Port str length command (#330)

Co-authored-by: Stefan Stanciulescu <contact@stefanstanciulescu.com>

crates/nu-command/src/default_context.rs

@@ -107,6 +107,7 @@ pub fn create_default_context() -> EngineState {
             StrDowncase,
             StrEndswith,
             StrIndexOf,
+            StrLength,
             StrFindReplace,
             StrKebabCase,
             StrPascalCase,

crates/nu-command/src/strings/str_/length.rs

@@ -0,0 +1,112 @@
+use nu_engine::CallExt;
+use nu_protocol::ast::Call;
+use nu_protocol::ast::CellPath;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+    fn name(&self) -> &str {
+        "str length"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("str length").rest(
+            "rest",
+            SyntaxShape::CellPath,
+            "optionally find length of text by column paths",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "outputs the lengths of the strings in the pipeline"
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        operate(engine_state, stack, call, input)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Return the lengths of multiple strings",
+                example: "'hello' | str length",
+                result: Some(Value::test_int(5)),
+            },
+            Example {
+                description: "Return the lengths of multiple strings",
+                example: "['hi' 'there'] | str length",
+                result: Some(Value::List {
+                    vals: vec![Value::test_int(2), Value::test_int(5)],
+                    span: Span::unknown(),
+                }),
+            },
+        ]
+    }
+}
+
+fn operate(
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+    input: PipelineData,
+) -> Result<PipelineData, ShellError> {
+    let head = call.head;
+    let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
+    input.map(
+        move |v| {
+            if column_paths.is_empty() {
+                action(&v, head)
+            } else {
+                let mut ret = v;
+                for path in &column_paths {
+                    let r =
+                        ret.update_cell_path(&path.members, Box::new(move |old| action(old, head)));
+                    if let Err(error) = r {
+                        return Value::Error { error };
+                    }
+                }
+                ret
+            }
+        },
+        engine_state.ctrlc.clone(),
+    )
+}
+
+fn action(input: &Value, head: Span) -> Value {
+    match input {
+        Value::String { val, .. } => Value::Int {
+            val: val.len() as i64,
+            span: head,
+        },
+        other => Value::Error {
+            error: ShellError::UnsupportedInput(
+                format!(
+                    "Input's type is {}. This command only works with strings.",
+                    other.get_type()
+                ),
+                Span::unknown(),
+            ),
+        },
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/strings/str_/mod.rs

@@ -6,6 +6,7 @@ mod downcase;
 mod ends_with;
 mod find_replace;
 mod index_of;
+mod length;
 
 pub use capitalize::SubCommand as StrCapitalize;
 pub use case::*;
@@ -15,3 +16,4 @@ pub use downcase::SubCommand as StrDowncase;
 pub use ends_with::SubCommand as StrEndswith;
 pub use find_replace::SubCommand as StrFindReplace;
 pub use index_of::SubCommand as StrIndexOf;
+pub use length::SubCommand as StrLength;