Support different toolchains per folder

With the introduction of swiftly's `.swift-version` file the active
toolchain can now be per-folder instead of global. If the user has
multiple different packages open they may each be using a different
toolchain as defined by their `.swift-version` file.

In order to support this new paradigm the `toolchain` has been moved
from `WorkspaceContext` to `FolderContext`. Each time a folder (package)
is added to the workspace a new toolchain is created, as it might be
different from folder to folder.

The toolchain created respects the `.swift-version` file. If the
toolchain specified in the `.swift-version` file is not installed an
error message is shown prompting the user to install the version with
swiftly.

There is still a `globalToolchain` on the `WorkspaceContext` which
refers to the globally available toolchain. This would be the toolchain
used when you run `swift` outside of a workspace folder. This is mainly
used as a fallback toolchain for when there are no workspace folders.

It is generally advisable to use the toolchain provided on the
`FolderContext` to ensure you don't end up using mismatched versions.

This PR also refactors the `LanguageClientManager` so that one instance
of sourcekit-lsp is started per-toolchain, coordinating startup so that
the server from a given toolchain starts up when a folder using that
toolchain is added to the workspace.

While this PR adds support for .swift-version files, there is still
quite a bit of work to do to make using swiftly with the VS Code Swift
extension a nicer experience including: Installing swiftly directly from
the extension, downloading missing toolchains automatically,
listing/picking/downloading toolchains via `swiftly list`, a smoother
toolchain switching experience that would optionally write the
`.swift-version` file, and more.

Author: plemarquand

src/FolderContext.ts

@@ -23,6 +23,7 @@ import { BackgroundCompilation } from "./BackgroundCompilation";
 import { TaskQueue } from "./tasks/TaskQueue";
 import { isPathInsidePath } from "./utilities/filesystem";
 import { SwiftOutputChannel } from "./ui/SwiftOutputChannel";
+import { SwiftToolchain } from "./toolchain/toolchain";
 
 export class FolderContext implements vscode.Disposable {
     private packageWatcher: PackageWatcher;
@@ -39,13 +40,13 @@ export class FolderContext implements vscode.Disposable {
      */
     private constructor(
         public folder: vscode.Uri,
+        public toolchain: SwiftToolchain,
         public linuxMain: LinuxMain,
         public swiftPackage: SwiftPackage,
         public workspaceFolder: vscode.WorkspaceFolder,
         public workspaceContext: WorkspaceContext
     ) {
         this.packageWatcher = new PackageWatcher(this, workspaceContext);
-        this.packageWatcher.install();
         this.backgroundCompilation = new BackgroundCompilation(this);
         this.taskQueue = new TaskQueue(this);
     }
@@ -71,16 +72,19 @@ export class FolderContext implements vscode.Disposable {
     ): Promise<FolderContext> {
         const statusItemText = `Loading Package (${FolderContext.uriName(folder)})`;
         workspaceContext.statusItem.start(statusItemText);
+
+        const toolchain = await SwiftToolchain.create(folder);
         const { linuxMain, swiftPackage } =
             await workspaceContext.statusItem.showStatusWhileRunning(statusItemText, async () => {
                 const linuxMain = await LinuxMain.create(folder);
-                const swiftPackage = await SwiftPackage.create(folder, workspaceContext.toolchain);
+                const swiftPackage = await SwiftPackage.create(folder, toolchain);
                 return { linuxMain, swiftPackage };
             });
         workspaceContext.statusItem.end(statusItemText);
 
         const folderContext = new FolderContext(
             folder,
+            toolchain,
             linuxMain,
             swiftPackage,
             workspaceFolder,
@@ -97,6 +101,10 @@ export class FolderContext implements vscode.Disposable {
                 folderContext.name
             );
         }
+
+        // Start watching for changes to Package.swift, Package.resolved and .swift-version
+        await folderContext.packageWatcher.install();
+
         return folderContext;
     }
 
@@ -117,9 +125,13 @@ export class FolderContext implements vscode.Disposable {
         return this.workspaceFolder.uri === this.folder;
     }
 
+    get swiftVersion() {
+        return this.toolchain.swiftVersion;
+    }
+
     /** reload swift package for this folder */
     async reload() {
-        await this.swiftPackage.reload(this.workspaceContext.toolchain);
+        await this.swiftPackage.reload(this.toolchain);
     }
 
     /** reload Package.resolved for this folder */
@@ -134,7 +146,7 @@ export class FolderContext implements vscode.Disposable {
 
