Corrects a bug with an empty query in VSCode

packages/language-server/src/linting.ts

@@ -25,6 +25,7 @@ async function rawLintDocument(
 
   const query = document.getText();
   if (query.length === 0) {
+    sendDiagnostics([]);
     return;
   }
 

packages/vscode-extension/e2e_tests/fixtures/syntax-validation.cypher

@@ -0,0 +1 @@
+MATCH (n) RETURN m

packages/vscode-extension/e2e_tests/tests/syntax-validation.spec.ts

@@ -0,0 +1,92 @@
+import * as assert from 'assert';
+import * as vscode from 'vscode';
+import { eventually, getDocumentUri, openDocument } from '../helpers';
+
+type InclusionTestArgs = {
+  textFile: string;
+  expected: vscode.Diagnostic[];
+};
+
+export async function testSyntaxValidation({
+  textFile,
+  expected,
+}: InclusionTestArgs) {
+  await eventually(
+    () =>
+      new Promise((resolve, reject) => {
+        const docUri = getDocumentUri(textFile);
+        const diagnostics: vscode.Diagnostic[] =
+          vscode.languages.getDiagnostics(docUri);
+
+        try {
+          // We need to test diagnostics one by one
+          // because the ones returned by VSCode contain
+          // more information we don't care about in the tests
+          assert.equal(diagnostics.length, expected.length);
+          diagnostics.forEach((diagnostic, i) => {
+            const expectedDiagnostic = expected[i];
+            assert.equal(diagnostic.message, expectedDiagnostic.message);
+            assert.deepEqual(diagnostic.range, expectedDiagnostic.range);
+            assert.equal(diagnostic.severity, expectedDiagnostic.severity);
+          });
+          resolve();
+        } catch (e) {
+          reject();
+        }
+      }),
+  );
+}
+
+suite('Syntax validation spec', () => {
+  test('Correctly validates empty cypher statement', async () => {
+    const textFile = 'syntax-validation.cypher';
+    const docUri = getDocumentUri(textFile);
+
+    await openDocument(docUri);
+
+    const editor = vscode.window.activeTextEditor;
+
+    await editor.edit((editBuilder) =>
+      editBuilder.replace(
+        // Select the whole file
+        new vscode.Range(
+          new vscode.Position(0, 0),
+          new vscode.Position(100, 0),
+        ),
+        'MATCH (n)',
+      ),
+    );
+
+    // We need to wait here because diagnostics are eventually
+    // consistent i.e. they don't show up immediately
+    await testSyntaxValidation({
+      textFile: 'syntax-validation.cypher',
+      expected: [
+        new vscode.Diagnostic(
+          new vscode.Range(
+            new vscode.Position(0, 0),
+            new vscode.Position(0, 9),
+          ),
+          'Query cannot conclude with MATCH (must be a RETURN clause, an update clause, a unit subquery call, or a procedure call with no YIELD)',
+          vscode.DiagnosticSeverity.Error,
+        ),
+      ],
+    });
+
+    await editor.edit((editBuilder) =>
+      editBuilder.replace(
+        // Select the whole file
+        new vscode.Range(
+          new vscode.Position(0, 0),
+          new vscode.Position(100, 0),
+        ),
+        '',
+      ),
+    );
+
+    await testSyntaxValidation({
+      textFile: 'syntax-validation.cypher',
+      expected: [],
+    });
+  });
+});