Fixing captures (#723)

* WIP fixing captures

* small fix

* WIP

* Rewrite to proof-of-concept better parse_def

* Add missing file

* Finish capture refactor

* Fix tests

* Add more tests

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

@@ -0,0 +1,9 @@
+use std::collections::HashMap;
+
+use crate::{BlockId, Value, VarId};
+
+#[derive(Clone, Debug)]
+pub struct CaptureBlock {
+    pub block_id: BlockId,
+    pub captures: HashMap<VarId, Value>,
+}

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

@@ -154,6 +154,7 @@ pub const SCOPE_VARIABLE_ID: usize = 1;
 pub const IN_VARIABLE_ID: usize = 2;
 pub const CONFIG_VARIABLE_ID: usize = 3;
 pub const ENV_VARIABLE_ID: usize = 4;
+// NOTE: If you add more to this list, make sure to update the > checks based on the last in the list
 
 impl EngineState {
     pub fn new() -> Self {

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

@@ -1,9 +1,11 @@
 mod call_info;
+mod capture_block;
 mod command;
 mod engine_state;
 mod stack;
 
 pub use call_info::*;
+pub use capture_block::*;
 pub use command::*;
 pub use engine_state::*;
 pub use stack::*;

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

@@ -62,7 +62,10 @@ impl Stack {
             return Ok(v.clone());
         }
 
-        Err(ShellError::NushellFailed("variable not found".into()))
+        Err(ShellError::NushellFailed(format!(
+            "variable (var_id: {}) not found",
+            var_id
+        )))
     }
 
     pub fn add_var(&mut self, var_id: VarId, value: Value) {
@@ -80,7 +83,24 @@ impl Stack {
         }
     }
 
-    pub fn collect_captures(&self, captures: &[VarId]) -> Stack {
+    pub fn captures_to_stack(&self, captures: &HashMap<VarId, Value>) -> Stack {
+        let mut output = Stack::new();
+
+        output.vars = captures.clone();
+
+        // FIXME: this is probably slow
+        output.env_vars = self.env_vars.clone();
+        output.env_vars.push(HashMap::new());
+
+        let config = self
+            .get_var(CONFIG_VARIABLE_ID)
+            .expect("internal error: config is missing");
+        output.vars.insert(CONFIG_VARIABLE_ID, config);
+
+        output
+    }
+
+    pub fn gather_captures(&self, captures: &[VarId]) -> Stack {
         let mut output = Stack::new();
 
         for capture in captures {