From b09c6ae51a1c7f7be81fd614feed6c4c468e92fc Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Mon, 5 Sep 2022 15:26:05 +0100
Subject: [PATCH 01/10] Implement working preview of selected item in Searcher.

---
 app/gui/src/controller/searcher.rs   | 63 +++++++++++++++++++++++++---
 app/gui/src/presenter/graph.rs       | 22 ++++++----
 app/gui/src/presenter/graph/state.rs | 25 +++++++++++
 app/gui/src/presenter/project.rs     |  2 +
 app/gui/src/presenter/searcher.rs    | 21 ++++++++--
 app/gui/view/src/project.rs          |  1 -
 6 files changed, 117 insertions(+), 17 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index 8fb938bb188e..92d5d9e2b350 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -696,15 +696,68 @@ impl Searcher {
     }
 
     /// Preview the suggestion in the searcher.
-    pub fn preview_entry_as_suggestion(&self, index: usize) {
+    pub fn preview_entry_as_suggestion(&self, index: usize) -> FallibleResult {
         tracing::debug!("Previewing entry: {:?}", index);
-        //TODO[MM] the actual functionality here will be implemented as part of task #182634050.
+        let error = || NoSuchAction { index };
+        let suggestion = {
+            let data = self.data.borrow();
+            let list = data.actions.list().ok_or_else(error)?;
+            list.get_cloned(index).ok_or_else(error)?.action
+        };
+        if let Action::Suggestion(picked_suggestion) = suggestion {
+            self.preview_suggestion(picked_suggestion)?;
+        };
+
+        Ok(())
     }
 
     /// Use action at given index as a suggestion. The exact outcome depends on the action's type.
-    pub fn preview_suggestion(&self, selected_suggestion: action::Suggestion) {
-        //TODO[MM] the actual functionality here will be implemented as part of task #182634050.
-        tracing::debug!("Previewing suggestion: {:?}", selected_suggestion);
+    pub fn preview_suggestion(&self, picked_suggestion: action::Suggestion) -> FallibleResult {
+        tracing::debug!("Previewing suggestion: {:?}", picked_suggestion);
+
+        let id = self.data.borrow().input.next_completion_id();
+        let picked_completion = FragmentAddedByPickingSuggestion { id, picked_suggestion };
+        let code_to_insert = self.code_to_insert(&picked_completion).code;
+        tracing::debug!("Code to insert: \"{}\"", code_to_insert);
+        let added_ast = self.ide.parser().parse_line_ast(&code_to_insert)?;
+        let pattern_offset = self.data.borrow().input.pattern_offset;
+        let new_expression = match self.data.borrow_mut().input.expression.clone() {
+            None => {
+                let ast = ast::prefix::Chain::from_ast_non_strict(&added_ast);
+                ast::Shifted::new(pattern_offset, ast)
+            }
+            Some(mut expression) => {
+                let new_argument = ast::prefix::Argument {
+                    sast:      ast::Shifted::new(pattern_offset.max(1), added_ast),
+                    prefix_id: default(),
+                };
+                expression.args.push(new_argument);
+                expression
+            }
+        };
+        let expr_and_method = || {
+            let input_chain = Some(new_expression);
+
+            let expression = match (self.this_var(), input_chain) {
+                (Some(this_var), Some(input)) =>
+                    apply_this_argument(this_var, &input.wrapped.into_ast()).repr(),
+                (None, Some(input)) => input.wrapped.into_ast().repr(),
+                (_, None) => "".to_owned(),
+            };
+            let intended_method = self.intended_method();
+            (expression, intended_method)
+        };
+        let (expression, intended_method) = expr_and_method();
+
+        self.graph.graph().module.with_node_metadata(
+            self.mode.node_id(),
+            Box::new(|md| md.intended_method = intended_method),
+        )?;
+        tracing::debug!("Previewing expression: {:?}", expression);
+
+        self.graph.graph().set_expression(self.mode.node_id(), expression)?;
+
+        Ok(())
     }
 
     /// Execute given action.
diff --git a/app/gui/src/presenter/graph.rs b/app/gui/src/presenter/graph.rs
index 0d81baada535..136ea748444b 100644
--- a/app/gui/src/presenter/graph.rs
+++ b/app/gui/src/presenter/graph.rs
@@ -115,7 +115,7 @@ impl Model {
 
     /// Node position was changed in view.
     fn node_position_changed(&self, id: ViewNodeId, position: Vector2) {
-        self.update_ast(
+        self.log_action(
             || {
                 let ast_id = self.state.update_from_view().set_node_position(id, position)?;
                 Some(self.controller.graph().set_node_position(ast_id, position))
@@ -125,7 +125,7 @@ impl Model {
     }
 
     fn node_visualization_changed(&self, id: ViewNodeId, path: Option<visualization_view::Path>) {
-        self.update_ast(
+        self.log_action(
             || {
                 let ast_id =
                     self.state.update_from_view().set_node_visualization(id, path.clone())?;
@@ -141,9 +141,15 @@ impl Model {
         );
     }
 
