feat: add examples for length,lines,reject,benchmark and drop column (#4547)

crates/nu-command/src/filters/drop/column.rs

@@ -2,8 +2,8 @@ use nu_engine::CallExt;
 use nu_protocol::ast::{Call, CellPath};
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, FromValue, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError,
+    Category, Example, FromValue, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
-    Signature, Span, SyntaxShape, Value,
+    ShellError, Signature, Span, SyntaxShape, Value,
 };
 
 #[derive(Clone)]
@@ -47,6 +47,21 @@ impl Command for DropColumn {
 
         dropcol(engine_state, span, input, columns_to_drop)
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Remove the last column of a table",
+            example: "echo [[lib, extension]; [nu-lib, rs] [nu-core, rb]] | drop column",
+            result: Some(Value::List {
+                vals: vec![Value::Record {
+                    cols: vec!["lib".into()],
+                    vals: vec![Value::test_string("nu-lib"), Value::test_string("nu-core")],
+                    span: Span::test_data(),
+                }],
+                span: Span::test_data(),
+            }),
+        }]
+    }
 }
 
 fn dropcol(

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

@@ -2,8 +2,8 @@ use nu_engine::column::get_columns;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError, Signature,
+    Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError,
-    Span, Value,
+    Signature, Span, Value,
 };
 
 #[derive(Clone)]
@@ -38,6 +38,21 @@ impl Command for Length {
             length_row(call, input)
         }
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Count the number of entries in a list",
+                example: "echo [1 2 3 4 5] | length",
+                result: Some(Value::test_int(5)),
+            },
+            Example {
+                description: "Count the number of columns in the calendar table",
+                example: "cal | length -c",
+                result: Some(Value::test_int(7)),
+            },
+        ]
+    }
 }
 
 // this simulates calling input | columns | length

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

@@ -1,7 +1,8 @@
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Value,
+    Category, Example, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Span,
+    Value,
 };
 
 #[derive(Clone)]
@@ -144,4 +145,15 @@ impl Command for Lines {
             }
         }
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Split multi-line string into lines",
+            example: "echo $'two(char nl)lines' | lines",
+            result: Some(Value::List {
+                vals: vec![Value::test_string("two"), Value::test_string("lines")],
+                span: Span::test_data(),
+            }),
+        }]
+    }
 }

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

@@ -2,8 +2,8 @@ use nu_engine::CallExt;
 use nu_protocol::ast::{Call, CellPath};
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, FromValue, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, ShellError,
+    Category, Example, FromValue, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
-    Signature, Span, SyntaxShape, Value,
+    ShellError, Signature, Span, SyntaxShape, Value,
 };
 
 #[derive(Clone)]
@@ -39,6 +39,28 @@ impl Command for Reject {
         let span = call.head;
         reject(engine_state, span, input, columns)
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Lists the files in a directory without showing the modified column",
+                example: "ls | reject modified",
+                result: None,
+            },
+            Example {
+                description: "Reject the specified field in a record",
+                example: "echo {a: 1, b: 2} | reject a",
+                result: Some(Value::Record {
+                    cols: vec!["b".into()],
+                    vals: vec![Value::Int {
+                        val: 2,
+                        span: Span::test_data(),
+                    }],
+                    span: Span::test_data(),
+                }),
+            },
+        ]
+    }
 }
 
 fn reject(

crates/nu-command/src/system/benchmark.rs

@@ -3,7 +3,9 @@ use std::time::Instant;
 use nu_engine::{eval_block, CallExt};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{CaptureBlock, Command, EngineState, Stack};
-use nu_protocol::{Category, IntoPipelineData, PipelineData, Signature, SyntaxShape, Value};
+use nu_protocol::{
+    Category, Example, IntoPipelineData, PipelineData, Signature, SyntaxShape, Value,
+};
 
 #[derive(Clone)]
 pub struct Benchmark;
@@ -56,4 +58,12 @@ impl Command for Benchmark {
 
         Ok(output.into_pipeline_data())
     }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Benchmarks a command within a block",
+            example: "benchmark { sleep 500ms }",
+            result: None,
+        }]
+    }
 }