lines command

crates/nu-command/src/default_context.rs

@@ -7,7 +7,7 @@ use nu_protocol::{
 
 use crate::{
     where_::Where, Alias, Benchmark, BuildString, Def, Do, Each, External, For, Git, GitCheckout,
-    If, Length, Let, LetEnv, ListGitBranches, Ls, Table,
+    If, Length, Let, LetEnv, Lines, ListGitBranches, Ls, Table,
 };
 
 pub fn create_default_context() -> Rc<RefCell<EngineState>> {
@@ -50,6 +50,8 @@ pub fn create_default_context() -> Rc<RefCell<EngineState>> {
 
         working_set.add_decl(Box::new(External));
 
+        working_set.add_decl(Box::new(Lines));
+
         // This is a WIP proof of concept
         working_set.add_decl(Box::new(ListGitBranches));
         working_set.add_decl(Box::new(Git));

crates/nu-command/src/lib.rs

@@ -12,6 +12,7 @@ mod if_;
 mod length;
 mod let_;
 mod let_env;
+mod lines;
 mod list_git_branches;
 mod ls;
 mod run_external;
@@ -32,6 +33,7 @@ pub use if_::If;
 pub use length::Length;
 pub use let_::Let;
 pub use let_env::LetEnv;
+pub use lines::Lines;
 pub use list_git_branches::ListGitBranches;
 pub use ls::Ls;
 pub use run_external::External;

crates/nu-command/src/lines.rs

@@ -0,0 +1,83 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EvaluationContext};
+use nu_protocol::{Signature, Span, Value, ValueStream};
+
+pub struct Lines;
+
+const SPLIT_CHAR: char = '\n';
+
+impl Command for Lines {
+    fn name(&self) -> &str {
+        "lines"
+    }
+
+    fn usage(&self) -> &str {
+        "Converts input to lines"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("lines")
+    }
+
+    fn run(
+        &self,
+        _context: &EvaluationContext,
+        _call: &Call,
+        input: Value,
+    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
+        let value = match input {
+            Value::String { val, span } => {
+                let iter = val
+                    .split(SPLIT_CHAR)
+                    .map(|s| Value::String {
+                        val: s.into(),
+                        span,
+                    })
+                    .collect::<Vec<Value>>(); // <----- how to avoid collecting?
+
+                Value::Stream {
+                    stream: ValueStream(Rc::new(RefCell::new(iter.into_iter()))),
+                    span: Span::unknown(),
+                }
+            }
+            Value::Stream { stream, span: _ } => {
+                let iter = stream
+                    .into_iter()
+                    .filter_map(|value| {
+                        if let Value::String { val, span } = value {
+                            let inner = val
+                                .split(SPLIT_CHAR)
+                                .filter_map(|s| {
+                                    if !s.is_empty() {
+                                        Some(Value::String {
+                                            val: s.into(),
+                                            span,
+                                        })
+                                    } else {
+                                        None
+                                    }
+                                })
+                                .collect::<Vec<Value>>();
+
+                            Some(inner)
+                        } else {
+                            None
+                        }
+                    })
+                    .flatten()
+                    .collect::<Vec<Value>>(); // <----- how to avoid collecting?
+
+                Value::Stream {
+                    stream: ValueStream(Rc::new(RefCell::new(iter.into_iter()))),
+                    span: Span::unknown(),
+                }
+            }
+            _ => unimplemented!(),
+        };
+
+        Ok(value)
+    }
+}