+    /// Node expression was edited in the view. Should be called whenever the user changes the
+    /// contents of a node during editing.
+    fn node_expression_set(&self, id: ViewNodeId, expression: String) {
+        self.state.update_from_view().set_node_expression(id, expression);
+    }
+
     /// Node was removed in view.
     fn node_removed(&self, id: ViewNodeId) {
-        self.update_ast(
+        self.log_action(
             || {
                 let ast_id = self.state.update_from_view().remove_node(id)?;
                 Some(self.controller.graph().remove_node(ast_id))
@@ -154,7 +160,7 @@ impl Model {
 
     /// Connection was created in view.
     fn new_connection_created(&self, id: ViewConnection) {
-        self.update_ast(
+        self.log_action(
             || {
                 let connection = self.view.model.edges.get_cloned_ref(&id)?;
                 let ast_to_create = self.state.update_from_view().create_connection(connection)?;
@@ -166,7 +172,7 @@ impl Model {
 
     /// Connection was removed in view.
     fn connection_removed(&self, id: ViewConnection) {
-        self.update_ast(
+        self.log_action(
             || {
                 let ast_to_remove = self.state.update_from_view().remove_connection(id)?;
                 Some(self.controller.disconnect(&ast_to_remove))
@@ -176,7 +182,7 @@ impl Model {
     }
 
     fn nodes_collapsed(&self, collapsed: &[ViewNodeId]) {
-        self.update_ast(
+        self.log_action(
             || {
                 debug!(self.logger, "Collapsing node.");
                 let ids = collapsed.iter().filter_map(|node| self.state.ast_node_id_of_view(*node));
@@ -190,7 +196,7 @@ impl Model {
         );
     }
 
-    fn update_ast<F>(&self, f: F, action: &str)
+    fn log_action<F>(&self, f: F, action: &str)
     where F: FnOnce() -> Option<FallibleResult> {
         if let Some(Err(err)) = f() {
             error!(self.logger, "Failed to {action} in AST: {err}");
@@ -550,6 +556,7 @@ impl Graph {
             eval view.on_edge_endpoint_unset(((edge_id,_)) model.connection_removed(*edge_id));
             eval view.nodes_collapsed(((nodes, _)) model.nodes_collapsed(nodes));
             eval view.enabled_visualization_path(((node_id, path)) model.node_visualization_changed(*node_id, path.clone()));
+            eval view.node_expression_set(((node_id, expression)) model.node_expression_set(*node_id, expression.clone()));
 
 
             // === Dropping Files ===
@@ -617,6 +624,7 @@ impl Graph {
     /// content of a node. For example, the searcher uses this to allow the edit field to have a
     /// preview that is different from the actual node AST.
     pub fn allow_expression_auto_updates(&self, id: AstNodeId, allow: bool) {
+        tracing::debug!("Setting auto updates for {id:?} to {allow}");
         self.model.state.allow_expression_auto_updates(id, allow);
     }
 }
diff --git a/app/gui/src/presenter/graph/state.rs b/app/gui/src/presenter/graph/state.rs
index c85e67cb742d..614d750571ec 100644
--- a/app/gui/src/presenter/graph/state.rs
+++ b/app/gui/src/presenter/graph/state.rs
@@ -444,6 +444,12 @@ impl<'a> ControllerChange<'a> {
         };
         let mut nodes = self.nodes.borrow_mut();
         let displayed = nodes.get_mut_or_create(ast_id);
+        tracing::debug!(
+            "Setting node expression from controller: {} -> {}",
+            displayed.expression,
+            new_displayed_expr
+        );
+
         if displayed.expression != new_displayed_expr {
             displayed.expression = new_displayed_expr.clone();
             let new_expressions =
@@ -650,6 +656,25 @@ impl<'a> ViewChange<'a> {
             None
         }
     }
+
+    /// Set the node expression.
+    pub fn set_node_expression(&self, id: ViewNodeId, expression: String) -> Option<AstNodeId> {
+        let mut nodes = self.nodes.borrow_mut();
+        let ast_id = nodes.ast_id_of_view(id)?;
+        let displayed = nodes.get_mut(ast_id)?;
+        let expression = node_view::Expression::new_plain(expression);
+        tracing::debug!(
+            "Setting node expression from view: {} -> {}",
+            displayed.expression,
+            expression
+        );
+        if displayed.expression != expression {
+            displayed.expression = expression;
+            Some(ast_id)
+        } else {
+            None
+        }
+    }
 }
 
