feat: provide Svelte 5 component migration command

Author: dummdidumm

packages/language-server/src/plugins/svelte/SveltePlugin.ts

@@ -15,7 +15,7 @@ import {
     WorkspaceEdit
 } from 'vscode-languageserver';
 import { Plugin } from 'prettier';
-import { getPackageInfo, importPrettier } from '../../importPackage';
+import { getPackageInfo, importPrettier, importSvelte } from '../../importPackage';
 import { Document } from '../../lib/documents';
 import { Logger } from '../../logger';
 import { LSConfigManager, LSSvelteConfig } from '../../ls-config';
@@ -288,6 +288,10 @@ export class SveltePlugin
         command: string,
         args?: any[]
     ): Promise<WorkspaceEdit | string | null> {
+        if (command === 'migrate_to_svelte_5') {
+            return this.migrate(document);
+        }
+
         if (!this.featureEnabled('codeActions')) {
             return null;
         }
@@ -300,6 +304,36 @@ export class SveltePlugin
         }
     }
 
+    private migrate(document: Document): WorkspaceEdit | string {
+        try {
+            const compiler = importSvelte(document.getFilePath() ?? '') as any;
+            if (!compiler.migrate) {
+                return 'Your installed Svelte version does not support migration';
+            }
+
+            const migrated = compiler.migrate(document.getText(), {
+                filename: document.getFilePath() ?? undefined
+            });
+
+            return {
+                changes: {
+                    [document.uri]: [
+                        TextEdit.replace(
+                            Range.create(
+                                document.positionAt(0),
+                                document.positionAt(document.getTextLength())
+                            ),
+                            migrated.code
+                        )
+                    ]
+                }
+            };
+        } catch (error: any) {
+            Logger.error('Failed to migrate Svelte file', error);
+            return error?.message ?? 'Failed to migrate Svelte file';
+        }
+    }
+
     async getSelectionRange(
         document: Document,
         position: Position

packages/language-server/src/server.ts

@@ -290,6 +290,7 @@ export function startServer(options?: LSOptions) {
                               'constant_scope_2',
                               'constant_scope_3',
                               'extract_to_svelte_component',
+                              'migrate_to_svelte_5',
                               'Infer function return type'
                           ]
                       }
@@ -592,15 +593,13 @@ export function startServer(options?: LSOptions) {
             return null;
         }
 
-        if (doc) {
-            const compiled = await sveltePlugin.getCompiledResult(doc);
-            if (compiled) {
-                const js = compiled.js;
-                const css = compiled.css;
-                return { js, css };
-            } else {
-                return null;
-            }
+        const compiled = await sveltePlugin.getCompiledResult(doc);
+        if (compiled) {
+            const js = compiled.js;
+            const css = compiled.css;
+            return { js, css };
+        } else {
+            return null;
         }
     });
 

packages/svelte-vscode/package.json

@@ -540,6 +540,10 @@
                 "command": "svelte.extractComponent",
                 "title": "Svelte: Extract Component"
             },
+            {
+                "command": "svelte.migrate_to_svelte_5",
+                "title": "Svelte: Migrate Component to Svelte 5 Syntax"
+            },
             {
                 "command": "svelte.typescript.findAllFileReferences",
                 "title": "Svelte: Find File References"

packages/svelte-vscode/src/extension.ts

@@ -259,6 +259,8 @@ export function activateSvelteLanguageServer(context: ExtensionContext) {
 
     addExtracComponentCommand(getLS, context);
 
+    addMigrateToSvelte5Command(getLS, context);
+
     languages.setLanguageConfiguration('svelte', {
         indentationRules: {
             // Matches a valid opening tag that is:
@@ -495,6 +497,22 @@ function addExtracComponentCommand(getLS: () => LanguageClient, context: Extensi
     );
 }
 
+function addMigrateToSvelte5Command(getLS: () => LanguageClient, context: ExtensionContext) {
+    context.subscriptions.push(
+        commands.registerTextEditorCommand('svelte.migrate_to_svelte_5', async (editor) => {
+            if (editor?.document?.languageId !== 'svelte') {
+                return;
+            }
+
+            const uri = editor.document.uri.toString();
+            getLS().sendRequest(ExecuteCommandRequest.type, {
+                command: 'migrate_to_svelte_5',
+                arguments: [uri]
+            });
+        })
+    );
+}
+
 function createLanguageServer(serverOptions: ServerOptions, clientOptions: LanguageClientOptions) {
     return new LanguageClient('svelte', 'Svelte', serverOptions, clientOptions);
 }