Add metadata command (#569)

* Add metadata command

* Add string interpolation to testing

crates/nu-command/src/core_commands/for_.rs

@@ -168,24 +168,23 @@ impl Command for For {
                     span,
                 }),
             },
-            // FIXME? Numbered `for` is kinda strange, but was supported in previous nushell
-            // Example {
-            //     description: "Number each item and echo a message",
-            //     example: "for $it in ['bob' 'fred'] --numbered { $\"($it.index) is ($it.item)\" }",
-            //     result: Some(Value::List {
-            //         vals: vec![
-            //             Value::String {
-            //                 val: "0 is bob".into(),
-            //                 span,
-            //             },
-            //             Value::String {
-            //                 val: "0 is fred".into(),
-            //                 span,
-            //             },
-            //         ],
-            //         span,
-            //     }),
-            // },
+            Example {
+                description: "Number each item and echo a message",
+                example: "for $it in ['bob' 'fred'] --numbered { $\"($it.index) is ($it.item)\" }",
+                result: Some(Value::List {
+                    vals: vec![
+                        Value::String {
+                            val: "0 is bob".into(),
+                            span,
+                        },
+                        Value::String {
+                            val: "1 is fred".into(),
+                            span,
+                        },
+                    ],
+                    span,
+                }),
+            },
         ]
     }
 }

crates/nu-command/src/core_commands/metadata.rs

@@ -0,0 +1,103 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+    Category, DataSource, Example, PipelineData, PipelineMetadata, Signature, Value,
+};
+
+#[derive(Clone)]
+pub struct Metadata;
+
+impl Command for Metadata {
+    fn name(&self) -> &str {
+        "metadata"
+    }
+
+    fn usage(&self) -> &str {
+        "Get the metadata for items in the stream"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("metadata").category(Category::Core)
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        let head = call.head;
+        let ctrlc = engine_state.ctrlc.clone();
+
+        let metadata = input.metadata();
+
+        input.map(
+            move |x| {
+                let span = x.span();
+
+                let mut cols = vec![];
+                let mut vals = vec![];
+
+                cols.push("span".into());
+                if let Ok(span) = span {
+                    vals.push(Value::Record {
+                        cols: vec!["start".into(), "end".into()],
+                        vals: vec![
+                            Value::Int {
+                                val: span.start as i64,
+                                span,
+                            },
+                            Value::Int {
+                                val: span.end as i64,
+                                span,
+                            },
+                        ],
+                        span: head,
+                    });
+                }
+
+                if let Some(x) = &metadata {
+                    match x {
+                        PipelineMetadata {
+                            data_source: DataSource::Ls,
+                        } => {
+                            cols.push("source".into());
+                            vals.push(Value::String {
+                                val: "ls".into(),
+                                span: head,
+                            })
+                        }
+                    }
+                }
+
+                Value::Record {
+                    cols,
+                    vals,
+                    span: head,
+                }
+            },
+            ctrlc,
+        )
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Get the metadata of a value",
+            example: "3 | metadata",
+            result: None,
+        }]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(Metadata {})
+    }
+}

crates/nu-command/src/core_commands/mod.rs

@@ -13,6 +13,7 @@ mod hide;
 mod history;
 mod if_;
 mod let_;
+mod metadata;
 mod module;
 mod source;
 mod use_;
@@ -33,6 +34,7 @@ pub use hide::Hide;
 pub use history::History;
 pub use if_::If;
 pub use let_::Let;
+pub use metadata::Metadata;
 pub use module::Module;
 pub use source::Source;
 pub use use_::Use;

crates/nu-command/src/default_context.rs

@@ -38,6 +38,7 @@ pub fn create_default_context() -> EngineState {
             History,
             If,
             Let,
+            Metadata,
             Module,
             Source,
             Use,

crates/nu-command/src/example_test.rs

@@ -16,6 +16,8 @@ use super::{Ansi, Date, From, Into, Math, Path, Random, Split, Str, StrCollect,
 
 #[cfg(test)]
 pub fn test_examples(cmd: impl Command + 'static) {
+    use crate::BuildString;
+
     let examples = cmd.examples();
     let mut engine_state = Box::new(EngineState::new());
 
@@ -25,6 +27,7 @@ pub fn test_examples(cmd: impl Command + 'static) {
         let mut working_set = StateWorkingSet::new(&*engine_state);
         working_set.add_decl(Box::new(Str));
         working_set.add_decl(Box::new(StrCollect));
+        working_set.add_decl(Box::new(BuildString));
         working_set.add_decl(Box::new(From));
         working_set.add_decl(Box::new(To));
         working_set.add_decl(Box::new(Into));

crates/nu-protocol/src/pipeline_data.rs

@@ -37,12 +37,12 @@ pub enum PipelineData {
     Stream(ValueStream, Option<PipelineMetadata>),
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct PipelineMetadata {
     pub data_source: DataSource,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum DataSource {
     Ls,
 }
@@ -52,6 +52,13 @@ impl PipelineData {
         PipelineData::Value(Value::Nothing { span }, None)
     }
 
+    pub fn metadata(&self) -> Option<PipelineMetadata> {
+        match self {
+            PipelineData::Stream(_, x) => x.clone(),
+            PipelineData::Value(_, x) => x.clone(),
+        }
+    }
+
     pub fn into_value(self, span: Span) -> Value {
         match self {
             PipelineData::Value(Value::Nothing { .. }, ..) => Value::nothing(span),