     /** Load Swift Plugins and store in Package */
     async loadSwiftPlugins(outputChannel: SwiftOutputChannel) {
-        await this.swiftPackage.loadSwiftPlugins(this.workspaceContext.toolchain, outputChannel);
+        await this.swiftPackage.loadSwiftPlugins(this.toolchain, outputChannel);
     }
 
     /**

src/PackageWatcher.ts

@@ -12,10 +12,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+import * as path from "path";
+import * as fs from "fs/promises";
 import * as vscode from "vscode";
 import { FolderContext } from "./FolderContext";
 import { FolderOperation, WorkspaceContext } from "./WorkspaceContext";
 import { BuildFlags } from "./toolchain/BuildFlags";
+import { Version } from "./utilities/version";
 
 /**
  * Watches for changes to **Package.swift** and **Package.resolved**.
@@ -28,6 +31,8 @@ export class PackageWatcher {
     private resolvedFileWatcher?: vscode.FileSystemWatcher;
     private workspaceStateFileWatcher?: vscode.FileSystemWatcher;
     private snippetWatcher?: vscode.FileSystemWatcher;
+    private swiftVersionFileWatcher?: vscode.FileSystemWatcher;
+    private currentVersion?: Version;
 
     constructor(
         private folderContext: FolderContext,
@@ -38,11 +43,12 @@ export class PackageWatcher {
      * Creates and installs {@link vscode.FileSystemWatcher file system watchers} for
      * **Package.swift** and **Package.resolved**.
      */
-    install() {
+    async install() {
         this.packageFileWatcher = this.createPackageFileWatcher();
         this.resolvedFileWatcher = this.createResolvedFileWatcher();
         this.workspaceStateFileWatcher = this.createWorkspaceStateFileWatcher();
         this.snippetWatcher = this.createSnippetFileWatcher();
+        this.swiftVersionFileWatcher = await this.createSwiftVersionFileWatcher();
     }
 
     /**
@@ -54,6 +60,7 @@ export class PackageWatcher {
         this.resolvedFileWatcher?.dispose();
         this.workspaceStateFileWatcher?.dispose();
         this.snippetWatcher?.dispose();
+        this.swiftVersionFileWatcher?.dispose();
     }
 
     private createPackageFileWatcher(): vscode.FileSystemWatcher {
@@ -99,6 +106,43 @@ export class PackageWatcher {
         return watcher;
     }
 
+    private async createSwiftVersionFileWatcher(): Promise<vscode.FileSystemWatcher> {
+        const watcher = vscode.workspace.createFileSystemWatcher(
+            new vscode.RelativePattern(this.folderContext.folder, ".swift-version")
+        );
+        watcher.onDidCreate(async () => await this.handleSwiftVersionFileChange());
+        watcher.onDidChange(async () => await this.handleSwiftVersionFileChange());
+        watcher.onDidDelete(async () => await this.handleSwiftVersionFileChange());
+        this.currentVersion =
+            (await this.readSwiftVersionFile()) ?? this.folderContext.toolchain.swiftVersion;
+        return watcher;
+    }
+
+    async handleSwiftVersionFileChange() {
+        try {
+            const version = await this.readSwiftVersionFile();
+            if (version && version.toString() !== this.currentVersion?.toString()) {
+                this.workspaceContext.fireEvent(
+                    this.folderContext,
+                    FolderOperation.swiftVersionUpdated
+                );
+            }
+            this.currentVersion = version ?? this.folderContext.toolchain.swiftVersion;
+        } catch {
+            // do nothing
+        }
+    }
+
+    private async readSwiftVersionFile() {
+        const versionFile = path.join(this.folderContext.folder.fsPath, ".swift-version");
+        try {
+            const contents = await fs.readFile(versionFile);
+            return Version.fromString(contents.toString().trim());
+        } catch {
+            return undefined;
+        }
+    }
+
     /**
      * Handles a create or change event for **Package.swift**.
      *

src/SwiftSnippets.ts

@@ -26,9 +26,9 @@ import { TaskOperation } from "./tasks/TaskQueue";
  */
 export function setSnippetContextKey(ctx: WorkspaceContext) {
     if (
-        ctx.swiftVersion.isLessThan({ major: 5, minor: 7, patch: 0 }) ||
         !ctx.currentFolder ||
-        !ctx.currentDocument
+        !ctx.currentDocument ||
+        ctx.currentFolder.swiftVersion.isLessThan({ major: 5, minor: 7, patch: 0 })
     ) {
         contextKeys.fileIsSnippet = false;
         return;
@@ -97,7 +97,7 @@ export async function debugSnippetWithOptions(
                 reveal: vscode.TaskRevealKind.Always,
             },
         },
-        ctx.toolchain
+        folderContext.toolchain
     );
     const snippetDebugConfig = createSnippetConfiguration(snippetName, folderContext);
     try {

src/TestExplorer/TestExplorer.ts

@@ -67,9 +67,9 @@ export class TestExplorer {
             this.onDidCreateTestRunEmitter
         );
 
