txt
+            | lines
+            | append "testme"
+            | nth 3
+            | echo $it
+        "#
+    ));
+
+    assert_eq!(actual, "testme");
+}
+
 #[test]
 fn edit_plugin() {
     let actual = nu!(