Fix an exception in diagnostics

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - (Ruby) Support `And` and `But` step definition annotations ([#211](https://github.com/cucumber/language-service/pull/211))
 - (Python) Title variants of Behave's decorators (`Step`, `Given`, `When`, `Then`) ([#213](https://github.com/cucumber/language-service/pull/213))
 - (PHP) Scoped query to match annotations only (`@Given`) ([#214](https://github.com/cucumber/language-service/pull/214))
+- Exception thrown for unterminated docstrings ([#216](https://github.com/cucumber/language-service/pull/216))
 
 ## [1.6.0] - 2024-05-12
 ### Added

src/service/getGherkinDiagnostics.ts

@@ -19,8 +19,13 @@ export function getGherkinDiagnostics(
     error instanceof Errors.CompositeParserException ? error.errors : error ? [error] : []
   for (const error of errors) {
     if (error instanceof Errors.GherkinException) {
-      const line = error.location.line - 1
-      const character = error.location.column !== undefined ? error.location.column - 1 : 0
+      let line = error.location.line - 1
+      let character = error.location.column !== undefined ? error.location.column - 1 : 0
+      if (line >= lines.length) {
+        // EOF issue, e.g. something is not properly terminated
+        line = lines.length - 1
+        character = lines[line].length
+      }
       const diagnostic: Diagnostic = {
         severity: DiagnosticSeverity.Error,
         range: {

test/service/getGherkinDiagnostics.test.ts

@@ -203,4 +203,32 @@ describe('getGherkinDiagnostics', () => {
     const expectedDiagnostics: Diagnostic[] = []
     assert.deepStrictEqual(diagnostics, expectedDiagnostics)
   })
+
+  it('returns diagnostic for incomplete docstring', () => {
+    const diagnostics = getGherkinDiagnostics(
+      `Feature: Hello
+  Scenario: Hi
+    Given a defined step
+      """`,
+      [new CucumberExpression('a defined step', new ParameterTypeRegistry())]
+    )
+    const expectedDiagnostics: Diagnostic[] = [
+      {
+        message: '(5:0): unexpected end of file, expected: #DocStringSeparator, #Other',
+        range: {
+          start: {
+            line: 3,
+            character: 9,
+          },
+          end: {
+            line: 3,
+            character: 9,
+          },
+        },
+        severity: DiagnosticSeverity.Error,
+        source: 'Cucumber',
+      },
+    ]
+    assert.deepStrictEqual(diagnostics, expectedDiagnostics)
+  })
 })