Enable incremental text sync and handle incremental didChange edits

Author: AJenbo

docs/CHANGELOG.md

@@ -43,6 +43,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- **Incremental text sync.** The server now uses incremental document sync, receiving only changed ranges from the editor instead of the full file content on every keystroke.
 - **Replace FQCN with import.** Now replaces all occurrences of the same FQCN throughout the file in one action, not just the one under the cursor. A new "Replace all FQCNs with imports" action appears when the file contains multiple distinct FQCNs, replacing all of them at once (skipping those with import conflicts).
 - **LSP responsiveness.** Hover, go-to-definition, signature help, code actions, rename, and other handlers now run on background threads. Slow requests no longer block other requests or cancellations.
 - **Faster analysis.** Analysis time cut significantly on large projects.

docs/todo.md

@@ -26,6 +26,7 @@ within the same impact tier.
 | #   | Item                                                                                                                    | Impact      | Effort      |
 | --- | ----------------------------------------------------------------------------------------------------------------------- | ----------- | ------ |
 | P13 | [Tiered storage: drop per-file maps for non-open files](todo/performance.md#p13-tiered-storage-drop-per-file-maps-for-non-open-files) | Medium-High | Medium-High |
+| P10 | [Redundant `parse_and_cache_file` from multiple threads](todo/performance.md#p10-redundant-parse_and_cache_file-from-multiple-threads)                                      | Medium      | Low         |
 | D10 | [PHPMD diagnostic proxy](todo/diagnostics.md#d10-phpmd-diagnostic-proxy)                                                | Low         | Medium      |
 |     | **Release 0.8.0**                                                                                                       |             |             |
 
@@ -144,7 +145,6 @@ unlikely to move the needle for most users.
 | F5  | [Call hierarchy](todo/lsp-features.md#f5-call-hierarchy) (incoming/outgoing calls)                                                                                          | Medium      | Medium      |
 | F2  | [Partial result streaming via `$/progress`](todo/lsp-features.md#f2-partial-result-streaming-via-progress)                                                                  | Medium      | Medium-High |
 | F7  | [Evaluatable expression support (DAP integration)](todo/lsp-features.md#f7-evaluatable-expression-support-dap-integration)                                                  | Low-Medium  | Low         |
-| F3  | Incremental text sync                                                                                                                                                       | Low-Medium  | Medium      |
 | F8  | [Test ↔ implementation navigation via `@covers`](todo/lsp-features.md#f8-test--implementation-navigation-via-covers)                                                        | Low         | Medium      |
 |     | **[Signature Help](todo/signature-help.md)**                                                                                                                                |             |             |
 | S1  | [Attribute constructor signature help](todo/signature-help.md#s1-attribute-constructor-signature-help)                                                                      | Medium      | Medium      |
@@ -168,7 +168,6 @@ unlikely to move the needle for most users.
 | P13 | [Tiered storage: drop per-file maps for non-open files](todo/performance.md#p13-tiered-storage-drop-per-file-maps-for-non-open-files)                                       | Medium-High | Medium-High |
 | P14 | [Eager docblock parsing into structured fields](todo/performance.md#p14-eager-docblock-parsing-into-structured-fields)                                                      | Medium      | Medium      |
 | P9  | [`resolved_class_cache` generic-arg specialisation](todo/performance.md#p9-resolved_class_cache-generic-arg-specialisation)                                                 | Medium      | Medium      |
-| P10 | [Redundant `parse_and_cache_file` from multiple threads](todo/performance.md#p10-redundant-parse_and_cache_file-from-multiple-threads)                                      | Medium      | Low         |
 | P11 | [Uncached base-resolution in `build_scope_methods_for_builder`](todo/performance.md#p11-uncached-base-resolution-in-build_scope_methods_for_builder)                        | Low-Medium  | Low         |
 | P3  | Parallel pre-filter in `find_implementors`                                                                                                                                  | Low-Medium  | Medium      |
 | P4  | `memmem` for block comment terminator search                                                                                                                                | Low         | Low         |

src/definition/member/file_lookup.rs

@@ -114,9 +114,7 @@ impl Backend {
         }
         // Fallback: the target file may have been closed (didClose clears
         // ast_map).  Check class_index which survives close (issue #99).
-        .or_else(|| {
-            self.class_index.read().get(class_name).cloned()
-        })?;
+        .or_else(|| self.class_index.read().get(class_name).cloned())?;
 
