Fix some edits not being sent to LangServ (#3186)

Some edits were not being sent by IDE to Language Server, resulting in 3003 "Invalid version" errors being returned by LangServ, and forcing full invalidation (resynchronization) of text contents in LangServ.

This change fixes such errors observed when opening a new project, creating a new project, or adding a new node to a project. 

Fixes #3094

### Important Notes

The root cause showed up to be actually two separate issues, both of them reproduced by an "opening a new project" scenario:

 1. The automatic addition of `import Standard.Visualization` line, [done internally when opening a new project in `controller::Project::initialize()`](https://github.com/enso-org/enso/blob/c14a2d81698217349394597fea778fd86bba47df/app/gui/src/controller/project.rs#L137-L141), was not reaching the Language Server. The cause of it was a race condition with [`self.model.subscribe()` in `Module::runner()`](https://github.com/enso-org/enso/blob/c14a2d81698217349394597fea778fd86bba47df/app/gui/src/model/module/synchronized.rs#L268). In particular, the addition of the import was executed before the subscription, which resulted in an edition notification being lost and not sent to LangServer. The fix employed for this is to make the `subscribe()` call synchronous during the initialization of a project, instead of scheduling it for a non-deterministic later time.
 2. There was [a bug in `synchronized::Module::edit_for_snipped()`](https://github.com/enso-org/enso/blob/7467efda592ab5d7ce29122af20020293f9ceacf/app/gui/src/model/module/synchronized.rs#L362), making it erroneously "optimize out" any code insertions detected by `TextEdit::from_prefix_postfix_differences()`. The fix employed for this was to improve the "optimizing out" condition, together with adding an accompanying test case verifying correct behavior (protecting against a future regression).

Additionally, as a drive-by improvement, some statements in `ParsedSourceFile<>::serialize()` were reordered, to make them better match how the actual contents of an .enso file are structured, and thus make it easier to read/analyze the code.

app/gui/CHANGELOG.md

@@ -6,10 +6,14 @@
 - [Fixed broken node whose expression contains non-ASCII characters.][3166]
 - [Fixed developer console warnings about views being created but not
   registered.][3181]
+- [Fixed developer console errors related to Language Server (mentioning code
+  3003 and "Invalid version"), occurring during project opening and after new
+  node cration.][3186]
 
 [3153]: https://github.com/enso-org/enso/pull/3153
 [3166]: https://github.com/enso-org/enso/pull/3166
 [3181]: https://github.com/enso-org/enso/pull/3181
+[3186]: https://github.com/enso-org/enso/pull/3186
 
 # Enso 2.0.0-alpha.18 (2021-10-12)
 

app/gui/language/parser/src/api.rs

@@ -183,13 +183,14 @@ fn to_json_single_line(val: &impl Serialize) -> std::result::Result<String, serd
 impl<M: Metadata> ParsedSourceFile<M> {
     /// Serialize to the SourceFile structure,
     pub fn serialize(&self) -> std::result::Result<SourceFile, serde_json::Error> {
+        let code = self.ast.repr();
         let before_tag = "\n".repeat(NEWLINES_BEFORE_TAG);
         let before_idmap = "\n";
-        let before_metadata = "\n";
-        let code = self.ast.repr();
         let json_id_map = JsonIdMap::from_id_map(&self.ast.id_map(), &code);
         let id_map = to_json_single_line(&json_id_map)?;
+        let before_metadata = "\n";
         let metadata = to_json_single_line(&self.metadata)?;
+
         let id_map_start = code.len() + before_tag.len() + METADATA_TAG.len() + before_idmap.len();
         let id_map_start_bytes = Bytes::from(id_map_start);
         let metadata_start = id_map_start + id_map.len() + before_metadata.len();

app/gui/src/model/module/synchronized.rs

@@ -256,29 +256,32 @@ impl API for Module {
 // === Synchronizing Language Server ===
 
 impl Module {
-    /// The asynchronous task scheduled during struct creation which listens for all module changes
-    /// and send proper updates to Language Server.
-    async fn runner(
+    /// Returns the asynchronous task which listens for all module changes and sends proper updates
+    /// to Language Server.
+    fn runner(
         self: Rc<Self>,
         initial_ls_content: ContentSummary,
         first_invalidation: impl Future<Output = FallibleResult<ParsedContentSummary>>,
-    ) {
-        let first_invalidation = first_invalidation.await;
-        let mut ls_content = self.new_ls_content_info(initial_ls_content, first_invalidation);
+    ) -> impl Future<Output = ()> {
         let mut subscriber = self.model.subscribe();
-        let weak = Rc::downgrade(&self);
-        drop(self);
-
-        loop {
-            let notification = subscriber.next().await;
-            let this = weak.upgrade();
-            match (notification, this) {
-                (Some(notification), Some(this)) => {
-                    debug!(this.logger, "Processing a notification: {notification:?}");
-                    let result = this.handle_notification(&ls_content, notification).await;
-                    ls_content = this.new_ls_content_info(ls_content.summary().clone(), result)
+
+        async move {
+            let first_invalidation = first_invalidation.await;
+            let mut ls_content = self.new_ls_content_info(initial_ls_content, first_invalidation);
+            let weak = Rc::downgrade(&self);
+            drop(self);
+
+            loop {
+                let notification = subscriber.next().await;
+                let this = weak.upgrade();
+                match (notification, this) {
+                    (Some(notification), Some(this)) => {
+                        debug!(this.logger, "Processing a notification: {notification:?}");
+                        let result = this.handle_notification(&ls_content, notification).await;
+                        ls_content = this.new_ls_content_info(ls_content.summary().clone(), result)
+                    }
+                    _ => break,
                 }
-                _ => break,
             }
         }
     }
@@ -359,7 +362,7 @@ impl Module {
         debug_assert_eq!(start.column, 0.column());
 
         let edit = TextEdit::from_prefix_postfix_differences(&source, &target);
-        (edit.range.start != edit.range.end)
+        (edit.range.start != edit.range.end || !edit.text.is_empty())
             .as_some_from(|| edit.move_by_lines(start.line.as_usize()))
     }
 
@@ -716,4 +719,23 @@ pub mod test {
         };
         Runner::run(test);
     }
+
+    #[test]
+    fn handle_insertion_edits_bug180558676() {
+        let source = Text::from("from Standard.Base import all\n\nmain =\n    operator1 = 0.up_to 100 . to_vector . map .noise\n    operator1.sort\n");
+        let target = Text::from("from Standard.Base import all\nimport Standard.Visualization\n\nmain =\n    operator1 = 0.up_to 100 . to_vector . map .noise\n    operator1.sort\n");
+        let edit = Module::edit_for_snipped(
+            &Location { line: 0.into(), column: 0.into() },
+            source,
+            target,
+        );
+        let expected = Some(TextEdit {
+            range: TextRange {
+                start: Position { line: 1, character: 0 },
+                end:   Position { line: 1, character: 0 },
+            },
+            text:  "import Standard.Visualization\n".to_string(),
+        });
+        assert_eq!(edit, expected);
+    }
 }