-        this.lspTestDiscovery = new LSPTestDiscovery(
-            folderContext.workspaceContext.languageClientManager
-        );
+        const workspaceContext = folderContext.workspaceContext;
+        const languageClientManager = workspaceContext.languageClientManager.get(folderContext);
+        this.lspTestDiscovery = new LSPTestDiscovery(languageClientManager);
 
         // add end of task handler to be called whenever a build task has finished. If
         // it is the build task for this folder then update the tests
@@ -182,10 +182,10 @@ export class TestExplorer {
                         break;
                     case FolderOperation.focus:
                         if (folder) {
-                            workspace.languageClientManager.documentSymbolWatcher = (
-                                document,
-                                symbols
-                            ) => TestExplorer.onDocumentSymbols(folder, document, symbols);
+                            const languageClientManager =
+                                workspace.languageClientManager.get(folder);
+                            languageClientManager.documentSymbolWatcher = (document, symbols) =>
+                                TestExplorer.onDocumentSymbols(folder, document, symbols);
                         }
                 }
             }
@@ -307,7 +307,7 @@ export class TestExplorer {
                             }
                         });
                 }
-                const toolchain = explorer.folderContext.workspaceContext.toolchain;
+                const toolchain = explorer.folderContext.toolchain;
                 // get build options before build is run so we can be sure they aren't changed
                 // mid-build
                 const testBuildOptions = buildOptions(toolchain);

src/TestExplorer/TestRunner.ts

@@ -396,7 +396,7 @@ export class TestRunner {
         this.xcTestOutputParser =
             testKind === TestKind.parallel
                 ? new ParallelXCTestOutputParser(
-                      this.folderContext.workspaceContext.toolchain.hasMultiLineParallelTestOutput
+                      this.folderContext.toolchain.hasMultiLineParallelTestOutput
                   )
                 : new XCTestOutputParser();
         this.swiftTestOutputParser = new SwiftTestingOutputParser(
@@ -774,7 +774,7 @@ export class TestRunner {
                     prefix: this.folderContext.name,
                     presentationOptions: { reveal: vscode.TaskRevealKind.Never },
                 },
-                this.folderContext.workspaceContext.toolchain,
+                this.folderContext.toolchain,
                 { ...process.env, ...testBuildConfig.env },
                 { readOnlyTerminal: process.platform !== "win32" }
             );
@@ -859,7 +859,7 @@ export class TestRunner {
 
             const buffer = await asyncfs.readFile(filename, "utf8");
             const xUnitParser = new TestXUnitParser(
-                this.folderContext.workspaceContext.toolchain.hasMultiLineParallelTestOutput
+                this.folderContext.toolchain.hasMultiLineParallelTestOutput
             );
             const results = await xUnitParser.parse(
                 buffer,

src/WorkspaceContext.ts

@@ -19,7 +19,7 @@ import { StatusItem } from "./ui/StatusItem";
 import { SwiftOutputChannel } from "./ui/SwiftOutputChannel";
 import { swiftLibraryPathKey } from "./utilities/utilities";
 import { isPathInsidePath } from "./utilities/filesystem";
-import { LanguageClientManager } from "./sourcekit-lsp/LanguageClientManager";
+import { LanguageClientToolchainCoordinator } from "./sourcekit-lsp/LanguageClientToolchainCoordinator";
 import { TemporaryFolder } from "./utilities/tempFolder";
 import { TaskManager } from "./tasks/TaskManager";
 import { makeDebugConfigurations } from "./debugger/launch";
@@ -45,7 +45,7 @@ export class WorkspaceContext implements vscode.Disposable {
     public currentDocument: vscode.Uri | null;
     public statusItem: StatusItem;
     public buildStatus: SwiftBuildStatus;
-    public languageClientManager: LanguageClientManager;
+    public languageClientManager: LanguageClientToolchainCoordinator;
     public tasks: TaskManager;
     public diagnostics: DiagnosticsManager;
     public subscriptions: vscode.Disposable[];
@@ -69,11 +69,11 @@ export class WorkspaceContext implements vscode.Disposable {
         extensionContext: vscode.ExtensionContext,
         public tempFolder: TemporaryFolder,
         public outputChannel: SwiftOutputChannel,
-        public toolchain: SwiftToolchain
+        public globalToolchain: SwiftToolchain
     ) {
         this.statusItem = new StatusItem();
         this.buildStatus = new SwiftBuildStatus(this.statusItem);
-        this.languageClientManager = new LanguageClientManager(this);
+        this.languageClientManager = new LanguageClientToolchainCoordinator(this);
         this.tasks = new TaskManager(this);
         this.diagnostics = new DiagnosticsManager(this);
         this.documentation = new DocumentationManager(extensionContext, this);
@@ -200,8 +200,8 @@ export class WorkspaceContext implements vscode.Disposable {
         this.subscriptions.length = 0;
     }
 