 
diff --git a/app/gui/src/presenter/project.rs b/app/gui/src/presenter/project.rs
index ac73d6b2103c..18d115bd0dbc 100644
--- a/app/gui/src/presenter/project.rs
+++ b/app/gui/src/presenter/project.rs
@@ -129,6 +129,8 @@ impl Model {
     fn editing_aborted(&self) {
         let searcher = self.searcher.take();
         if let Some(searcher) = searcher {
+            let node = self.graph.ast_node_of_view(searcher.input_view()).unwrap();
+            self.graph.allow_expression_auto_updates(node, true);
             searcher.abort_editing();
         } else {
             warning!(self.logger, "Editing aborted without searcher controller.");
diff --git a/app/gui/src/presenter/searcher.rs b/app/gui/src/presenter/searcher.rs
index 24e1776a740f..1e230aa1f0ea 100644
--- a/app/gui/src/presenter/searcher.rs
+++ b/app/gui/src/presenter/searcher.rs
@@ -120,7 +120,9 @@ impl Model {
     /// Should be called if an entry is selected but not used yet. Only used for the old searcher
     /// API.
     fn entry_selected_as_suggestion(&self, entry_id: view::searcher::entry::Id) {
-        self.controller.preview_entry_as_suggestion(entry_id);
+        if let Err(error) = self.controller.preview_entry_as_suggestion(entry_id) {
+            tracing::warn!("Failed to preview  entry {entry_id:?} because of error: {error:?}");
+        }
     }
 
     fn commit_editing(&self, entry_id: Option<view::searcher::entry::Id>) -> Option<AstNodeId> {
@@ -151,7 +153,9 @@ impl Model {
     /// Should be called if a suggestion is selected but not used yet.
     fn suggestion_selected(&self, entry_id: list_panel::EntryId) {
         let suggestion = self.suggestion_for_entry_id(entry_id).unwrap();
-        self.controller.preview_suggestion(suggestion);
+        if let Err(error) = self.controller.preview_suggestion(suggestion) {
+            tracing::warn!("Failed to preview suggestion {entry_id:?} because of error: {error:?}");
+        }
     }
 
     fn suggestion_accepted(
@@ -404,7 +408,6 @@ impl Searcher {
         let created_node = graph_controller.add_node(new_node)?;
 
         graph.assign_node_view_explicitly(input, created_node);
-        graph.allow_expression_auto_updates(created_node, false);
 
         let source_node = source_node.and_then(|id| graph.ast_node_of_view(id.node));
 
@@ -425,14 +428,19 @@ impl Searcher {
         let SearcherParams { input, .. } = parameters;
         let ast_node = graph.ast_node_of_view(input);
 
-        match ast_node {
+        let mode = match ast_node {
             Some(node_id) => Ok(Mode::EditNode { node_id }),
             None => {
                 let (new_node, source_node) =
                     Self::create_input_node(parameters, graph, graph_editor, graph_controller)?;
                 Ok(Mode::NewNode { node_id: new_node, source_node })
             }
+        };
+        let target_node = mode.as_ref().map(|mode| mode.node_id());
+        if let Ok(target_node) = target_node {
+            graph.allow_expression_auto_updates(target_node, false);
         }
+        mode
     }
 
     /// Setup new, appropriate searcher controller for the edition of `node_view`, and construct
@@ -509,6 +517,11 @@ impl Searcher {
     /// editing finishes.
     pub fn abort_editing(self) {}
 
+    /// Returns the node view that is being edited by the searcher.
+    pub fn input_view(&self) -> ViewNodeId {
+        self.model.input_view
+    }
+
     /// Returns true if the entry under given index is one of the examples.
     pub fn is_entry_an_example(&self, entry: view::searcher::entry::Id) -> bool {
         use crate::controller::searcher::action::Action::Example;
diff --git a/app/gui/view/src/project.rs b/app/gui/view/src/project.rs
index ff82fdfbce90..023406d5e1ba 100644
--- a/app/gui/view/src/project.rs
+++ b/app/gui/view/src/project.rs
@@ -621,7 +621,6 @@ impl View {
                 graph.deselect_all_nodes();
                 graph.select_node(node);
             });
-            eval adding_aborted  ((node) graph.remove_node(node));
 
 
             // === Editing ===

From c200c14121beaf79c158098942deb67b6e28a779 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Wed, 7 Sep 2022 15:10:42 +0100
Subject: [PATCH 02/10] Update changelog.

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4aaee0784caf..e56040315766 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -62,6 +62,9 @@
   new node is created.][3645]
 - [IDE uses new visualization API.][3661]
 - [Visualization of long textual values improved][3665]
+- [Selecting a suggestion from the searcher or component browser now updates the 
+  visualisation of the edited node to preview the results of applying the 
+  suggestion.][3691]
 
 #### EnsoGL (rendering engine)
 
@@ -305,6 +308,7 @@
 [3647]: https://github.com/enso-org/enso/pull/3647
 [3673]: https://github.com/enso-org/enso/pull/3673
 [3684]: https://github.com/enso-org/enso/pull/3684
+[3691]: https://github.com/enso-org/enso/pull/3691
 
 #### Enso Compiler
 

From 0853b2715da22cf36fadc10747e8c8341e8d4a68 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Wed, 7 Sep 2022 15:34:19 +0100
Subject: [PATCH 03/10] Prettier.

