From f57f7b2defa985dc1fc6f521947bfc6549659c77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20=C5=BD=C3=A1dn=C3=ADk?= <kubouch@gmail.com>
Date: Sun, 26 Sep 2021 13:53:52 +0300
Subject: [PATCH] Allow adding definitions from module into scope

---
 crates/nu-parser/src/parser.rs                | 26 ++++++++++++++-----
 crates/nu-protocol/src/ast/block.rs           |  6 ++---
 crates/nu-protocol/src/engine/engine_state.rs | 14 ++++++++++
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index 822fd2f403..805c637484 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -10,7 +10,7 @@ use nu_protocol::{
         RangeInclusion, RangeOperator, Statement,
     },
     engine::StateWorkingSet,
-    span, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
+    span, DeclId, Flag, PositionalArg, Signature, Span, SyntaxShape, Type, VarId,
 };
 
 #[derive(Debug, Clone)]
@@ -2653,6 +2653,9 @@ pub fn parse_module(
     working_set: &mut StateWorkingSet,
     spans: &[Span],
 ) -> (Statement, Option<ParseError>) {
+    // TODO: Currently, module is closing over its parent scope (i.e., defs in the parent scope are
+    // visible and usable in this module's scope). We might want to disable that. How?
+
     let mut error = None;
     let bytes = working_set.get_span_contents(spans[0]);
 
@@ -2719,7 +2722,7 @@ pub fn parse_module(
             }
         }
 
-        let mut exports: Vec<Vec<u8>> = vec![];
+        let mut exports: Vec<(Vec<u8>, DeclId)> = vec![];
 
         let block: Block = output
             .block
@@ -2736,10 +2739,15 @@ pub fn parse_module(
                             let (stmt, err) = parse_def(working_set, &pipeline.commands[0].parts);
 
                             if err.is_none() {
-                                let def_name =
+                                let decl_name =
                                     working_set.get_span_contents(pipeline.commands[0].parts[1]);
+
+                                let decl_id = working_set
+                                    .find_decl(decl_name)
+                                    .expect("internal error: failed to find added declaration");
+
                                 // TODO: Later, we want to put this behind 'export'
-                                exports.push(def_name.into());
+                                exports.push((decl_name.into(), decl_id));
                             }
 
                             (stmt, err)
@@ -2825,8 +2833,10 @@ pub fn parse_use(
 
         let module_name_bytes = module_name.as_bytes().to_vec();
 
-        let block = if let Some(block_id) = working_set.find_module(&module_name_bytes) {
-            working_set.get_block(block_id)
+        let exports = if let Some(block_id) = working_set.find_module(&module_name_bytes) {
+            // TODO: Since we don't use the Block at all, we might just as well create a separate
+            // Module that holds only the exports, without having Blocks in the way.
+            working_set.get_block(block_id).exports.clone()
         } else {
             return (
                 garbage_statement(spans),
@@ -2834,6 +2844,10 @@ pub fn parse_use(
             );
         };
 
+        // Extend the current scope with the module's exports
+        working_set.activate_overlay(exports);
+
+        // Create the Use command call
         let use_decl_id = working_set
             .find_decl(b"use")
             .expect("internal error: missing use command");
diff --git a/crates/nu-protocol/src/ast/block.rs b/crates/nu-protocol/src/ast/block.rs
index 33de58ca84..a5ea245664 100644
--- a/crates/nu-protocol/src/ast/block.rs
+++ b/crates/nu-protocol/src/ast/block.rs
@@ -1,6 +1,6 @@
 use std::ops::{Index, IndexMut};
 
-use crate::Signature;
+use crate::{Signature, DeclId};
 
 use super::Statement;
 
@@ -8,7 +8,7 @@ use super::Statement;
 pub struct Block {
     pub signature: Box<Signature>,
     pub stmts: Vec<Statement>,
-    pub exports: Vec<Vec<u8>>, // Assuming just defs for now
+    pub exports: Vec<(Vec<u8>, DeclId)>, // Assuming just defs for now
 }
 
 impl Block {
@@ -50,7 +50,7 @@ impl Block {
         }
     }
 
-    pub fn with_exports(self, exports: Vec<Vec<u8>>) -> Self {
+    pub fn with_exports(self, exports: Vec<(Vec<u8>, DeclId)>) -> Self {
         Self {
             signature: self.signature,
             stmts: self.stmts,
diff --git a/crates/nu-protocol/src/engine/engine_state.rs b/crates/nu-protocol/src/engine/engine_state.rs
index bd51f47647..ede56b40c1 100644
--- a/crates/nu-protocol/src/engine/engine_state.rs
+++ b/crates/nu-protocol/src/engine/engine_state.rs
@@ -312,6 +312,20 @@ impl<'a> StateWorkingSet<'a> {
         block_id
     }
 
+    pub fn activate_overlay(&mut self, overlay: Vec<(Vec<u8>, DeclId)>) {
+        // TODO: This will overwrite all existing definitions in a scope. When we add deactivate,
+        // we need to re-think how make it recoverable.
+        let scope_frame = self
+            .delta
+            .scope
+            .last_mut()
+            .expect("internal error: missing required scope frame");
+
+        for (name, decl_id) in overlay {
+            scope_frame.decls.insert(name, decl_id);
+        }
+    }
+
     pub fn next_span_start(&self) -> usize {
         self.permanent_state.next_span_start() + self.delta.file_contents.len()
     }