plugin path for $nu (#398)

Cargo.toml

@@ -37,7 +37,7 @@ ctrlc = "3.2.1"
 # mimalloc = { version = "*", default-features = false }
 
 [features]
-plugin = ["nu-plugin", "nu-parser/plugin", "nu-command/plugin", "nu-protocol/plugin"]
+plugin = ["nu-plugin", "nu-parser/plugin", "nu-command/plugin", "nu-protocol/plugin", "nu-engine/plugin"]
 dataframe = ["nu-command/dataframe"]
 default = ["plugin"]
 

crates/nu-engine/Cargo.toml

@@ -5,7 +5,10 @@ edition = "2018"
 
 [dependencies]
 nu-parser = { path = "../nu-parser" }
-nu-protocol = { path = "../nu-protocol" }
+nu-protocol = { path = "../nu-protocol", features = ["plugin"] }
 nu-path = { path = "../nu-path" }
 itertools = "0.10.1"
 chrono = { version="0.4.19", features=["serde"] }
+
+[features]
+plugin = []

crates/nu-engine/src/eval.rs

@@ -507,6 +507,17 @@ pub fn eval_variable(
             });
         }
 
+        #[cfg(feature = "plugin")]
+        if let Some(path) = &engine_state.plugin_signatures {
+            if let Some(path_str) = path.to_str() {
+                output_cols.push("plugin-path".into());
+                output_vals.push(Value::String {
+                    val: path_str.into(),
+                    span,
+                });
+            }
+        }
+
         if let Ok(cwd) = std::env::var("PWD") {
             output_cols.push("pwd".into());
             output_vals.push(Value::String { val: cwd, span })