         // Get the file content.
         let file_content = if uri == current_uri {

src/server.rs

@@ -140,7 +140,7 @@ impl LanguageServer for Backend {
                 }),
                 inlay_hint_provider: Some(OneOf::Left(true)),
                 text_document_sync: Some(TextDocumentSyncCapability::Kind(
-                    TextDocumentSyncKind::FULL,
+                    TextDocumentSyncKind::INCREMENTAL,
                 )),
                 hover_provider: Some(HoverProviderCapability::Simple(true)),
                 definition_provider: Some(OneOf::Left(true)),
@@ -469,29 +469,53 @@ impl LanguageServer for Backend {
     async fn did_change(&self, params: DidChangeTextDocumentParams) {
         let uri = params.text_document.uri.to_string();
 
-        if let Some(change) = params.content_changes.first() {
-            let text = Arc::new(change.text.clone());
+        if params.content_changes.is_empty() {
+            return;
+        }
+
+        // Apply incremental edits to the current content.
+        // Each change event either has a range (incremental) or replaces
+        // the entire document (range is None).
+        let text = {
+            let open_files = self.open_files.read();
+            let mut current = open_files
+                .get(&uri)
+                .map(|s| s.to_string())
+                .unwrap_or_default();
+            drop(open_files);
+
+            for change in &params.content_changes {
+                if let Some(range) = change.range {
+                    let start = crate::util::position_to_byte_offset(&current, range.start);
+                    let end = crate::util::position_to_byte_offset(&current, range.end);
+                    current.replace_range(start..end, &change.text);
+                } else {
+                    // Full content replacement (fallback)
+                    current = change.text.clone();
+                }
+            }
+            Arc::new(current)
+        };
 
-            // Update stored content
-            self.open_files
-                .write()
-                .insert(uri.clone(), Arc::clone(&text));
+        // Update stored content
+        self.open_files
+            .write()
+            .insert(uri.clone(), Arc::clone(&text));
 
-            // Re-parse and update AST map, use map, and namespace map
-            let signature_changed = self.update_ast(&uri, &text);
+        // Re-parse and update AST map, use map, and namespace map
+        let signature_changed = self.update_ast(&uri, &text);
 
-            // Schedule diagnostics in a background task with debouncing.
-            // This returns immediately so that completion, hover, and
-            // signature help are never blocked by diagnostic computation.
-            self.schedule_diagnostics(uri.clone());
+        // Schedule diagnostics in a background task with debouncing.
+        // This returns immediately so that completion, hover, and
+        // signature help are never blocked by diagnostic computation.
+        self.schedule_diagnostics(uri.clone());
 
-            // When a class signature changed (method/property added,
-            // removed, or modified; class renamed; parent changed; etc.)
-            // other open files may have stale diagnostics that reference
-            // the affected classes.  Queue them all for a re-check.
-            if signature_changed {
-                self.schedule_diagnostics_for_open_files(&uri);
-            }
+        // When a class signature changed (method/property added,
+        // removed, or modified; class renamed; parent changed; etc.)
+        // other open files may have stale diagnostics that reference
+        // the affected classes.  Queue them all for a re-check.
+        if signature_changed {
+            self.schedule_diagnostics_for_open_files(&uri);
         }
     }
 

tests/integration/definition_classes.rs

@@ -284,10 +284,7 @@ async fn test_goto_definition_after_target_did_close() {
 
     match result.unwrap() {
         GotoDefinitionResponse::Scalar(location) => {
-            assert_eq!(
-                location.uri, uri_b,
-                "Should jump to ClassB.php"
-            );
+            assert_eq!(location.uri, uri_b, "Should jump to ClassB.php");
         }
         other => panic!("Expected Scalar location, got: {:?}", other),
     }

