Use FileWatcher for background compilation (#1431)

* Use FileWatcher for background compilation

This `swift.backgroundCompilation` setting listened for file save events
from VS Code and triggered the build task. This meant that only
modifications made by saving in a VS Code editor would trigger
background compilation.

Switch to using a `vscode.FileWatcher` so background compilation still
gets kicked off even if a file is modified from outside VS Code. This is
useful if you have a command plugin that modifies source files like
swift-format.

Issue: #1274

Author: plemarquand

package-lock.json

@@ -1648,6 +1648,7 @@
     "@types/glob": "^7.1.6",
     "@types/lcov-parse": "^1.0.2",
     "@types/lodash.throttle": "^4.1.9",
+    "@types/lodash.debounce": "^4.0.9",
     "@types/mocha": "^10.0.10",
     "@types/mock-fs": "^4.13.4",
     "@types/node": "^18.19.80",
@@ -1671,6 +1672,7 @@
     "eslint": "^8.57.0",
     "eslint-config-prettier": "^10.1.1",
     "lodash.throttle": "^4.1.1",
+    "lodash.debounce": "^4.0.8",
     "mocha": "^10.8.2",
     "mock-fs": "^5.5.0",
     "node-pty": "^1.0.0",

package.json

@@ -13,63 +13,67 @@
 //===----------------------------------------------------------------------===//
 
 import * as vscode from "vscode";
-import * as path from "path";
-import { isPathInsidePath } from "./utilities/filesystem";
 import { getBuildAllTask } from "./tasks/SwiftTaskProvider";
 import configuration from "./configuration";
 import { FolderContext } from "./FolderContext";
-import { WorkspaceContext } from "./WorkspaceContext";
 import { TaskOperation } from "./tasks/TaskQueue";
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import debounce = require("lodash.debounce");
 
-export class BackgroundCompilation {
-    private waitingToRun = false;
+export class BackgroundCompilation implements vscode.Disposable {
+    private workspaceFileWatcher?: vscode.FileSystemWatcher;
+    private configurationEventDisposable?: vscode.Disposable;
+    private validFileTypes = ["swift", "c", "cpp", "h", "hpp", "m", "mm"];
+    private disposables: vscode.Disposable[] = [];
 
-    constructor(private folderContext: FolderContext) {}
-
-    /**
-     * Start onDidSave handler which will kick off compilation tasks
-     *
-     * The task works out which folder the saved file is in and then
-     * will call `runTask` on the background compilation attached to
-     * that folder.
-     * */
-    static start(workspaceContext: WorkspaceContext): vscode.Disposable {
-        const onDidSaveDocument = vscode.workspace.onDidSaveTextDocument(event => {
-            if (configuration.backgroundCompilation === false) {
-                return;
-            }
-
-            // is document a valid type for rebuild
-            const languages = ["swift", "c", "cpp", "objective-c", "objective-cpp"];
-            let foundLanguage = false;
-            languages.forEach(lang => {
-                if (event.languageId === lang) {
-                    foundLanguage = true;
+    constructor(private folderContext: FolderContext) {
+        // We only want to configure the file watcher if background compilation is enabled.
+        this.configurationEventDisposable = vscode.workspace.onDidChangeConfiguration(event => {
+            if (event.affectsConfiguration("swift.backgroundCompilation", folderContext.folder)) {
+                if (configuration.backgroundCompilation) {
+                    this.setupFileWatching();
+                } else {
+                    this.stopFileWatching();
                 }
-            });
-            if (foundLanguage === false) {
-                return;
             }
+        });
+
+        if (configuration.backgroundCompilation) {
+            this.setupFileWatching();
+        }
+    }
 
-            // is editor document in any of the current FolderContexts
-            const folderContext = workspaceContext.folders.find(context => {
-                return isPathInsidePath(event.uri.fsPath, context.folder.fsPath);
-            });
+    private setupFileWatching() {
+        const fileTypes = this.validFileTypes.join(",");
+        const rootFolders = ["Sources", "Tests", "Snippets", "Plugins"].join(",");
+        this.disposables.push(
+            (this.workspaceFileWatcher = vscode.workspace.createFileSystemWatcher(
+                `**/{${rootFolders}}/**/*.{${fileTypes}}`
+            ))
+        );
 
-            if (!folderContext) {
-                return;
-            }
+        // Throttle events since many change events can be recieved in a short time if the user
+        // does a "Save All" or a process writes several files in quick succession.
+        this.disposables.push(
+            this.workspaceFileWatcher.onDidChange(
+                debounce(
+                    () => {
+                        this.runTask();
+                    },
+                    100 /* 10 times per second */,
+                    { trailing: true }
+                )
+            )
+        );
+    }
 
-            // don't run auto-build if saving Package.swift as it clashes with the resolve
-            // that is run after the Package.swift is saved
-            if (path.join(folderContext.folder.fsPath, "Package.swift") === event.uri.fsPath) {
-                return;
-            }
+    private stopFileWatching() {
+        this.disposables.forEach(disposable => disposable.dispose());
+    }
 
-            // run background compilation task
-            folderContext.backgroundCompilation.runTask();
-        });
-        return { dispose: () => onDidSaveDocument.dispose() };
+    dispose() {
+        this.configurationEventDisposable?.dispose();
+        this.disposables.forEach(disposable => disposable.dispose());
     }
 
     /**

src/BackgroundCompilation.ts

@@ -54,6 +54,7 @@ export class FolderContext implements vscode.Disposable {
         this.linuxMain?.dispose();
         this.packageWatcher.dispose();
         this.testExplorer?.dispose();
+        this.backgroundCompilation.dispose();
     }
 
     /**

src/FolderContext.ts

@@ -22,7 +22,6 @@ import { isPathInsidePath } from "./utilities/filesystem";
 import { LanguageClientManager } from "./sourcekit-lsp/LanguageClientManager";
 import { TemporaryFolder } from "./utilities/tempFolder";
 import { TaskManager } from "./tasks/TaskManager";
-import { BackgroundCompilation } from "./BackgroundCompilation";
 import { makeDebugConfigurations } from "./debugger/launch";
 import configuration from "./configuration";
 import contextKeys from "./contextKeys";
@@ -121,7 +120,6 @@ export class WorkspaceContext implements vscode.Disposable {
                     });
             }
         });
-        const backgroundCompilationOnDidSave = BackgroundCompilation.start(this);
         const contextKeysUpdate = this.onDidChangeFolders(event => {
             switch (event.operation) {
                 case FolderOperation.remove:
@@ -174,7 +172,6 @@ export class WorkspaceContext implements vscode.Disposable {
             swiftFileWatcher,
             onDidEndTask,
             this.commentCompletionProvider,
-            backgroundCompilationOnDidSave,
             contextKeysUpdate,
             onChangeConfig,
             this.tasks,