Line charts. Chart plugin sub command extraction. (#2627)

crates/nu-cli/src/commands/chart.rs

@@ -0,0 +1,52 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{ReturnSuccess, Signature, UntaggedValue};
+
+#[derive(Clone)]
+pub struct Chart;
+
+#[async_trait]
+impl WholeStreamCommand for Chart {
+    fn name(&self) -> &str {
+        "chart"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("chart")
+    }
+
+    fn usage(&self) -> &str {
+        "Displays charts."
+    }
+
+    async fn run(
+        &self,
+        _args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        if registry.get_command("chart bar").is_none() {
+            return Err(ShellError::untagged_runtime_error(
+                "nu_plugin_chart not installed.",
+            ));
+        }
+
+        let registry = registry.clone();
+        Ok(OutputStream::one(Ok(ReturnSuccess::Value(
+            UntaggedValue::string(crate::commands::help::get_help(&Chart, &registry))
+                .into_value(Tag::unknown()),
+        ))))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Chart;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Chart {})
+    }
+}