support binary input in length (#14224)

Closes #13874

# User-Facing Changes

`length` now supports binary input:

```nushell
> random binary 1kb | length
1000
```

crates/nu-command/src/filters/length.rs

@@ -1,3 +1,5 @@
+use std::io::Read;
+
 use nu_engine::command_prelude::*;
 
 #[derive(Clone)]
@@ -9,12 +11,15 @@ impl Command for Length {
     }
 
     fn description(&self) -> &str {
-        "Count the number of items in an input list or rows in a table."
+        "Count the number of items in an input list, rows in a table, or bytes in binary data."
     }
 
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("length")
-            .input_output_types(vec![(Type::List(Box::new(Type::Any)), Type::Int)])
+            .input_output_types(vec![
+                (Type::List(Box::new(Type::Any)), Type::Int),
+                (Type::Binary, Type::Int),
+            ])
             .category(Category::Filters)
     }
 
@@ -44,6 +49,11 @@ impl Command for Length {
                 example: "[{a:1 b:2}, {a:2 b:3}] | length",
                 result: Some(Value::test_int(2)),
             },
+            Example {
+                description: "Count the number of bytes in binary data",
+                example: "0x[01 02] | length",
+                result: Some(Value::test_int(2)),
+            },
         ]
     }
 }
@@ -64,6 +74,19 @@ fn length_row(call: &Call, input: PipelineData) -> Result<PipelineData, ShellErr
                 src_span: span,
             })
         }
+        PipelineData::Value(Value::Binary { val, .. }, ..) => {
+            Ok(Value::int(val.len() as i64, call.head).into_pipeline_data())
+        }
+        PipelineData::ByteStream(stream, _) if stream.type_().is_binary_coercible() => {
+            Ok(Value::int(
+                match stream.reader() {
+                    Some(r) => r.bytes().count() as i64,
+                    None => 0,
+                },
+                call.head,
+            )
+            .into_pipeline_data())
+        }
         _ => {
             let mut count: i64 = 0;
             // Check for and propagate errors

crates/nu-command/tests/commands/length.rs

@@ -1,4 +1,6 @@
+use nu_test_support::fs::Stub::FileWithContent;
 use nu_test_support::nu;
+use nu_test_support::playground::Playground;
 
 #[test]
 fn length_columns_in_cal_table() {
@@ -20,3 +22,14 @@ fn length_fails_on_echo_record() {
 
     assert!(actual.err.contains("only_supports_this_input_type"));
 }
+
+#[test]
+fn length_byte_stream() {
+    Playground::setup("length_bytes", |dirs, sandbox| {
+        sandbox.mkdir("length_bytes");
+        sandbox.with_files(&[FileWithContent("data.txt", "😀")]);
+
+        let actual = nu!(cwd: dirs.test(), "open data.txt | length");
+        assert_eq!(actual.out, "4");
+    });
+}