---
 CHANGELOG.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e56040315766..3c3718da013d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -62,8 +62,8 @@
   new node is created.][3645]
 - [IDE uses new visualization API.][3661]
 - [Visualization of long textual values improved][3665]
-- [Selecting a suggestion from the searcher or component browser now updates the 
-  visualisation of the edited node to preview the results of applying the 
+- [Selecting a suggestion from the searcher or component browser now updates the
+  visualisation of the edited node to preview the results of applying the
   suggestion.][3691]
 
 #### EnsoGL (rendering engine)

From 33bd77495a611751f0777fa93ad301b6ad7aef39 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Mon, 12 Sep 2022 11:17:27 +0100
Subject: [PATCH 04/10] Implement review feedback.

---
 app/gui/src/controller/searcher.rs |  6 +++++-
 app/gui/src/presenter/project.rs   | 12 ++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index 92d5d9e2b350..5a8dc9e8ce27 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -661,8 +661,12 @@ impl Searcher {
                 ast::Shifted::new(pattern_offset, ast)
             }
             Some(mut expression) => {
+                const MINIMUM_PATTERN_OFFSET: usize = 1;
                 let new_argument = ast::prefix::Argument {
-                    sast:      ast::Shifted::new(pattern_offset.max(1), added_ast),
+                    sast:      ast::Shifted::new(
+                        pattern_offset.max(MINIMUM_PATTERN_OFFSET),
+                        added_ast,
+                    ),
                     prefix_id: default(),
                 };
                 expression.args.push(new_argument);
diff --git a/app/gui/src/presenter/project.rs b/app/gui/src/presenter/project.rs
index 18d115bd0dbc..34cc27e5705a 100644
--- a/app/gui/src/presenter/project.rs
+++ b/app/gui/src/presenter/project.rs
@@ -129,11 +129,15 @@ impl Model {
     fn editing_aborted(&self) {
         let searcher = self.searcher.take();
         if let Some(searcher) = searcher {
-            let node = self.graph.ast_node_of_view(searcher.input_view()).unwrap();
-            self.graph.allow_expression_auto_updates(node, true);
-            searcher.abort_editing();
+            let input_node_view = searcher.input_view();
+            if let Some(node) = self.graph.ast_node_of_view(input_node_view) {
+                self.graph.allow_expression_auto_updates(node, true);
+                searcher.abort_editing();
+            } else {
+                tracing::warn!("When porting editing the AST node of the node view {input_node} could not be found.");
+            }
         } else {
-            warning!(self.logger, "Editing aborted without searcher controller.");
+            tracing::warn!("Editing aborted without searcher controller.");
         }
     }
 

From 3afd1ca20c821e03c4cfc1c783378ea2b33a6abe Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Mon, 12 Sep 2022 11:19:49 +0100
Subject: [PATCH 05/10] Implement review feedback.

---
 app/gui/src/controller/searcher.rs | 7 +++++--
 app/gui/src/presenter/project.rs   | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index 5a8dc9e8ce27..8795d242dfec 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -49,6 +49,7 @@ pub const ASSIGN_NAMES_FOR_NODES: bool = true;
 const ENSO_PROJECT_SPECIAL_MODULE: &str =
     concatcp!(project::STANDARD_BASE_LIBRARY_PATH, ".Enso_Project");
 
+const MINIMUM_PATTERN_OFFSET: usize = 1;
 
 
 // ==============
@@ -661,7 +662,6 @@ impl Searcher {
                 ast::Shifted::new(pattern_offset, ast)
             }
             Some(mut expression) => {
-                const MINIMUM_PATTERN_OFFSET: usize = 1;
                 let new_argument = ast::prefix::Argument {
                     sast:      ast::Shifted::new(
                         pattern_offset.max(MINIMUM_PATTERN_OFFSET),
@@ -732,7 +732,10 @@ impl Searcher {
             }
             Some(mut expression) => {
                 let new_argument = ast::prefix::Argument {
-                    sast:      ast::Shifted::new(pattern_offset.max(1), added_ast),
+                    sast:      ast::Shifted::new(
+                        pattern_offset.max(MINIMUM_PATTERN_OFFSET),
+                        added_ast,
+                    ),
                     prefix_id: default(),
                 };
                 expression.args.push(new_argument);
diff --git a/app/gui/src/presenter/project.rs b/app/gui/src/presenter/project.rs
index 34cc27e5705a..3181b84ac2ed 100644
--- a/app/gui/src/presenter/project.rs
+++ b/app/gui/src/presenter/project.rs
@@ -134,7 +134,7 @@ impl Model {
                 self.graph.allow_expression_auto_updates(node, true);
                 searcher.abort_editing();
             } else {
-                tracing::warn!("When porting editing the AST node of the node view {input_node} could not be found.");
+                tracing::warn!("When porting editing the AST node of the node view {input_node_view} could not be found.");
             }
         } else {
             tracing::warn!("Editing aborted without searcher controller.");

From 4a8935e6a662464fab1a73567df36661c5825846 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Mon, 12 Sep 2022 11:27:34 +0100
Subject: [PATCH 06/10] Implement review feedback.

