fix: language server would crash if main class could not be identified (

#578)

Fixes forcedotcom/salesforcedx-vscode#4994.

Co-authored-by: Cristina Cañizales <113132642+CristiCanizales@users.noreply.github.com>

packages/lwc-language-server/src/javascript/__tests__/compiler.test.ts

@@ -33,6 +33,21 @@ export default class Foo extends LightningElement {
     @api property = true;
 }
 `;
+const codeWithoutDefaultExportSingleClass = `
+import { api, LightningElement } from 'lwc';
+class Foo extends LightningElement {
+    @api foo;
+}
+`;
+const codeWithoutDefaultExportMultipleClasses = `
+import { api, LightningElement } from 'lwc';
+class Foo extends LightningElement {
+    @api foo;
+}
+class Bar extends LightningElement {
+    @api bar;
+}
+`;
 
 it('can get metadata from a simple component', async () => {
     await compileSource(codeOk, 'foo.js');
@@ -46,6 +61,21 @@ it('displays an error for a component with syntax error', async () => {
     expect(diagnostic.message).toMatch('Unexpected token (4:17)');
 });
 
+it('returns empty metadata for a script without a clear main component class', async () => {
+    const result = await compileSource(codeWithoutDefaultExportMultipleClasses, 'foo.js');
+    expect(result.metadata?.decorators).toHaveLength(0);
+    expect(result.metadata?.classMembers).toHaveLength(0);
+    expect(result.metadata?.exports).toHaveLength(0);
+});
+
+it('returns metadata for a script with one component class, even when not exported', async () => {
+    const result = await compileSource(codeWithoutDefaultExportSingleClass, 'foo.js');
+    console.log(result);
+    expect(result.metadata?.decorators).toHaveLength(1);
+    expect(result.metadata?.classMembers).toHaveLength(1);
+    expect(result.metadata?.exports).toHaveLength(0);
+});
+
 it('displays an error for a component with other errors', async () => {
     const result = await compileSource(codeError, 'foo.js');
     expect(result.metadata).toBeUndefined();

packages/lwc-language-server/src/javascript/type-mapping.ts

@@ -541,9 +541,24 @@ function getExports(lwcExports: LwcExport[]): InternalModuleExports[] {
  * LWC language server to analyze code in a user's IDE.
  */
 export function mapLwcMetadataToInternal(lwcMeta: ScriptFile): InternalMetadata {
-    const mainClassObj = lwcMeta.classes.find(classObj => {
-        return classObj.id == lwcMeta.mainClass.refId;
-    });
+    let mainClassObj;
+    if (lwcMeta.mainClass) {
+        mainClassObj = lwcMeta.classes.find(classObj => {
+            return classObj.id == lwcMeta.mainClass.refId;
+        });
+    } else if (lwcMeta.classes.length === 1) {
+        mainClassObj = lwcMeta.classes[0];
+    }
+
+    // If we are unable to identify the main class object from the provided metadata,
+    // it will not be possible calculate decorators, members, etc.
+    if (!mainClassObj) {
+        return {
+            decorators: [],
+            classMembers: [],
+            exports: [],
+        };
+    }
 
     const defaultExport = lwcMeta.exports.filter((exp) => exp.defaultExport)[0];
     const declarationLoc = externalToInternalLoc(defaultExport?.location ?? mainClassObj.location);