fix: properly handle types manifest with only comments (#241)

Author: Vampire

src/main/kotlin/it/krzeminski/githubactionstyping/parsing/TypesManifestParsing.kt

@@ -1,5 +1,6 @@
 package it.krzeminski.githubactionstyping.parsing
 
+import com.charleskorn.kaml.EmptyYamlDocumentException
 import com.charleskorn.kaml.Yaml
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
@@ -32,4 +33,11 @@ private val myYaml = Yaml(
 )
 
 fun parseTypesManifest(manifestString: String): TypesManifest =
-    myYaml.decodeFromString(manifestString)
+    runCatching {
+        myYaml.decodeFromString<TypesManifest>(manifestString)
+    }.getOrElse {
+        if (it is EmptyYamlDocumentException) {
+            return TypesManifest()
+        }
+        throw it
+    }

src/test/kotlin/it/krzeminski/githubactionstyping/validation/ManifestsToReportTest.kt

@@ -157,6 +157,40 @@ class ManifestsToReportTest : FunSpec({
         }
     }
 
+    test("comment-only types YAML") {
+        // when
+        val manifest = """
+            name: GitHub Actions Typing
+            description: Bring type-safety to your GitHub actions' API!
+            author: Piotr Krzemiński
+            runs:
+              using: 'docker'
+              image: 'Dockerfile'
+        """.trimIndent()
+        val typesManifest = "#"
+
+        // when
+        val (isValid, report) = manifestsToReport(Path("action.yml"), manifest, typesManifest)
+
+        // then
+        assertSoftly {
+            isValid shouldBe true
+            report shouldBe """
+                For action with manifest at 'action.yml':
+                Result:
+                ${'\u001b'}[32m✔ VALID${'\u001b'}[0m
+
+                Inputs:
+                None.
+                
+                Outputs:
+                None.
+
+
+            """.trimIndent()
+        }
+    }
+
     test("enum: missing allowed values") {
         // when
         val manifest = """