---
 app/gui/src/presenter/graph/state.rs | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/app/gui/src/presenter/graph/state.rs b/app/gui/src/presenter/graph/state.rs
index 614d750571ec..1b9655193750 100644
--- a/app/gui/src/presenter/graph/state.rs
+++ b/app/gui/src/presenter/graph/state.rs
@@ -668,12 +668,8 @@ impl<'a> ViewChange<'a> {
             displayed.expression,
             expression
         );
-        if displayed.expression != expression {
-            displayed.expression = expression;
-            Some(ast_id)
-        } else {
-            None
-        }
+        let expression_has_changed = displayed.expression != expression;
+        expression_has_changed.as_some(ast_id)
     }
 }
 

From c85e8ac597269d2205bbbc4d38297687d9c8658e Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Tue, 13 Sep 2022 12:49:17 +0100
Subject: [PATCH 07/10] Implement Adam's review feedback.

---
 app/gui/src/controller/searcher.rs | 64 +++++++++++++++---------------
 app/gui/src/model/module.rs        |  5 ++-
 2 files changed, 37 insertions(+), 32 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index 8795d242dfec..dc8de861a93a 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -728,7 +728,7 @@ impl Searcher {
         let new_expression = match self.data.borrow_mut().input.expression.clone() {
             None => {
                 let ast = ast::prefix::Chain::from_ast_non_strict(&added_ast);
-                ast::Shifted::new(pattern_offset, ast)
+                Some(ast::Shifted::new(pattern_offset, ast))
             }
             Some(mut expression) => {
                 let new_argument = ast::prefix::Argument {
@@ -739,22 +739,11 @@ impl Searcher {
                     prefix_id: default(),
                 };
                 expression.args.push(new_argument);
-                expression
+                Some(expression)
             }
         };
-        let expr_and_method = || {
-            let input_chain = Some(new_expression);
-
-            let expression = match (self.this_var(), input_chain) {
-                (Some(this_var), Some(input)) =>
-                    apply_this_argument(this_var, &input.wrapped.into_ast()).repr(),
-                (None, Some(input)) => input.wrapped.into_ast().repr(),
-                (_, None) => "".to_owned(),
-            };
-            let intended_method = self.intended_method();
-            (expression, intended_method)
-        };
-        let (expression, intended_method) = expr_and_method();
+        let expression = self.get_expression(new_expression);
+        let intended_method = self.intended_method();
 
         self.graph.graph().module.with_node_metadata(
             self.mode.node_id(),
@@ -864,24 +853,15 @@ impl Searcher {
         if let Some(guard) = self.node_edit_guard.deref().as_ref() {
             guard.prevent_revert()
         }
-        let expr_and_method = || {
-            let input_chain = self.data.borrow().input.as_prefix_chain(self.ide.parser());
-
-            let expression = match (self.this_var(), input_chain) {
-                (Some(this_var), Some(input)) =>
-                    apply_this_argument(this_var, &input.wrapped.into_ast()).repr(),
-                (None, Some(input)) => input.wrapped.into_ast().repr(),
-                (_, None) => "".to_owned(),
-            };
-            let intended_method = self.intended_method();
-            (expression, intended_method)
-        };
 
         let node_id = self.mode.node_id();
+        let input_chain = self.data.borrow().input.as_prefix_chain(self.ide.parser());
         // We add the required imports before we edit its content. This way, we avoid an
         // intermediate state where imports would already be in use but not yet available.
         self.add_required_imports()?;
-        let (expression, intended_method) = expr_and_method();
+        let expression = self.get_expression(input_chain);
+        let intended_method = self.intended_method();
+
         self.graph.graph().set_expression(node_id, expression)?;
         if let Mode::NewNode { .. } = self.mode.as_ref() {
             self.graph.graph().introduce_name_on(node_id)?;
@@ -897,6 +877,16 @@ impl Searcher {
         Ok(node_id)
     }
 
+    fn get_expression(&self, input_chain: Option<ast::Shifted<ast::prefix::Chain>>) -> String {
+        let expression = match (self.this_var(), input_chain) {
+            (Some(this_var), Some(input)) =>
+                apply_this_argument(this_var, &input.wrapped.into_ast()).repr(),
+            (None, Some(input)) => input.wrapped.into_ast().repr(),
+            (_, None) => "".to_owned(),
+        };
+        expression
+    }
+
     /// Adds an example to the graph.
     ///
     /// The example piece of code will be inserted as a new function definition, and in current
@@ -1328,7 +1318,11 @@ impl EditGuard {
                 module.with_node_metadata(
                     self.node_id,
                     Box::new(|metadata| {
-                        metadata.edit_status = Some(NodeEditStatus::Edited { previous_expression });
+                        let previous_intended_method = metadata.intended_method.clone();
+                        metadata.edit_status = Some(NodeEditStatus::Edited {
+                            previous_expression,
+                            previous_intended_method,
+                        });
                     }),
                 )
             }
@@ -1371,7 +1365,7 @@ impl EditGuard {
                 tracing::debug!("Deleting temporary node {} after aborting edit.", self.node_id);
                 self.graph.graph().remove_node(self.node_id)?;
             }
-            Some(NodeEditStatus::Edited { previous_expression }) => {
+            Some(NodeEditStatus::Edited { previous_expression, previous_intended_method }) => {
                 tracing::debug!(
                     "Reverting expression of node {} to {} after aborting edit.",
                     self.node_id,
@@ -1379,6 +1373,13 @@ impl EditGuard {
                 );
                 let graph = self.graph.graph();
                 graph.set_expression(self.node_id, previous_expression)?;
+                let module = &self.graph.graph().module;
+                module.with_node_metadata(
+                    self.node_id,
+                    Box::new(|metadata| {
+                        metadata.intended_method = previous_intended_method;
+                    }),
+                )?;
             }
         };
         Ok(())
@@ -2472,7 +2473,8 @@ pub mod test {
                     assert_eq!(
                         metadata.edit_status,
                         Some(NodeEditStatus::Edited {
-                            previous_expression: node.info.expression().to_string(),
+                            previous_expression:      node.info.expression().to_string(),
+                            previous_intended_method: None,
                         })
                     );
                 }),
diff --git a/app/gui/src/model/module.rs b/app/gui/src/model/module.rs
index 7bc635fd9fda..3c561043d01f 100644
--- a/app/gui/src/model/module.rs
+++ b/app/gui/src/model/module.rs
@@ -369,12 +369,15 @@ pub struct IdeMetadata {
 }
 