-    get swiftVersion() {
-        return this.toolchain.swiftVersion;
+    get globalToolchainSwiftVersion() {
+        return this.globalToolchain.swiftVersion;
     }
 
     /** Get swift version and create WorkspaceContext */
@@ -246,19 +246,21 @@ export class WorkspaceContext implements vscode.Disposable {
             contextKeys.currentTargetType = undefined;
         }
 
-        // Set context keys that depend on features from SourceKit-LSP
-        this.languageClientManager.useLanguageClient(async client => {
-            const experimentalCaps = client.initializeResult?.capabilities.experimental;
-            if (!experimentalCaps) {
-                contextKeys.supportsReindexing = false;
-                contextKeys.supportsDocumentationLivePreview = false;
-                return;
-            }
-            contextKeys.supportsReindexing =
-                experimentalCaps[ReIndexProjectRequest.method] !== undefined;
-            contextKeys.supportsDocumentationLivePreview =
-                experimentalCaps[DocCDocumentationRequest.method] !== undefined;
-        });
+        if (this.currentFolder) {
+            const languageClient = this.languageClientManager.get(this.currentFolder);
+            languageClient.useLanguageClient(async client => {
+                const experimentalCaps = client.initializeResult?.capabilities.experimental;
+                if (!experimentalCaps) {
+                    contextKeys.supportsReindexing = false;
+                    contextKeys.supportsDocumentationLivePreview = false;
+                    return;
+                }
+                contextKeys.supportsReindexing =
+                    experimentalCaps[ReIndexProjectRequest.method] !== undefined;
+                contextKeys.supportsDocumentationLivePreview =
+                    experimentalCaps[DocCDocumentationRequest.method] !== undefined;
+            });
+        }
 
         setSnippetContextKey(this);
     }
@@ -643,6 +645,8 @@ export enum FolderOperation {
     packageViewUpdated = "packageViewUpdated",
     // Package plugins list has been updated
     pluginsUpdated = "pluginsUpdated",
+    // The folder's swift toolchain version has been updated
+    swiftVersionUpdated = "swiftVersionUpdated",
 }
 
 /** Workspace Folder Event */

src/commands.ts

@@ -135,7 +135,7 @@ export function register(ctx: WorkspaceContext): vscode.Disposable[] {
         vscode.commands.registerCommand("swift.runScript", () => runSwiftScript(ctx)),
         vscode.commands.registerCommand("swift.openPackage", () => {
             if (ctx.currentFolder) {
-                return openPackage(ctx.toolchain.swiftVersion, ctx.currentFolder.folder);
+                return openPackage(ctx.currentFolder.swiftVersion, ctx.currentFolder.folder);
             }
         }),
         vscode.commands.registerCommand(Commands.RUN_SNIPPET, target =>
@@ -146,9 +146,13 @@ export function register(ctx: WorkspaceContext): vscode.Disposable[] {
         ),
         vscode.commands.registerCommand(Commands.RUN_PLUGIN_TASK, () => runPluginTask()),
         vscode.commands.registerCommand(Commands.RUN_TASK, name => runTask(ctx, name)),
-        vscode.commands.registerCommand("swift.restartLSPServer", () =>
-            ctx.languageClientManager.restart()
-        ),
+        vscode.commands.registerCommand("swift.restartLSPServer", async () => {
+            if (!ctx.currentFolder) {
+                return;
+            }
+            const languageClientManager = ctx.languageClientManager.get(ctx.currentFolder);
+            await languageClientManager.restart();
+        }),
         vscode.commands.registerCommand("swift.reindexProject", () => reindexProject(ctx)),
         vscode.commands.registerCommand("swift.insertFunctionComment", () =>
             insertFunctionComment(ctx)

src/commands/build.ts

@@ -60,7 +60,7 @@ export async function folderCleanBuild(folderContext: FolderContext) {
             presentationOptions: { reveal: vscode.TaskRevealKind.Silent },
             group: vscode.TaskGroup.Clean,
         },
-        folderContext.workspaceContext.toolchain
+        folderContext.toolchain
     );
 
     return await executeTaskWithUI(task, "Clean Build", folderContext);