Handle dependencies with an empty manifest field

This happens sometimes with snapshots. We just want them to be displayed properly in the HTML output.

__tests__/summary.test.ts

@@ -27,6 +27,45 @@ const defaultConfig: ConfigurationOptions = {
   comment_summary_in_pr: true
 }
 
+const changesWithEmptyManifests: Changes = [
+  {
+    change_type: 'added',
+    manifest: '',
+    ecosystem: 'unknown',
+    name: 'castore',
+    version: '0.1.17',
+    package_url: 'pkg:hex/[email protected]',
+    license: null,
+    source_repository_url: null,
+    scope: 'runtime',
+    vulnerabilities: []
+  },
+  {
+    change_type: 'added',
+    manifest: '',
+    ecosystem: 'unknown',
+    name: 'connection',
+    version: '1.1.0',
+    package_url: 'pkg:hex/[email protected]',
+    license: null,
+    source_repository_url: null,
+    scope: 'runtime',
+    vulnerabilities: []
+  },
+  {
+    change_type: 'added',
+    manifest: 'python/dist-info/METADATA',
+    ecosystem: 'pip',
+    name: 'pygments',
+    version: '2.6.1',
+    package_url: 'pkg:pypi/[email protected]',
+    license: 'BSD-2-Clause',
+    source_repository_url: 'https://github.com/pygments/pygments',
+    scope: 'runtime',
+    vulnerabilities: []
+  }
+]
+
 test('prints headline as h1', () => {
   summary.addSummaryToSummary(
     emptyChanges,
@@ -65,6 +104,22 @@ test('only includes "No license issues found"-message if "vulnerability_check" i
   expect(text).toContain('✅ No license issues found.')
 })
 
+test('groups dependencies with empty manifest paths together', () => {
+  summary.addSummaryToSummary(
+    changesWithEmptyManifests,
+    emptyInvalidLicenseChanges,
+    defaultConfig
+  )
+  summary.addScannedDependencies(changesWithEmptyManifests)
+  const text = core.summary.stringify()
+
+  expect(text).toContain('<summary> </summary>')
+  expect(text).toContain('castore')
+  expect(text).toContain('connection')
+  expect(text).toContain('<summary>python/dist-info/METADATA</summary>')
+  expect(text).toContain('pygments')
+})
+
 test('does not include status section if nothing was found', () => {
   summary.addSummaryToSummary(
     emptyChanges,