 /// Metadata about a nodes edit status.
+#[allow(clippy::large_enum_variant)]
 #[derive(Clone, Debug, Deserialize, PartialEq, Serialize, Eq)]
 pub enum NodeEditStatus {
     /// The node was edited and had a previous expression.
     Edited {
         /// Expression of the node before the edit was started.
-        previous_expression: String,
+        previous_expression:      String,
+        /// Intended method of the node before editing (if known).
+        previous_intended_method: Option<MethodId>,
     },
     /// The node was created and did not previously exist.
     Created,

From 2794f3f7f49991d246be50cd17bbfdefcc2f3100 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Wed, 14 Sep 2022 13:17:28 +0100
Subject: [PATCH 08/10] Code cleanup based on review feedback.

---
 app/gui/src/controller/searcher.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index dc8de861a93a..7ec1767b54cd 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -725,7 +725,7 @@ impl Searcher {
         tracing::debug!("Code to insert: \"{}\"", code_to_insert);
         let added_ast = self.ide.parser().parse_line_ast(&code_to_insert)?;
         let pattern_offset = self.data.borrow().input.pattern_offset;
-        let new_expression = match self.data.borrow_mut().input.expression.clone() {
+        let new_expression_chain = match self.data.borrow_mut().input.expression.clone() {
             None => {
                 let ast = ast::prefix::Chain::from_ast_non_strict(&added_ast);
                 Some(ast::Shifted::new(pattern_offset, ast))
@@ -742,7 +742,7 @@ impl Searcher {
                 Some(expression)
             }
         };
-        let expression = self.get_expression(new_expression);
+        let expression = self.get_expression(new_expression_chain);
         let intended_method = self.intended_method();
 
         self.graph.graph().module.with_node_metadata(
@@ -854,14 +854,14 @@ impl Searcher {
             guard.prevent_revert()
         }
 
-        let node_id = self.mode.node_id();
-        let input_chain = self.data.borrow().input.as_prefix_chain(self.ide.parser());
         // We add the required imports before we edit its content. This way, we avoid an
         // intermediate state where imports would already be in use but not yet available.
         self.add_required_imports()?;
+
+        let node_id = self.mode.node_id();
+        let input_chain = self.data.borrow().input.as_prefix_chain(self.ide.parser());
         let expression = self.get_expression(input_chain);
         let intended_method = self.intended_method();
-
         self.graph.graph().set_expression(node_id, expression)?;
         if let Mode::NewNode { .. } = self.mode.as_ref() {
             self.graph.graph().introduce_name_on(node_id)?;

From 6babdff4fad8c2ae66fa7a43bdd414063a6e3d88 Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Thu, 15 Sep 2022 11:27:37 +0100
Subject: [PATCH 09/10] Review feedback.

---
 app/gui/src/controller/searcher.rs | 75 +++++++++++++-----------------
 app/gui/src/presenter/searcher.rs  | 19 ++++----
 2 files changed, 42 insertions(+), 52 deletions(-)

