Add debug and describe (#351)

* Add debug and describe

* Fix test

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

@@ -0,0 +1,57 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Value};
+
+#[derive(Clone)]
+pub struct Debug;
+
+impl Command for Debug {
+    fn name(&self) -> &str {
+        "debug"
+    }
+
+    fn usage(&self) -> &str {
+        "Debug print the value(s) piped in."
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("describe").category(Category::Core)
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let head = call.head;
+        let config = stack.get_config()?;
+
+        input.map(
+            move |x| Value::String {
+                val: x.debug_string(", ", &config),
+                span: head,
+            },
+            engine_state.ctrlc.clone(),
+        )
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Describe the type of a string",
+            example: "'hello' | debug",
+            result: Some(Value::test_string("hello")),
+        }]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_examples() {
+        use super::Debug;
+        use crate::test_examples;
+        test_examples(Debug {})
+    }
+}

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

@@ -0,0 +1,55 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Value};
+
+#[derive(Clone)]
+pub struct Describe;
+
+impl Command for Describe {
+    fn name(&self) -> &str {
+        "describe"
+    }
+
+    fn usage(&self) -> &str {
+        "Describe the value(s) piped in."
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("describe").category(Category::Core)
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let head = call.head;
+        input.map(
+            move |x| Value::String {
+                val: x.get_type().to_string(),
+                span: head,
+            },
+            engine_state.ctrlc.clone(),
+        )
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Describe the type of a string",
+            example: "'hello' | describe",
+            result: Some(Value::test_string("string")),
+        }]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_examples() {
+        use super::Describe;
+        use crate::test_examples;
+        test_examples(Describe {})
+    }
+}

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

@@ -1,5 +1,7 @@
 mod alias;
+mod debug;
 mod def;
+mod describe;
 mod do_;
 mod echo;
 mod export;
@@ -15,7 +17,9 @@ mod source;
 mod use_;
 
 pub use alias::Alias;
+pub use debug::Debug;
 pub use def::Def;
+pub use describe::Describe;
 pub use do_::Do;
 pub use echo::Echo;
 pub use export::ExportCommand;

crates/nu-command/src/default_context.rs

@@ -36,7 +36,9 @@ pub fn create_default_context() -> EngineState {
             DateNow,
             DateToTable,
             DateToTimezone,
+            Debug,
             Def,
+            Describe,
             Do,
             Each,
             Echo,

crates/nu-protocol/src/engine/engine_state.rs

@@ -1120,7 +1120,7 @@ mod engine_state_tests {
     }
 
     #[test]
-    fn merge_states() {
+    fn merge_states() -> Result<(), ShellError> {
         let mut engine_state = EngineState::new();
         engine_state.add_file("test.nu".into(), vec![]);
 
@@ -1130,10 +1130,12 @@ mod engine_state_tests {
             working_set.render()
         };
 
-        engine_state.merge_delta(delta);
+        engine_state.merge_delta(delta)?;
 
         assert_eq!(engine_state.num_files(), 2);
         assert_eq!(&engine_state.files[0].0, "test.nu");
         assert_eq!(&engine_state.files[1].0, "child.nu");
+
+        Ok(())
     }
 }