tests/integration/server_lifecycle.rs

@@ -294,3 +294,122 @@ async fn test_did_close_cleans_up_ast_map() {
         "ast_map should be cleaned up after did_close"
     );
 }
+
+#[tokio::test]
+async fn test_did_change_incremental_sync() {
+    let backend = create_test_backend();
+
+    let uri = Url::parse("file:///incremental.php").unwrap();
+    //                     0123456789...
+    let initial = "<?php\nclass A {\n    function first() {}\n}\n".to_string();
+
+    let open_params = DidOpenTextDocumentParams {
+        text_document: TextDocumentItem {
+            uri: uri.clone(),
+            language_id: "php".to_string(),
+            version: 1,
+            text: initial,
+        },
+    };
+    backend.did_open(open_params).await;
+
+    let classes = backend.get_classes_for_uri(uri.as_ref()).unwrap();
+    assert_eq!(classes[0].methods.len(), 1);
+
+    // Send an incremental change: insert a second method before the closing brace.
+    // The closing "}\n" is at line 3, col 0. Insert before it.
+    let change_params = DidChangeTextDocumentParams {
+        text_document: VersionedTextDocumentIdentifier {
+            uri: uri.clone(),
+            version: 2,
+        },
+        content_changes: vec![TextDocumentContentChangeEvent {
+            range: Some(Range {
+                start: Position {
+                    line: 3,
+                    character: 0,
+                },
+                end: Position {
+                    line: 3,
+                    character: 0,
+                },
+            }),
+            range_length: None,
+            text: "    function second() {}\n".to_string(),
+        }],
+    };
+    backend.did_change(change_params).await;
+
+    let classes = backend.get_classes_for_uri(uri.as_ref()).unwrap();
+    assert_eq!(classes[0].methods.len(), 2);
+    let names: Vec<&str> = classes[0].methods.iter().map(|m| m.name.as_str()).collect();
+    assert!(names.contains(&"first"));
+    assert!(names.contains(&"second"));
+}
+
+#[tokio::test]
+async fn test_did_change_incremental_multiple_edits() {
+    let backend = create_test_backend();
+
+    let uri = Url::parse("file:///multi_edit.php").unwrap();
+    let initial = "<?php\nclass B {\n    function alpha() {}\n}\n".to_string();
+
+    let open_params = DidOpenTextDocumentParams {
+        text_document: TextDocumentItem {
+            uri: uri.clone(),
+            language_id: "php".to_string(),
+            version: 1,
+            text: initial,
+        },
+    };
+    backend.did_open(open_params).await;
+
+    // Two incremental edits in one event: rename "alpha" to "beta" and add a method.
+    // "alpha" starts at line 2, char 13, ends at char 18.
+    // After that edit the file is: "<?php\nclass B {\n    function beta() {}\n}\n"
+    // Then insert before closing brace (now line 3, char 0).
+    let change_params = DidChangeTextDocumentParams {
+        text_document: VersionedTextDocumentIdentifier {
+            uri: uri.clone(),
+            version: 2,
+        },
+        content_changes: vec![
+            TextDocumentContentChangeEvent {
+                range: Some(Range {
+                    start: Position {
+                        line: 2,
+                        character: 13,
+                    },
+                    end: Position {
+                        line: 2,
+                        character: 18,
+                    },
+                }),
+                range_length: None,
+                text: "beta".to_string(),
+            },
+            TextDocumentContentChangeEvent {
+                range: Some(Range {
+                    start: Position {
+                        line: 3,
+                        character: 0,
+                    },
+                    end: Position {
+                        line: 3,
+                        character: 0,
+                    },
+                }),
+                range_length: None,
+                text: "    function gamma() {}\n".to_string(),
+            },
+        ],
+    };
+    backend.did_change(change_params).await;
+
+    let classes = backend.get_classes_for_uri(uri.as_ref()).unwrap();
+    assert_eq!(classes[0].methods.len(), 2);
+    let names: Vec<&str> = classes[0].methods.iter().map(|m| m.name.as_str()).collect();
+    assert!(names.contains(&"beta"));
+    assert!(names.contains(&"gamma"));
+    assert!(!names.contains(&"alpha"));
+}