diff --git a/app/gui/src/controller/searcher.rs b/app/gui/src/controller/searcher.rs
index 7ec1767b54cd..89401bc9f44a 100644
--- a/app/gui/src/controller/searcher.rs
+++ b/app/gui/src/controller/searcher.rs
@@ -607,7 +607,7 @@ impl Searcher {
     /// in a new action list (the appropriate notification will be emitted).
     #[profile(Debug)]
     pub fn set_input(&self, new_input: String) -> FallibleResult {
-        tracing::debug!("Manually setting input to {}.", new_input);
+        tracing::debug!("Manually setting input to {new_input}.");
         let parsed_input = ParsedInput::new(new_input, self.ide.parser())?;
         let old_expr = self.data.borrow().input.expression.repr();
         let new_expr = parsed_input.expression.repr();
@@ -649,14 +649,32 @@ impl Searcher {
     /// searcher's input will be updated and returned by this function.
     #[profile(Debug)]
     pub fn use_suggestion(&self, picked_suggestion: action::Suggestion) -> FallibleResult<String> {
-        tracing::info!("Picking suggestion: {:?}", picked_suggestion);
+        tracing::info!("Picking suggestion: {picked_suggestion:?}.");
         let id = self.data.borrow().input.next_completion_id();
         let picked_completion = FragmentAddedByPickingSuggestion { id, picked_suggestion };
         let code_to_insert = self.code_to_insert(&picked_completion).code;
-        tracing::debug!("Code to insert: \"{}\"", code_to_insert);
+        tracing::debug!("Code to insert: \"{code_to_insert}\"");
         let added_ast = self.ide.parser().parse_line_ast(&code_to_insert)?;
         let pattern_offset = self.data.borrow().input.pattern_offset;
-        let new_expression = match self.data.borrow_mut().input.expression.take() {
+        let new_expression_chain = self.create_new_expression_chain(added_ast, pattern_offset);
+        let new_parsed_input = ParsedInput {
+            expression:     Some(new_expression_chain),
+            pattern_offset: 1,
+            pattern:        "".to_string(),
+        };
+        let new_input = new_parsed_input.repr();
+        self.data.borrow_mut().input = new_parsed_input;
+        self.data.borrow_mut().fragments_added_by_picking.push(picked_completion);
+        self.reload_list();
+        Ok(new_input)
+    }
+
+    fn create_new_expression_chain(
+        &self,
+        added_ast: Ast,
+        pattern_offset: usize,
+    ) -> ast::Shifted<ast::prefix::Chain> {
+        match self.data.borrow_mut().input.expression.take() {
             None => {
                 let ast = ast::prefix::Chain::from_ast_non_strict(&added_ast);
                 ast::Shifted::new(pattern_offset, ast)
@@ -672,17 +690,7 @@ impl Searcher {
                 expression.args.push(new_argument);
                 expression
             }
-        };
-        let new_parsed_input = ParsedInput {
-            expression:     Some(new_expression),
-            pattern_offset: 1,
-            pattern:        "".to_string(),
-        };
-        let new_input = new_parsed_input.repr();
-        self.data.borrow_mut().input = new_parsed_input;
-        self.data.borrow_mut().fragments_added_by_picking.push(picked_completion);
-        self.reload_list();
-        Ok(new_input)
+        }
     }
 
     /// Use action at given index as a suggestion. The exact outcome depends on the action's type.
@@ -701,7 +709,7 @@ impl Searcher {
 
     /// Preview the suggestion in the searcher.
     pub fn preview_entry_as_suggestion(&self, index: usize) -> FallibleResult {
-        tracing::debug!("Previewing entry: {:?}", index);
+        tracing::debug!("Previewing entry: {index:?}.");
         let error = || NoSuchAction { index };
         let suggestion = {
             let data = self.data.borrow();
@@ -717,40 +725,23 @@ impl Searcher {
 
     /// Use action at given index as a suggestion. The exact outcome depends on the action's type.
     pub fn preview_suggestion(&self, picked_suggestion: action::Suggestion) -> FallibleResult {
-        tracing::debug!("Previewing suggestion: {:?}", picked_suggestion);
+        tracing::debug!("Previewing suggestion: \"{picked_suggestion:?}\".");
 
         let id = self.data.borrow().input.next_completion_id();
         let picked_completion = FragmentAddedByPickingSuggestion { id, picked_suggestion };
         let code_to_insert = self.code_to_insert(&picked_completion).code;
-        tracing::debug!("Code to insert: \"{}\"", code_to_insert);
+        tracing::debug!("Code to insert: \"{code_to_insert}\".",);
         let added_ast = self.ide.parser().parse_line_ast(&code_to_insert)?;
         let pattern_offset = self.data.borrow().input.pattern_offset;
-        let new_expression_chain = match self.data.borrow_mut().input.expression.clone() {
-            None => {
-                let ast = ast::prefix::Chain::from_ast_non_strict(&added_ast);
-                Some(ast::Shifted::new(pattern_offset, ast))
-            }
-            Some(mut expression) => {
-                let new_argument = ast::prefix::Argument {
-                    sast:      ast::Shifted::new(
-                        pattern_offset.max(MINIMUM_PATTERN_OFFSET),
-                        added_ast,
-                    ),
-                    prefix_id: default(),
-                };
-                expression.args.push(new_argument);
-                Some(expression)
-            }
-        };
-        let expression = self.get_expression(new_expression_chain);
+        let new_expression_chain = self.create_new_expression_chain(added_ast, pattern_offset);
+        let expression = self.get_expression(Some(new_expression_chain));
         let intended_method = self.intended_method();
 
         self.graph.graph().module.with_node_metadata(
             self.mode.node_id(),
             Box::new(|md| md.intended_method = intended_method),
         )?;
-        tracing::debug!("Previewing expression: {:?}", expression);
-
+        tracing::debug!("Previewing expression: \"{:?}\".", expression);
         self.graph.graph().set_expression(self.mode.node_id(), expression)?;
 
