fix(sveltekit): Ensure target file exists before applying auto instrumentation

packages/sveltekit/src/vite/autoInstrument.ts

@@ -40,7 +40,7 @@ type AutoInstrumentPluginOptions = AutoInstrumentSelection & {
  * @returns the plugin
  */
 export function makeAutoInstrumentationPlugin(options: AutoInstrumentPluginOptions): Plugin {
-  const { load: shouldWrapLoad, serverLoad: shouldWrapServerLoad, debug } = options;
+  const { load: wrapLoadEnabled, serverLoad: wrapServerLoadEnabled, debug } = options;
 
   return {
     name: 'sentry-auto-instrumentation',
@@ -49,7 +49,7 @@ export function makeAutoInstrumentationPlugin(options: AutoInstrumentPluginOptio
 
     async load(id) {
       const applyUniversalLoadWrapper =
-        shouldWrapLoad &&
+        wrapLoadEnabled &&
         /^\+(page|layout)\.(js|ts|mjs|mts)$/.test(path.basename(id)) &&
         (await canWrapLoad(id, debug));
 
@@ -60,7 +60,7 @@ export function makeAutoInstrumentationPlugin(options: AutoInstrumentPluginOptio
       }
 
       const applyServerLoadWrapper =
-        shouldWrapServerLoad &&
+        wrapServerLoadEnabled &&
         /^\+(page|layout)\.server\.(js|ts|mjs|mts)$/.test(path.basename(id)) &&
         (await canWrapLoad(id, debug));
 
@@ -90,7 +90,19 @@ export function makeAutoInstrumentationPlugin(options: AutoInstrumentPluginOptio
  * @returns `true` if we can wrap the given file, `false` otherwise
  */
 export async function canWrapLoad(id: string, debug: boolean): Promise<boolean> {
+  // Some 3rd party plugins add ids to the build that actually don't exist.
+  // We need to check for that here, otherwise users get get a build errors.
+  if (!fs.existsSync(id)) {
+    debug &&
+      // eslint-disable-next-line no-console
+      console.log(
+        `Skipping wrapping ${id} because it doesn't exist. A 3rd party plugin might have added this as a virtual file to the build`,
+      );
+    return false;
+  }
+
   const code = (await fs.promises.readFile(id, 'utf8')).toString();
+
   const mod = parseModule(code);
 
   const program = mod.$ast.type === 'Program' && mod.$ast;

packages/sveltekit/test/vite/autoInstrument.test.ts

@@ -21,6 +21,12 @@ vi.mock('fs', async () => {
         return fileContent || DEFAULT_CONTENT;
       }),
     },
+    existsSync: vi.fn().mockImplementation(id => {
+      if (id === '+page.virtual.ts') {
+        return false;
+      }
+      return true;
+    }),
   };
 });
 
@@ -198,15 +204,20 @@ describe('canWrapLoad', () => {
     'export const loadNotLoad = () => {}; export const prerender = true;',
     'export function aload(){}; export const prerender = true;',
     'export function loader(){}; export const prerender = true;',
-    'let loademe = false; export {loadme}',
+    'let loadme = false; export {loadme}',
     'const a = {load: true}; export {a}',
     'if (s === "load") {}',
     'const a = load ? load : false',
     '// const load = () => {}',
     '/* export const load = () => {} */ export const prerender = true;',
     '/* export const notLoad = () => { const a = getSomething() as load; } */ export const prerender = true;',
-  ])('returns `false` if no load declaration exists', async (_, code) => {
+  ])('returns `false` if no load declaration exists', async code => {
     fileContent = code;
-    expect(await canWrapLoad('+page.ts', false)).toEqual(true);
+    expect(await canWrapLoad('+page.ts', false)).toEqual(false);
+  });
+
+  it("returns `false` if the passed file id doesn't exist", async () => {
+    fileContent = DEFAULT_CONTENT;
+    expect(await canWrapLoad('+page.virtual.ts', false)).toEqual(false);
   });
 });