         Ok(())
@@ -824,7 +815,7 @@ impl Searcher {
             let list = data.actions.list().ok_or_else(error)?;
             list.get_cloned(index).ok_or_else(error)?.action
         };
-        tracing::debug!("Previewing action: {:?}", action);
+        tracing::debug!("Previewing action: {action:?}");
         Ok(())
     }
 
@@ -1391,8 +1382,7 @@ impl Drop for EditGuard {
         if self.revert_expression.get() {
             self.revert_node_expression_edit().unwrap_or_else(|e| {
                 tracing::error!(
-                    "Failed to revert node edit after editing ended because of an error: {}",
-                    e
+                    "Failed to revert node edit after editing ended because of an error: {e}"
                 )
             });
         } else {
@@ -1401,8 +1391,7 @@ impl Drop for EditGuard {
         if self.graph.graph().node_exists(self.node_id) {
             self.clear_node_edit_metadata().unwrap_or_else(|e| {
                 tracing::error!(
-                "Failed to clear node edit metadata after editing ended because of an error: {}",
-                e
+                "Failed to clear node edit metadata after editing ended because of an error: {e}"
             )
             });
         }
diff --git a/app/gui/src/presenter/searcher.rs b/app/gui/src/presenter/searcher.rs
index 1e230aa1f0ea..237a6aa79a50 100644
--- a/app/gui/src/presenter/searcher.rs
+++ b/app/gui/src/presenter/searcher.rs
@@ -97,7 +97,7 @@ impl Model {
     #[profile(Debug)]
     fn input_changed(&self, new_input: &str) {
         if let Err(err) = self.controller.set_input(new_input.to_owned()) {
-            tracing::error!("Error while setting new searcher input: {}", err);
+            tracing::error!("Error while setting new searcher input: {err}.");
         }
     }
 
@@ -111,7 +111,7 @@ impl Model {
                 Some((self.input_view, new_code_and_trees))
             }
             Err(err) => {
-                tracing::error!("Error while applying suggestion: {}", err);
+                tracing::error!("Error while applying suggestion: {err}.");
                 None
             }
         }
@@ -121,7 +121,7 @@ impl Model {
     /// API.
     fn entry_selected_as_suggestion(&self, entry_id: view::searcher::entry::Id) {
         if let Err(error) = self.controller.preview_entry_as_suggestion(entry_id) {
-            tracing::warn!("Failed to preview  entry {entry_id:?} because of error: {error:?}");
+            tracing::warn!("Failed to preview entry {entry_id:?} because of error: {error:?}.");
         }
     }
 
@@ -131,7 +131,7 @@ impl Model {
             None => self.controller.commit_node().map(Some),
         };
         result.unwrap_or_else(|err| {
-            tracing::error!("Error while executing action: {}", err);
+            tracing::error!("Error while executing action: {err}.");
             None
         })
     }
@@ -154,7 +154,9 @@ impl Model {
     fn suggestion_selected(&self, entry_id: list_panel::EntryId) {
         let suggestion = self.suggestion_for_entry_id(entry_id).unwrap();
         if let Err(error) = self.controller.preview_suggestion(suggestion) {
-            tracing::warn!("Failed to preview suggestion {entry_id:?} because of error: {error:?}");
+            tracing::warn!(
+                "Failed to preview suggestion {entry_id:?} because of error: {error:?}."
+            );
         }
     }
 
@@ -178,7 +180,7 @@ impl Model {
                 Some((self.input_view, new_code_and_trees))
             }
             Err(err) => {
-                tracing::error!("Error while applying suggestion: {}", err);
+                tracing::error!("Error while applying suggestion: {err}.");
                 None
             }
         }
@@ -192,7 +194,7 @@ impl Model {
             self.suggestion_accepted(entry_id);
         }
         self.controller.commit_node().map(Some).unwrap_or_else(|err| {
-            tracing::error!("Error while committing node expression: {}", err);
+            tracing::error!("Error while committing node expression: {err}.");
             None
         })
     }
@@ -476,8 +478,7 @@ impl Searcher {
             if source_node.is_none() {
                 if let Err(e) = searcher_controller.set_input("".to_string()) {
                     tracing::error!(
-                        "Failed to clear input when creating searcher for a new node: {:?}",
-                        e
+                        "Failed to clear input when creating searcher for a new node: {e:?}."
                     );
                 }
             }

From 27651d0b3296efb74ed044aa3ada8dd6405070cf Mon Sep 17 00:00:00 2001
From: Michael Mauderer <michael.mauderer@enso.org>
Date: Thu, 15 Sep 2022 12:47:11 +0100
Subject: [PATCH 10/10] Bump wasm-size.

---
 build-config.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build-config.yaml b/build-config.yaml
index 8973dbd9e4b9..027a192fa2ad 100644
--- a/build-config.yaml
+++ b/build-config.yaml
@@ -1,6 +1,6 @@
 # Options intended to be common for all developers.
 
-wasm-size-limit: 14.45 MiB
+wasm-size-limit: 14.46 MiB
 
 required-versions:
   cargo-watch: ^8.1.1